Mechanics

4.3L NO START

GMC Sierra

2000 gmc sierra 4.3L 83k the truck will tun over but not start. It also backfires (up thru the throttle body intake) a small amount while trying to start. After a rough start, the truck ran fine the day before. But today it would not (fire) start. I tried replacing the crank position sensor, ignition coil and ingition control module( I think that what its called - its a small eletrical device on the side of the coil). No difference. I have 60 psi of fuel pressure. I replaced the fuel filter. And its got decent spark. The plug is wet with fuel. Also either (and gas down the intake) only makes if backfire worse. I have checked all fuses-none blown. It's acting like it's out of time, but it ran the day before? It has a mechanical type distributor that seems to be working fine- I took the cap off and it is spinning and the contacts are not pitted. Any info would help! Im stuck! : I work on diesels-not gassers.? : Wink:
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Tennykimble
February 26, 2007.



Hmm, any codes show up? There is one thing, the cam sensor in the distributor, the cam sensor adjusts fuel for each cylinder, its more like ia timing device, if it goes bad it has a one in six chance of fueling the correct cylinder, fuel pressure sounds good

how long since the plugs have been replaced

let me know jim

Tiny
CHEVYII
Feb 26, 2007.
A p1351 code showed up? It came up as " IC CIRCUT HIGH VOLTAGE" I cleared it and it didnt come back. The plugs looked okay- i'll pick a set up just to be sure, but I dont think that is the problem. Is the cam sensor in the distributor or in the engine block? Thanks for the advise! Any info is much appreciated! : D

Tiny
Tennykimble
Feb 27, 2007.
The cam sensor is under the rotor, the ic code directly effects your symptoms and it wont come back until the vehicle is running, it is located next to the coil its actually called ignition control module and it works off the crank sensor, if someone close has a truck with a 4.3 96 and up would work, swap one out just to test it

hope this helps

jim

oh the gm plugs are a must, I used to have customers come in with random misfires right after replaing their plugs and we put delcos back in and wham its good so I swear by them

Tiny
CHEVYII
Feb 27, 2007.
My 2000 Sierra 4.3 has the same problem.

Have you fixed yours? If so, what was it?

Mine is down and I am running out of money!

Tiny
Jboyd103
Apr 16, 2007.
Iwas running ok then it would die and start right back up till finally it started no more. I have spark fuel system is all good getting the backfire through the throttle body. I am strongly thinking its the timing chain going to take it off and check the alignment but I replace alot of stuff and a know go even disconnected the exhaust thinking stopped up cat convertor no go there but it will take me a few days so I'll try and keep you informed

Tiny
Kirbster269
Jun 26, 2007.