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Discussion Starter · #1 ·
I'm stumped and have run this problem by a half dozen mechanics who usually give me the expensive answer. I've got a GMC 1998 Suburban K1500 5.7 with 250,000 miles. It only starts with starter fluid now and then idles fine, maybe a bit rough, but purrs right along. So I replaced the fuel pump relay and the fuel filter but that didn't help. Then I had a mechanic replace the fuel pump and that fixed the problem. Started right up, all was good and well for a few hundred miles until it reverted back to its old self, not starting without starter fluid. (He never flushed the tanks to wash out any dirt or debris, I don't recall).


As the pump was under warranty the mechanic replaced that pump and all was well again, fired right up and I was happy, for a few hundred miles when it happened once more. It's taking longer to start now even with the starter fluid.



So, my fuel pressure gauge test measured the following. Key on, key off 50 psi where it held steady (It should be 60 - 62). At an idle it ran at 52 psi. I turned it off and pressure dropped to 48 where it held solid for 10 minutes.



From what I've read, because pressure held steady at 48 psi after I turned it off the problem isn't a leaky spider fuel injector or a leaky fuel pressure regulator under the intake manifold - and a real pain to get to. Am I right? Or, can the pressure regulator be causing problems even if it does not leak? And how would I know? Is leakage the only problem that can arise with the regulator? With two brand new fuel pumps I find it unlikely that's the problem, but what else could it be? And, if it was the spider injector or pressure regulator leaking I would think it still wouldn't have started up even with those new fuel pumps. Opinions run the course. And what are the odds of two new fuel pumps being bad right out of the box?


Maybe there's a clogged fuel line? Some obstruction? One fellow told me he had the same problem with a small piece of paper towel caught in the line. Now, here's a clue. I've driven this rig thousands and thousands of miles on dusty dirt roads in the Southwest deserts and off-road in the Rockies. Is it possible that dirt or dust or gunk is in the tank that is blocking something? I know clogged fuel filters and this isn't it. In my experience the truck usually sputters and bumps along if the filter is really clogged, but not this rig. And, I had the filter changed.


Or, is there a valve of some kind in the line that might be stuck open or shut? I have no idea, but I don't want the mechanic to throw parts at it randomly, like replacing the spider injectors or the pressure regulator, expensive as that is. Any ideas? Thanks.
 

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VATS security system? At 250k it’s about that time for it to fail. It blocks the ground to the injector.
 

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Discussion Starter · #3 ·
VATS security system? At 250k it’s about that time for it to fail. It blocks the ground to the injector.
But if it's a faulty VATS security system, why does installing a new pump, two new pumps, actually, fix the problem for 400 hundred miles? If it's a bad VATS system or any other electrical component, that problem would remain and it would continue not to start,I would think.
 

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Discussion Starter · #4 ·
Well, folks, I got her fixed with a new NAPA-supplied fuel pump. The Burb starts and runs ... for now, and we'll see what she does in a month or two. I knew it was going to start and run with a new pump just like the previous two times the new pumps were installed. Finding the culprit, the one thing killing those three pumps, was the main issue.

So I dropped her off with my new mechanic and passed on the sage advice you all offered. He didn't think there was contamination in the tank and verified that after inspecting it. No debris in sight. In addition to the pump he installed a new filter and module which he says he always does when installing a new pump. And now my fuel gauge also works, too! All of my grounds and ground wires were good. With key on, engine off, pressure at the rail was I think 50 or so, and he left the gauge on overnight for 10 - 12 hours and pressure dropped to 40. He said most likely the pump was bleeding off in the tank, although it's always possible there might be some leakage in the injectors or fuel pressure regulator.

Now, as for a faulty oil pressure switch, I pressed him that that could be the problem and even showed him some of your comments to that effect. But he wouldn't have it and didn't believe the oil pressure switch had anything to do with the problem, and he felt pulling the relay while it was running would kill the engine anyway because of the lack of voltage to the pump. I wasn't brave enough to pull the relay myself while it was running and left that to him. But I was adamant that he change the oil pressure switch anyway which he did. The part was around $45, and it didn't take long to swap out. A YouTube video showed one fellow reaching down below the distributor and with his special wrench he changed it in around ten minutes. But now I can rest easier knowing if the new pump goes out it can't be the oil pressure switch. Also got a new cap and rotor, and it runs good, for now. Needs front-end work, to my dismay.

He tells me these pumps go bad ALL OF THE TIME. So, I want to thank everyone who commented and helped me sort this mess out. Greatly appreciated. Really. I was beyond frustrated having run into too many mechanics on the road who simply had no clue. Before the internet it would be only me and the mechanic and a lot of blind trust, and maybe a second opinion from somewhere. Times really have changed - twenty heads really are better than one. Again, thanks everyone for your help. Over and out.

Mark
 
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