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Thread: LS1 fuel injection help

  1. #1
    Senior Member SENIOR BUILDER
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    LS1 fuel injection help

    Hello guys,
    Dumb question, I have a 98 T/A LS1 6 speed that has 50,xxx miles on it. I bought it cheap enough because it had been wreck in the nose, no frame damage. I got it home about 5 months ago started it up 2 or 3 times on the trailer, then started it, backed it off the trailer and parked it for later. 2 days later I tried to start it. It cranks but never hit a lick. Ok air, compression and fuel. Air, check! compression, check!, fuel, check? OOPS no fuel. Checked the blasted fuel pump and bingo nada! Well I have let it sit due to time and finally ordered a new pump through a place on Ebay. I got it in and the pump cycles and the engine will try and hit. But won't ever start. Well it has old gas and I added some new and replaced the fuel filter too. Now then the pump will cycle fine but still won't fire. I don't have a pressure gauge but you can cycle it 5 times and then go check for pressure at the shradder valve ( I know I can't spell, LOL) and it doesn't even trickle. You can hold(press) it open and cycle the key and it'll spew gas out. Now then is there a regulator in the back that is allowing the pressure to bleed off or is my new pump crap. I never ran into this 1 before. I would be a big help to my marriage to get this yard art moving again. Any help would be appriecated. Thanks Breck :? ops:

  2. #2
    Senior Member DYNO OPERATOR
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    You could have a defective fuel pressure regulator. You can replace it with stock or buy aftermarket adjustable regulators. Possibly it is stuck or allowing enough fuel to allow you to get a little pressure while holding the schrader valve open by hand but not near enough to fire and run the engine.

    I never buy parts store variety electric fuel pumps to replace factory pumps with. That can also be your culprit as well as the filter, is it installed backwards? If that is possible with what you have. I use only the new factory fuel pumps. Reason is it is not fun replacing them for warranties even if the parts store makes it good. On ebay lots of luck.

    The fact the pump does come on and cycle is a good sign though. That at least tells you it is not a computer or fuel pump relay problem.

    You may have a fuel pressure guage without knowing it. If you have a vacuum/presure guage that will rewad up to 50 psi, all you need to do is to either get a fitting to screw in the shrader valve port and connect the fitting to your vacuum/pressure guage. Or you can unscrew the valve inside and clamp a hose to the sides of the schrader valve with a hose clamp and watch the guage while cranking.; If you are not cranking at least 38 pisi (guessing) it will probably not start. i AM THINKING IT NEEDS 43 LBS, BUT MAYBE MY MEMORY IS TOO FUZZY. lOOK IT UP IN A REPAIR BOOK AND SEE. (sorry for the caps)

    eD
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  3. #3
    Senior Member SENIOR BUILDER
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    Thanks Ed,
    I had a brain fart, went out and looked at my old pump. On the LS1 motors guess where the regulator is? The pump assembly. I took the new pump out and the regualtor wasn't even in it. Oh wow, have I found the problem? I was hoping. I turned to key on several times to prime the fuel system up and it still didn't do anything but crank. Well you know us hard heads I just kept turning the key on and off and trying it. Well the best it would do before the battery went completely dead was start and run very rough for a couple of secs to a a minute. If you tried to give it gas it would die immediately. Burnt up my battery charger trying to get it to run. Now I have a new 1 and letting it charge again for another go.

  4. #4
    Senior Member SENIOR BUILDER
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    New info, after frying the battery charger and getting a new 1, I managed to get it to run for about a minute. Then by pumping the gas just slightly got it to run for a while and then to halfway idle. Now then I got it to run, and idle, not great and has no real throttle response. After letting it run and idle and even trying to rev it up to clear it out. I noticed a little smoke and a sorry smell. I looked under it for the smoke and seen both pipes glowing pretty good. I have shut it off for a while then went to check what happens. The oil is full and looks clean but has a strong gas oder. And when warms up has like 20 psi. The heat goes from 190-220 and a little more which isn't right for a LS1. I know it wasn't good for it to sit and the bad gas in it isn't helping. My question now since it's more then likely running lean, is do I put injector cleaner in it, octane boost until the bad gas is totally out, or buy a new set of injectors? I need this thing streetable yesterday, Thanks again.

  5. #5
    Senior Member DYNO OPERATOR
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    Where did you previously say anything about bad gas?

    Get all of that gas out of there before you burn your engine up. Bad gas will burn very slow and will still be burning when the exhaust valve is open and even after the exhust valve is closed and it will keep burning until it is gone. At times it can be so bad that it is still burning when the intake valve opens.

    Do anything it takes to remove bad gas. Do not strat engine again.

    Ed
    " Let all things that hath breath, praise the Lord. Praise Ye the Lord" Psalms 150 vs 6.

  6. #6
    Senior Member SENIOR BUILDER
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    Ok, I have started it again a few times after it cooled off. Still runs like crap. Although when it's cold it carries 45psi of oil and 70 when you give it gas. I have no idea how to get all the bad gas out but I'll jack it up and disconnect the fuel filer. I may have to cycle it a few times but I'll try and get it mostly out. Thanks Breck


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