i have a 1993 gmc jimmy and when i try to start it sometimes it will start...
- Thread starter Matt
- Start date
Molson02536
New member
If you put battery voltage to the pump and the engine will not start you need to do a fuel pressure test.
Fuel pressure is very critical in these 1992-1995 (W) engines. The engine needs a minimum of 58 PSI to run it should hold pressure, acceptable drop once running is 3-10 PSI You should obtain 72 PSI at filter (dead headed).
If not you have a weak pump if it has high resistance which having only 10.5 volts (acceptable drop is 11.2 volts). This high resistance may have shown up in a high current draw (could have blown fuse, that supplies relay).
If your pressure is good you need to have a look inside the intake manifold look for puddles of raw gas indicator of a bad fuel distributor (spider). If you have raw gas you need new Spider fuel injector ($400.00). Note the pressure regulator is now available separately, so if that is leaking just change it.
The fuel pump relay should come on for 2 seconds when the key is turned on no matter what the oil pressure switch is doing, so we can eliminate a bad oil sending unit.
1. Remove the fuel pump relay, check for 12v to the relay on the Orange wire. If no voltage check ECM-B fuse or the wire between the fuse and the relay.
2. If OK, jumper the Orange and Gray wires together.
3. The fuel pump should now run.
4. If so, replace the fuel pump relay.
5. If not, leave jumper in place, test for 12v back at the fuel pump, Gray wire to a Black/White wire.
Looking at the schematic, it shows a black wire that goes directly to ground. If you have power at the gray wire and the pump does not run, or is weak. The ground side is where the problem will be, check for a black wire back there. I would say it's pretty certain you do not have a good ground. According to the schematic, it attaches to the frame, and given the location. I'd say it would be prone to corrode. Check that ground.
I hope this helps, it also may not be bad to replace your fuel filter, you never know that is may just be a simple dirty fuel filter that is causing your no start problems.
The other thing also that may be causing your no start issue is a bad ICM, (ignition control module) it's located in the distributor under the rotor, you can have your ICM tested at Auto Zone and pick one up there also if yours has gone bad. A faulty ICM starts off as a no start or stalling and eventually will fail 100% causing 100% no start.
In short, start with the simple and replace the Fuel filter. Check electrical connection to ignition system, ( coil, distributor, ICM ) and check for fuel pressure and wire leads and connection to fuel pump sending unit.
