Timing mark jumping, motor dying when taken out of gear
08-17-2012, 12:13 PM
#1
Registered User
Thread Starter
Timing mark jumping, motor dying when taken out of gear
'87 pickup 22R carb'd with a weber 32/36.
Problem began when I took the truck off non-op a couple weeks ago. It had been sitting for a year, during which time it got a new suspension as well as a new Weber 32/36 carb.
At this point the truck ran and drove fine, except that it dieseled for 10-15 seconds after shut down and made a sound like candy wrappers crinkling at full throttle in the bottom of gears 3-5.
We checked the timing and the mark indicated that it was about 20 degrees retarded. So we moved it to zero.
Then the truck still dieseled badly. And the motor began dying whenever I took it out of gear after a high rpm run. In any gear, 2-5. Crinkling sound also occurred.
In this condition I drove to Georgetown. On the way there it also ran scary hot and vapor-locked.
So in Georgetown we stuck a screwdriver down the #1 plug hole and found top dead center. The distributor was waaaay off, more than 45 degrees. The timing mark on the crank pulley was apparently wrong. Not really sure how it was running at all. So we moved the timing to match TDC and made a new mark.
Then all symptoms disappeared, except that the crinkling persisted.
Ran the Rubicon. No motor issues.
After a couple hours on the highway coming home, the motor began dying whenever I took it out of gear. It dieseled twice, though not badly.
Checked the timing again and now it's back to where it was when we started, with the original mark appearing 20 degrees retarded. Took the valve cover off and the black chain link correlates perfectly to the mark on the top gear. So at least the cam's TDC. Screwdriver in the hole says the piston's TDC-ish. Chain guides are intact. Chain isn't obviously loose or marked up.
So now we're stumped. The timing mark appears to have moved several times, and it seems not to accurately correlate to timing. And it seems to me that if the timing mark on the pulley still correlates to crankshaft position, my motor should have died in a glorious display of valve-piston collisions at some point. The pulley doesn't seem frozen or wobbly. No screaming belts or signs of it moving at a different rate than the motor.
Current best theory is that the hydraulic tensioner isn't working properly and the chain is skipping on the bottom gear under load. And that the crinkling is the chain rattling around. I figure if I'm right I should be able to pull the timing cover and see the marks line up on the top pulley, top chain link and bottom chain link. And the mark on the bottom gear should be off.
But I would love to hear some other ideas. Ideas of what else to test before yanking the timing cover are also very much welcome.
It's also worth noting that the oil is in terrible condition. Black and sooty. We're thinkin' maybe the tensioner is just plugged, but it seems like a long shot that the problem can be solved with a dose of seafoam and an oil change.
Thanks for your ideas!
Problem began when I took the truck off non-op a couple weeks ago. It had been sitting for a year, during which time it got a new suspension as well as a new Weber 32/36 carb.
At this point the truck ran and drove fine, except that it dieseled for 10-15 seconds after shut down and made a sound like candy wrappers crinkling at full throttle in the bottom of gears 3-5.
We checked the timing and the mark indicated that it was about 20 degrees retarded. So we moved it to zero.
Then the truck still dieseled badly. And the motor began dying whenever I took it out of gear after a high rpm run. In any gear, 2-5. Crinkling sound also occurred.
In this condition I drove to Georgetown. On the way there it also ran scary hot and vapor-locked.
So in Georgetown we stuck a screwdriver down the #1 plug hole and found top dead center. The distributor was waaaay off, more than 45 degrees. The timing mark on the crank pulley was apparently wrong. Not really sure how it was running at all. So we moved the timing to match TDC and made a new mark.
Then all symptoms disappeared, except that the crinkling persisted.
Ran the Rubicon. No motor issues.
After a couple hours on the highway coming home, the motor began dying whenever I took it out of gear. It dieseled twice, though not badly.
Checked the timing again and now it's back to where it was when we started, with the original mark appearing 20 degrees retarded. Took the valve cover off and the black chain link correlates perfectly to the mark on the top gear. So at least the cam's TDC. Screwdriver in the hole says the piston's TDC-ish. Chain guides are intact. Chain isn't obviously loose or marked up.
So now we're stumped. The timing mark appears to have moved several times, and it seems not to accurately correlate to timing. And it seems to me that if the timing mark on the pulley still correlates to crankshaft position, my motor should have died in a glorious display of valve-piston collisions at some point. The pulley doesn't seem frozen or wobbly. No screaming belts or signs of it moving at a different rate than the motor.
Current best theory is that the hydraulic tensioner isn't working properly and the chain is skipping on the bottom gear under load. And that the crinkling is the chain rattling around. I figure if I'm right I should be able to pull the timing cover and see the marks line up on the top pulley, top chain link and bottom chain link. And the mark on the bottom gear should be off.
But I would love to hear some other ideas. Ideas of what else to test before yanking the timing cover are also very much welcome.
It's also worth noting that the oil is in terrible condition. Black and sooty. We're thinkin' maybe the tensioner is just plugged, but it seems like a long shot that the problem can be solved with a dose of seafoam and an oil change.
Thanks for your ideas!
08-21-2012, 07:01 AM
#2
Registered User
Thread Starter
Well, timing chain was stretched. Thankfully not enough to result in interference.
Still getting the dying motor symptom. It may be a main jet size issue, or possibly I need to advance my timing more for the weber....
Still getting the dying motor symptom. It may be a main jet size issue, or possibly I need to advance my timing more for the weber....
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