Ignition Timing
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Ignition Timing
2002 RAM 1500 4x4 5.9 200k miles
Truck quit while on expressway and would not restart
All seemed to check out ok ignition, fuel, etc.
I finally determined the ignition timing was nearly 30 ATDC
New cap, rotor, wires, timing chain, crank position sensor.
It struggles to start, but only run about 700 RPM WOT
No trouble codes
Not sure where to go next ??????
PCM flash ????????
Truck quit while on expressway and would not restart
All seemed to check out ok ignition, fuel, etc.
I finally determined the ignition timing was nearly 30 ATDC
New cap, rotor, wires, timing chain, crank position sensor.
It struggles to start, but only run about 700 RPM WOT
No trouble codes
Not sure where to go next ??????
PCM flash ????????
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Yes after i replaced each item i fired it up and it ran exactly the same
The timing chain was the last item to replace and i did it out of desperation
It was worn but not bad enough to skip a tooth
This entire time the timing has been way retarded
When i start it up it starts hard but if i hold it on the mat it actually runs quite smooth
Exhaust manifolds get very hot fast
The timing chain was the last item to replace and i did it out of desperation
It was worn but not bad enough to skip a tooth
This entire time the timing has been way retarded
When i start it up it starts hard but if i hold it on the mat it actually runs quite smooth
Exhaust manifolds get very hot fast
Moose, I know this is a long shot, but did you check the keyway on the crank sprocket to make sure it was lined up right on the crank, same for cam?? From what you're describing it really sounds like something moved with the timing somewhere.
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Yes i did check
Timing chain was my last attempt at finding the problem
I was careful to check everything because nothing was obviously wrong
One thing i noticed while reading up on the ignition timing is that the timing will jump around alot while the computer makes constant adjustments so checking with a timing light is useless. So while attempting to check the timing just to see if its somewhere in the neighborhood it is very stable at 30-35 ATDC. Why is it not trying to adjust even a little? this why i am leaning towards the PCM
Timing chain was my last attempt at finding the problem
I was careful to check everything because nothing was obviously wrong
One thing i noticed while reading up on the ignition timing is that the timing will jump around alot while the computer makes constant adjustments so checking with a timing light is useless. So while attempting to check the timing just to see if its somewhere in the neighborhood it is very stable at 30-35 ATDC. Why is it not trying to adjust even a little? this why i am leaning towards the PCM
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I would try to fuel sync it first!
If you're getting erratic timing after fuel sync I would suggest checking your crank sensors & knock sensors. PCM would affect timing if it had a bad knock sensor or didn't like what the knock sensor was seeing due to conditions causing predetonation/ping/spark knock. It could be as simple as bad gas or blown plenum gasket. In the case of the blown plenum gasket the pcm will try to compensate for the vacuum leak which can cause spark knock via bad air/fuel ratio thus affecting timing when the PCM sees that condition. If you didn't change your plenum gasket change it because its toast!. Every single Magnum motor I've ever worked on from 40,000 miles to 330,000 miles has a blown plenum gasket even on "great running" engines. Even if you or other mechanics say theres no symptoms, theres a steel belly plate on the bottom of an aluminum plenum and I assure you its the nature of the beast and its going to leak unless its been properly addressed with a new gasket PLUS copper permatex to cushion the expansion rate of heat soaked metal or its been upgraded to an aluminum belly plate.
Now for the Fuel sync:
The PCM ultimately determines when the engine fires, but since it still uses a distributor it can still affect where that spark goes and how strong it goes. Believe it or not, moving the distributor actually controls the injector pulse timing instead of spark timing in the classic sense. I don't care what anyone says, getting that distributor rotor as close as possible to the plug wire that fires the cylinder its supposed to is still part of "timing" a V8 with a distributor.
Now you can still technically affect & adjust timing by moving the distributor but for our purposes we will be doing it to get the distributor on the same page as the crank sensor. Instead of paying a garage or dealer $50 to "Fuel Sync" it or you can do it yourself and its pretty easy.
REPAIR PROCEDURE:
This procedure outlines an alternative distributor indexing procedure.
Connect a voltmeter to the distributor sensor connector by removing the end seal and carefully back probing the connector. Connect the positive lead to the sensor output pin (pin 3, either a tan wire with a yellow tracer or a gray wire, depending on vehicle application). Connect the negative lead to the sensor ground pin (pin 2, a black wire with a light blue tracer).
Rotate the engine clockwise as viewed from the front, until the number one piston is at Top Dead Center (TDC) of the compression stroke. The timing mark on the vibration damper should line up with the zero degree
(TDC) mark on the timing chain case cover.
Continue to rotate the engine slowly clockwise until the V8 mark lines up with the zero degree (TDC) mark on the timing chain case cover. The V8 mark is 17.5�after TDC. NOTE: DO NOT ROTATE THE ENGINE COUNTER CLOCKWISE. IF THE ENGINE IS ROTATED BEYOND THE MARK, RETURN TO STEP 2 AND REPEAT THE PROCEDURE.
Loosen the distributor clamp bolt.
With the ignition switch in the ON position, rotate the distributor slightly in either direction until the voltmeter switches between the sensor transition point of 0 and 5 volts.
Adjust the distributor as close as possible to either side of this transition point and tighten the distributor clamp bolt to 19-26 N-m (170-230 in.lbs.).
If you're getting erratic timing after fuel sync I would suggest checking your crank sensors & knock sensors. PCM would affect timing if it had a bad knock sensor or didn't like what the knock sensor was seeing due to conditions causing predetonation/ping/spark knock. It could be as simple as bad gas or blown plenum gasket. In the case of the blown plenum gasket the pcm will try to compensate for the vacuum leak which can cause spark knock via bad air/fuel ratio thus affecting timing when the PCM sees that condition. If you didn't change your plenum gasket change it because its toast!. Every single Magnum motor I've ever worked on from 40,000 miles to 330,000 miles has a blown plenum gasket even on "great running" engines. Even if you or other mechanics say theres no symptoms, theres a steel belly plate on the bottom of an aluminum plenum and I assure you its the nature of the beast and its going to leak unless its been properly addressed with a new gasket PLUS copper permatex to cushion the expansion rate of heat soaked metal or its been upgraded to an aluminum belly plate.
Now for the Fuel sync:
The PCM ultimately determines when the engine fires, but since it still uses a distributor it can still affect where that spark goes and how strong it goes. Believe it or not, moving the distributor actually controls the injector pulse timing instead of spark timing in the classic sense. I don't care what anyone says, getting that distributor rotor as close as possible to the plug wire that fires the cylinder its supposed to is still part of "timing" a V8 with a distributor.
Now you can still technically affect & adjust timing by moving the distributor but for our purposes we will be doing it to get the distributor on the same page as the crank sensor. Instead of paying a garage or dealer $50 to "Fuel Sync" it or you can do it yourself and its pretty easy.
REPAIR PROCEDURE:
This procedure outlines an alternative distributor indexing procedure.
Connect a voltmeter to the distributor sensor connector by removing the end seal and carefully back probing the connector. Connect the positive lead to the sensor output pin (pin 3, either a tan wire with a yellow tracer or a gray wire, depending on vehicle application). Connect the negative lead to the sensor ground pin (pin 2, a black wire with a light blue tracer).
Rotate the engine clockwise as viewed from the front, until the number one piston is at Top Dead Center (TDC) of the compression stroke. The timing mark on the vibration damper should line up with the zero degree
(TDC) mark on the timing chain case cover.
Continue to rotate the engine slowly clockwise until the V8 mark lines up with the zero degree (TDC) mark on the timing chain case cover. The V8 mark is 17.5�after TDC. NOTE: DO NOT ROTATE THE ENGINE COUNTER CLOCKWISE. IF THE ENGINE IS ROTATED BEYOND THE MARK, RETURN TO STEP 2 AND REPEAT THE PROCEDURE.
Loosen the distributor clamp bolt.
With the ignition switch in the ON position, rotate the distributor slightly in either direction until the voltmeter switches between the sensor transition point of 0 and 5 volts.
Adjust the distributor as close as possible to either side of this transition point and tighten the distributor clamp bolt to 19-26 N-m (170-230 in.lbs.).
Last edited by JoshSlash87; Jun 21, 2016 at 08:08 AM.
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Man I actually just signed on here to ask a very similar question but started reading first and saw this . My truck did the exact same thing today. It is also a 2002 1500 4x4 with a 5.9. Last week i drove it to work fine then went to start it to leave and it would not start. changed the cap ,rotor, plugs, wires and ended up changing the coil. Ran good. Last night had to drive 2 hours to pick up a car on my car trailer and ran perfect. This morn I drove it to work,unloaded the car , started the truck to move it and it stalled. I re started it and it was sputtering like the timing was off or something. came up with p1391 so we changed the crank position sensor and the cam position sensor. still tries to start but wont. I tried another computer, i replaced the plugs again, checked fuel pressure, checked injector pulse. put it at top dead center and checked that the rotor was pointed at 1. cleaned the batt terminals. I think I have the same prob as you! If i get it I will be sure to let you know and ill be watching for an answer here ...I hope!
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Well this morning we went back to the auto parts store we deal with cause they said they had another cam and crank sensor to try so we put them in and still nothing. Checked the wires from the sensors to the pcm and they were good so while i had the connectors off the pcm I tried the spare pcm I had. started right up! I think that one of the sensors they gave me yesterday was bad that's why when I tried the spare computer yesterday it didn't work.Your symptoms sound just like mine so if you can find a pcm to try I would definitely give that a try
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Just getting back to this project
I checked the fuel pressure and it's 20 psi cycling the key and 40 psi when I can get it to run.
A dealer mechanic I talked to was sure it was low fuel pressure, he said 48 psi
Another thing I noticed is when the engine is stone cold it will start hard and run only about 600 RPM from half to WOT. Sounds OK but just like the ignition timing is retarded.
After 30 seconds or so it becomes harder to keep running and/or start.
I checked the fuel pressure and it's 20 psi cycling the key and 40 psi when I can get it to run.
A dealer mechanic I talked to was sure it was low fuel pressure, he said 48 psi
Another thing I noticed is when the engine is stone cold it will start hard and run only about 600 RPM from half to WOT. Sounds OK but just like the ignition timing is retarded.
After 30 seconds or so it becomes harder to keep running and/or start.