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Fuel Pressure bleeding off

This is a discussion on Fuel Pressure bleeding off within the General Help forums, part of the LSx Technical Help Section category; I agree...the racetronix kit is the one I would go with also. Actually....it is the one I went with. I ...

  1. #21
    Veteran 0rion's Avatar
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    98 Formula
    06 duramax

    I agree...the racetronix kit is the one I would go with also. Actually....it is the one I went with. I have a 98 so no venturi needed for the bucket but it's a well put together kit. I did the hotwire kit also.

  2. #22
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    Red
    2002 WS6 Trans Am

    Update and new problem! Turned out it was the regulator on the assembly. We decided to hook it all back up and check it before bolting the tank back in the car, and I am sure glad we did as the new pump and hose did not fix the problem. Long story short, I ended up buying a whole new assembly because you can't buy the regulator separately for this car. Put it all back together and everything was working fine, holding pressure and starts right up every time! However, while driving it yesterday the I looked down at the gauge cluster and the check gauges light was on and the fuel gauge is buried below empty. And I know it has plenty of gas in it. It was working fine up until that time. Obviously I'm thinking the sending unit may have went bad in my brand new pump assembly! The gauge moves when you turn the key on but barely. Any thoughts or suggestions? Is there a way I can test the wiring to pinpoint if the problem is in fact the sending unit or perhaps the gauge? Very frustrated!

  3. #23
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    I went through this with mine......you can ohm the sender coming out of the tank at the harness by the rear. Mine ended up being a ground issue. I cleaned the ground up by the drivers side brake hose mount and all was well. I will have to look it all back up again as it's been years but the 2 purple wires are your sender's wires and the ohms aren't 0-90 like the older cars.....they're like 40-259. I'll have to look it all back up again though to get you the exact colors and ohms. It really kicked my ass figuring mine out. I chased wires for days. I ended up grinding the ground down to bare metal and haven't had an issue with it for 8 years.
    First step is to ohm that harness coming out of the tank to make sure your sender or the wiring back to the sender isn't your issue.
    Last edited by 0rion; 05-05-2014 at 10:22 AM.

  4. #24
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    Red
    2002 WS6 Trans Am

    Very helpful. Next step is to go by an ohm meter. Thanks.

  5. #25
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    remembering that this was 8 years ago for me.....I remember it being a huge pain in the ass. I worked on it and worked on it before finally redoing the grounds and getting it working. I've always said it was a ground issue but honestly I don't what the hell I did I just know it started working again. I had cleaned that ground prior but the last time I took it to bare metal and that seems to be what did it. I went as far as ohming it out at the pcm to see if there was a broken wire between the tank and pcm. I pulled the pump again and cleaned the sender and switched my wires. All kinds of goofy shit. I will say that if you can ohm it at the harness coming off the tank and it ohms out correctly with what you think should be in the tank (40ohms is empty and 259 is full) then that'll save you from dropping the tank because that rules your sender and harness out. After that I would check your ground and then check connections at your plug. Things like that.

  6. #26
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    Red
    2002 WS6 Trans Am

    Yep...as soon as I saw that gauge down below E, I knew it was going to be a pain in the ass! OK, I crawled under the car and unplugged the connector that goes to the tank. It has seven wires! Green, Purple, Orange, Gray, Black, Black with white stripe, and Gray with black stripe....Not sure how to check ohms

  7. #27
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    Well... nuts. The new pump works great but pressure is still bleeding off. I read through the fuel system diagnostic in the service manual this morning and it appears that it should hold pressure for at least one minute after the ignition is energized. It isn't supposed to stick at 58 psi the entire minute, but it also should not fall to zero. The likely culprits are a leaky injector, bad fuel pressure regulator or a hole in a hose. Looks like I may be replacing the regulator so glad I went with a trap door rather than dropping the tank.

  8. #28
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    I can't find my schematic but I know for sure that the purple is your sender wire so you should be able to check it across that and blk. There's no voltage on the tank side of that harness so it won't hurt to probe the wires.

  9. #29
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    Red
    2002 WS6 Trans Am

    I tried purple and black and got nothing. Will try purple and everything else whenever I can get back to it. pajeff02- it is probably your regulator like mine was. I may have to pull mine back apart to, but wasn't smart enough to do the trap door thing. Can you tell me exactly where to cut in case I do have to go back in. I don't want to drop this tank again!

  10. #30
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    grey/blk I believe is the other ground. Solid grey is power. Don't let these trap door people sway you....it's always better to do it without hacking up your car. If you clearance that filler neck area it's not bad at all.

  11. #31
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    grey/blk I believe is the other ground. Solid grey is power. Don't let these trap door people sway you....it's always better to do it without hacking up your car. If you clearance that filler neck area it's not bad at all. If you're not getting anything from that sender it looks like you'll need to drop the tank and check the wiring to the sender and the sender itself. Make sure it's making contact to the resistor and that the resistor is clean. As the float rises and falls the arm slides up and down that resistor.

  12. #32
    Moderator Firebirdjones's Avatar
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    Orion will steer you in the right direction. Don't do the trap door mess, do it the right way. It's not bad to drop the tank as Orion said, clearance the filler neck area, let the rearend droop, and that thing just about falls out

  13. #33
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    Red
    2002 WS6 Trans Am

    Thanks guys. One more dumb question though...What do you mean by "clearance the filler neck area"?

  14. #34
    Moderator Firebirdjones's Avatar
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    Orion is talking about the small sheetmetal opening where the filler neck fits through before it meets the quarter panel. By trimming that you then don't have to approach the car with the tank as such an extreme angle to install or remove it.

    Maybe Orion could explain it better

  15. #35
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    that's pretty much it....the best time to have done that was when it was out the first time. It's not hard to find really.....it's where the filler neck hits that opening and makes it a pain in the ass to get out. Grind that back some and that filler neck just slides right now. Don't forget to hit the spot you ground out with paint though to prevent rust. It's behind the quarter panel so you can't see it.

  16. #36
    Moderator Firebirdjones's Avatar
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    Orion, do the 98's have a rubber tube connection on the filler neck? I'm thinking since you have a steel tank, then probably not???
    I know the 2000+ Fbodies do with their plastic tanks, and on mine that rubber tubing allowed me to manipulate the filler neck a bit to make lining things up easier too.

  17. #37
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    nope.....all metal filler neck. That's what makes it such a pain in the ass. You have to roll that tank and have the car way up in the air to get it out of there.

  18. #38
    Moderator Firebirdjones's Avatar
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    Okay that's what I was thinking. So trimming that sheetmetal around the neck is a big plus.

  19. #39
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    2002 WS6 Trans Am

    Got it. The first time io was out I had it on a lift at my buddy's shop and he did most of the work. If I have to drop it again I'm going to do it in the garage because I don't want to pay the shop fee's again. I've already invested way more in this project than anticipated...I guess that's how it usually goes though...

  20. #40
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    Checked all the wires from the sender, got nothing. I guess the problem is up there....Damn I don't want to drop that tank, may put it off a while and just watch the mileage. I'm not sure how you get the tank out with the muffler right under it and it the way?

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