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Timing and ignition - maybe  Rating:  Rating
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 Posted: 08-01-2005 10:55 pm
   
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andrewo
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Talk about one step forward, two steps back. I solved the starter problem and the engine cranks, but does not fire. Since the gear on my distributor does not seem to have any marks, I used an ohmmeter to determine when the points were open and closed, and managed to get the timing set to the point where #1 is actually firing a couple of degrees before TDC, or at least I think it is. Using a timing light when running on the starter, this appears to be the case.

Here are some relevant details:

1. The engine has been completely rebuilt.

2. The points, condenser, rotor, and cap are all new.

3. The carberetturs were not rebuilt. I bought them complete with intake off of someone who switched to Delortos and represented them as fine, so I shelved my set and just bolted them on.

4. The cam gears are lined up properly.

How do I verify that the distributor pulley is in the right position? What else should I check? Are there any San Diego area folks who are good at troubleshooting and might want to take a look? Pizza, beer, etc., would be on me.

Thanks - Andrew

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 Posted: 08-02-2005 01:07 am
   
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Mark Rosenbaum
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Carburetors.
Strombergs are VERY reliable and the only things likely to go wrong with them are wear, damage caused by somebody jamming a screwdriver where it didn't belong, blocked passages due to rust from the fuel tank, and corrosion if there's lots of water in the fuel.  For each carb, make sure you can lift the vacuum piston all the way to the top of the carb opening with force from a single finger, and that the piston when released will then glide all the way down by itself, within a couple of seconds at most.  If not, you'll need to fix whatever's wrong inside the carb in question. 

Ignition.
It's my understanding that the alignment marks for the gear that drives the distributor were for Lotus' convenience during engine assembly, to make sure the distributor would be installed correctly.  In any event, if the ignition timing is right, the gear's orientation does not matter.

If you are getting spark at what seems to be the right time, and if you have fuel in the carbs and have applied a little bit of 'choke', but the engine won't even cough, then possibly the plug wires are not in the correct order. You could have the wires in the distributor 180^ out so that the #1 cylinder is firing when the #4 should fire, etc.

Fortunately, it is easy to check for that.  Set the engine to #1 TDC making sure that the crank timing marks are aligned and the two cam gear marks point to each other.  Pop the distributor cap, and note where the rotor is pointing.  Line up the dist. cap to the distributor body and determine which plug wire turret the rotor points to.  Manually trace the plug wire from that turret and ensure that it goes to the #1 (front) cylinder.

If so, the next wire, moving COUNTER-clockwise while looking at the top (wire side) of the dist. cap, should go to the #3 cylinder, followed by the wires to the #4 and #2 cylinders.  If this is the case, the spark plug wires are correctly installed.

However, if the wire does NOT go to the #1 cylinder, disconnect all four plug wires from the dist. cap.  Next, manually trace the wire from the #1 cylinder until you find the dist. end, then install that wire into the turret to which the dist. rotor is pointing.  Moving COUNTER-clockwise while looking at the top (wire side) of the dist. cap, the next turret should go to the #3 plug wire, followed by the #4 plug wire, and finally the #2 plug wire.

Reinstall the dist. cap and make sure the wire from the coil is still in place.  Try to start the engine again.  It should fire right up.  You'll still need to set the timing with a timing light but this should not be a problem.

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 Posted: 08-02-2005 03:43 am
   
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Dave
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Most often when I've had the problem that the engine does not fire at all - no cough, sputter, or other engine noise, it's something basic that I've overlooked. Pull the fuel line, put it into a jar and crank the engine making sure that you're getting gas flow to the carbs. Pull the plugs, put them on the engine block and crank making sure you're getting good spark to all the plugs and they're hitting in the right order. Make sure the main distributor wire is set in place tight. Are the wires really old and maybe shorting out due to dry rot or just losing too much amp on the way to the engine? Check the spark with a volt meter (that can handle the volts from the coil). Is your coil good? Try blasting the carbs with some carb cleaner just in case something is stuck from sitting too long after the PO replaced them with the dell's. If you've got gas and spark you should be getting some engine sounds, then it's just a matter of getting the RIGHT engine sounds:)

Sorry if this is too basic, but I've missed this kind of stuff too often....

Good luck,

Dave

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 Posted: 08-02-2005 04:09 pm
   
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andrewo
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Thank you Dave and Mark for the suggestions. After checking everything that you mentioned, and some other tinkering, I am starting to think that maybe I am firing on the exhaust stroke. Since the crank turns twice for every turn of the distributor, I should be able to solve this by removing the timing belt, rotating the crank once, and replacing the belt. If I do this at low speed with a wrench, do I risk any damage to the valves? BTW, my impression seemed to be confirmed when, after checking everything else, I tried a little starter fluid, and it backfired through the carbs.

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 Posted: 08-02-2005 05:02 pm
   
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Mark Rosenbaum
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If you disconnect the timing belt and rotate the crank 180^, the pistons WILL hit any open valves and will almost certainly bend them.

As Dave points out, it's awfully tempting to ignore the simple stuff simply because it is so basic.  If the engine currently is firing on the exhaust stroke, that just means the distributor is 180^ out of phase -- i.e. the rotor points to the #4 spark plug turret when it should be pointing to the #1 turret.

The easy fix is to move the spark plug wires as described in my post above.  The hard fix is to slip the timing belt off the auxiliary shaft (distributor) gear, rotate the gear 180^, then put the belt back on.  The 'easy' method is quicker and a bit safer as it does not involve disturbing the timing belt.

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 Posted: 08-02-2005 05:35 pm
   
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Brett Gibson JH5 20497
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Andrew, listen to Mark, do not turn that crank shaft with the belt lose, line your crank timing mark up, make sure the cam marks line up with each other, pop #1 cylinder spark plug and make sure the piston is at the top, take the distributor cap off and guess what, your rotor will probably be pointing at #4 spark plug wire connections, just loosen the dizzy up so it comes out a bit and turn the rotor so it lines up with the #1 cylinder, push the dizzy back in engaging the slot and retighten, or as Mark writes, instead of moving the dizzy just move the spark plug wires around.

It really sounds like your almost there to get it running, let us know.

Brett. 

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 Posted: 08-02-2005 06:03 pm
   
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andrewo
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Okay, clearly rotating the crank is a bad idea, but I am still puzzled. When I attach an inuductive timing light to #1 wire, it is firing as the timing mark on the crank pulley reaches TDC. If I move the plug wires, then won't a different cylinder be firing at TDC? What about the relationship (2:1) between crank rotation and distributor rotation? I think maybe I'm just obtuse, but it seems like moving wires would make the problem worse, not better. The more I think about it, the more confused I seem to get.

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 Posted: 08-02-2005 06:29 pm
   
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Mitch Ware
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The 2:1 ratio between the distributor and the crank is exactly your problem. For each 360^ the crank turns, the dizzy turns 180^. This means that each time the crank timing mark is at TDC the rotor is either pointing at #1, or pointing 180^ away from #1. If you take off the cap when #1 is at TDC and all of the valves for #1 are closed and the rotor is pointing 180^ away from the #1 wire, then you simply move the #1 wire to where the rotor is pointing and put the other wires in the right holes relative to the new #1 position.

Mitch Ware
1974 JH-5 #111119670
1971 TR-6 #CC66950LO

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 Posted: 08-02-2005 06:38 pm
   
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andrewo
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Okay, this is starting to penetrate, I think. If I understand this, what you are all saying is that there are actually two points in the timing cycle that the crank pully will indicate TDC. Once is really when the #1 plug should be firing, and once is when the third cylinder to fire will be firing (not actually #3 as I recall). So I have to rotate the engine, with the belt engaged, by 360 degrees, away from the point at which #1 currently fires, and that should result in a 180 degree revolution of the dizzy, which is where I really want #1 to fire. I then move the wires accordingly.

Could someone verify that I understand what you are all saying, and that I have the procedure correct?

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 Posted: 08-02-2005 06:57 pm
   
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Brett Gibson JH5 20497
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Andrew, if your at TDC on the crank pully and the cam marks lign up you should be firing on the #1 spark plug, anything else is WRONG.

So shift your wires around till the rotor points at #1 spark plug wire.

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 Posted: 08-02-2005 07:35 pm
   
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Mark Rosenbaum
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Andrew, your understanding is basically correct, though most folks find it easiest to set the engine so the crank timing marks indicate TDC and the cam marks are aligned, then make the spark plug wires match up with whatever the distributor happens to be doing.

The trick to understanding a four-stroke car engine is to recall that each piston does four things, each thing taking a half turn of the crankshaft.  This means that the crank makes two full rotations in the course of one complete engine cycle.  Meanwhile, the distributor and camshafts make one full rotation.  This is why it's the camshaft position, not the crankshaft position, that determines where in its cycle an engine happens to be.  Of course all the bits have to be properly synchronized if the engine is to run.

It may help to make a simple table showing the state of the engine at the start of each 180^ rotation of the crank.  In this table, P = power, E = exhaust, I = intake, and C = compression.

Rotation   #1   #3   #4   #2
0/4           P     C     I     E
1/4           E     P     C    I
2/4           I      E     P    C
3/4           C     I      E    P

For simplicity you can assume that ignition occurs at the start of the power stroke and that the intake and exhaust valves snap open at the start of their cycles, and snap shut at the end.  It's then easy to see that if you get a spark in the #1 cylinder when the #4 is at the start of its power stroke, you'll get backfiring through the intake.

Hope this clarifies things.

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 Posted: 08-02-2005 11:42 pm
   
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Dan Collier
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Couldn't help it. Had to post this.


Dan Collier
JH74 14381 2.2L
Jensen-Healey Preservation Photo Gallery

 

Last edited on 08-04-2005 03:59 am by Dan Collier

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 Posted: 08-02-2005 11:55 pm
   
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andrewo
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Thank you all for your help. I finally understood what you were trying to explain, and the engine fires.

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 Posted: 08-04-2005 12:36 am
   
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Panini
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andrewo.

Tune in the carbs and head over to Tx. and help me do it.

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 Posted: 03-28-2006 08:42 pm
   
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colinw59
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Hi Mark, maybe you can help me here?  I'm restoring #15851 and she ran on the second turn of the key, albeit rough and lumpy (rebuilt carbs not set or balanced probably being the cause). The car has engine # b74.02.6163 with new:-  plugs (set to 0.035"), leads, rotor arm, distibutor cap, Petronix ignitor, Petronix flamethrower coil. Timing is set to 8 deg BTDC. 

With the engine runnng and good oil pressure, an oil leak resulted which forced me to replace the front cover gasket & oil seal. This was the perfect time to replace the timing belt and the tensioner bearings. The belt was tensioned with cylinder #1  at TDC and cam sprocket marks in line at 110 IN and 110 EX, with the rotor arm pointing at the distributor contact for plug #1, which I'm sure is correct for this engine number. I cranked over the engine manualy first to make sure I wasn't going to bend a valve, all was ok. Now she won't run. In fact I have an intermittent spark at #1, then no spark. I checked this with the timing light across each plug lead and the high tension lead, no flashing light! I also checked the voltage across the coil (with a jumper wire ran from earth to the earth terminal on the coil) and there was 8 volts across the coil, which is what I think it should be.  I have continuety from the earth lead from the ignitor to earth and all the other electrical conections in the spark/run circuit are good.  I also tried a coil from an 74 MGB that I know to be good, this made no difference. I've narrowed it down to 2 things, either the Petronix ignitor is bad (but I don't see how something that works of off magnetic pulses or by producing an EMF can be intermitent) which would just so happened to coincide with changing the timing belt. Or I've selected the incorrect marks on the cam spockets a direct result of changing this belt.

Am I missing something Mark? 

http://jhppg.com/gallery/74-Jensen-Healey-15851

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 Posted: 03-28-2006 09:47 pm
   
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Rory Clark
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My best guess is that you let the Distributer sprocket turn on you when you replaced the belt.  (I know I did it) Therefore your timing is off.

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 Posted: 03-28-2006 10:43 pm
   
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Mitch Ware
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Are you sure you got the distributor all the way in? It can be a real pain to get it seated all the way. With the cap off, have someone turn the engine over and see if the rotor is spinning.

 

Mitch Ware

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 Posted: 03-28-2006 11:07 pm
   
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colinw59
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Hi Rory        I thought of that, so I checked it. With #1 at TDC and the cam sprockets lining up, the rotor is pointing to the correct contact within the distributor.  Thanks

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 Posted: 03-28-2006 11:09 pm
   
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colinw59
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Hi Mitch       That happened the first time I put the distributor back on. The second time I made sure it was seated correctly and the rotor turned when we cranked the engine. Thanks

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 Posted: 03-29-2006 12:41 am
   
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Mark Rosenbaum
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I'm assuming from the exchange above that colin59's car still has its problem.

The mechanical cam timing sounds correct, as does the stated static ignition timing.  And while problems in these areas might prevent an engine from running, they would not prevent the ignition system from working.

The stated 0.035" spark plug gap is too big.  And while a good ignition system will often give a spark across such a large gap, the time to experiment is after everything else is working fine.  Initially, at least, the correct gap is 0.025" with Strombergs and 0.023" with Dellortos. 

Installation of a new Pertronix coil was mentioned.  If this is the type of coil that requires an external ballast, then it is hooked up exactly as is the stock coil, with the ballast resistor being connected between coil and ignition switch and the ballast bypass wiring (from the starter solenoid) also connected.  Note that a coil that requires an external ballast, if run without one, WILL overheat and may fail in a very short period of time, giving precisely the symptoms mentioned.  However, the substitute coil speaks against this as the problem.  However, with sufficient bad luck, the current through the coil could have been so high that the switching transistor inside the Pertronix module was destroyed.

On the other hand, if the coil contains an internal ballast, then the wire from the ignition switch connects directly to coil (+) and the ballast and the ballast bypass wiring from the starter solenoid are ignored.  A coil with an internal ballast, that is wired up with an external ballast as well, may not produce enough high voltage to create a spark across a wide spark plug gap. 

Deal with the issues above and see if the car runs.  If not, then the problem sounds like the basic 'No Spark'.  When that occurs, I usually suggest the following:

1.  Manually rotate the engine so that the distributor rotor aligns with one of the spark plug turrets on the distributor cap.  Do not guess, do not assume, pop the cap, take a look, and make SURE.  Check a second time as you put the distributor cap back on.  This is particularly important in a JH as many if not most of its ignition problems involve incorrect ignition timing of one form or another.

2.  Trace the high voltage wire from the turret to which the rotor points, to the associated spark plug.  Disconnect this high voltage wire from this spark plug, and connect it instead to a test spark plug having the correct gap.  Ensure that the body of the spark plug is in firm contact with the engine block, and that it is possible to see the spark plug electrodes.

3.  Unplug the wire attached to the coil (-) terminal.  Place the ignition switch to the RUN position and verify the presence of +12 volts on the coil (+) terminal.

4.  Repeatedly make and unmake a connection between the coil (-) terminal and chassis ground using a test wire, screwdriver blade, etc.  Each time the connection is unmade, there should be a bright blue spark between the electrodes of the test spark plug.
     4a.  If so, then the basic problem is either incorrect ignition timing, some sort of mechanical problem in the distributor or its drive, defective points / condenser / Pertronix, or (very rarely) a coil whose high voltage output is so low that it can make a spark in air but not in a cylinder under compression.
     4b.  If not, the problem is a defective coil, a defective high voltage wire between coil and distributor or between distributor and spark plug, or a defective distributor cap or rotor.
     4c.  In either case, you'll have a direction in which to proceed. 

To verify Pertronix operation, connect the coil wiring as appropriate, then rotate the engine and verify that the voltage on the coil (-) terminal goes from zero volts to +12 volts and back to zero twice per engine revolution, just as it would if points were installed and were opening and closing.  If not, either there is something wrong with the Pertronix or the distributor shaft isn't turning.

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