I just bought a '95 GMC Jimmy -- 4.3L V6 Vortec engine 4WD Automatic .. After about 2500 miles a chugging problem began to occur. I brought it to a garage and they said that the wiring harness needed replacement .. I found that when i tugged on the wire (red+blue wire that goes into the plenum) that attaches to the top of the spider injector it would start .. about a week ago this trick didn't work anymore .. I replaced the spider injector .. also replaced the MAP sensor O2 Sensor temp sensor .. i put new spark plugs in a month ago. It tries to start but its as though no gas is gettin to the engine .. I cant afford to spend much money on fixing the car .. Are there any tests I can do to try and isolate the problem? I have no scanning tools so those tests are out .. anything i can do ?

 

check for fuel pressure. not sure if 95's are the same, but does your fuel pump hum for about 2 seconds after you turn your key to the on position?

 

While you were in there, did you replace the wiring harness? If pulling on the harness allowed it to start, then the harness was likely the only bad component and could have been purchased for ~$10...

 

thanks for the response .. i was told by a garage that they wiring harness did need replacing but i figured if i replaced the spider injector it would run .. the wire that attaches to the top of the spider I did replace .. is that what you mean by "harness"? I'm not too sure if that wire is exactly what you mean .. it has 2 wires on it .. one red and one blue .. again thanks for your response

 

Yes, that is the wiring harness I am talking about. So that was replaced.

Have you tested fuel pressure and leak down rate?

 

i checked the fuel pressure and it seems to be fine .. i do hear a hum when i put it in start .. could the problem be in the poppets? is there a way to check? i appreciate your help ..

 

If the spider is new, I doubt the poppets are a problem. What was the specific fuel pressure it reached and how long did it hold that pressure after the pump shut off?

 

Thanks for the heads up on how to respond .. I just joined today and still trying to figure that part out .. I'll go ahead and get a fuel pressure guage tomorrow .. thanks again for your input .. I'll post an updaye tomorrow after I test the pressure .. do you think it may be a fuel pump problem? When the car was running it would spontaneously start chuggin .. I would pull over and tug on that wire and it would restart .. after the last time it didnt start I couldnt do my little "trick" .. this has gotten me frustrated to no end ... I drove to Florida from California for a holiday visit with family and now have found myself stranded 2500 miles from home with no financial resources to alleviate my new found problem .. Thank you for all your help

what is the leak down rate and how do i check that?

I noticed on the old spider injector that one of the prongs had been worn down .. I figured that since the surface wasnt fully intact it wasnt making a connection ... this seemed to be the only problem with the car when it stopped running ..

I dont have access to any pressure gauges so I tested the fuel pressure by depressing the fuel pressure guage in back of the manifold .. it squirted up .. but every once in awhile .. I did that a few times .. the pressure just dribbled out ..

is there a way to test the fuel pump? it seems to be running fine .. i hear a whirring in the gas tank when i take the cap off .. i also hear the pressure regulating when i turn the key to start ..

 

Ok. First things first, please combine your thoughts into ONE post. Consecutive posting is prohibited by the rules of the forum. If you think of something you forgot to ask, edit your post.

You MUST use a fuel pressure gauge to measure fuel pressure. There is absolutely no way you can discern between 50psi, which is too low, and 55psi which is the minimum requirement of your engine.

As far as the fuel pressure leak down test, you just watch the gauge after the pump shuts off. The pressure should not drop more than a few psi after the pump shuts off and should hold.

The way to test the fuel pump is with a fuel pressure gauge.

 

Just checked fuel pressure and is at 56 .. drip rate seems fine also ..