Has the motor jumped timing?

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Jadaharabi

Jadaharabi

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A couple of questions on timing and carburation.
1986, 1/2 ton, /6, automatic Truck stopped running had no spark we eliminated the computer and set up a GM module with the ecoil. Reset the plug gap to 45. The motor will not run unless the timing is set to 20-24 degrees btdc. Even then it has a miss.
When I set the idle to where it would start and run it wants to run at 1500 RPM or more. And then the next time I start it it wants to idle at about 800. The carburetor is junk I would like to replace it with a non-smog carburetor. What are thoughts on that.
 
Jadaharabi said:
A couple of questions on timing and carburation.
1986, 1/2 ton, /6, automatic Truck stopped running had no spark we eliminated the computer and set up a GM module with the ecoil. Reset the plug gap to 45. The motor will not run unless the timing is set to 20-24 degrees btdc. Even then it has a miss.
When I set the idle to where it would start and run it wants to run at 1500 RPM or more. And then the next time I start it it wants to idle at about 800. The carburetor is junk I would like to replace it with a non-smog carburetor. What are thoughts on that.
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The timing problem could be as simple as the outer ring on the damper has slipped and the timing mark is not at TDC, so agree that needs to be checked.
It is also possible that the two wires going to the distributor are paired incorrectly. Try swapping those two and see if the motor runs better.
As part of the HEI upgrade did you remove the lean burn distributor and install an electronic Mopar slant six distributor with a vacuum advance can? The lean burn distributor has locked ignition timing.
Lastly, if the carb on the motor has wires going to it from the OE Lean Burn set up. That carb will never work right with the Lean Burn removed. You need a non Lean Burn carb.
 
my68barracuda said:
The timing problem could be as simple as the outer ring on the damper has slipped and the timing mark is not at TDC, so agree that needs to be checked.
It is also possible that the two wires going to the distributor are paired incorrectly. Try swapping those two and see if the motor runs better.
As part of the HEI upgrade did you remove the lean burn distributor and install an electronic Mopar slant six distributor with a vacuum advance can? The lean burn distributor has locked ignition timing.
Lastly, if the carb on the motor has wires going to it from the OE Lean Burn set up. That carb will never work right with the Lean Burn removed. You need a non Lean Burn carb.
Click to expand...

Replaced the lean burn distributor with a Chrysler two wire electronic. Both Distributors had broken teeth. So we installed a new plastic gear on the electronic before we put it in. And the carburetor has about 6 wires going to it.

Professor Fate said:
Also check the (plastic) distributor drive gear.
Click to expand...

As stated above we replaced the distributor gear before we put it in.
 
You need a new non comp controlled carb. sorry posted dist before
 
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You are describing, what to me, is just a reversed polarity at the pick-up.
Chrysler slanty distributors run in opposite rotation to SBMs; and the magnetic pick-ups are directional-specific.
IIRC
the SBMS have one Orange and one Violet wire.
IDK the colors of the slanty but am thinking NOT Orange
The SBM pick-up can be used by cutting the wires and resplicing in opposite polarity.
I could be wrong.
Looks like I am; See post #29
 
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slant and la motors run clockwise, B/RB CCW Pickup wire colors on a slant are white/black if Mopar, red black all V8's. MP pickups are usually different
 
AJ/FormS said:
You are describing, what to me, is just a reversed polarity at the pick-up.
Chrysler slanty distributors run in opposite rotation to SBMs; and the magnetic pick-ups are directional-specific.
IIRC
the SBMS have one Orange and one Violet wire.
IDK the colors of the slanty but am thinking NOT Orange
The SBM pick-up can be used by cutting the wires and resplicing in opposite polarity.
I could be wrong.
Looks like I am; See post #29
Click to expand...
Pay attention:

As others have said, possibilities are
1....Slipped outer balancer ring, check with piston stop
2.....Timing chain slipped
3.....As in the quoted post---reversed pickup wires known also as ROTOR PHASING. Reversing those wires changes the spark event in time in relation to rotor position.

 
Jadaharabi said:
The carburetor has about 6 wires going to it.
Click to expand...

That is a Lean Burn carb at least. It might also be a feedback carburetor. Post a picture of it, and check the rear face of your exhaust manifold's central collector area; is there an oxygen sensor in it, with a single wire going to it? Either way, a Lean Burn-to-conventional changeover involves the carburetor, too, not just the distributor.

Does this vehicle still have its catalytic converter(s)?

Jadaharabi said:
we replaced the distributor gear before we put it in.
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There are many ways this can go badly. It's tempting to use the hole that comes pre-drilled in the new distributor gear, but that's wrong; it has to be done right. And reinstalling the distributor sometimes requires patience and persistence as well.

It's not a bad idea to check for a slack timing chain, but you already know the truck quit because no spark, which means unless you have terrible luck and the T-chain jumped at the same time your ignition system failed, you can pretty well rule out a sudden T-chain problem for now.
 
slantsixdan said:
That is a Lean Burn carb at least. It might also be a feedback carburetor. Post a picture of it, and check the rear face of your exhaust manifold's central collector area; is there an oxygen sensor in it, with a single wire going to it? Either way, a Lean Burn-to-conventional changeover involves the carburetor, too, not just the distributor.

Does this vehicle still have its catalytic converter(s)?


There are many ways this can go badly. It's tempting to use the hole that comes pre-drilled in the new distributor gear, but that's wrong; it has to be done right. And reinstalling the distributor sometimes requires patience and persistence as well.

It's not a bad idea to check for a slack timing chain, but you already know the truck quit because no spark, which means unless you have terrible luck and the T-chain jumped at the same time your ignition system failed, you can pretty well rule out a sudden T-chain problem for now.
Click to expand...
I do not see an oxygen sensor on the exhaust. At the back of the manifold it has the pipe coming around that went to the anti backfire valve and then went to the EGR pump or air pump or smog pump.
We have blocked that off and eliminated the air pump.
It still has a catalytic converter but the converter is not plugged.
As for installing the new distributor gear the gear came with a shim and only one side of the gear was drilled so therefore we shimmed it and drilled it. I am not in a position to where I can get a picture of that carburetor or the motor at this time.

Prior to losing Spark the only way we could get this motor running was at 15 before top dead center. So there was something wrong with it prior to it losing Spark. And it still had the computer in it at that point.
 
A compression test will very quickly confirm whether it has jumped timing.
 
And my experience with jumping chains is that it takes a lot of throttle to keep it running, not just a lot of timing. Whereas ;
increasing the timing on a properly cam-timed engine will require less throttle to maintain a decent idle-speed. But if the idle speed is too high, and the screw is mostly backed off, then the timing is too much.
If BOTH the timing AND the throttle have to be increased, then the engine is down on idle-power. Could be crossed wires, or compression, but more likely is that there is a load on the engine such as; an overfilled crankcase or a dragging trans.
A locked transmission will try to drive the rear wheels in Neutral. This condition may decrease the idle rpm lower than normal. To get some Idle-power back, the timing will have to be increased and probably the curb-idle as well.
To test for this, get the drive wheels off the ground. Put the trans in Neutral. Now try to bring the timing and idle-speed back to normal.
If you can, and if the wheels, one or both, are spinning, then try the brakes. If the brakes cannot easily stop the wheels or the idle speed drags down, you gotta trans or convertor problem.
Good luck
 
Just sent a PM, I may have some parts and info that can help you, from only about 100 miles down the road. . We met at the Indy swap.

When I first got my 85, it had 2 converters. The front one (just below the manifold) had self destructed, and I found it's guts blocking the 2nd converter under the pass side floorboards.
That part is fixed, and can't cause me any more trouble haha
 
Need to use something heavier than PB blaster like regular motor oil doesn't look like it jumped time. #5 could have valve issues
 
Jadaharabi said:
I do not see an oxygen sensor on the exhaust. At the back of the manifold it has the pipe coming around that went to the anti backfire valve and then went to the EGR pump or air pump or smog pump.
We have blocked that off and eliminated the air pump.
It still has a catalytic converter but the converter is not plugged.
Click to expand...
It's gonna be, very soon, because with the ignition and carburetion changes you're making and disabling the air pump (sometimes called "smog pump"; never called "EGR pump" because there's no such thing), you are sending much dirtier exhaust to the converter, which will heat up and melt down.

Jadaharabi said:
1. 118
2. 115
3. 110
4. 103
5. 80
6. 97
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Doesn't say "jumped timing", but does indicate a tired motor and/or one with problems in № 5 and № 6, which are too low.

One thing you should do sooner than later is check if the timing mark on your harmonic balancer is accurate. On the \6 the outer ring (with the mark on it) can slip relative to the hub, then the mark no longer indicates actual timing.
 
I was going to say what AJ said, but he beat me to it in post #8. P/up polarity reversed.
 
Randall, I think the first thing I would do......and it may not get it running, BUT I would do a valve adjustment. That could very well cause the low compression on the two cylinders. If that fixes it, that's saved you a lot right there. Just kinda spitballin.
 
slantsixdan said:
No such thing on an '81-up Slant-6 with hydraulic lifters.
Click to expand...
I was under the impression he had converted to mechanical lifters. I may have him confused with another member.
 
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