What's wrong with my fuel gauge after GT500 pump install?

[bigray327]

EDIT: Solution found, see post 47.

I recently had dual GT500 pumps installed, with big fat lines and Aeromotive fuel rails. Since I also threw in an aftercooler, I had the car re-tuned by one of the big three tuners here in Houston.

Since then, the car has no idea how much fuel I have onboard. When the gauge gets to a quarter of a tank, it drops instantly to empty and reads "0 miles till empty." When it is showing there is fuel in the tank, it reads some ridiculous number of miles till empty, like 300 when the tank is full. I wish! But I only get 12 MPG or so in the city, so that ain't happening.

Here's what I've done for troubleshooting:

• Searched all of the major forums and only found this thread, not much help.
• Used two bottles of Techron to see if maybe something was stuck, no change.
• Disconnected the negative terminal of the battery overnight to try to reset the computer, no change.
• Ran the car while it's reading empty for 20 miles or so, knowing there's a quarter of a tank in there, hoping the computer would catch itself. ONE TIME, the gauge went back up to a quarter of a tank for about 30 seconds, then went back to reading empty.
• Have contacted one of the other local tuners to set up an appointment for a second opinion, but haven't been there yet... dang Shuttle flight is hogging all my time for two weeks.
• I believe the fuel delivery TSB (if it's an issue for 07s) is not an issue here since the stock fuel pump was replaced.

I think this is a computer tune or voltage table issue, but my tuner - who is a smart guy with a very good reputation - insists it is not. In fact, he said the GT500 pumps don't require new voltage tables at all in our S197s, which seems to go against popular opinion here. I don't think it's a sender issue in one of the FPDMs, because it seems to be working normally for three quarters of a tank.

Do any of you guys running dual GT500 pumps have any suggestions for me?

Thanks much,

 

[Freaknazty]

well i have no opinions but i have the pumps and have no problems like that as far as it goofing up , and wtf you get 12mpg ? damn now i really love this turbo lmao im still mid to upper 20's well when im acting right and not sliding sideways on the stock tires lol

 

[bigray327]

well i have no opinions but i have the pumps and have no problems like that as far as it goofing up , and wtf you get 12mpg ? damn now i really love this turbo lmao im still mid to upper 20's well when im acting right and not sliding sideways on the stock tires lol

Yeah, but I drive like a damn fool and don't do ANY highway driving at all. When I'm on the highway, I see over 20 MPGs.

This problem sucks. Dear computer: .

 

[Dex]

Did you take the 2 wires out of the GT harness and put them into the GT500 harness?

 

[SteveP]

Only issue I had is when i unplugged the fuel pump relay by accident.

You might have damaged the fuel level unit when you were messing around with it.

 

[bigray327]

Did you take the 2 wires out of the GT harness and put them into the GT500 harness?

I had it professionally installed by the aforementioned shop, so I don't know. Is there a particular write-up step you can point me to, or a picture?

 

[bigray327]

You might have damaged the fuel level unit when you were messing around with it.

I thought about that, but a) it looked fine during visual inspection when it dropped it off at the installer, and b) it works fine for three quarters of a tank.

 

[Dex]

I had it professionally installed by the aforementioned shop, so I don't know. Is there a particular write-up step you can point me to, or a picture?

There are some online instructions somewhere on the forum. I'll bet you they didnt do it.

 

[bigray327]

There are some online instructions somewhere on the forum. I'll bet you they didnt do it.

Reading step 30 here, I bet you're right. I'll check tonight. Thanks much.

 

[bigray327]

What would the symptoms be if the crossover feed wasn't connected?

 

[Nickoli]

I fought this same battle last winter. The problem i had was that the fuel cross over from the pass. side was not pumping/sucking the fuel to the drivers side where the pumps are. When you know your getting low on gas pop open the pass access hole and see if the pass side is still full. you have to be very carefull lowering the pumps into the tank because the cross over line will pop off easily. I ended up using zip ties to hold the line inplace so it would not pop off during re-install. Maybe your really getting around 24mpg (whitch sounds about right) and its only using half the tanks compasity???
http://www.modularfords.com/forums/showthread.php?t=107000&page=1

 

[bigray327]

Thanks, Nickoli. I had a feeling it might be that. I can't get to page 2 of your linked thread, for some reason, but I think it's the crossover hose leaking a little.

By the way, that picture of your car makes my naughty parts move.

 

[Dex]

I would check those two things. Check the wires first.

 

[Nickoli]

Thanks, Nickoli. I had a feeling it might be that. I can't get to page 2 of your linked thread, for some reason, but I think it's the crossover hose leaking a little.

By the way, that picture of your car makes my naughty parts move.

wayyyy too much info lol

 

[bigray327]

I broke into the fuel tank tonight. The wiring seemed to be OK. But look what I found...

The lock ring wasn't fully seated. I fixed it, which is a bitch to do with only two hands, and I'll drive it for a while and see what happens. It seems logical that the computer wouldn't read the correct fuel pressure if there's an air leak in the system.

I noticed that when I blip the gas, the fuel pressure on my gauge doesn't dip down to almost zero before it goes back up. Now it only goes to 10 psi or so before it goes back up.

Hopefully this will fix me up.

 

[05stroker]

I broke into the fuel tank tonight. The wiring seemed to be OK. But look what I found...

The lock ring wasn't fully seated. I fixed it, which is a bitch to do with only two hands, and I'll drive it for a while and see what happens. It seems logical that the computer wouldn't read the correct fuel pressure if there's an air leak in the system.

I noticed that when I blip the gas, the fuel pressure on my gauge doesn't dip down to almost zero before it goes back up. Now it only goes to 10 psi or so before it goes back up.

Hopefully this will fix me up.

Good luck and keep us posted.

 

[Wyld]

Let me guess, DTE FLI fuel DATA error? Thats what it would be flashing if its doing what your saying its doing. Its bad gas give it sometime i have had the same problem. Also i noticed your in houston.. which is wierd because it did this to me in Freindswood houston after I got gas at cheveron. Its not the fuel pump either. I never had the problem with it after that, but then again i havent been back to cheveron. My lock ring was fully seated at the time!

 

[bigray327]

By the way, I still had gas fumes in my garage this morning. It's less noticable than before, but still there. I bought a new o-ring and should have changed it out when I was in there, but the old one looked fine so I left it. I should have changed it just because I was there... it was only $6. No puddles in the garage, though, so it's obviously leaking fumes, not liquid gasoline.

Let me guess, DTE FLI fuel DATA error?

Nope, didn't get that one. I'll check it again when it drops to 0 again, just to be sure.

Its bad gas give it sometime i have had the same problem.

Interesting. I read an advisory about the gas in Houston on one of the local tuners' sites, but I haven't seen any performance issues. Are you thinking that the bad gas is causing the arm to stick? It seemed to be moving in its full range of motion just fine when I was in there last night. I figured the two bottles of Techron in the last two weeks should have covered it.

 

[Wyld]

By the way, I still had gas fumes in my garage this morning. It's less noticable than before, but still there. I bought a new o-ring and should have changed it out when I was in there, but the old one looked fine so I left it. I should have changed it just because I was there... it was only $6. No puddles in the garage, though, so it's obviously leaking fumes, not liquid gasoline.


Nope, didn't get that one. I'll check it again when it drops to 0 again, just to be sure.

Interesting. I read an advisory about the gas in Houston on one of the local tuners' sites, but I haven't seen any performance issues. Are you thinking that the bad gas is causing the arm to stick? It seemed to be moving in its full range of motion just fine when I was in there last night. I figured the two bottles of Techron in the last two weeks should have covered it.

Well everytime ive went to cheveron that has happend to me, it never fails! I had it do this to me today after going there so I will be taking my car to the dealer soon if it persists.

 

[bigray327]

Well everytime ive went to cheveron that has happend to me, it never fails! I had it do this to me today after going there so I will be taking my car to the dealer soon if it persists.

Holy crap. Thanks for the heads up. I usually go to Shell, but since this issue has been happening, I've been using Chevron because of the techron in the gas. Ugh.