Hello all... I have been trying my best to determine (on my own) why my truck won't start but, I am still at a loss.
I run a 95' GMC Jimmy, 4.3ltr., 4x4, AT, w/ 116k. I have tried fixingnearly everything that I can find wrong,without taking it to a shop. So here's where I'm at....
[ol][*]New: Cap,rotor, wires, plugs[*]Starter[*]Fuel Filter[*]TPS, IAT, O2(b1 sens.1)[*]Vac lines[*]Fuel PressureRegulator[*]Replaced battery[*]Resurfaced all major grounds (including fuel pump ground)[/ol]
All the while I am trying to find the easiest way out as, I'm not the richest college student around. What it has all boiled down to, even after a thorough investigation under the upper plennum, is the truck only primes and starts when I jump it from another vehicle. When I say prime I mean that the fuel pump primes only with the aditional charge of the other vehicle.The engine cranks very well without the jump but never seems to be enough to start.
Should I be looking to the alternator, or am I due to make that loving trip to the junkyard. Thanks for everyones help.

 

Try looking at your power connections starting with the positive cable and working your way back to the fuel pump. Check the plastic connectors at the fuel pump for proper voltages...

 

Something doesn't make sense to me. The engine doesn't start without a boost? So it does start and run with a boost?

Obviously if it starts with a jump, you have spark fuel, compression and timing.

You say that you replaced the battery. Have you load tested the new battery?
Your engine won't start if the voltage is less than about 10V.........sounds like a voltage issue to me if it starts and runs with a jump.
Have you checked the charging system when it's running?

 

The charging system was my next venture but I have to go to an AutoZone or someplace so I can use their voltage reader. But, yes it is like you say I have all major components up to calliber and no start. The battery I just put in is the second one. The first gained a memory from to many no starts and so I replaced it two days ago. With the voltage to the pump, I have not yet checked that because I don't own a voltage reader, however I have no problems what so ever with fuel delivery as soon as the engine starts. Thanks for the replies, I am going to try and fix this before tomorrow evening so sorry for the late posts.
P.S. I have read something about an oil pressure sender, and how it takes over when the fuel pump relay fails. My fuel pump relay has not yet failed but could this have something to do with the no-starty?

 

Alright

First off you are seeking in the WRONG areas for this problem.

Man you have spent a load that was WAY not NEEDED.

If you put in a fully charged battery and it still wont start without a jump is that what you are saying?

If so then this is your issue:

Terminal Connections (if not contacting correctly they will not pull enough from battery)
[this is possible due to the jump carries enough, but the connections from wire to battery might be decayed enough not to pull hard enough from the battery to start up] Try running jumper cables from your battery (disconnected from the wires)to the wires and see if it starts, If it does then your issue is with the connection ends.
or
Starter (needs the extra boost to engage the Solenoid, or the brushes could be shot making poor contact)
or
Starter Relay (if faulty could need the extra bump to engage)

If I had to lay my odds down, I would say starter. Cheap enough to get a bone yard one (cheaper then buying new to test). Or pull your starter and take it to Autozone for the free test (even cheaper due to no charge to test). Then I would check the wire connections at battery.

If it runs fine after it does start, then that rules out the Alternator due to it would run like crap or not at allif the alternator was going bad.

 

I understand what you're sayin MNHawk. I replaced the starter about one month ago and it cranks strong, the battery terminals if bad are broken or corroding somewhere other than at the batt. connections, because I have re-set those at the posts. I'm not sure where the starter relay is but that sounds like a good thing to check. That'll be next. Otherwise, like I said I do get a good crank without a boost, it just does not seem to be enough to get the pump to prime. I'll keep looking, thanks agian.

 

My roommates truck did this, it ended up being a bad cell in the battery. Get the battery tested.

 

Ignition contol module? Coil? Starter solenoid?

 

The battery while brand new is actually the second brand new battery I've had, I get plenty of juice from it. I have not yet checked the ICM, the coil put out a good charge (trust me I've felt it)and if the starter solenoid is what I think it is that got replaced with the starter. I could be mistaken though. With the ICM, do you think that the ICM would malfunction only during starting? Because as soon as the truck starts I have no studdering or miss-fires.

 

Ok
And you said you checked the Fuel Pressure right?
Did it also need the jump to show or did it show on its own without the boost?

And what do you mean by reset the terminal connections?
Only sure fire way to fix these to to either cut off the bad ones and replace or replace the whole wire.