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How not to hook up your fuel pump (solution inside)
I (edit: definitely) hooked up something wrong on my 04 CTT.
Replaced left pump, fpr, and filter. Installed updated "pipe" elbow. Right pump was working (driving on it using the pulled fuse trick about a week).
Before I replaced everything, left pump was 30psi, and when I pulled the left fuse and ran right pump, it was 60psi.
Now, (jumpering the relays to manually run the pumps), the left pump will run for about 5 seconds before building pressure to 60psi. As soon as I remove the jumper wire and the left pump stops, fuel pressure drops to zero. Immediately.
The car will run but is very slow to start and will starve if the fuel level gets too low.
The right pump will run and run and not make any pressure, no matter how long it runs.
Additionally, the right pump level indicator reads 35L on a full tank (about 48ohms) and the left one reads 30L (170 ohms). Instrument cluster shows about 2/3 of a tank full even though the tank is full.
Last edited by knfeparty; 03-15-2016 at 07:44 PM.
Reason: solved
Does "t/s" mean transsiberian? Knowing what model/year we're talking about might help make an intelligent answer.
A FWIW - I had a similar problem with my '06 when I first got it. It went through one dealership who failed to recognize this as a problem (I doubt if they ever did a fuel pressure test, or if they did they didn't notice it dropped as soon as the pumps were turned off..)
You have a leak. The two pumps come together at the fuel filter assembly. It turned out, after the second dealership replaced everything else that there is a check valve - undocumented - in the fuel filter, and mine had failed open. So when the pumps shut down the pressure in the fuel rail immediately dropped. This was after replacing both pumps, and the pressure-regulator.
Replacing the filter fixed it. It was fine from then out.
If I had to guess - and that's all it is - something is leaking from the connection between your left pump and the fuel filter. Or - within the fuel filter.
Where was the revised elbow installed? Since that's been changed that would be the first place I'd check. While it's apart you should look at the connections to the two float assemblies. Apparently it's easy to pull these off while installing the pumps - after they fixed the fuel filter - mine similarly showed 2/3 tank when the tank was full. It was one of the float assembly electrical connections coming loose.
T/S means "troubleshooting." Oddly enough, I am an engineer who fixes things for a living, yet I managed to mess this up.
However, I did find the culprit! (me)
The tiny hose from the left pump goes to one of the existing longer hoses, towards a sucking jet pump I think. I had, instead, hooked it up to the fuel filter using the revised elbow pipe. The line from the right pump that was supposed to go to the filter was instead going to the sucking jet pump, hence the output of the right pump never went anywhere.
The gauge was reading too low because that jet pump line was basically laying down on the float.
Getting the hoses hooked up right solved all the problems- I now have 60 psi from either pump, I retain pressure at the fuel rail with the pumps off, and my gauge reads correctly.
I did what this guy did. See the small hose from the left pump, hooked up to the filter? It shouldn't be there. It should be hooked up to the jet pump line. See the long hose coming from the right side, hooked up to nothing? That goes on the filter, not the jet pump line. The connectors are the same size.
If you would...please post a picture of the correct configuration. I save these in a file for possible repairs in my future. A shot of the incorrect setup will not be of help.
If you would...please post a picture of the correct configuration. I save these in a file for possible repairs in my future. A shot of the incorrect setup will not be of help.
I would, but the right fuel pump is still in the car, so I don't have it available to take a picture of.
The pic of the "wrong" way to do it has all but two hoses right. Just don't hook up the tiny hose from the left pump to the fuel filter, and you'll be fine. Remember that the long hose coming from the right pump has to go to the fuel filter.
It certainly looks similar. I have a new-in-box Porsche left pump so I'll take a look. If it's the same, it would be a STEAL over the Porsche or even the VDO pump.
03-15-2016, 06:19 PM
How not to hook up your fuel pump (solution inside)
