mcnatprice

My wife was driving her C4 home from a 100 mile trip and it died about a mile from home (I know...thank goodness) She restarted it and it ran and drove for a few seconds, then died again. It started one more time only for an even shorter period and hasn't started since. I had it towed home thinking I would be able to figure it out. I got a Durametric tool and pulled the codes:

P1130 - Porsche Code 361 O2 sensing adaptation, idle range bank 2
P1128 - Porsche Code 360 O2 sensing adaptation, idle range bank 1
P0455 - Porsche Code 94 - Tank vent system (this is an ongoing issue, replaced cap twice)
P1124 - Porsche Code 167 - Fuel Pump Relay, below limit value

Because the code 167 was fuel related, I thought this was the culprit and replaced the Fuel Pump Relay. No love. I still get the code after the replacement. I used the Durametric to turn the fuel pump on and it pumps at about 5lbs psi at the test location under the A/C lines on the right side of the engine. The car turns over fine, but will not fire.

So, I'm thinking either DME Relay (not sure where it's located), the pulse sender (not sure how to test without buying one), or possibly an immobilizer problem (although no code showed that would lead me to suspect it, a Porsche tech (not at dealer) thought it could be the issue)

Any help would be appreciated, I'm running out of hair...thanks.

fpb111

is fuel @ 5psi enough to run one of these?

mcnatprice

I'm not sure...I can't specs anywhere that state what it should be.

mcnatprice

I guess if it's too low, it could be a partially clogged fuel filter, but that's probably a long shot and my life is never that easy!

speed rII

No, pressure should be around 40psi.
5psi would be enough for carburated aplications

Clogged fuelfilter won't cause that. When priming the system, flow is so litle that the pressures would balance.

Fuelpump or fuelpressure regulator.
Or some electrical issue, like fuelpump not getting enough power.

Try to override the fuelpumprelay, and measure the fuelpressure when the pump is on.

mcnatprice

I charged the battery fully since I have been trying to start the car several times and figured the battery may be too low, then checked the pressure:

1.) with the relay in and key on
2.) key off and jumpered the relay pins
3.) using Durametric to turn pump on

I could hear the pump running each time but the pressure only showed 5 lbs on each attempt. So, it seems that if it is narrowed down to either regulator or pump, is there any way to rule out the regulator...bypass or test in any way...before I spend the money on a $400 fuel pump or a $130 regulator?

speed rII

Service Manual

Here you can find manual for the car.
Download the group2 Fuel & Exhaust.

mcnatprice

Thanks for the link to the service manual. I ordered the fuel pump, fuel pressure regulator and fuel filter (figured if I'm gonna smell like gas might as well replace it as well) removed the battery, and fuel sending unit ok, however, the fuel pump looks nothing like the manual and has more connectors than shown...I'm kinda confused. Is there a cover over the fuel pump that isn't shown?

fpb111

If you are looking at the fuel pump on your C4s then you found that it does not live under the battery like a C2.
It also has more tubing that enables it to pick up the fuel from the isolated section of your "saddle" tank.

C4 pump access.

fpb111

There can also be problems with the fuel lines/pickups in the tank. I can't find the thread but there is one that shows some problems with the lines degrading that caused fuel pickup problems when the tank was low.

*If you leave the battery connected then pull the sending unit and turn on the key any time you might have gauge accuracy problems when you put it back together.

EDIT Looks like 55-60lbs fuel pressure. 3.3 - 3.8 bar

*I had bad info here. I changed it from "pull the battery" to "turn on ign with sender pulled."

From the Manual:
l
“The fuel level sensor system need not be calibrated if the battery was disconnected or a plug connection on the instrument cluster or fuel level sensor was removed. The values remain in the instrument cluster.”
20 15 01 Calibrating fuel level sensor system 20-9

mcnatprice

Unfortunately I figured out AFTER removing the battery and it's mount that it wasn't there. Once I removed the correct cover, I removed the sending unit with no problem. However, this is where I got confused. The fuel pump 'appears' to either have some sort of shroud (see blue arrow) over it, or it is totally different than I was expecting. None of the hoses marked with a yellow arrow attach to the actual fuel pump.

The Porsche tech manual says nothing about this...it just says give the pump a 15º turn to the left and remove it. I sure don't want to break anything!

Thanks for all the help.

fpb111

Hard to tell from the pic. Is the whole fuel acumulator attached to the pump? Or does the black rubber line and T need to come off, is there a removable connector, or do you have to cut one of the Oetiker clamps, then pull wires and rotate the pump to remove?
I'm guessing but the rest of it looks like it might be a fuel accumulator/distribution setup that stays with the car.?
Add "Help need to remove C4 fuel pump" to your thread title. Maybe that will get someone that has done this to wade in.

Just yank it out of there! What the worst that can happen? (not)

fpb111

What does the replacement pump look like? Maybe there is a clue there.

mcnatprice

New fuel appears to have one side that possibly connects in some fashion to what I'm guessing, thanks to you, is the accumulator.

mcnatprice

I decided to try to unmount the fuel pump from the bottom of the tank to see if there is a way to separate the fuel pump from all the additional hoses. I turned it just as described in the manual and it came loose. I still don't see any way to disengage the extra hoses to fully remove from tank.