VIKING_MECHANIC
GMT 400 obsessed Swede.
I was working on my 89 on Saturday trying to figure out why is wasn't starting(unrelated to this - i think). I adjusted the valves yet again and when I had my buddy crank the engine, I noticed there was no fuel coming out the injectors.
Okay, here we go.
First thing I checked was the ignition fuse. Not blown. So I moved on. I listened for the pump as my buddy KOEO, nothing coming from the pump. I grabbed my power probe and checked the body side of harness. I had ground, but only 8.5v. Hmm not good. I also checked to see if the pump was working, which is was. Although that doesn't rule out a pressure issue with the pump itself.
I checked the relay next. I got 12.4v and ground at the connector. Honestly not sure how to test the relay itself, as from what I understand, you have to test the relay with it connected and I'm not sure how to do that. I then next checked the fuse and there was no voltage at all on either side of the connector. I took apart the harness and starting looking for broken wires but everything I could see was in good shape. At this point I stopped as I wasn't sure which direction to go in.
Correct me if I'm wrong, but the fuel pump module was only in the 25 and 3500s with a 5.7 right? I've read that it regulates voltage to the pump, but only in the trucks that have them.
I also have my oil pressure sender disconnected for the last several months and haven't had this issue.
Okay, here we go.
First thing I checked was the ignition fuse. Not blown. So I moved on. I listened for the pump as my buddy KOEO, nothing coming from the pump. I grabbed my power probe and checked the body side of harness. I had ground, but only 8.5v. Hmm not good. I also checked to see if the pump was working, which is was. Although that doesn't rule out a pressure issue with the pump itself.
I checked the relay next. I got 12.4v and ground at the connector. Honestly not sure how to test the relay itself, as from what I understand, you have to test the relay with it connected and I'm not sure how to do that. I then next checked the fuse and there was no voltage at all on either side of the connector. I took apart the harness and starting looking for broken wires but everything I could see was in good shape. At this point I stopped as I wasn't sure which direction to go in.
Correct me if I'm wrong, but the fuel pump module was only in the 25 and 3500s with a 5.7 right? I've read that it regulates voltage to the pump, but only in the trucks that have them.
I also have my oil pressure sender disconnected for the last several months and haven't had this issue.
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