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Pete, GMC Technician
Category: GM
Satisfied Customers: 29116
Experience:  14 years GM dealership technician and training.
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1995 sonoma: it wont start..fuel pump relay..fuel filter..injectors

Customer Question

I have a 1995 sonoma with a 2.2L. it wont start until i unplug the fuel pump relay. it dies when i plug it back in, and it dies if i don't plug it in. i changed the computer, fuel pressure regulator, fuel filter, plugs, and injectors. what could be wrong? All the parts i put on were new, ecxept the injectors. i put the original parts back on. Could it still be a faulty injector or injectors?
Submitted: 6 years ago.
Category: GM
Expert:  Pete replied 6 years ago.
Hello,I will be glad to try and assist you with this,Welcome to Just Answer.


I just need a little more info to assist better.

With the relay installed,turn the key to the on position and see if you hear a hum or buzz noise from the fuel tank for the first two seconds the key is switched on?

Do you have a test light or multimeter for testing?

Let me know so we can continue,Thanks Pete!
Customer: replied 6 years ago.
the pump stops like it normally should. i also have about 65 psi up to the fuel filter, thats where i tested it at. and i do have a test light and a multi meter. i get 5 volts to all the sensors that i checked. the tps has around .485 v at idle, and 4.5 v at full throttle
Expert:  Pete replied 6 years ago.
Try this,

Try swapping the fuel pump relay with the same part number relay in your vehicle and see if it starts and runs then in case the relay you have here is faulty and is causing this problem as this may be the case here.I have had to replace some faulty relays for conditions like this if the relay is internally shorted.

If you don't have another relay in the vehicle with the same part number you may want to purchase one at a dealer or after market parts store to see if it corrects this failure.

From what is described it sounds like the relay may be the component at fault and is causing this problem.

Your fuel pressure is good and the sensor data looks good from what you have described so I don't think any of these are the cause here.

Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!
Customer: replied 6 years ago.
there are 2 relays in the glove box with the same part #. The motor does the same thing with both relays.
Customer: replied 6 years ago.
there are 2 relays in the glove box with the same part #. The motor does the same thing with both relays. i bought a fuel oil pressure switch, im going to install that on sat, cause my truck is not at home. if that dont work, i will replace all 4 injectors. ( i only changed the 2 rear injectors the last time. i think one or both front injectors are leaking causing the engine to burn too rich and stall out.
Expert:  Pete replied 6 years ago.
I apologize for the delay.

If something was contaminating the fuel it could have taken out all four injectors like this and it may need the others to correct this problem here.

It should run with the fuel pump relay in if the fuel pump is operating properly.We would have to test the fuel pump relay circuits to see if any of the circuits are at fault.

But it may not be running because of how rich it is and this can be caused by injectors but its hard to say for sure from here.I can help you test some of the circuits to see what may be at fault if you want to go this route.

Thanks Pete!