Fuel accumulator or fuel pump?

RazorRacer · 04-30-2002, 04:53 AM

To my fellow Porsche owners, here is a question for you.

Should I change the fuel accumulator or the fuel pump? I want to change the fuel pump, but it costs about four times more. Here's a little background:

1978 Targa
Aquired one month ago, third owner
65K miles
No record of fuel pump replacement
Fuel filter has been changed 3 times (once by me)
Fuel accumulator has been changed twice
Fuel pump has never been changed

The problem is the engine is starved for fuel when it gets hot. I am going to test the performance difference between a full tank and a low tank.

Here are some related links:

I thought the fuel filter fixed the problem, but it didn't

Then I thought it was a clutch problem, but it wasn't

I vote for the fuel pump. What is your vote?

Joe Bob · Joe Bob's Garage

Try the check valve that screws into the neck of the fuel pump. 18 dollar part.

makaio · 04-30-2002, 05:30 AM

Have you done a fuel system pressure test? That will tell you if your fuel pump is bad or not.

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rlane · 04-30-2002, 06:44 AM

Razor...in my run thru this same problem I replaced the fuel filter...then the accumulator..then the check valve...finally we checked the pressures...it was difficult because mine only happened when really warmed up. I had told the shop guys this but I think they only got the engine/engine oil temp up...I think the fuel pump itself must get a little warm because my problem only occured after 20 minutes or so of driving in 60-70 deegree ambient temp) Anyhow the fuel pump was replaced and it has been purr-fect ever since!

Superman · 04-30-2002, 08:10 AM

Richard had a good result from replacing the FP, but I strongly recommend testing first. The FP should be capable of achieving a certain fuel pressure, and also it should be able to move a specific volume of fuel in one minute. If it does these two things, then it is not your problem.

I have replaced many, many parts in my day that did not need replacing. This happens when I GUESS at what is wrong. Fuel pumps are among the parts I have replaced needlessly. I have found plugged (usually with rust) and bent/kinked fuel lines to be a problem more often than faulty fuel parts.

rlane · 04-30-2002, 05:37 PM

Good point Superman..this was my first significant problem with my car and I needlessly replaced a bunch of parts due to guesswork and faulty logic. I would have been better getting the pressures and volume checked first (but hey it was a good learning experience and I learned a lot about my fuel and ignition systems!!

Joe Bob · Joe Bob's Garage

Hot start problems after a long drive on two of my 3.0 CIS motors BOTH turned out to be check valve problems.....I diagnosed it by checking fuel pressure after a long drive......

Fuel pressure bled off immediately.....not as designed.

RazorRacer · 05-16-2002, 04:11 AM

On the 1978 they call the check valve a fitting. The part doesn't look like a check valve. It looks like it takes the fuel and splits it into two directions.

How is changing this going to solve the problem?

wckrause · wckrause's Garage

The item in red is the check valve. It's about $16. Of all of the components that help to hold residual pressure it's the cheapest.

http://www.pelicanparts.com/catalog/images/fuel_injection/new_images/fi_fuelsystem_2-1c34a.jpg

RazorRacer · 07:00 PM

Yes. This is the part that I have at my house (ordered it about 1 week ago). But it's not a check valve the way I know a check valve. It's more like a flow splitter. I will change it, but I don't see how this will fix the problem.

Also, note that it's not called a check valve on the 1977-1979 models. It is called a connection. Could it be that this part became a check valve on 1980-1989 model 911 cars?