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Working on a 09/96 Chevy C3500HD w/7.4l(454ci). It comes with a non-adjustable dist(via hold down bracket). Well someone ahead of me has swapped out dist and bracket, so now there is no solid reference to set the base of the dist for timing. Is there any way to disable ECU/ECM so I can set the base timing(no spout conn)?
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To my knowledge you need a scan tool to set timing on those systems. If you have a scan tool with live data, it can give you the timing reading as you do the adjustment.
Yes tried that but as I adjust it(ECM) keeps re-adjusting it back to 25 btdc. The way I see it the ECM has a certain amout of adjustment it can make(be it +/- say 25 degrees). So if your base timing is W/out ECM control set at 10btdc, then ECM can set it from 35 btdc thru 15 atdc. Is this the way the system works or otherwise in theory you would be able to drop the dist in at any position and it would adjust it to what it wanted. Long story short w/out the right dist and hold down I need to find the spot where the base timing is right according to the book then give control back over to the ECM. I think(I am not always the sharpest knife in the drawer)
technically if your cyl #1 is at TDC then your rotor should be lined up with the contact point for your cyl #1 wire. It sounds like as long as that’s close then the ECU should make up for the rest.
What really gets messed up when the distributor rotor is not pointing at #1,#1 piston at top dead center with both #1 cyl. valves closed is the fuel injector sequence. The cam sensor controls that.
You may need to have someone with a TECH1 (GM scan tool) do the adjustment. I believe there are some procedures that need to be followed in order to correctly set ignition timing on one of those systems.
You won’t need a scan tool to set the timing on your engine. As quickNpainless stated: You have to be sure the #1 cylinder is at TDC compression stroke. (Distributor rotor pointing at #1, #1 piston at top dead center with both #1 cyl. valves closed)
If you removed the distributor, let me know and I’ll tell you the procedure for installation.
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