Hi Patrick, I also took a picture of the gauge between the fuel pump and accumulator but i cannot insert the pic here either. ): But i did disconnect the line from the accumulator and the line does in fact go to the front of the car so I am assuming that's the line that feeds from the fuel pump. Also, I sucked on that line and fuel came out so I am almost 100% sure that it comes from the fuel pump/tank. The fuel pump is a bosch 0580254984 which should have an integrated check valve. Is it possible that this particular pump did not come with a check valve? A check valve is 20 quid so I might as well buy one and see if my system maintains pressure. I mean the pump is new. And to clarify, when i put the gauge between the fuel pump and accumulator the pressure went to a little over 70psi and dropped back to 0 immediately after i switched the fuel pump off. It also read the same when i put the gauge between the WUR and fuel distributor. I think this is the part i need. https://www.ebay.co.uk/itm/PORSCHE-944-Fuel-Pump-Check-Valve-for-electric-pumps/184390805025?hash=item2aee8c6621:g:-fQAAOSwdwpfKpsY

Not sure if the 944 uses the same check valve as a 911 but ill do more research. This does come with the 3 washers though. (:

Hi Tony, I am sorry I don't follow. What valve are you talking about? The valve on the gauge is closed.

Landyman96,

that is the correct check valve and the three crush fitting washers but you need the end cap nut to hold the banjo fuel line onto the check valve. the banjo fuel line is connected to the fuel pump by a bolt that is hollow with side holes to allow the fuel to flow into the banjo fitting. You replace the bolt with the check valve which means you need the end cap nut.I did not realize that I need the end cap nut until I tried to put it together. I don't remember where i acquired the nut.

This is a picture of the parts you need for the external check valve.

http://forums.pelicanparts.com/uploa...1604183871.jpg

Residual pressure test.........
 

Landyman,

The 70 psi. reading (gauge installed between FP & FA) you were getting is the system pressure and the shut-off valve was open. If it was closed, you will get a reading between 90~100 psi. with a good fuel pump. When the gauge is installed between the FD & WUR, control pressure (valve open) and system pressure (valve closed).

Repeat the test and take some pictures. The fuel pump comes separately without check valve. The 944 check valve will work if you have compatible banjo fitting. I used a 944 check valve for my ‘78 SC.

The FP check valve has 2 spec (inlet/outlet). Inlet connects to the FP and outlet to the banjo fitting of the main delivery line.

Tony

My 1980 SC targa came with the built in check valve and it was cheaper to just add the external check valve. The external check valve has been on the car for over 20 years.

Hello, I purchased the external check valve and from the pictures I took, my fuel pump has the end cap required. Looks exactly like the one on your drawing Pat, thank you. I will install the check valve and see if it fixes my problem and if not I'll do some more digging. Ill keep you guys posted.

Hi Everyone, I purchased the wrong check valve so I had to wait another week for it hence the lack of updates. Anyways, i learned a few things which i will list as it might help someone else. 1st, fuel pump part # 0580254984 has an external check valve (at least mine did, a 1980 911 sc US spec). I've read in numerous places that these pumps don't. 2nd, the check valve for this fuel pump is part #893906093. Their are 2 types of check valves, 911's need the one with the aforementioned part #.

Now, after much messing around with the car I am still having problems with both hot and cold starting. The new check valve seems to have made the fuel pump run a lot quieter however the car is still very hard to start. After testing pressures in both hot and cold i realized something quite interesting. It seems that my fuel pump sometimes does not build pressure. The fuel pump is running but it acts like it doesn't have any fuel. If you turn the fuel pump off and back on again it starts building pressure again. This leads me to believe that the fuel pump, although new looking, is defective. Also, new symptom, car stalls sometimes which i presume is because the fuel pump stops pumping fuel even though it is running.

One last question for all the Jetronic Guru's in this forum. What does the shutoff valve do exactly on a fuel pressure gauge?

Thank you in advance,
Landyman

Have you retested the hold pressure from the fuel accumulator/fuel pump? The shut off valve is actually a switch valve that provide fuel pressure from two sources and you switch between the two sources while performing a test setup on the cis.

Hi Pat, I did check the residual fuel pressure and again I got 0 PSI almost immediately after i shutdown the fuel pump. Now my new problem is that my pump is hit or a miss. Sometimes I get 70-80 PSI while other times I get 40 PSI which is when the engine starts to stumble and sometimes I get 0 PSI which is when i stop being able to restart the car. The fuel pump seems to act up more and more the warmer the car gets. I double checked that my gauge was working by opening the line connecting to the WUR and seeing if fuel comes out with the fuel pump on and it was dry. Then I fiddled with with the fuel pump again by turning it off and back on again and again opening the line connecting to the WUR and fuel did come out this time. This time the engine started first try. With the new check valve my fuel pump seems to run much quieter. l'll order a new fuel pump this week to install it on the car next weekend.

Would a bad fuel pump influence residual fuel pressure? The scenario I came up with in my mind is that a new fuel pump and new accumulator were installed on the car to fix the residual fuel pressure issue which it didn't so they decided to wire the pump to run with the ignition in the on position. I believe that the check valve was the original issue but since the pump had to work so much harder to maintain fuel pressure, it wore out hence it was so loud. Now with the new check installed, the pump is much quieter yet its on its last legs which is why sometimes i have fuel pressure and sometimes i don't. Does this sound like a plausible conclusion or am i just trying to rationalize buying a new fuel pump?

sent you a PM

The check valve you install is supposed to prevent any pressurized fuel from going backward from the fuel delivery system back into the fuel pump. An intermittent pump ought not to produce the symptoms you describe with respect to residual pressure.

One other thing to check is the supply of fuel to the fuel pump. While I doubt it, it is conceivable there is some kind of blockage in the short hose which connects the tank outlet to the pump. A slightly more likely possibility is some blockage inside the tank itself. You can get a fairly decent look inside the tank if you remove the fuel level sender. Trickier is seeing down into the bottom of the tank, where trouble could reside, with fuel in the tank. Draining the tank might be useful both to allow better inspection, and to make swapping pumps easier. Normally, one pinches off the rubber line with vice grips or the tools made specifically to pinch off lines. If you have drained the fuel you don't have to wrestle with that. But most pump changes are made with fuel in the tank, and draining it has its own challenges.

Correct me if I'm wrong when it comes to a CIS fuel tank....but I'm pretty sure that once you drain the fuel from the tank and remove the fuel level sender to shine a light down into the bottom of the tank, all you are going to see is a brownish-red bakelite/plastic swirl pot with a clipped on lid covering the outlet port of the fuel tank.

You are correct that you cannot see inside the swirl pot, but if some jellied old gasoline, or significant rust, or foreign objects, are to be found you know more than you knew before.

You could pull the big plug, and extract the swirl pot, or parts, if I remember what I once did, but that is more of an undertaking than looking through the hole on the top.

Swirl Pot.......
 

Walt,

The plastic swirl pot is installed before the 2 halves of the fuel tank are welded. Once they are welded together, you can not take the big swirl pot out of the fuel tank unless you cut a big hole to extract it out.

Tony

Tony - doesn't part of the swirl pot - the filter, for instance, come out or can be removed if you remove the big plug on the bottom of the tank? Or is my memory failing once again. I recall having some of this stuff apart when I had the fuel tank empty and out of the car - it let me understand what was going on, because I was interested in why I had fuel starvation on the race track when the tank was down to 1/4th (sometimes even higher per the gauge) tank. Porsche didn't design the tank to work well cornering at >1G at those fuel levels, despite the fuel being collected from the center of the tank. And reassured me that there was no gunk in there (and nothing I could do but start sessions with more fuel in the tank).

I'd rate a problem in the tank as being low on the list for the problem here, but it is a possibility. If you hunt around for pictures of the insides of fuel tanks you will find some which were in pretty bad shape.

Hi Walt, thank you for the reply. I already ordered a new fuel pump as it is cheap enough to buy. I will address one problem at a time. First I will work on the fuel pressure issue and then I will work on the residual fuel pressure issue as there is no point in working on residual pressure if I have no pressure/ erratic pressure to begin with. I will look into the tank through the fuel sender unit to see if there is anything nasty in there as a blockage could definitely create some fuel deliver problems. If its too nasty I will not install the new pump. This is a low mileage car with 0 rust which might actually mean that the tank is full of jello state fuel. This car was driven around 300 miles in the last 10 years. I will keep you guys posted.

Hello everyone, today I managed to replace the fuel pump. Two things i found out. 1st thing, gas tank seems ok. I looked inside of it through the fuel sender hole and it looked surprisingly well. The gas that i drained out of it was fresh, clear and with very little debris. 2nd thing I found out was that the alleged new fuel pump was a cheap Chinese knockoff of the Bosch unit. Upon further inspection I noticed that the little ball and spring was out of center. The other 2 pumps I have, have the ball and spring dead center of the neck. Something there does not look right.

To cold start it I had to crank it around 20 seconds to get it to fire up. Not too happy about that but the entire system was bone dry after draining the gas and replacing the pump so maybe it was priming itself. After the car started it car idled well but I had to wait a few minutes in order to get it to rev up. I believe something is not right, perhaps the warm up regulator. I will look into that tomorrow.

After getting it started and warmed up, I gave it a few laps around my yard. Ran beautifully, gave it a few revs and turned it off. Unlike last weekend, the car did not hesitate so there is definite progress. Then I waited exactly 30 minutes to see how it would restart. 1st try, cranked it almost started but didn't catch. 2nd try, cranked it and when it started to catch I gave it a little bit of throttle and started almost immediately.

So my question to everyone, what would be considered a normal cranking length in the cold? 2nd question, do you guys have to give it a little bit of gas when it starts catching when you are trying to start it 30 minutes after a heat cycle?

I've owned all types of classic cars and I do realize some are more difficult to start then others but I've never owned a 911 so your input would be greatly appreciated.

All and all there is definite progress, the car doesn't hesitate and unlike before I don't need to mess around with the sensor plate to get it started.

Normally once started the warm up regulator should increase rpms to 1200 during a cold start. As the engine warms the rpms drop gradually to the idle level ~950 rpms. Make sure the car is at operating temp and shut down try starting after 30 min and see if it warm starts. Ruff running and no wur operation may require throttle to keep running

Hi Pat, thank you for the reply. My idle RPM never rises or drops. If i disconnect the WUR connector nothing changes. When I started the car this morning it idled well, what it didn't want to do is Rev up until it warmed up. That's my new problem. The joys of a project car.