96 4.3 Sonoma cranks but will not fire whatsoever

Asked by Mar 25, 2017 at 02:04 PM about the 1996 GMC Sonoma 2 Dr SLE Standard Cab SB

Question type: Maintenance & Repair

Anything helps here cause I'm 2 months
without a vehicle and need to make
headway. I have a 2 wheel drive 1996 GMC
Sonoma with the 4.3 and a manual
transmission. I was leaving work and as I
shifted into 2nd gear it died and hasn't ran
since. Fuel pump kicks on, good spark, 175
lbs of compression(requires 155 or so) and
it doesn't turn over lightly as if the timing
chain broke (doesn't rule it out but had that
happen before on another s10 and this
doesn't seem the same). All the fuses are
good and nothing in plain site is out of order.
Here's the kicker, I know the plastic
manifolds explode on these if they backfire
when ether or fuel is introduced to the
intake. After days of messing with it and a
particularly awful 12 hour night shift, I tried it
knowing the risk....still wouldn't fire, let alone
back fire, at all. And now here is where it
gets even more impossible, neither of the
scanners at my disposal will communicate
with the ecm due to aftermarkets and/or the
chip added by the previous
owners(assuming this, could be wrong,
that's why I'm here). With that being said,
where would a guy start?

3 Answers

73,035

I'll try to help, I know a lot about Chevys, but not everything. First you say you have good spark which means the camshaft is turning over ruling out the timing chain being broke, not to say it jumped time tho. Is the battery good? because you say "it doesn't turn over lightly". I would first have you check the engine timing, #1 up on the compression stroke to TDC and see where the rotor is pointing.

Thank you for your time. The battery is brand new but I suppose it could still be bad. And what I meant by it not turning over lightly is that it cranks normally. When the timing chain broke on the last one I had you could clearly hear only part of the engine was engaging. But I don't know if that's enough to rule it out. I feel like the fact that ether and fuel in the intake won't even make it fire should tell me a lot but I don't have the knowledge to put 2 and 2 together.

73,035

Then get a fuel pressure gauge and hook it up to the Schrader Valve and see what the fuel pressure is. It should be 56 to 63 lbs. Build up fuel pressure on the gage by just turning the key to the on position. Then turn the key to off and watch the fuel pressure. It should not drop more that 5 lbs. in 3 minutes. This is checking spider injector assembly if it is leaking.

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