2000 Silverado low fuel pressure

jerhap · April 5, 2016

Hi guys, I'm pretty lost on this 2500 Silverado. I have 35-40 PSI at the fuel rail. I just did a ton of work to this vehicle and it had no fuel pressure issue that I know of prior to this. Original issues with this truck were blown out brake lines and no reverse in the trans. I've found other issues along the way, which I've fixed as well. in the past few weeks I've replaced brake lines, had trans rebuilt, replaced sections of rusty fuel lines plus new fuel filter, and water pump. I went for a test drive after and found the check engine light flashing so I checked it out and found a P0300. I spoke to my buddy and he said the intake gaskets have issues on these trucks so I replaced the intake gaskets with the new updated green gaskets. Test drove again and the same issue.

I also did spark plugs and wires since they have never been replaced and the truck has close to 100,000 miles. That did not make a difference either. I went to test drive the truck again thinking maybe it was carbon buildup or something and the truck broke down about 2 miles from my house. I swapped the fuel pump relay out and it started back up but it ran really bad and hesitated a lot. Once I got home I tried starting it again and it wouldn't start. The fuel pump relay wouldn't even turn on. swapped relays again with another one and no change. I took the cover off of the relay and touched the contacts together and the pump came on. The truck still ran like crap though. I put a gauge on it and 35-40 PSI which is way to low. I checked codes and had a P0230 fuel pump relay malfunction.

I notice that i have 2 different issues here. 1. the PCM is not energizing the fuel pump relay and 2. the fuel pump is not putting enough pressure to the rail. I checked all the grounds on the PCM and all the engine grounds. Then checked the ground at the fuel pump and even cleaned that ground on the frame, all grounds worked fine with test light and Still same results. I followed a flow chart for the P0230 code and it told me to replace the PCM. It had me disconnect the PCM and checked the green and white control wire from the PCM and supply it to power and the fuel pump relay switched on. I've came to the conclusion the PCM is bad, but still doesn't make sense to me how all this happened on a test drive and why the fuel pressure is low?

I still had no idea why I couldn't get enough fuel pressure to the rail. My thought was that the fuel pump shorted out the PCM and they were both fried, so against my better judgement I put a fuel pump in it. Of course same results, low fuel pressure. I took the fuel filter back off and looked for a restriction but couldn't find one. I even took the quick disconnect lines off up on the rail and blew compressed air through the whole line. I really have no idea where to go from here. I ordered a PCM and should be here tomorrow, but I won't be installing until the weekend. I also threw a fuel pressure regulator on it. At this point I'm literally throwing parts at this thing hoping it fixes it. This is my wife's dads truck and I did all of this work for free because they do not have much money. Guess this is what I get for being a nice guy lol. I'm sorry for the long story but I felt it was necessary to give all the details in case anyone is able to help. Any help is greatly appreciated. Thanks!

00Silverado4x4 · April 6, 2016

Did you check the fuel pressure regulator on top of the engine? It may have failed and would be causing similar issues.

jerhap · April 6, 2016

I replaced the fuel pressure regulator on the fuel rail. Is there another fuel pressure sensor or something you're referring to?

jerhap · April 7, 2016

anyone have any other ideas?

00Silverado4x4 · April 11, 2016

I personally am not sure what else it could be if the pump and regulator are working correctly except to maybe try a new fuel filter. I know you said you checked it but you never know.

jerhap · April 11, 2016

The fuel filter is new and I even took the new one back off then blew through it. I have a theory on what happened. I think my computer failed while I was driving, then the vehicle was starving for fuel and some rust or debris was sucked through the line. I think the issue might be inside my fuel rail. I'm pulling it off today and inspecting.

jerhap · April 11, 2016

Well the issue is still there. I pulled off the fuel rail and pulled off the crossover pipe, then blew compressed air through it. I couldn't see any issues with it. I also took all the injectors out and looked in the inlets to see if there was an issue with them. I still only have like 35psi at the rail. maybe I have bad gas, but I didn't think that could cause low pressure. I just don't get it. If anyone has anymore ideas I'm open to anything. Thank you.

txab · April 11, 2016

How are you checking fuel pressure? key on engine off? Have you checked voltage at fuel pump. Do you have the correct fuel pump? Is it a cheap ass pump? Have you installed the new PCM you ordered?

jerhap · April 11, 2016

Yes, key on engine off but even if I start it it's about the same. I have 12 volts at the pump, checked with a meter and a test light. Yes, I have the correct fuel pump and it was like $270 and had good reviews but I put a fuel pump in and it's at the exact same pressure so I think there was nothing wrong with my old fuel pump. I just plugged the new pcm in to test and see if my fuel pump relay came on and it did, so I know the PCM fixed that issue. Waiting for my buddy to come program it. Probably will come by this weekend.

TAZ DEVIL · April 13, 2016

Any news ?

I had issues with a '01 s-10. Almost same deal as you. Getting 12v at pump, ... but when checking voltage, I used chassis ground. I found later that the pump harness ground was bad, so pump wasn't getting correct voltage.

jerhap · April 13, 2016

Taz Devil,

I checked voltage using the pump ground and power and had 12 volts. I also used a test light and it lit bright so I don't really know. I used a test light so it would past over a load and it seemed fine. I've never seen something like this before, so this is a pretty crazy issue to me. I won't be working on it again until Friday or Saturday. I might just literally hook a battery directly up to the pump and take all the wiring out of the equation. If I still have low pressure then there has to be a restriction I'm missing. If all else fails I'll push it off a cliff lol. I let you guys know what I find out this weekend.

TAZ DEVIL · April 14, 2016

Some,(lots of) times I miss carbs.

jerhap · April 16, 2016

Well this problem is finally resolved. the MAC fuel pressure gauge I was using was reading 35-40 PSI and I checked everything in the fuel system, so it was either get another new fuel pump or buy a new fuel pressure tester. I bought a new tester and I am getting 58 PSI at the rail. What is funny about this is I bought a POS $30 tester and it reads correctly but the MAC tester that is like $100 plus doesn't read right??? The truck was still running like crap and seemed like it was starving for fuel, but now I know the computer was causing all of that. I finally got the computer programmed today and it still ran like crap but not as bad. I went and put fresh fuel in it, then drove it around and it started clearing up. The check engine light is not flashing anymore and it runs great now. I can't believe an inaccurate fuel pressure test caused me all this wasted time. What kills me is the truck was acting like it had a fuel issue too. it was bogging every time I hit the throttle. I'm glad this damn truck is finally fixed. MAC fuel pressure tester is in the trash!!! Thanks for the input guys.