Home 

 Moderated by: Greg Fletcher  
AuthorPost
terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
i've read all the articles here on oil pumps, and really need a step by step photographic lesson to achieve a rebuild. Only purched car 5 weeks ago and Engine was allways slow on pressure pickup (1-2 minutes)so I changed oil and filter 2 days ago with non return filter and 20W 40 oil. pressure increased for 1 day, although still very slow to pick up and today drove for 5kms and noticed No pressure. My question, is oil too low a viscosity (thin) or am I in deep trouble? and in need of a new pump and are they available

Greg Fletcher
Administrator


Joined: 03-11-2005
Location: Lake Nacimiento, California USA
Posts: 421
Status: 
Offline
I'd only use a traditional 20w50 oil in this engine, but I doubt that is the nature of your problem. I would also avoid running the engine with no oil pressure as that can result in catastrophic failure in a short time. Oil pressure should build up in a few seconds, 1-2 minutes indicates significant issues.

On the 907, very poor oil pressure can be caused by wear on the main bearings, oil pump problems or even contamination in the oil pump relief valve in the oil pump housing as well as a broken or blocked oil pressure tube, so you'll have a number of things to investigate.

The oil pump is a fairly simple arrangement. The inner and outer rotor are what create the pumping action. These run a tight clearance and significant mileage will make them sloppy, but not normally anything close to what you are describing. It's usually worth investigating the oil relief valve spring. I'd remove it, clean everything well and reinstall with a good quality moly lube.

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
I'll be aiming for 5W-50 as a first stop, if oil pressure is highish at full temp I will go down to 5W-40 to reduce wear in the cooler Norwegian climate.

Terry, are you sure you oil cooler hasn't clogged up? The oil in mine was so thick even diesel had a hard time passing. The oil cooler sandwich plate does NOT have a bypass mechanism, so if the cooler clogs up, you will have exactly 0 pressure. Before I started tearing things apart, I was seeing the same symptom as you.

Mind you, I haven't put everything back together yet, so I can't tell what helps and what doesn't, but I am really contemplating swapping the sandwich plate for one with a thermostat. Those never close off the bypass stream completely.

--
Joachim

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
Thanks for all the advice, I pulled cooler hoses off and blew out with compressor and found no blockage, then removed distributor and brass plug on top of oil pump, then pumped the relief valve? in and out a couple of dozen times and managed to get a few lumps of crap to squirt out. Reinstalled everything and low and behold 55lbs at above 1200 rpm and 20lbs at fast idle. It still however has a mind of its own and tends to drop to around 5-10 lbs at low idle. Have purchased a 2nd hand pump off a Lotus supplier in England and when it arrives I can have a go at a proper rebuild. Another thing I noticed was after removing plugs and HT lead from coil and turning engine over via starter motor was a click sound that really sounded like HT spark jumping, could this have been the relief valve operating or the distributor shorting internally? also don't like that stupid plastic oil pressure line to gauge, can it be replaced with an electric sender unit on motor and new electric pressure gauge and if so where would I source the parts?

thanks for your help

Greg Fletcher
Administrator


Joined: 03-11-2005
Location: Lake Nacimiento, California USA
Posts: 421
Status: 
Offline
That's very hopeful then. What you really must do however is completely remove the spring from the housing and clean it so that it SPOTLESS. The smallest bit of debris or silicon can restrict the travel and in turn effect your oil pressure (this happened to me once so I know all about this problem). You need to drive out the little pin in the side that positions the piston end and remove the spring. Use moly or graphite lube on it when putting it back in.

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
Ok Greg I will have a go at that, How? do I take pull the dizzie and the cone section off or do I have to remove the whole auxillary gizmo off the block?

Terry

Greg Fletcher
Administrator


Joined: 03-11-2005
Location: Lake Nacimiento, California USA
Posts: 421
Status: 
Offline
I had the entire housing on the bench when I did it, my guess is that it would considerably easier that way, but you may be able to remove the distributor and drive the pin out with a small punch. If you decide to remove the housing, you'll need to set the engine at TDC, loosen the timing belt and mark the bottom most position of the front of the ignition pulley.

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
thanks Greg, do you know of a web site that has an exploded view of the whole arrangement? I have seen a picture on the Delta site, but its not too good. Also where is the pin? do I access it from within dizzie hole or ?

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
Over weekend did two engine flushes and got pressure back to 50lbs, still takes ages to come up on start, pulled auxillary housing and as per Delta exploded view of oil pump I did not have the compression olive or the sealing plug installed. So I have gone no further with the pump untill I get a response from the forum. BTW the pump looks as if it may have been rebuilt at some stage not long ago as all new gaskets and gasget cement. Any thoughts?

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
Any leak on the suction side of the pump will cause priming to take longer. I think you will find the missing parts at SJ Sportscars

--
Joachim

Last edited on 03-28-2010 10:14 pm by subwoofer

907heaven
Member
 

Joined: 04-01-2010
Location:  
Posts: 17
Status: 
Offline
What year is your car?  The slow oil pick up on early models was caused by the lack of an air bleed in the pump.  On later models there is a very small hole 1.5mm (from memory) that bleeds air out of the pump on start up and allows the pump to prime much faster.  My fist Healey used to take something like 40 seconds to make oil pressure after start up.  There was a service bulletin from the factory on how to drill the Aux housing to alleviate the problem, I did the modification and oil pressure came up in a few seconds.  The same thing can happen if the bleed hole gets clogged up.  I'll bet your car doesn't have the drilling, if you are taking the aux hosuing off to work on the pump it is easy to do - but you need a long drill bit as the position of the hole is tucked down inside a hollow.  Garry

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
thanks for the info Gary, my car is 13599 off the production line 5/9/73 and is classed as a 1974 Mk2, I have the auxilliary housing off and think my problem is the olive and nut not correctly sealing the pickup pipe. It looks as if it has been tampered with over the years and a section of copper pipe has been added for a quick fix,  can you explain to me then exact position to look for the oil drilling?

Do I need to pull the pump apart to drill or is it in an oil gallery on the side plate?

thanks Terry

907heaven
Member
 

Joined: 04-01-2010
Location:  
Posts: 17
Status: 
Offline
Hi Terry,

watch the oil pipe - they tend to get "necked" or "pinched" where the nylon olive squeezes the pipe - if your pipe is pinched-in you stand no chance of getting an air tight seal.  Copper won't be strong enough to resist being crushed.  Remember to change the nylon olive for a new one. It needs torquing to 55lbs / ft. 

I am new to this forum; is it possible to post a photo?  If so I can take a photo of a correctly drilled housing and post it up. 

Regards

GARRY

 

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
Gary, i'm new on the forum as well and have no idea how to post pics, you can email me direct if you want at terryhowarth@netspace.net.au

thanks Terry

907heaven
Member
 

Joined: 04-01-2010
Location:  
Posts: 17
Status: 
Offline
Terry,

Greg kindly explained how to post a photo, so here is one - I'll mail you some extra ones.

GARRY

Attachment: P1020257.JPG (Downloaded 152 times)

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
Garry, thanks for the pics, mine is drilled. I had a bit of a go at the pickup pipe yesterday and was able to move it up and down by hand, so that looks to be the reason for slow pressure pickup. I am going to have ago at using a plumbers copper pipe expansion die on it today and if that does not work, out comes the engine!

thanks again to all

Terry

 

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
Gary, I just found out the bleed hole was drilled in the wrong place and had been blocked up again, so I drilled a new hole in the pump, expanded the pipe and now 8 seconds to 55lbs at cold start up and almost immediate when hot. Will need a new clutch soon so I will pull the engine and do the job correctly. But at the moment I can enjoy it.

thanks to all

907heaven
Member
 

Joined: 04-01-2010
Location:  
Posts: 17
Status: 
Offline
Great Result Terry - takes the stress out of starting the engine!

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
Hi All I'm reviving this Oil pressure string instead of starting a new one just to keep the topic consolidated.

Here's our situation:
We removed engine to replace header pipe. While engine was out took the opportunity to clean engine, replace front and rear main seals, new cam cover gaskets, new timing belt and idler  bearings. After we put everything back together the car started right up ran good and had good oil pressure (maybe even a bit better than before).  Took the car down to the exhaust shop to have a flange attachment fabricated for the new header, about a 3 mile trip, no problem, drove home next day, no problem.  My son took the car out a few days later and about 4 mi from home he said it started running rough, oil pressure dropped and the car died. Couldn't restart it. I went to meet him and did get the car to run rough briefly, but still no oil pressure.
Towed car home.

Car now starts fine but still no oil pressure.  Read above string, pulled oil pump housing, gears look ok, cleaned out relief valve, blew out oil line to gauge, still no oil pressure. Removed oil cooler adapter and reinstalled filter (to remove clogged oil cooler from the equation) still no oil pressure.

Now I'm thinking oil pickup pipe. 
My thoughts are that the rough running/stall and the loss of oil pressure were only some what related.   We did have the engine on a stand and rotated around a bit (not upside down but sideways to clean off the bottom of the sump) and it's possible some debris in the carb may have jarred loose and cause the rough running/stall (as I said the car starts and runs fine now).  Now I wonder if tilting the engine might have caused the pickup pipe to loosen and lose it's seal.  Seem far fetched but I'm out of ideas.

I have the factory parts catalog but it's not very clear on the relation between the pump housing and the pickup pipe.  Does the pickup pipe come out with the aux housing as a unit?

Any other ideas are appreciated, especially if it involves less work than pulling the aux housing.   Thanks,  Doug

Last edited on 06-21-2011 05:47 am by dmatth

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
dmatth wrote:
Now I'm thinking oil pickup pipe. 
My thoughts are that the rough running/stall and the loss of oil pressure were only some what related.   We did have the engine on a stand and rotated around a bit (not upside down but sideways to clean off the bottom of the sump) and it's possible some debris in the carb may have jarred loose and cause the rough running/stall (as I said the car starts and runs fine now).  Now I wonder if tilting the engine might have caused the pickup pipe to loosen and lose it's seal.  Seem far fetched but I'm out of ideas.


Unless it is really rotten nothing should come apart by tilting the engine. This is what a pickup in bad shape (but still working) looks like:


I have the factory parts catalog but it's not very clear on the relation between the pump housing and the pickup pipe.  Does the pickup pipe come out with the aux housing as a unit?

Nope. The pickup pipe is locked to the block with a rubber donut and a special nut. It goes out downwards.

Any other ideas are appreciated, especially if it involves less work than pulling the aux housing.   Thanks,  Doug

Idiot mode question: Is there enough oil on it? Have you actually checked? It is VERY easy to install the rear oil seal so that it leaks, then you may lose a quart of oil in 20 minutes of driving easily. I know from experience.

--
Joachim

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
Yeah, plenty of oil. Our repairs were successful in reducing the amount of escaping oil.

So if the Pickup pipe goes out downward is there really no way to check it without removing the engine/sump?  Obviously there is some connection between the pickup pipe and the aux housing for the simple reason of supplying oil to the pump.  If I remove the aux housing will I have access to the pickup pipe enough to see if I can draw oil up it?

Is there any other simple gizmos like clips or such in the pump that could go wrong, without horrifying noise, but make the pump non-functional?

Doug

Greg Fletcher
Administrator


Joined: 03-11-2005
Location: Lake Nacimiento, California USA
Posts: 421
Status: 
Offline
Contamination in the oil relief spring (inside the auxiliary housing) can create a no-oil pressure situation. A very small piece of stray silicon sealer is enough to make that happen.

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
The oil pump consists of a rotor pressed onto the shaft and secured with a circlip, an annulus piece and the housing. I have never actually heard a really failed one, but I have seen a picture where the annulus had broken into 5 pieces or so. I would imagine it to be noisy.

Access to the top of the pickup pipe is easy once you have the aux housing off, the hole is 3/4" or so in diameter. To have a look at the pickup the sump must be dropped. I would not recommend trying that with the engine in place, although I think Dan (Florida) actually did it.

My priority would have been to check the condition of the sump contents, on my "new" engine the pickup filter screen was 2/3 covered in old gasket material and other gunk. It still had good oil pressure, but needless to say I cleaned it well. I think yours may be really clogged with old gunk.

Another idiot mode question: are you sure the gauge is working? Have you tried connecting another gauge?

--
Joachim

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
Thanks for the suggestions!

Greg,
 I did clean out the spring/plunger in the Pump Housing.  Is there another something in the Aux Housing or are we talking about the same thing?

Joachim,
Thanks for the description. I guess the next step will be to remove the Aux Housing and see if i can draw oil up the pipe. Any idea how much/little effort should typically bring results?  As for the gauge, that was on my agenda for today thought I might send 25lbs of air pressure up the tube and see if the gauge needle moves.  Not feeling the the gauge is the culprit though since my test yesterday of removing oil cooler adapter seemed to leave the oil filter dry.

Another thing I thought of trying is to drive the pump with a power tool to see if I can get a response.

Doug

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
I would hold back on removing the aux housing, I'm not quite sure taking it off would prove. Clean the relief valve again, making sure everything is squeaky clean. If you already have the cam belt off, try driving the aux shaft with some power tool to see if any pressure build. If you have had the distributor out, was the O-ring in good condition? The pump will not prime if the distributor is removed.

If you spin the aux shaft with a drill, try taking the oil filter and oil cooler sandwich off to see if it pumps oil at all. No back pressure should make the oil flow.

If there still is no sign of oil pressure, I'd drop the sump next.

--
Joachim

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
I like the idea of not removing the aux housing (less work=more better), but I'm wondering if a clogged bleed hole could be a factor. Maybe with a mirror I'll be able to find the bleed hole with just the pump housing taken off.

I'll be tinkering tonight, hopefully with some results.

Doug

SpeedyMitch
Member


Joined: 12-17-2009
Location: Hailey, Idaho USA
Posts: 83
Status: 
Offline
dmatth wrote: I'm wondering if a clogged bleed hole could be a factor
Hay Doug,

When I purchased my early JH last year it had never had the FSB applied to drill the air bleed hole in the Aux Housing. Without the air bleed hole it would take 20-30 seconds to build oil pressure. After drilling the bleed hole it now builds pressure in less than 5 seconds.

If your JH is taking longer than 30 seconds to build oil pressure I doubt it is a plugged air bleed hole.

Just my 2-cents (and worth every penny).

Speedy Mitch

terryhowarth
Member
 

Joined: 03-02-2010
Location: Canberra, Australia
Posts: 19
Status: 
Offline
Hi all, I should have updated my problem months ago with the low oil pressure. As it turned out the PO had NEVER installed an olive into the pipe pickup at the block, all he did was ram some 1/2" plastic pipe down the oil pickup pipe and seal it with a piece of garden water hose & nut over that and sealing goop of some description. Then to top it off, a length of coiled metal spring about 12" long was shoved down that to stop the plastic pipe from being deformed by the engine oil heat. I removed the lot, fitted a new olive and nut and hey presto NO more oil pressure problems. might be worth checking it out as I'm sure there is more than 1 moron in the world.

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
SpeedyMitch wrote:

If your JH is taking longer than 30 seconds to build oil pressure I doubt it is a plugged air bleed


Good point. We've gone from good pressure (15-20 warm idle 45-50 running), to zero. So doubtful it's the bleed hole, I'll check it while I'm in there anyway.

Greg Fletcher
Administrator


Joined: 03-11-2005
Location: Lake Nacimiento, California USA
Posts: 421
Status: 
Offline
The bleed hole may not be a big deal. It's great to put it in if that is not present when you are doing a rebuild, but my early Jensen Healeys never had it and they have always had excellent/instant oil pressure at startup. New oil pump rotors and engine bearings to spec will make a hugh difference compared to a high mileage engine.

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
So  last night I tested the gauge, (it's working), pulled the oil pump housing, (the bypass plunger and spring are free and moving, I'll grease em up anyway). This weekend I'll put the pump housing and dist back on and give it a spin test with power tool. Not feeling very optimistic.

After that I guess the next step is to pull the Aux Housing and see if I can draw up any oil manually (I'm thinking high tech – tubing, duct tape and shop vac).  If not, then there must be something wrong/clogged at the pickup pipe.

Then it's time for that garden hose clamp, tubing and a long spring  q:)

This is driving me bonkers. There aren't that many parts to the system. A pool of oil, a pump and some passages. Is it possible for a blocked passage to stop the pump from working?

Oh BTW, when I put stuff back together I've been making paper gaskets and using a bit of gasket sealer instead of using Permatex silicon. Greg got me worried about goop squishing out to the inside and fouling stuff up.

Doug

Last edited on 06-24-2011 12:02 am by dmatth

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
The only place blockage before the rotor is likely is the pickup filter screen. The pickup line is such a massive diameter for anything to clog.

My money is on the filter screen.

--
Joachim

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
OK, so its got to be the oil pump.
today we lubed up the bypass plunger with molly/graphite grease, and put the pump housing back on.  I had a right-angle drive for a power drill and put an allen driver in the chuck and used that to the drive the pump at 1200 rpm with the oil filter off, (figuring that the oil pump sprocket is twice the size of the crank sprocket that would be equivalent to 2400 engine RPM). Not a trickle of oil pumped out.  We removed the Aux housing and using the shop vac, duct tape and plastic tubing, we easily were able to draw oil up the pickup pipe. (at least I don't have to pull the engine again.)
So what can go wrong in such a simple mechanism as an oil pump? All I can think of now is if the inner rotor is somehow no longer being driven by the shaft.  Even worn rotors might drop your pressure some but we went from good pressure too zero.

Doug

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
Are you positive the distributor is mounted correctly and the O-ring intact? If there is an air leak there, the oil pump may not prime. Others have tried getting oil pressure with the distributor removed and failed.

Edit: Idiot question mode again: You are sure you are spinning the pump the right way?

--
Joachim

Last edited on 06-27-2011 04:56 pm by subwoofer

pbahr
Member


Joined: 04-15-2005
Location: Moorestown, New Jersey USA
Posts: 198
Status: 
Offline
Joachim beat me to the question about an air leak.........
YELODOG

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
Well.... Yes, I'm positive we were spinning the pump the correct way, and yes the "O" ring on the dist is intact but no way of knowing if it is sealing other than the evidence that car does not seem to have been leaking oil at the dist mount, but then I guess once it looses its seal there would be no oil pressure nor oil to leak. (?)  There is a very small hole at the back of the housing behind the inner rotor and drilled parallel to the drive shaft that I presume is the bleed hole from earlier discussions, it is blocked but appears to have been blocked for some time (really solidly blocked), and another larger hole (maybe .080 - .125 dia) angled up and looks to terminate at the gasket.

Edit: We did have the dist mounted but without the cap in place.

Looking at the rotors... If I saw these at a junk yard I'd buy them. No discernible signs of excess wear (car has 104k mi).  The housing where the outer rotor spins shows some sign of scuffing but so little that there is no ridging between where the rotor spins and where it doesn't.  The rotor fits with maybe (haven't measured yet) .010 clearance to the outside wall.

Any ideas on how to bench test the pump??  Would I be able to spin it and just feel if it was drawing a vacuum?

Last edited on 06-27-2011 09:09 pm by dmatth

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
New update:
Talked with Delta Mortorsports today to order gaskets to put this thing back together and here's something that might be an issue: The gasket for the Pump housing is a "Precision" part at about .004" thickness. So my homemade paper gaskets may be the most recent problem.  This still doesn't explain the sudden loss of pressure but hopefully with the right gaskets I can get this thing back on the road. The pessimist in me still wants to bench test before installing though. Don't want to mess up a $7 Aux Housing gasket until I am confident it's going to work.
Thanks all, I'll let you know how it works.

Doug

Last edited on 06-28-2011 08:11 pm by dmatth

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
I am at a loss here. There really are only two possible reasons, either it is drawing air somewhere, or something is clogged solid.

For bench testing, you could possibly turn the aux housing over and pour oil into the oil intake while spinning the pump just to see that oil makes it to the other side, but I'm not sure if that will prove anything.

--
Joachim

dmatth
Member
 

Joined: 06-12-2011
Location:  
Posts: 10
Status: 
Offline
Here's the final chapter:
Put everything together with the proper gaskets and Eureka, Oil pressure, Lots of it. Fired up with a cold start pressure at about 55lbs. So it seems obvious that the gasketing after my initial cleaning was the problem. However the mystery remains as to what caused the initial loss of pressure. My best guess would be the Oil Pump Housing gasket (the .004" mylar one) or the Dist seal, both of which were replaced. (The housing gasket came off in pieces)

On another note, yes you can bench test an Oil Pump. I set the whole assembly on a workmate bench, used a piece of thick wall 3/4" OD plastic tubing, wrapped some electrical tape around one end so it fit snug in the oil pick up and the other end in a container of oil, taped off the upper hole to force the oil toward the filter passages, and use my DeWalt cordless with a 6mm alan driver in the chuck to drive the pump.
On the first attempt the tubing was too long (in the real world the pump only draws up about 8-10"). With a shorter tube I was able to make a huge mess on the lower shelf of the workmate.
Thanks everyone for your input!
Doug

Attachment: IMG_1374.JPG (Downloaded 67 times)

subwoofer
Member
 

Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 583
Status: 
Offline
Good to hear that everything worked out in the end!

--
Joachim

Spaceman
Member


Joined: 05-30-2017
Location:  
Posts: 14
Status: 
Offline
my first post to the forum since joining, my problem is too high of oil pressure, possibly caused by a stuck relief valve. Does anyone have an explanation of how the valve works? I have a spare, but dont' know if the guts are any good. Also, I have successfully repaired a busted oil gauge and am very proud of myself, if anyone would like to see the process, I can post some pics.

Screenplay
Member
 

Joined: 07-12-2013
Location: San Francisco, California USA
Posts: 121
Status: 
Offline

Last edited on 06-13-2017 08:37 pm by Screenplay

redracer
Member
 

Joined: 09-10-2012
Location:  
Posts: 119
Status: 
Offline
yes; I can help(as I'm sure many others can as well). Please try to explain where/what/how the "rebuild" is going.
bruce madden

Esprit2
Member
 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
Status: 
Offline
See the attached JPEG clipping from the JH Parts Manual.

On the back end of the oil pump housing, next to the bore where the distributor installs, you'll see a second bore with a pressed-in steel plug. Under that plug there is a sleeve/ cylinder with ports cut in it's sides, a piston in the sleeve, and a coil spring pressing the piston down to the bottom/ far end of the bore. The bore is a through hole, and breaks into the oil pump's 'working' area, on the high pressure side of the rotor and annulus (ring).

As the pump builds oil pressure, the pressure pushes the spring loaded up the bore. Eventually the piston moves far enough up the bore to uncover the ports in the sleeve/ cylinder wall, and oil vents out of the port. The ports dump oil into an angled drilled passage that goes back to the inlet/ low pressure side of the oil pump.

The port position (how far up the cylinder bore it's placed) and the strength of the coil spring determine the pressure at which the relief valve vents. That's designed and built in, and is not intended to be adjustable. However, some racers in search of a little more pressure have been known to shim the coil spring with a washer or two. Or, old springs can fatigue and weaken over the years, allowing the piston to move too easily and vent oil at too low of a pressure.

I do not know the correct spring rate, and to the best of my knowledge, replacement parts are no longer available. If any new s do exist do exist, they will be from JH specialists, since Lotus never did sell them. Instead, Lotus preferred that you buy a replacement oil pump that is correctly calibrated.

The piston can stick in the bore for a number of reasons, including galling, sludge gumming up the works, and corrosion. If the piston sticks at the bottom of the bore, no oil pressure will ever be vented, and peak pressure can become quite high... in excess of 60 psi. If the piston sticks at the top of the bore, with the ports uncovered, then oil pressure will vent and be low to non-existent. The piston can stick anywhere along the bore, so the failure symptoms can be either very high or very low oil pressure. Or it can be irratic.

*~*~*
Oil pressure that builds very slowly on cold start-up is probably caused by something other than a faulty pressure relief valve. Never say never, but don't focus exclusively on the relief valve and over-look other possibilities.

Other possibilities include a plugged breather hole in the auxiliary housing, just inside where the oil pump bolts on, a plugged oil pick-up screen, or an air leak anywhere on the suction side of the oil pump or the passages that feed oil lto it.

Good luck,
Tim Engel

Attachment: 9XX Lubrication - Oil Pump, Pressure Relief Valve - Exploded Parts - All 9XX.jpg (Downloaded 20 times)

Esprit2
Member
 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
Status: 
Offline
Here are the pressure relief valve's internal parts laid out. It's not my photo, but I don't recall where I got it. These parts are typical of the Lotus and Mk II JH oil pumps, while the Mk I JH has a different piston config. Look past the details, and both versions work basically the same way.

Regards,
Tim Engel

Attachment: 9XX Lubrication - Oil Pressure Regulator 06.jpg (Downloaded 21 times)

Last edited on 06-15-2017 08:58 pm by Esprit2

Esprit2
Member
 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
Status: 
Offline
And another view, with the parts nested together.

Attachment: 9XX Lubrication - Oil Pressure Regulator 08.jpg (Downloaded 21 times)

Esprit2
Member
 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
Status: 
Offline
For 'slow' oil pressure build-up on cold start, make certain this air bleed hole is clean, and not plugged with sludge.

Attachment: 9XX Lubrication - Oil Pump, Aux Housing Air Bleed Location - illus, cropped with notes.jpg (Downloaded 22 times)



UltraBB 1.172 Copyright © 2007-2011 Data 1 Systems