Help! My poor Porsche is dead! (Fuel Pump Trouble)

Just this Friday night, I replaced the fuel pump on my 1973 911T, with a rebuilt original type fuel pump. When I purchased the car it had the wrong type of pump on it, so after discussing it here on the bulletin board, I decided to change it to the correct one. This afternoon, I decided to go for a ride. I didn't get very far. Every time I took my foot off the gas pedal, the car would die. Eventually, the car wouldn't start up again at all. I checked just about everything, did I just get unlucky with my rebuilt pump? I'm very inexperienced with Porsche's any suggestions would be much appreciated!!!

Stephanie

Oops! Forgot to mention its Mechanical Injection!

[This message has been edited by Femalew911T (edited 05-27-2001).]

If your car is carbureted and early Porsche fuel pumps are like those non-porsche ones I'm familiar with, then rebuilt pumps can and should work just fine.

I'm wondering if it ran better just after the fuel pump change. Still, you should certainly re-check your mixture, though it should not have changed.

Applicable to most older style, low-pressure fuel pumps, you can test their volume easily. Take the hose off the carburetor, and stick it in a pop bottle. Run the pump (start the car, for example...there is still gas in the carbs) the pop bottle will fill quite quickly if the pump is working. Less than a minute, perhaps less than 30 seconds.

If the car's not running, you woudl still see a half cup of gas or so in just 10 seconds of running the starter. Keep us posted.

If your '73 is not carbureted, then....Oops, nevemind.

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'83 SC



[This message has been edited by Superman (edited 05-27-2001).]

Stephanie,

The first thing to check is the output volume of the pump ... it should be 900 cc to 1000 cc in thirty seconds. If it is low, the pump may not be at fault. The steel supply line through the tunnel may be partly clogged, or the brass screen prefilter inside the tank may be clogged, too!

When testing the pump, a clear glass jar is best to collect the gas, and be looking out for rust particles in the gas after it is collected.

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Warren Hall
1973 911S Targa

I just went through this, I added a glass filter in the rear to see what was comming in, sure enough there there are small chuncks of rust from the tank. I added another filter in front of the pump to try and save the new one I just installed, but I dont think it has the same pressure now.

Tom
71T 2.4

Hey Warren? "Brass screen pre filter inside the tank"...care to elaborate more about that, the proper solution if it is plugged? Thanks!

The screen was described less than a week ago in this thread:
http://www.pelicanparts.com/ultimate/Forum3/HTML/009081.html

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Warren Hall
1973 911S Targa

Steph, try the easiest thing first. Switch out the new pump with the old and see if that fixes the problem. If it does you either have a bad pump or you hooked it up wrong.

Kurt V
72 911E

Another simple thing that a lot of people don't check is the in-line fuel filter. For sure, you should have changed that when you changed the fuel pump. Those things can get clogged enough to prevent enough fuel from passing through and a lot of times people mistake a clogged filter for other kinds of problems.

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Marv Evans
'72 911E

Could you have a low pressure carb type fuel pump. I know the CIS injection uses a high pressure pump. What does Mech. injection use? Maybe you have the wrong pump! Not the first time someone has gotten the wrong part.

Randy Jones
1971 911

Hello

The MFT have a special Bosch Fuelfilter.

I would go in following steps.

1.) Make sure the fuel IN and Out are not changed on the pump or on the filterhousing.

The car normaly starts and drives but will stall under higher load.

2,) messure the pressure from the fuelintake side. 1 bar is ok. If you have a higher pressure you have the wrong pump or the overpressurevalve is defective.

3.) Remove Fuelpump from car and get two equal sized plastic 5L canisters. Use new hoses and following setup. Overpressure and suction in the filled fuel canister and Prssure into the empty. Run the system one minute amd messure the level. Schould be 2 -3 Liter so both canisters should have the same level.

Next step is too hook up the returnline from the engine and the presure feetline to the engine. Then fill up and run engine from fuelcanister.

OK this is something that is risky. Fuel will not selfignite but the fumes are risky.
Avoid sparking by using a long wire with a switch to run the fuelpump.

If your engine will not start then open the fuelines to check if you have any pressure on the fuelrails injectors. Normaly you can see it. As this is very high pressure wear googles.

If the engines starts but run poor it might be the filter or the coldstartdevice. Also check the base rodlenght to the MFI actuator ( I think 127 mm ). Make sure FE is around the marks ( +/- 5° ).

Grüsse

Stephanie,

I live in Manhattan and I am always out on Long Island. I have owned 8 MFI cars and I would be more than willing to take a stab at your problem... schedule permitting.

Regards,

Marc Weintraub