Fuel pumps running versus inop gas gauge

[RevRon]

I am in the middle of a fuel pump night mare. HISTORY - bought my 2006 Cayenne Turbo S from a couple of serial liars on fleabay. Ran OK when it came off the transporter, so I put about a half tank of gas in it. Next morning battery was dead. Jumped it and drove it to charge the battery - OK. Next morning battery dead again. Huge current draw somewhere - not solved yet. Internet expert suggested disconnecting the ground wire to keep battery from discharging. So made some repairs to previously burned driver's seat wiring. A week later connected the battery. Car would start but then die. Checked fuel pressure 4 bar at start but then would fall off and die. Everybody said fuel pumps . so I changed them. Same problem. They I noticed the gauge was not working. So I replaced both senders, the filter and the regulator. Same problem. NOW - to move the car, I pulled the relays and jumped hot wired the pumps. Car starts and runs fine!!! I THINK - the computer is getting an empty tank reading like the gauge so shuts the pumps off after start up to prevent damage. I DON'T KNOW - how to reset the computer??? I have recently purchased an icarsoft POR3.0 but can't see any info on the fuel system - yet. But lots of other codes to clear. Any idea where I should start? Thank you, Ron

[BRAIDusa]

Originally Posted by RevRon

I am in the middle of a fuel pump night mare. HISTORY - bought my 2006 Cayenne Turbo S from a couple of serial liars on fleabay. Ran OK when it came off the transporter, so I put about a half tank of gas in it. Next morning battery was dead. Jumped it and drove it to charge the battery - OK. Next morning battery dead again. Huge current draw somewhere - not solved yet. Internet expert suggested disconnecting the ground wire to keep battery from discharging. So made some repairs to previously burned driver's seat wiring. A week later connected the battery. Car would start but then die. Checked fuel pressure 4 bar at start but then would fall off and die. Everybody said fuel pumps . so I changed them. Same problem. They I noticed the gauge was not working. So I replaced both senders, the filter and the regulator. Same problem. NOW - to move the car, I pulled the relays and jumped hot wired the pumps. Car starts and runs fine!!! I THINK - the computer is getting an empty tank reading like the gauge so shuts the pumps off after start up to prevent damage. I DON'T KNOW - how to reset the computer??? I have recently purchased an icarsoft POR3.0 but can't see any info on the fuel system - yet. But lots of other codes to clear. Any idea where I should start? Thank you, Ron

Wow. This sounds like a nightmare. I don't have any suggestions for you though, sorry. Do let us know what it was once you solve it.

[fintstone]

When you replace the filter/pumps, the mess of hoses and wires in the tank can interfere with float movement. I had a shop replace my pumps and the gas gauge did not work correctly. They told me it was a bad instrument cluster, and I would have to live with it (no accurate fuel gage) or replace the instrument panel. I opened up the tank and solved the problem by rerouting lines inside.

[RevRon]

Update. Traced the problem to "the computer" that sends the signal to the sensors. If it does not send the signal(s) it thinks the car has no gas and shuts the pumps off after about 15 secs. I removed both fuel pump relays, ran wires from both "always hot" terminals (#30) to toggle switches under the dashboard. Wires then go back to the #87 terminals, which go directly to the fuel pumps. Now the fuel pumps run when the switches are on and the car drives as normal. What I don't know is why "the computer" decided to stop sending a signal to the sensors, nor how to fix/reset it. Any ideas?