chevyboy_21

I have a 1995 gmc jimmy awd. 4.3 cpi, automatic transmission. Sometimes it cranks right up or it will spin over about 15-30 times before it cranks does this hot or cold. When it does crank you smell fuel odor bad and blows just a little black smoke as if it was flooding just a little. It seems to have a ruff idle and lacks power too. I have done a full tune-up, as rotor button distributor cap, wires, spark plugs. I have also changed out the fuel regulator, and checked to see if there was any carbon build up in the air denium.I have also changed the fuel pump and filter about six month ago, I also had the injector rail(spider) replaced. This truck is obd1 and has no crankshaft sensor or camshaft sensor. I am out of ideas and hopefully somebody can help me out. Thanks

old_master

Have you checked fuel pressure and leakdown? This will check the fuel delivery system for problems. It will NOT tell you what the problem is, it will only tell you if a problem exists.

Key on, engine off, fuel pump running, fuel pressure must be 58psi to 64psi. Pressure must remain above 53psi for 3 to 5 minutes after the fuel pump shuts off. Post your results.

NOTE: These specs are for the '95 CMFI system, (fuel lines enter the plenum horizontally at the rear of the plenum). These specs do not apply to the CSFI system, (lines enter plenum vertically, just behind throttle body).

chevyboy_21

I have checked the fuel pressure and leak down. When i turn the key on the pump comes on and the pressure is about 60 when the pump shuts off it is at 55-56 and then decreases to zero in matter of seconds.

old_master

There's a leak either in the plenum or in the fuel tank. The only way to tell where the leak is coming from is to install a temporary shut off valve in the fuel pressure line near the fuel filter. The valve will isolate the fuel pump from the rest of the system. Immediately after the pump pressurizes the system, close the valve. If fuel pressure holds, the leak is in the tank, if it drops, the leak is in the plenum.