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  #1  
Old 06-10-2021, 05:02 PM
Dave Jeeper Dave Jeeper is offline
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Won't start, timing chain slip?????

Is there a simple way to check for a slipped timing chain?

Whole, long story:



1989 G Wag, 95k miles. Howell fuel injection. My GW sat for 15 years before being restored. I did not run the engine before draining the tank, installing a Howell 50 state and putting on a lift, brakes, tires, etc. The reason that it stopped running 18 years ago was a bad duraspark ignition module on the fender. New plugs, module and distributor cap/rotor got the engine working with the newly installed Howell 50 state TBI. It did not have enough power.



I installed a cheap HEI distributor/ignition but made a mistake by powering it off the yellow 12v/6v wire from the original coil. After installing the HEI I did not have more power. I later found (last 12 months) that the throttle plate was not fully opening at WOT and my fuel hose from the tank to the hard line on the frame was kinking, reducing fuel pressure and flow.


About a month after installing the HEI I had occasional loss of power while driving as if the engine was starved of fuel. The Howell won't give gas unless there is a tach signal, so if no spark, then no fuel. This began happening more frequently and for longer periods. This was at the same time that there was a problem with the throttle plate not fully opening and intermittently kinking fuel line.


15 months ago I took the vehicle way up into the mountains and it did great. It sat for an hour and then barely made it home. I believe that was a kinked fuel line. I repaired the throttle linkage and fixed the kinked fuel line but did not drive the vehicle due to a terrible tranny leak. Recently repaired the tranny leak. Pulled a lot on my wiring harnesses while doing the tranny job.


After the tranny job I would take the vehicle around the block, it would run rough and then it would stall and it would have to sit a long time before restarting. I believe that the HEI coil and maybe module have gone bad.


I reinstalled the duarspark ignition, but I have not been able to get the engine to start (run without the starter spinning it). I had just installed an HEI relay and diode, so I bypassed the HEI diode on the alternator emitter wire, but no change. It sounds like it wants to start but won't catch. There is fuel spraying into the throttle body. The #1 piston is at TDC when the harmonic balancer mark is at 0 degrees. I attached the #1 spark plug wire to a spare plug and laid it on the block and we had a yellow spark while trying to start. I could not fit a camera into the #1 cylinder to see the valves when it is at TDC.



My Buddy thinks that the timing chain has probably slipped a tooth or two. I am not sure how to check it without removing the timing chain cover or a valve cover.



Last year I checked compression and it varied from 117 to 130 psi with 10 cranks. I did not do leak down or wet testing.


Is there a simple way to check for a slipped timing chain? Do I need to run another compression check?



I am considering ordering another cheap HEI ($75) to see if it will run with a new coil and module. I don't want to spend tons more money now if the engine won't run. If it runs on a new HEI then I can buy a better one later if need be.


Later I will try moving the plug wires 180 degrees around the cap to be sure that I am not 180 degrees off on the distributor install.


Thanks for any help.


Dave
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  #2  
Old 06-10-2021, 05:44 PM
Dave Jeeper Dave Jeeper is offline
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I swapped each wire for the one on the opposite side of the cap to rotate 180 degrees. Engine would not start, even with rotating distributor back and forth to alter timing.
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Old 06-10-2021, 06:00 PM
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yellow spark is no bueno. need to figure out why...
bad module/coil/wiring/etc.

timing chain extremely unlikely to "slip"

my guess would be weak spark+very bad fuel
or above+wiped out cam gear due to hei
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Old 06-10-2021, 06:08 PM
Dave Jeeper Dave Jeeper is offline
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New fuel, fully charged battery, been using the original gear on the bottom of the distributors (OEM and HEI).
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Old 06-10-2021, 06:20 PM
Dave Jeeper Dave Jeeper is offline
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The only electrical connector that is not in great shape is the three wire connector on the wiring harness that connects to the distributor's reluctor pickup and carries that signal to the ignition module on the fender.


I am getting a spark, so I figure that this must be making a connection.
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  #6  
Old 06-11-2021, 08:45 AM
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Duraspark is sensitive to connector contact quality. BTDT. Suggest you use electrical contact cleaner and a flux brush and clean the contacts between the module and the harness, and the distributor and harness (reluctor connector). I suggest a thin coat of dielectric grease on the contacts at assembly.

May not solve your problem, but you'll want to eliminate the possibility.
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  #7  
Old 06-11-2021, 09:20 AM
Dave Jeeper Dave Jeeper is offline
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Thanks, I will check on the contacts. I went ahead and ordered another HEI to see if that will work. If not then I need to check for slipped timing. Is there any way to do this without pulling the timing cover?


Dave
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Old 06-22-2021, 03:19 PM
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rang-a-stang rang-a-stang is offline
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You might be able to see the timing chain if you remove the fuel pump but
a) I am sure your timing chain is loose (they almost always are)
b) I don't think it's a timing chain problem, either.
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  #9  
Old 06-22-2021, 03:33 PM
Dave Jeeper Dave Jeeper is offline
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I got all new electronics for my HEI and reinstalled that. Still not starting. I have spark and fuel, engine turns but doesn't catch. I am going to rent a compression tester and leak down tester. I will start with leak down on cylinder 1 at TDC. If it's not holding air on 1 and on other cylinders, I will assume that I need a new timing chain and gears.



If I need to replace the timing set, I will probably pull the valve covers to inspect the valves. Would a bent valve stem be visible with the cover removed?
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Old 06-22-2021, 05:54 PM
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Pull all of the spark plugs and set the timing with a timing light and someone cranking the starter.
If you can get the timing set correctly that way and #1 is at TDC, it is not a timing chain issue.
A engine will run with low compression and or a bent valve. They will even start with all of the odd numbered plug wires unhooked.
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Old 06-22-2021, 06:14 PM
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the only chains that will "jump" on an amc were the nylon encased 70's gear.
the later ones it isn't gonna happen.
what does the cam gear look like?

are you getting injector spray when cranking?
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Old 07-03-2021, 10:44 AM
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I had similar issues ended up being..

https://www.jegs.com/i/JEGS+Performa...hoCYawQAvD_BwE

Your mileage may vary.

Sorry Dave I didn't read down far enough. I see you went through your HEI.

Have you pulled the valve covers and made sure everything is moving right and nothing is bent? ( pushrods )

These are known to wipe cam lobes as well.

I second the advice of setting the timing etc.

I would humbly suggest, instead of trying to chase the problem, start at zero.

First check and set your timing. It's one way to see if you've jumped time without surgery.
Double check your firing order, I know it sounds dumb but do it. That way you know what it's not.

Then make sure you have fuel at the proper pressure, FI can be really picky as you've found out.

Then go back over your ignition. When I converted over to my HEI I used the main power that went to my Duraspark box. I know it gets 12v when on AND cranking and it is more or less on it's own circuit.
Have you tested your coil? It's remote but they do go bad from time to time. Have you tested your module? Your pickup coil? Test when hot and cold?

I'm probably not telling you anything you don't already know. Just trying to lay out how I would go about it.
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Last edited by Mars : 07-03-2021 at 11:00 AM.
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  #13  
Old 07-04-2021, 04:54 PM
Dave Jeeper Dave Jeeper is offline
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I have had trouble with it running rough and backfiring on multiple cylinders. I changed all of the modules in the HEI with new. I found the compression stoke on cylinder 1, stopped the engine at the 18 degree before tdc and adjusted the distr. to have the rotor point at the cylinder 1 electrode in the cap. Turns but won't catch or run. I have spark and fuel. The fuel pressure is correct for the Howell injection. 95k miles and I am suspecting a slipped timing chain. I have not pulled the valve covers.


Compression before the problem was 117 through 130psi. I have not retested compression.

Before it started running poorly, it ran great going up into the mountains. Shut it off for an hour and then it had no power coming home (down hill) and ran very rough. Almost didn't make it home. I doubt that the cam is ruined since it ran great and then it didn't. It has good oil pressure. There was no backfire when engine stopped running smooth and lost power. Not sure what would have caused the chain to slip, if it did. I have never had a problem with a timing chain before on any of my other vehicles.


The auto parts stores no longer rent leak down testers and it seems more straight forward to replace the timing chain than to pull valve covers, etc. The problem seems to be on all cylinders, not just one or two, so I doubt the problem is one or two bent valve stems. It happened suddenly, so I don't think that this is a worn cam issue. I reused the old distr. gear on the HEI and the distr is turning, so I don't think that the distr gear is the issue.



I have been told by a neighbor that at this mileage (96k) the chain is probably loose and could have slipped. That is the direction I am leaning towards at this point.


Still open to other ideas if anyone has suggestions.


Dave
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Old 07-06-2021, 11:18 AM
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Quote:
Originally Posted by Dave Jeeper
I have had trouble with it running rough and backfiring on multiple cylinders. I changed all of the modules in the HEI with new. I found the compression stoke on cylinder 1, stopped the engine at the 18 degree before tdc and adjusted the distr. to have the rotor point at the cylinder 1 electrode in the cap. Turns but won't catch or run. I have spark and fuel. The fuel pressure is correct for the Howell injection. 95k miles and I am suspecting a slipped timing chain. I have not pulled the valve covers.


Compression before the problem was 117 through 130psi. I have not retested compression.

Before it started running poorly, it ran great going up into the mountains. Shut it off for an hour and then it had no power coming home (down hill) and ran very rough. Almost didn't make it home. I doubt that the cam is ruined since it ran great and then it didn't. It has good oil pressure. There was no backfire when engine stopped running smooth and lost power. Not sure what would have caused the chain to slip, if it did. I have never had a problem with a timing chain before on any of my other vehicles.


The auto parts stores no longer rent leak down testers and it seems more straight forward to replace the timing chain than to pull valve covers, etc. The problem seems to be on all cylinders, not just one or two, so I doubt the problem is one or two bent valve stems. It happened suddenly, so I don't think that this is a worn cam issue. I reused the old distr. gear on the HEI and the distr is turning, so I don't think that the distr gear is the issue.



I have been told by a neighbor that at this mileage (96k) the chain is probably loose and could have slipped. That is the direction I am leaning towards at this point.


Still open to other ideas if anyone has suggestions.


Dave


what does the cam gear look like?

are you getting injector spray when cranking?

If you spray it with starting fluid will it fire/run?

Also any codes stored?
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Old 07-06-2021, 01:25 PM
Dave Jeeper Dave Jeeper is offline
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no codes, fuel is spraying on both barrels when cranking. I have not sprayed starter fluid. Is the cam gear the one down in the distributor hole?
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Old 07-06-2021, 01:31 PM
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yes on cam gear they can get chewed up and prevent spark @correct time(s)
was weak spark resolved by hei part?
is it flooded? what do plugs look like?
have you tried clear flood mode to start?
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Old 07-06-2021, 01:40 PM
Dave Jeeper Dave Jeeper is offline
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Plugs have carbon deposits over the ceramic, but no oil buildup. I have not checked the quality of the spark with the new HEI electronics, but I did put in an in-line spark light to verify spark. I lost my spark plug cleaner and have not cleaned the plugs yet. It is not easy to get the HEI out to check the gear, that will have to wait a bit. The rotor does not slip when turned by hand and I used the original OEM distributor gear on the HEI distributor.
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Old 07-07-2021, 06:13 AM
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Pull the valve cover when you get it to TDC and on the timing mark. If both valves aren't closed you have your answer. And you know where to go from there.
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Old 07-07-2021, 04:05 PM
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Honestly, you can get new plugs for almost nothing these days. I wouldn't even bother cleaning them. Get some Champion copper plugs and rule them out. They are usually less than $10 for a whole set of 8.
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