Problems with Gas pump!!!!

[Juan911]

Hi all, I just recently bought a 1991 Carrera 2 convertible and I drove it for about 3 months with no issues. about a month ago the car wouldn't start so I took it to my local mechanic. They figure out it was the gas pump so they replaced it and after a few hours of drive time it went out again. They have done it about three time already with the same results. Do anybody know if there are other parts that might need to be replaced? The car has 80K miles and it sat in storage for about 8 years without any drive time right before I bought it at an auction. Any help or leads will be greatly appreciated. Thanks

[aigel]

Could the tank be gummed up with sediment / sludge from the old gas?

George

[bazar01]

How did they figure out it was the fuel pump?
Did they drain and flushed the tank and lines before the pump?
Have they tried to replace the fuel filter as well?
May not be a bad idea to change the DME relay.

[Fast Corners]

I have seen the plastic tanks collapse because the vent was not functioning. Eventually the pump dies from trying to overcome the suction. If this happens again, open up the gas cap and listen for a rush of air into the filler neck. Another symptom of this is the fuel gage starts reading funny.

[bazar01]

Originally Posted by Fast Corners

I have seen the plastic tanks collapse because the vent was not functioning. Eventually the pump dies from trying to overcome the suction. If this happens again, open up the gas cap and listen for a rush of air into the filler neck. Another symptom of this is the fuel gage starts reading funny.

If the tank venting system is not functioning, you will have a hard time to fill up the tank to full. The head space will be trapped and air inside the tank can't escape.

[Juan911]

OK, that makes sense, every time I went to fill up the tank, I have to keep pressing the gas pump since it kept cutting out. I wasn't able to just let the pump at the gas station run consistently, I had to keep pressing the lever to pump the gas. So what do you recommend at this point?

[Juan911]

I dont' know exactly what they did after all those years of being stored. The car was running when I got it. I'll talk to my mechanic and see if they flushed the tank and lfuel lines and if they have replaced any other parts. Thanks for the reply.

[SAM DACOSTA]

Originally Posted by Juan911

OK, that makes sense, every time I went to fill up the tank, I have to keep pressing the gas pump since it kept cutting out. I wasn't able to just let the pump at the gas station run consistently, I had to keep pressing the lever to pump the gas. So what do you recommend at this point?

My 964 also would not fill by itself, I had to keep holding down the lever and re-starting often. Then I read to invert the pump handle and it would eliminate that issue. Since then, that's how I fill my tank and there has never been another issue. So I'm not sure if that is a correlation to your problem.

Just my 0.02

[Fast Corners]

Inverting the pump handle is exactly how I had to fill my 964. My thoughts on the issue were that the shape of the filler neck or the vent size was insufficient to let the gas go down into the tank with out backing up to the nozzle. This phenomenon should have little bearing on the collapsing tank issue though since this seems to be a standard complaint with this series car. The 964's that I saw with the colapsing tank issue had problems with the vent being clogged. It should be noted that the reservoir was updated in 93 with a new unit (96420107704). The next time the car will not start go open the gas cap and see if the tank has developed a vacuum. If it has this will equalize the negative pressure and hopefully allow the car to start.

[Juan911]

Thank you Fast Corners: First of all thank you all for the posts so far, it is giving a more clear understanding of what is going on with my car. So last night I got it back from the mechanic and i was able to drive it back home, about 8 miles, when I got home I let it sit for about 10 minutes and tried to started with no success just like it did before they changed the fuel pump and flushed the tank and lines. When I saw your post I went back to the car and opened the gas cap and let it breath for a few seconds and put it back. After a few minutes the car started again.

Can you please shed more light on the collapsing tank issue and the vent getting clogged? I think we are onto something and again, it sounds like the gas is not flowing correctly.

Thanks again and I will wait for your reply anxiously.

[Fast Corners]

Juan911,

First things first, you should check out the following website and go to page 102 of 568:
http://www.porsche.com/all/media/pdf/originalparts/en/E_964_KATALOG.pdf

This is a parts diagram and list for the 964 fuel tank, filler assembly and the vent system. Familiarizing yourself with this will help you visualize what the system is comprised of and what each piece looks like. There is no infringement issue here since it is available for download directly from Porsche.

8 miles is a short ride in my opinion for the tank to build enough vacuum to overcome the pump but maybe the shop had her running prior to your arrival to ensure the car was up and running fine. That being said, the car starting after opening the cas cap is a good sign.

From here there are two ways to go.

The first way is to pull the vent reservoir and the associated vent lines from the tank and check for blockages. Take care to look at the condition of the lines before removing them. You may discover that a vent line may be kinked or collapsed prior to removal. If this is the case then you are just that much closer to figuring out what is up.

The second way to go is to drive the car for a while, periodically stopping (keep the car running) and check under the bonnet to take a look at the tank. It is under the front carpet which should be removed for ease of inspection. Also prior to starting the trip you should open the gas cap to make sure the tank is free of vacuum. Check out how the tank looks before you go on the trip so you can see what shape it is supposed to be in. While on this trip, if you see that the tank is starting to change shape (which is fairly evident by the way the flat face above the securing strap looks) then you know the vent system is the culpret. Opening up the gas cap should relieve the vacuum and allow the tank to pop back into shape. Sometimes you can hear this.

Another sign that the tank is collapsing is that the fuel level sender sender starts bending back in towards the center of the tank. It does this a little bit from the factory but when the tank is deforming the deflection is much more pronounced.

On one car that I saw the tank would not pop back into shape. On this one I removed the fuel sender and blew hard into the tank and it popped back into shape. Then I started in on the vent system.

Keep us informed, good luck and ask questions if need be.

[Don Plumley]

Very informative Response - thank you!

Originally Posted by Fast Corners

Juan911,

First things first, you should check out the following website and go to page 102 of 568:
http://www.porsche.com/all/media/pdf/originalparts/en/E_964_KATALOG.pdf

This is a parts diagram and list for the 964 fuel tank, filler assembly and the vent system. Familiarizing yourself with this will help you visualize what the system is comprised of and what each piece looks like. There is no infringement issue here since it is available for download directly from Porsche.

8 miles is a short ride in my opinion for the tank to build enough vacuum to overcome the pump but maybe the shop had her running prior to your arrival to ensure the car was up and running fine. That being said, the car starting after opening the cas cap is a good sign.

From here there are two ways to go.

The first way is to pull the vent reservoir and the associated vent lines from the tank and check for blockages. Take care to look at the condition of the lines before removing them. You may discover that a vent line may be kinked or collapsed prior to removal. If this is the case then you are just that much closer to figuring out what is up.

The second way to go is to drive the car for a while, periodically stopping (keep the car running) and check under the bonnet to take a look at the tank. It is under the front carpet which should be removed for ease of inspection. Also prior to starting the trip you should open the gas cap to make sure the tank is free of vacuum. Check out how the tank looks before you go on the trip so you can see what shape it is supposed to be in. While on this trip, if you see that the tank is starting to change shape (which is fairly evident by the way the flat face above the securing strap looks) then you know the vent system is the culpret. Opening up the gas cap should relieve the vacuum and allow the tank to pop back into shape. Sometimes you can hear this.

Another sign that the tank is collapsing is that the fuel level sender sender starts bending back in towards the center of the tank. It does this a little bit from the factory but when the tank is deforming the deflection is much more pronounced.

On one car that I saw the tank would not pop back into shape. On this one I removed the fuel sender and blew hard into the tank and it popped back into shape. Then I started in on the vent system.

Keep us informed, good luck and ask questions if need be.

[SAM DACOSTA]

This is a very informative thread. Thanks to all who contributed, I've subsequently learned allot from this.

[Juan911]

Thank you all who has contributed so far to this thread. I am currently driving my car a bit more often and the great recommendation by Fast Corners has worked miracles. I have taken the car out and drove it for about 12 miles, stopped and turned the car off, let it sit for a few minutes then try to restart again. The car will not start until I open the fuel cap and let the tank breath. I have done it about 4 times with great success. I guess what I need to do now is to have my mechanic check for blockage of the lines and replaced them if needed.


This is great, I am very happy with the response I got from the thread and hopefully other will benefit as well. I will continue to post questions as I learn more.