1995 GMC Fuel Problem

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Hello, I am new to the forum but have owned my GMC for 19 years. It has a 305 and manual transmission with 212000 miles. Today it started running weird. It died at a stop light despite trying to feather the gas pedal to keep it going. It was hard to restart. Got it going and it ran OK after 1/2 a block. I figured it had to get "cleaned out". When I pulled it into the driveway, it was idling high (1500rpm) and the exhaust smelt bad. Took it out after dinner and it had a slight rolling idle until I drove it a few miles. Exhaust still smells weird.

Is this a sign of the fuel pump dying or is there another problem in the fuel system?

 

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Talking to a friend, he thinks it is the catalytic converter. I will check this out. Any comments welcome!

 

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Hopefully there are some ideas out there on the forum!

Latest news:
1. Catalytic seems to check out OK. Vacuum gauge indicates 19" at idle and other RPMs.
2. MAP sensor seems to work OK, voltage levels are consistent with manual: 0.3 VDC when engine OFF, 4.15VDC when engine running, 1.5VDC at WOT
3. Fuel pump(aftermarket unit with 7,000 miles on it) has sustained 12PSI fuel pressure at idle as measured at the fuel filter inlet (that was a tough one to measure! what a mess!)

Truck has throttle body injection and a 305. It sometimes runs OK, mostly runs at differing idle speeds (between 1500 and 900 rpm) and sometimes has no power when trying to let out the clutch to accelerate (accompanied by black smoke). When it runs bad, you really have to feather the gas pedal to keep it running.

Any ideas?? EGR? Injectors?

 

[Molson02536]

Hello, I am new to the forum but have owned my GMC for 19 years. It has a 305 and manual transmission with 212000 miles. Today it started running weird. It died at a stop light despite trying to feather the gas pedal to keep it going. It was hard to restart. Got it going and it ran OK after 1/2 a block. I figured it had to get "cleaned out". When I pulled it into the driveway, it was idling high (1500rpm) and the exhaust smelt bad. Took it out after dinner and it had a slight rolling idle until I drove it a few miles. Exhaust still smells weird.

Is this a sign of the fuel pump dying or is there another problem in the fuel system?

The TBI was always touchy with there fuel pressure, best thing to do is to keep it simple and clean out your throttle body and IAC vaive. Replace your fuel filter and make sure all your vacuum lines are good and don't miss the one behind the throttle body that controls your fuel pressure regulator.

Also a good thing to make sure your EGR valve is not stuck open from carbon build up or a bad vacuum line.

keep us posted and stay safe.

Molson02536

 

[Bill325]

Good advice from Molson ! One additional problem I found on my own 305 with throttle body fuel injection was an erratic electrical short in the wires that go to the fuel injectors.
On my truck, there is an aluminum spacer between the throttle body and the air cleaner. The injector wires were pinched between the throttle body and the spacer, and shorting out. Rerouting the wires to their proper location solved the problem. On the same truck, the throttle position sensor( TPS) and the manifold air presure sensor (MAP) also eventually needed replacement. Those components are fairly cheap, and just doing some parts swapping is often the easiest way to eliminate them as possible problems.