Jim bailey - 928 International

sounds like a dead pump...the sound of silence

RyanPerrella

Jim,

which one should be replaced? Do i start with the main pump or do i replace both, how do i diagnose the in tank pump?

Do you need both, why are there 2 pumps?

Jim bailey - 928 International

Porsche decided the GT needed the intank pump then used it on all later cars. When the intank pump fails it stresses the outside pump which is now sucking through a dead pump. Best to just replace BOTH !

RyanPerrella

Question being, I dont think both would fail at the same time. If the main pump, the one that mounts to the chassis dies shouldn't the in tank pump at least start the car. Or could I have been driving the car with the in tank pump dead for the past year and now that the main pump fails it just dosent run period?

RyanPerrella

Gotcha Jim.

Am I ok buying both used from you, or do you think I should just replace with new? Do you have both in stock, new and used?

Thanks

Jim bailey - 928 International

Try putting power directly to the pumps use a wire from the battery to the + terminal on the pumps. Drop down the metal cover at the rear of the fuel tank and see what happens. You can also reverse polarity to try to spin the pump backwards that SOMETIMES gets it going... BUT you really should probably buy new pumps the in tank pump especially because draining the tank is not much fun stuck on the side of the road at night in the rain with a real hottie riding in the passenger seat who is eager to get into your hottub....You get the point

RyanPerrella

CRAP!

And I just filled the tank up 3 miles before this happened!

What the hell do i do with 20 gallons of fuel??????

leperboy

Ryan, five gallon jugs are cheaper than five gallons of gas. Do you have another car you can put it in, five at a time? Then save the last five to put back in your car. At least you've got fresh gas.

Matt

RyanPerrella

is it not possible to get the in tank pump from the rear hatch. I remember on my car pulling up the carpet when doing the rear shocks that there is about a 6-8" hole in the body work with a large rubber cap that goes over it. I would assume like on other cars this is an access point to the fuel tank, but I could be wrong.

RyanPerrella

I just checked and it sure looks to me that the pump can be accessed from under the carpet in the rear hatch. I dont know if this wasnt available on the early production 928's but it sure looks like the fuel pump that i am looking at.

Is there still a need to drain the fuel and remove the tank itself to replace this pump?

Jim bailey - 928 International

You are looking at the fuel level sender and fuel return line ....the intank pump is screwed in from the bottom of the tank

Schocki

You should be able to clamp the fuel line from the tank to the main fuel pump. No draining necessary.

If you jump the fuel pump relay, the pump should run. Even with the ignition off. Buy all the pumps and a new fuel filter. Replace the main pump first and drive the tank empty. There are many 928's on the road with a broken intank pump and the owners have no idea...

Tails

As previously mentioned some of us have made relay jumper lead with a switch installed into the lead.

I have made my lead sufficiently long enough that I can jump terminal 30 and 87 of the fuel pump relay and then activate the circuit externally from any position around the car.

In your case to undertake a logical fault finding exercise regarding the internal and external fuel pump to determine which has failed I would suggest that you undertake the following fault finding exercise.

Note: The internal and external fuel pumps are in a parallel circuit powered from the fuel pump relay XXVI.

Step 1. Make up a long jumper lead with an on/off switch in the circuit and spade connectors at each end of the jumper lead.
Step 2. Remove fuel pump cover - passenger side under rear bumper, and expose external fuel pump and filter.
Step 3. Check fuel pump fuse - No. 15, just to be sure it is OK
Step 4. Disconnect battery negative lead
Step 5. Remove fuel pump relay XXVI
Step 6. Install jumper lead to terminal 30 and 87 of fuel pump relay socket ensuring switch is "OFF"
Step 7. Take jumper switch to rear of car so that you can activate switch whilst observing external fuel pump
Step 8. Reconnect negative lead to battery
Step 9. Turn on ignition
Step 10. Turn on jumper lead switch and observe or feel whether external pump is running or not.
If not then listen to see if internal pump is running. (Don't leave power on pumps for too long at a time in case they overheat as they require fuel to be passing through them to keep them cool)
Step 11. If external pump is not running and if as you describe you hear a "clunk" when power is applied, then the pump may have jammed due to foreign matter jamming the direct displacement rotor.
Step 12. If this is the case then you need to run the pump in reverse.
Step 13. Turn off jumper switch and ignition and reverse leads to external pump.
Step 14. Turn on ignition and turn on jumper switch in short cycles and see if pump frees up and runs in reverse, if it does then you have unjammed the rotor and the foreign object has moved.
Step 15. Turn off jumper switch and ignition
Step 16. Install a clamp on fuel line before fuel pump and filter. Remove fuel pump and filter and drain fuel pump out the suction end and hopefully the foreign object will come out with the fuel. As a check drain pump into a container through a fine filter (panty hose is a good filter medium). Check filter for foreign object. Hopefully you will find the object. If necessary you may need to flush the fuel pump with fuel via the outlet through to the suction to flush out the object.
Step 17. On reassembly recommend fit a new fuel filter(as a precaution to protect injectors)
Step 18. Reinstall fuel pump (don't run fuel pump externally of the system as any residue fuel or vapour may explode of catch fire within the pump and do you an injury).
Step 19. Switch on ignition and then switch on jumper switch and if pump runs- great work.

If the external pump runs then the internal pump maybe at fault. If so this pump is at fault it will reguire the internal puto be removed, which is a bigger job, requiring the fuel tank to be empied of fuel.

Step 1.Clamp off fuel line to external fuel pump, between internal fuel pump outlet and external fuel pump inlet.
Step 2. Disconnect negative terminal from battery
Step 3. Remove external fuel pump and filter
Step 4. Drain fuel tank into cotainers
Step 5. Disconnect electerical connection to internal pump
Step 6. Undo nut holding internal pump in fuel tank and remove pump
Step 7. Check filter to see if blocked
Step 8. Fully flush out pump with final flush with a non conducting - non-volatile liquid to remove any fuel or fuel vapours
Step 9. Carefully check pump operation with 12 volt power source (don't run for too long if it rotates
Step 10. If pump is OK reinstall into tank with new gaskets etc. If not OK renew internal pump.
Step 11. Install external pump, filter etc
Step 12. Bleed fuel through both pumps before tightening final clamp on outlet from fuel pump and filter and tighten clamp
Step 13. Reconnect battery, turn on ignition and then turn jumper switch on and check whether both pumps work. if so good job. If not then renew pumps as necessary

Tails 1990 928 S4 Auto

RyanPerrella

Tails,

Thanks for taking the time with those steps. I will try and run the pump in reverse as has been suggested.

I have gone ahead and ordered the 2 pumps. In the meantime I have plenty of other work to do on the car.

RyanPerrella

Schocki,

Thanks for the idea of installing the main pump and running the car till its empty and replacing the in-tank pump at that point.