1988 Chevy Truck Engine cranks but wont start

Tiny
RWARD9
  • MEMBER
  • 1988 CHEVROLET TRUCK
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Its a 1998 not 1988

Well, basically when I turn the switch over it sounds normal like its going to start for about 2 seconds but then it just cuts off. It just started doing this about a month ago and I still haven't figured out what is wrong with it. I've tested the fuel pump and fuel filter and they seem to be fine. Also none of the fuses are blown either. I've charged the battery but it continues to do the same thing. I've also hooked up an OBD tester and no codes have come up. At this point I'm stumped, I'm thinking it may an electrical problem or maybe the alternator, but I'm really not sure what else to do. I need help as soon as possible. Thanks.
Do you
have the same problem?
Yes
No
Sunday, August 8th, 2010 AT 3:44 PM

21 Replies

Tiny
RASMATAZ
  • MEMBER
Hi rward9, Welcome to 2carpros and TY for the donation

Do below and get back with me asap with some results we start here

Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs, coil's resistances, cap and rotor, distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 3:52 PM
Tiny
RWARD9
  • MEMBER
We Checked the spark plug and there was enough spark so I don't think that is it. And the fuel pump and filter and also putting out enough pressure.
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 4:20 PM
Tiny
RASMATAZ
  • MEMBER
What is the fuel pressure? I need to know this
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 4:22 PM
Tiny
RWARD9
  • MEMBER
Ok, just a few minutes we're trying to find a fuel pressure gauge.
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 4:30 PM
Tiny
RWARD9
  • MEMBER
Is there any other way to check the fuel pressure with out a fuel pressure gauge? It turns out we don't have one
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 4:46 PM
Tiny
RASMATAZ
  • MEMBER
EFI system don't like low fuel pressure its a must that you check the fuel pressure-No worry I'll be here, when you get back with the readings so that we can move on
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 4:54 PM
Tiny
RWARD9
  • MEMBER
Ok cool thanks. What should the fuel pressure be on a 4.3L Vortec 6cyln. 1/2 ton truck
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 5:03 PM
Tiny
RASMATAZ
  • MEMBER
My engine, fuel pressure should be 60-66 psi, anything else?
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 5:05 PM
Tiny
RWARD9
  • MEMBER
Ok thanks, no not right now not ill we get a fuel pressure gauge. Thanks a lot tho. I'll get back to you once we check it and hopefully it will work.
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 5:10 PM
Tiny
MX5-SPEED
  • MEMBER
Do You have TBI (Throttle Body Injection)? 88-94.
The TBI uses 10-14 lbs pressure. When you first turn key to run the fuel pump runs for 2 seconds. Then the fuel pump continues to run IF there is oil pressure.

My wiring shows the Oil Pressure Sender having 3 connectors. With Tan: Orange: Gray wires going to the OPS. The tan goes to the gauges. The Orange and gray are part of the fuel pump switch. If there is pressure the switch is closed and you should read 0 ohms (use a volt/ohm meter) across the orange and gray. The ALDL connector (the plastic connector under the dash near the fuses. You normally short Connectors A and B pins and it flashes the engine error code. Pin G is Fuel pump relay bypass. Use a fused wire from 12V to it and try to start the engine.

Ping G is the lower left.

If it runs with fused +12V into pin G (assuming pin G is connected) I feel the oil pressure sender is bad or the wiring. You stated the engine runs for 2 seconds, hence the fuel pump relay works.
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 7:31 PM
Tiny
RASMATAZ
  • MEMBER
4psi of oil pressure and the FP/OPSU powers the fuel pump from there? If you temove the fuel pump relay and it dies out, replace FP/OPSU when south-Is this what you trying to explain?
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 9:08 PM
Tiny
MX5-SPEED
  • MEMBER
Dunno how many psi needed to activate the OPS/FP switch. Around 4 would be at the low end I guess.

By putting 12V to pin G of the ALDL it powers the fuel pump directly. Which tells you everything is OK except how the fuel pump is powered, (if the engine runs)

Look at it this way. The fuel pump is normally energized in two different ways. 1) Start circuit. 2) Run Circuit

To start an engine GM uses a 2 second only circuit from the ECM to power the fuel pump. This circuit energizes the fuel pump relay. It is just wired differently, than the run circuit (ie not using the oil press sw).

The run circuit passes power through the oil pressure/Fuel pump switch. The Oil Pressure switch is just a switch between the 12V power source and the Fuel Pump relay. Bad switch and the relay does not work, and no fuel pressure.

If the switch tests good, connectors and wires have a habit of going bad for no particular reason.
Was this
answer
helpful?
Yes
No
Sunday, August 8th, 2010 AT 11:05 PM
Tiny
RASMATAZ
  • MEMBER


http://www.2carpros.com/forum/automotive_pictures/12900_fuel_pump_and_oil_pressure_sending_unit_8.jpg

Was this
answer
helpful?
Yes
No
Monday, August 9th, 2010 AT 12:46 AM
Tiny
RWARD9
  • MEMBER
Ok so we got a fuel pressure gauge and this is what happened. When I turned the switch on the on position and while you hear the pump running it goes to 60psi. As soon as the pump stops running it goes back to 55psi. Then when you try to start it, it drops from 55psi to 50psi but still doesn't start. While the gauge is on.
Was this
answer
helpful?
Yes
No
Thursday, August 12th, 2010 AT 6:09 PM
Tiny
RASMATAZ
  • MEMBER
Sounds like you have a MPFI or the vortec for the fuel pressure to be that high-Check if the injector/s are pulsing providing fuel to the cylinders.
Was this
answer
helpful?
Yes
No
Friday, August 13th, 2010 AT 6:15 PM
Tiny
RWARD9
  • MEMBER
How do you check if the injector/s are pulsing providing the fuel to the cylinders?
Was this
answer
helpful?
Yes
No
Friday, August 13th, 2010 AT 6:32 PM
Tiny
RASMATAZ
  • MEMBER
What I need to know here is what type of fuel injection do you have-
Was this
answer
helpful?
Yes
No
Friday, August 13th, 2010 AT 8:37 PM
Tiny
RWARD9
  • MEMBER
Ok so it turns out that may not be the problem this is our new suggestion.

The ignition cylinder lock was locking in position sometimes and sticking. Could this engage the security system and cut off fuel to the engine?
Was this
answer
helpful?
Yes
No
Saturday, August 14th, 2010 AT 12:17 PM
Tiny
RASMATAZ
  • MEMBER
We Checked the spark plug and there was enough spark so I don't think that is it. And the fuel pump and filter and also putting out enough pressure.

Above won't happen if there's a problem with the cylinder lock and security system

If its cranking over and giving spark and fuel pressure like you said earlier its should start-up, why don't you check the valve and ignition timing could be off
Was this
answer
helpful?
Yes
No
Saturday, August 14th, 2010 AT 2:57 PM
Tiny
RWARD9
  • MEMBER
I'm not trying to disagree or anything cause I'll defiantly check the valve and ignition timing, but I've heard that if the ignition key switch is being messed with like if someone was trying to break into it, it could cause it to stop working. Which actually happened last summer my truck got broken into and the ignition key switch had to be replaced, because it was torn apart. But it didn't start sticking and taking a few times for it to start until about two months ago, and I would have to jiggle it really hard for it to go back in the off position so I could turn it all the way again to start it. But I actually took out the ignition key switch this morning and some of the springs were stretched and bent. Also the part that covers the springs was bent which I think was causing it to get stuck. The person that was telling me this said I would most likely have to replace the ignition key switch, and then take it to a GM dealership so they can scan it to get to back to normal.
Was this
answer
helpful?
Yes
No
Saturday, August 14th, 2010 AT 3:34 PM

Please login or register to post a reply.

Recommended Guides