95 gmc jimmy 4.3 cranking problems and running prob

I have a 95 gmc jimmy 4.3 vin w sometimes it will crank sometimes it wont as if it had no fire but when it does crank it surges while it is at a idle. If you give it gas about 2500 rpms its like the fuel cuts out then comes back it runs rough and will back fire through the intake. If you let off the gas for it to return to idle it will keep falling all the way to zero, you try to crank it back up it won't hit a lick unless you let it sit then come back to it then it will crank up. With that being said I have checked tps, iac, computer, ignition module, plugs, wires, cap, rotor, map sensor, knock sensors, oxygen sensor, distributor , basic timing, fuel pressure , coil, spark is blue and is firing when it won't crank, camshaft, rocker arms, I have replaced the following to be sure computer, tps, map, both knock sensors, fuel pressure is about 60 when key is in the on position and maintains at 58 for about 2 min or so fuel is fine spark is fine and I have replace the spider injection about 11 months ago. I have burned the starter up trying to crank and test several things :banghead:so I will buy a starter and the 2 coolant sensors friday. I really getting to the point of what else could it be. It went from getting 18 mpg (city that is real good for this awd truck) to a yard ornament. Thanks for your time :banghead:

A few more parts and you will have a new truck.

I would start with some proper testing.
If you have good spark cranking or running.
Check fuel pressure with engine cranking and then when it runs.
post back pressure readings cranking and engine running and any fast leak down engine off.
When no start pull spark plugs and see if wet or dry on ends and post back which.
When no start give it a shot of carb cleaner and see if it will start on that.
Let us know on that.

Any codes or check engine lights on?
If so post back code no.

Is it a flat top dist or old style?
Have you checked or?
How did you check base time?

Good AC delco plugs?
Good fuel in tank?
Fuel filter good?

Starter won't be in till Friday :screwy: so I will do the tests then cause the starter is bad. There are no codes and the cel is off, old style distributer , I put #1 on tdc and put the rotor button pointing the #1 cylinder. Fuel filter good, I did replace the plugs w/ ac delco, fuel is good. I will post back Friday with the results from the tests. Thanks for your time and patience.

Starter won't be in till Friday :screwy: so I will do the tests then cause the starter is bad. There are no codes and the cel is off, old style distributer , I put #1 on tdc and put the rotor button pointing the #1 cylinder. Fuel filter good, I did replace the plugs w/ ac delco, fuel is good. I will post back Friday with the results from the tests. Thanks for your time and patience.

If you had dist out you need to go threw the base time procedure with a timing gight and disconnect the base time set wire.

Unplug some a sensor or two and see if check engine light will come on or it will set code?
How are you checking for codes?

i finally got the starter in and when it wouldn't crank, i had 58 psi fuel and it was firing i shot carb cleaner and it started then quit so i changed the spider. thanks for your advice.

i finally got the starter in and when it wouldn't crank, i had 58 psi fuel and it was firing i shot carb cleaner and it started then quit so i changed the spider. thanks for your advice.

55/61 specs on fuel pressure.

58 cranking is good.

If it fires on carb cleaner you have a fuel delivery problem.
Fuel presssure good that leaves no injector pulse or power to injector pos side.
Make sure 12 volt power to injector positive.

If so then check for injector pulse from VCM/PCM.
Injector Pulse is a ground pulse from computer
Best way to check is with a injector pulse tester..

Any add on remote start or anti theft stuff?

The 95 has 3 setups.
VCM or PCM or code W or Z engine.

Injector pos power with single injector pink wire to injector pos side afuse ign circuit.

On the single injector I have had problems with the injector wire and plugin from side of intake to injector.
When intake off is a good time to check the wire and plugin.

Let us know if you have injector pulse and power to injector at injector.