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98 Vortec Fuel Pressure Question/Problem

This is a discussion on 98 Vortec Fuel Pressure Question/Problem within the Technical / Maintenance forums, part of the General Discussion category; Over the last couple of weeks, my Tahoe (5.7 Vortec) had been increasingly hard to start in the mornings. Then ...

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    98 Vortec Fuel Pressure Question/Problem


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    Over the last couple of weeks, my Tahoe (5.7 Vortec) had been increasingly hard to start in the mornings. Then it wouldn't start at all!

    I started with the ignition system...all of it! Cap and rotor (really bad), coil, ingition module, cam sensor, crank sensor. I have spark at the coil and plugs (at least at #1 where I checked). Still cranks but no start.

    Before throwing more parts at this thing, with help from these forums, I decided to do a fuel pressure test. I just replaced the fuel pump and filter (by a mechanic friend) last year...that Can't be the problem...right?

    Anyway, I turn the key on, pump starts up and pressure holds at 45 psi. From my readings here, this isn't enough to start the truck, right? The pressure holds and doesn't bleed down. I'm taking this to mean theat my fuel pump is bad, but the rest is ok. Am I on the right track here?

    I don't want to change the pump in my garage and will have to have it towed to the repair shop.

    Any and all replies are appreciated!

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    Re: 98 Vortec Fuel Pressure Question/Problem

    By your readings,it's time for another fuel pump. I just went through the spider injector upgrade, and my pressure was 60# before and after. Oh, and mines a 98 as well.

    'Slot

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    Re: 98 Vortec Fuel Pressure Question/Problem

    After about 10 minutes or so it bleeds down to around 35.

    I'm guessing a tow is in order. This sucks!

    Thanks for the reply!

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    Re: 98 Vortec Fuel Pressure Question/Problem

    The fuel pump should cycle on for about 2 seconds and then shut off, key on engine off. The fuel pressure will bleed down after a while with the key off. when you try to crank it, what does the fuel pressure read? if it's losing a significant amount of pressure, it's not putting enough volume out. Another thing you can try to do is turn the key on, and let it sit until the fuel pump cycles off (about 2 sec) and then try to start it.
    '97 GMC 1500 350 w/305 heads & flows

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    Re: 98 Vortec Fuel Pressure Question/Problem

    Was the pump replaced with either a AC Delco pump or Carter brand pump? If not, I would guess its your pump. These are the only two pumps that hold up, I searched like crazy before buying a new pump for our old 98, and thats what was told. At 110k miles I put the carter in as the third fuel pump. Stock died at 95k ish, the aftermarket (non-carter brand) pump died at 110k.... they just dont last, so search out th Carter or the AC Delco pump this time..... We traded the truck in at 141k with no problems. The cheaper pump whined like crazy from new (it was the gf's truck, and she put that in before I met her)....

    BTW, when I tested hers, it was 50 psi, so I tried some other things like yourself first, and then bit the bullet and replaced the pump.
    Last edited by NateDiggity; 03-03-2008 at 10:49 PM.
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    Re: 98 Vortec Fuel Pressure Question/Problem

    You should rule out the fuel pressure regulator before installing a new pump - clamp off the fuel return line and turn ignition on, if pressure is now above 60 psi, your FPR is bad, if not likely your pump and/or check valve needs replacing.

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    Re: 98 Vortec Fuel Pressure Question/Problem

    I will definitely try that first.

    The pump sounds a little weak as I listen more closely.

    I know it wasn't a Carter or Delco. The next one will be.

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    Re: 98 Vortec Fuel Pressure Question/Problem

    you might be able to drive it to the shop, 45 MIGHT be enough to run, but not start, get some carb clean, spray it into the throttle body(the air tube off), reinstall the tube , and see if it starts and stays running
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    Re: 98 Vortec Fuel Pressure Question/Problem

    Tried starting fluid, she kicked and spit, but no start. She really wanted to!

    Anyway, towed it to the repair shop this afternoon. Hopefully it will be back tomorrow.

    If they find anything else, I'll be sure to update the thread.

    Thanks guys!

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    Re: 98 Vortec Fuel Pressure Question/Problem

    Ok, so I towed the Tahoe to the repair shop and instructed them to replace the fuel pump.

    So they ran a pressure test and said: It pumps up to 55psi so it should start. We checked the timing and it was WAY off. When #1 was at TDC the rotor was pointing at the steering wheel when it should be pointing at the drivers headlight.

    They pulled the dist. and it the gears looked fine. They thought the timing chain was the issue, so they tore that down. Sure enough....it was fine!

    So after putting everything back together, they adjusted the timing, but it still wouldn't start. It would run with starting fluid, but then die.

    It seems the fuel pump will build the pressure, but the VOLUME was inadequate. So now, after all that BS, they are replacing the fuel pump!

    They are not charging for the timing chain teardown, just pulling the distributor and replacing the fuel pump.

    Man, I just want my truck back!

    As soon as I pick it up, I'll let you know what happened.

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    Re: 98 Vortec Fuel Pressure Question/Problem

    Finally after all that crap, a new fuel pump has cured the problem. Just like I told them it would!

    Runs like a champ now!

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    Registered User TAHOE GUY's Avatar
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    Re: 98 Vortec Fuel Pressure Question/Problem

    I have 1999 chevy tahoe that I replaced the fuel pump last june and this last saturday I checked the pressure. It read 50 psi, do you guys think it needs a new fuel pump or could it be fuel pressure regulator? It stumbles little when I step on the gas hard. I put in new fuel filter last dec. too. any ideas. thanks

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    Re: 98 Vortec Fuel Pressure Question/Problem

    I would bet the pump is going bad. Do it soon before the warranty runs out.

    I think mine was deficient from the day it was installed. With the new Delphi OEM pump, my Tahoe starts easier and has more kick when it needs it.

    Unfortunately, mine was about 3 months out of warranty. I'm still trying to get them to take it back. My company buys a LOT of parts from this vendor.

    I just had another van 97 with 5.7 Vortec have the same symptoms, lots of cranking before it starts. Thankfully this was just a really old cap and rotor....170k miles old! Runs like a champ now! It was so bad the resistance caused the coil wire to arc against the firewall.

 

 

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