fuel pump only pushing 15-18 PSI???? Please help...

[TennesseeZ]

Thanks ChevyTech, just trying to help out and understand more and more about these trucks. I actually can "usually" diagnose and figure out my own at some point, but I normally only work on the ones I drive, ocassionally a few others. It's great to have guys like you willing to share the knowledge and help us out, maybe I should leave the diagnosis to y'all also.

[ChevyTech]

Originally Posted by TennesseeZ

Thanks ChevyTech, just trying to help out and understand more and more about these trucks. I actually can "usually" diagnose and figure out my own at some point, but I normally only work on the ones I drive, ocassionally a few others. It's great to have guys like you willing to share the knowledge and help us out, maybe I should leave the diagnosis to y'all also.

Please help out anywhere you can. Sorry if I sounded like I was scolding you. I did not mean to sound that way. I just meant to say you were talking TBI and he has a central port injected Vortec.

The TBI is the easiest to help with and the Vortec mess he owns is one of the worst systems to diagnose the GM ever built. I dislike this system so much that I have avoided ever owning any central port injected vehicle.

I only have a little free time that I can spend at the site right now, and any help anyone else can give is great with me.

[TennesseeZ]

HaHa at myself, I didn't even realize there was that much difference between the two. Thanks for the info, and apologies to OP.

[sfran]

TennesseeZ, no apologies necessary. I appreciate all input. Thanks!

Originally Posted by ChevyTech

Vortec mess he owns is one of the worst systems to diagnose the GM ever built. I dislike this system so much that I have avoided ever owning any central port injected vehicle.

^^^ You got that right, what a pain in the ass. But the good news is.......wait for it......

IT RUNS!!

I really want to thank everyone who helped out, and will never turn down any advice or someone just suggesting things. Especially with a situation like this, because I was ready to give up and burn this thing down. So a big thanks to you all.

So now on to the resolution. When I got home from work, I made up a cable and grounded one wire with the fuel pump ground, stuck the hot into the fuel pump 12v connector on the sending unit plug, and powered it with 12 volts from a jumper box. Presto, the pump fired right up, nice and loud, and 58 psi on the fuel rail. I knew then for sure it was wiring, but I really thought it was going to be the gray hot wire to the pump. Started narrowing it down after multiple continuity tests at the distribution block/relay. That's when it was found. Shame on me, believe it or not, it ended up being a bad ground. But not in the usual spot one would think, so before I get scolded, let me explain. I had a bad ground strap under the engine. As probably everyone knows, this grounds the battery, chassis, frame together. It was so corroded it broke into little pieces just from touching it. I do take responsibility for not checking the ground the way I should have. Every time I checked the ground, which believe me was a lot, I was not checking to the battery. I was checking the wiring to the frame, which the fuel pump was grounded to, duh! I knew that ground was good there, but should have taken the extra time to run a strap from the battery to my fuel pump ground and do a continuity test, would have saved me a lot of trouble. The frame ended being isolated from the ground from the battery. I know bad grounds cause some crazy things to happen, but this was insane.

I can't take all the credit though. My neighbor came over and as we were testing he thought of the chassis ground, not sure how long it would have taken me to figure that out. Really helps having another mind thinking of different things, which is what makes these forums so great. I was ready to just splice in under the distribution block and ground to the chassis, because that's one way I got it working. But in the end, it is fixed correctly, all new grounds from the battery to the chassis/frame done the right way.

Thanks to everyone who chimed in and threw out ideas, much appreciated. I hope documenting this situation helps people out in the future trouble shoot fuel pump problems, or any electrical problems for that matter. Just remember, always check your grounds, all of them!

Thanks again, Steve

[sfran]

Oh yeah, still got a check engine light, but I will address that after some time off from working on this thing. haha!

[ChevyTech]

Glad to hear that you got it fixed, and thanks for sharing what the problem was.

[sfran]

Originally Posted by ChevyTech

Glad to hear that you got it fixed, and thanks for sharing what the problem was.

Yeah I was getting pretty frustrated that I couldn't get it to work. But all is good now.

I try to document on the boards a resolution anytime I can. I know how much I rely on these boards, so anything I can do to help someone else out, I will. I am glad I had as much response on this that there was and hopefully, it will help someone else out in the future with similar types of issues. I know what the first thing is I will check next time. I am going to reground the pump off the frame and run it to a spot which is more accessible, or just double up the ground just in case.

I am actually going to throw the old pump back in tonight just to see if it will work. I just can't understand why when I beat on the bottom of the tank it started up originally.

[TennesseeZ]

Great you found it, and once again it turns out to be something basic that how many? poeople overlooked? I know a ground never even crossed my mind, I was off on a totally different goosechase, but it's great you found it, and also on the documentation here, no telling how many peeps it will help in the future. That's something I notice, and try to pass along, is going back to the basics, and K.I.S.S., seems it's so easy to focus on that one big part you're sure it's got to be, ya change out three of them, then remember to check the fuse or find something else equally simple. I'm glad you finally got it sfran, now get out there and get busy on that CEL!

[sfran]

Originally Posted by TennesseeZ

Great you found it, and once again it turns out to be something basic that how many? poeople overlooked? I know a ground never even crossed my mind, I was off on a totally different goosechase, but it's great you found it, and also on the documentation here, no telling how many peeps it will help in the future. That's something I notice, and try to pass along, is going back to the basics, and K.I.S.S., seems it's so easy to focus on that one big part you're sure it's got to be, ya change out three of them, then remember to check the fuse or find something else equally simple. I'm glad you finally got it sfran, now get out there and get busy on that CEL!

I totally agree with overlooking the basics and the K.I.S.S statement. But at least I found out from the hundred tests I performed that my frame and fuel pump ground wire are grounded together very, very well.....lol

That's usually how it is with me though. Dig in way to deep, because there's no way it could be something that easy, not with my luck. Oh well, at least I got the frame and undercarriage undercoated real good while the bed is off.

Still going to check the old pump before I put the bed back on.

And just for future reference, the bed does not have to be on the frame or the wiring plugged in for the fuel pump to work like someone had mentioned to me.

Thanks again, Steve