flyinmedic

Ok so we replaced the intake pump with an aftermarket pump on my 06 ZO6. Everything works fine except the fuel gauge. WHen the car is filled up with fuel it only reads 3/4 tank. As it goes down it will hit the 1/2 -1/3 mark and immediatley go to empty with a service fuel system warning. I can reset it with HP tuners but then it will only go to 1/4 tank and no farther. Has anyone had this problem? Any suggestions? The car only has 25K miles on it. Thanks in advance.

eboggs_jkvl

I'm guessing the crossover pipe isn't seated properly. I'm not the tank expert so someone else needs to chime in on this one.

Elmer

Motorhead-47

I'm going to state the obvious....you mucked up something with the driver's side tank fuel sending unit when the new pump went in. The Vette has two fuel sending units, one in each tank. It expects the driver's side sending unit to read full until the passenger side tank empties and the passenger side sending unit shows the tank is empty. When the car reads 1/2 full your driver's side tank is full and the passenger side tank is empty.

Any combination of gauge readings other than the scenario above results in the "service fuel system" generic message. Typically there are other error codes you'll get pointing to the fuel sending unit error in the tank.

Sounds like you'll get to drop that tank again and recheck all of your work.

taken19

Motorhead, I replaced my fuel pump with a walbro 255 unit and will be firing up the car for the first time later this week. The pump assembly came out a bit rough from the tank, but everything looked intact upon inspection. With regard to your statement above, would any of us see visible damage to the sending unit for the above symptoms, or is it internal damage? I even went so far to clean the wipe pattern with alcohol to be sure I wouldn't have issues.

Any history or personal experience may help someone attempt to diagnose the problem flyinmedic is having. Specifically, what could or should he be looking for if he drops the tank again?

hydbyj

it is next to impossible to get the fuel float hooked up to the sending unit on install when changing pumps. the pump measures close to the 4" hole it goes into, you need hemoststats like a surgeon would use during a heart transplant to try to snap the float properly into the sending unit. even experts have trouble with this one

Motorhead-47

Not knowing exactly what his replacement consisted of it is sort of hard to tell. There are 4 wires in the plug on the OEM pump. The two smaller gauge green wires are the fuel sending unit. If either of those two were damaged or if a terminal backed out of the harness on install (I've had this happen when I plugged that connector in on the bottom of the flange) then you'll get some very strange readings. I'd start with verifying that those wires are firmly inserted in the connector. Unfortunately that connection is on the bottom side of the flange.



I've seen a post some time ago that tells us what values should be on those two terminals when the tank is full and when the tank is empty. If we had those you could ohm out the connector while everything is still in the car and then you'd know for sure. Let me browse and see if I can find them.

flyinmedic

Thank you for the info, it would be great if you find those readings. The setup is an Aeomotive A1000 in tank pump and a DP 2000hp external pump. When the car is almost empty it will take over 13-14 gallons so hopefully it's something simple.

Motorhead-47

Out of my service manual....

Resistance

• Empty tank reading 247-253 ohms resistance

• Full tank reading 38.5-41.05 ohms resistance


I have not installed an A1000 but I believe it uses the stock fuel sending unit so those values should be good. The connector I spoke about above is NA in this case.

flyinmedic

Thank you, gonna get it fixed (hopefully) first week of Aug. I'll update what we find.

torquetube

GM inverted the sender's range in '07 or '08 so that a poor connection would cause the gauge to err on the empty side rather than full.

On the OP's '06 car, each sender should read 40 empty and 250 full.

To make certain that the float lever isn't hung up on anything after you've completely reassembled a tank, verify 40 ohms resistance with the tank right side up. Then hold it upside-down and check that the resistance has gone to 250.

Motorhead-47

Thanks for the correction..my service manual is for a 2009.

Question: If you walk into the dealership to buy a replacement fuel level sending unit for an earlier model car do you walk out the door with one that reads 40 empty and 250 full or 250 empty and 40 full?