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 Posted: 08-25-2016 01:54 pm
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NJ_Brit
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Looking for some advice here.  I've had my JH for a few months and am experiencing an intermittent problem that I'd like to identify some possible culprits for.  I know enough about engines to be dangerous...

The stock engine is running Dellorto's that were rebuilt by the previous owner, who added the rubber expansion gaskets to address vapor lock.  He also replaced the coil and distrbutor.  The car gets driven at least once a week and has fresh fuel.  The engine has good oil pressure, doesn't overheat and the electrical system seems ok (if you believe the gauges on the dashboard).

The engine starts up just fine, and idles smoothly more or less straight away.

However, at random, when accelerating up to or cruising at 30 - 40 mph the engine just flatlines.  The Rev Counter drops to zero RPM and there is no response at the throttle at all.  The engine is still running, but barely.

This happens at random, but usually a short while after starting the engine or restarting it.

On a couple of occasions I've had to shut down the engine completely, and then restart - which requires some cranking.  The last time it happened, the engine came back to life after I floored the throttle a few times, without needing a restart.

Once restarted the engine runs just fine with no issues.

My initial thought was that this was a fuel supply issue (bad pump, crap in the fuel supply), but I think the carbs are running a bit rich (I get a lot of pops and crackles through the exhaust on overrun) so it could be they need looking at.  However from reading through a few posts on here it could be electrical related.

Has anyone seen this, or do you have any advice where to start looking?

Last edited on 08-25-2016 02:12 pm by NJ_Brit

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 Posted: 08-25-2016 02:58 pm
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NigelK
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I'm no expert either, but it sounds like an electrical fault to me as well. One easy thing to check would be the coil - I know it was changed recently but even new coils can sometimes be duds. I think it would be worth buying another new coil (good brand) and seeing whether that fixes the problem. If not, at least you have a spare coil for future use...

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 Posted: 08-25-2016 03:28 pm
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NJ_Brit
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NigelK wrote: I'm no expert either, but it sounds like an electrical fault to me as well. One easy thing to check would be the coil - I know it was changed recently but even new coils can sometimes be duds. I think it would be worth buying another new coil (good brand) and seeing whether that fixes the problem. If not, at least you have a spare coil for future use...
Thanks.  There is a spare coil in the box o'bits that the previous owner gave me, but I'm not sure how old it is!

Last edited on 08-25-2016 03:28 pm by NJ_Brit

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 Posted: 08-25-2016 05:22 pm
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Screenplay
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Are you still running points and condenser? A few years ago I had a problem somewhat similar to yours... it wouldn't necessarily flatline but would randomly sputter, sometimes to a halt and sometimes right itself and be fine. After changing out pieces one by one, it turned out to be the condenser. It's been said here before (paraphrasing) "99% of fuel problems are ignition related."

Clinton

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 Posted: 08-25-2016 05:29 pm
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NJ_Brit
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Looks like it's still a problem in modern vehicles as well!

http://www.popularmechanics.com/cars/a22532/ford-recalls-cop-cars/

;-)

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 Posted: 08-25-2016 05:49 pm
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NJ_Brit
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"Are you still running points and condenser? A few years ago I had a problem somewhat similar to yours... it wouldn't necessarily flatline but would randomly sputter, sometimes to a halt and sometimes right itself and be fine. After changing out pieces one by one, it turned out to be the condenser. It's been said here before (paraphrasing) "99% of fuel problems are ignition related."

Clinton"


That level of knowledge is above my pay grade!

I am slightly dubious about some of the electrical/wiring, but mostly in the area of instruments and accessories (particularly the early 90's Alpine CD player and sub-woofer...).  That said, all of the instruments light up and all of the exterior lights work.

Last edited on 08-25-2016 05:58 pm by NJ_Brit

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 Posted: 08-26-2016 05:09 am
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Randallclary@icloud.com
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Have you checked the float setting on the Dellorto's. Also there is a filter basket that is attached to the fuel input portion of each carb and there is a very small filter that is just ahead of the needle valve for each float of each carb. Remove the needle valve for the floats and you will see the very small filter, If it is clogged, clean it and you should be on your merry way. Same problem with my car and finally traced it down to that. Should only take you 10 to 20 minutes to check and clean both sets of carbs.

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 Posted: 08-26-2016 05:50 am
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dwalls1
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The pathetic 3 fuse box has been the source of mysteries on my J-H. I thought it had run out of gas while idling in the driveway earlier this week. Gas gauge showed zero, cranked but would not run. Checked fuses and they were all OK. Pushed and swore on fuses Viola, every thing's OK again. I recall that I couldn't hear the fuel pump clicking and that's on the same fuse as the fuel (fool) gauge. The fuse box can lose continuity while the car is being driven and produce all kinds of symptoms. If you should ever hear the pump get louder, you are running out of fuel.

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 Posted: 08-26-2016 11:10 am
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subwoofer
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Fuse box is the most likely culprit. But beware rotors with a metal rivet in them, they can be a real problem - causing stalls whenever you lift off.

--
Joachim

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 Posted: 08-26-2016 01:15 pm
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NJ_Brit
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Randallclary@icloud.com wrote: Have you checked the float setting on the Dellorto's. Also there is a filter basket that is attached to the fuel input portion of each carb and there is a very small filter that is just ahead of the needle valve for each float of each carb. Remove the needle valve for the floats and you will see the very small filter, If it is clogged, clean it and you should be on your merry way. Same problem with my car and finally traced it down to that. Should only take you 10 to 20 minutes to check and clean both sets of carbs.
Thanks - this also used to happen on my Spitfire, and caused it to misfire on two cylinders.  I once spent an exciting 15 minutes at the side of a French Highway cleaning a filter...

Oh, and it also had a dodgy fuse box as well...!

Last edited on 08-26-2016 02:40 pm by NJ_Brit

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 Posted: 08-26-2016 02:40 pm
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NJ_Brit
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Thanks everyone.  Guess I'll be spending a couple of hours poking about under the hood this weekend.

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 Posted: 08-30-2016 09:53 am
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UKJames
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I'm inclined to lean towards fuelling, if the engine revs drop back but still ticks over, and you need to pump the throttle to get it restarted it sounds like maybe the fuel delivery is somehow compromised. Did you get it sorted last w/e?

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 Posted: 08-30-2016 03:10 pm
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NJ_Brit
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Found a slightly loose connection on the electrical feed to the fuel pump, so that was crimped and taped back up.

I have a few other areas I've spotted (for example, the fuse box doesn't have a cover), but spent a lot of time just poking around.  I could really use an annotated diagram of what the engine bay is supposed to look like, as there seem to be some components that I am not sure are supposed to be there, as well as some rather odd looking additions to the wiring loom.

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 Posted: 08-30-2016 04:45 pm
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dwalls1
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The lack of a fuse box cover interests me as mine came with an obviously home made cover. A box of glued together plexiglass bits. I don't remember how it was held in place when I got the car but, now it is held by a strip of Gorilla Tape. I just upgraded the top fuse holder that supplies the fuel pump with a small brass wood screw. The fuse seems more secure now and I expect won't give trouble again, until it gives trouble again. I've concluded that one does not fix these cars, one just fiddles with things until things work until one must fiddle with things again. But, I wouldn't have it any other way.

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 Posted: 08-30-2016 04:49 pm
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NJ_Brit
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dwalls1 wrote: The lack of a fuse box cover interests me as mine came with an obviously home made cover. A box of glued together plexiglass bits. I don't remember how it was held in place when I got the car but, now it is held by a strip of Gorilla Tape. I just upgraded the top fuse holder that supplies the fuel pump with a small brass wood screw. The fuse seems more secure now and I expect won't give trouble again, until it gives trouble again. I've concluded that one does not fix these cars, one just fiddles with things until things work until one must fiddle with things again. But, I wouldn't have it any other way.
My Spitfire was the same, no fuse box cover, and in the much damper UK, it caused a bunch of issues.  My temporary/permanent fix was to put cling wrap over the box body and hold it in place with rubber bands...

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 Posted: 08-30-2016 05:40 pm
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dwalls1
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Rubber bands aren't very British, you should use Velcro.:-)

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