Porsche 911 Startup problem

[rpaulish]

I have a 1980 911 SC. I am having a problem with the CIS system. I have replaced the fuel pump, fuel filter, fuel accumulator, warm up regulator, fuel distributor and fuel injectors because of bad fuel. Now I have a problem starting the engine. It starts and runs for 2 to 3 seconds and quits. The fuel pressure is about 90 psi at startup and maintains a pressure of 40 psi after and then slowly goes to zero.
Any suggestions?

[boyt911sc]

Originally Posted by rpaulish

I have a 1980 911 SC. I am having a problem with the CIS system. I have replaced the fuel pump, fuel filter, fuel accumulator, warm up regulator, fuel distributor and fuel injectors because of bad fuel. Now I have a problem starting the engine. It starts and runs for 2 to 3 seconds and quits. The fuel pressure is about 90 psi at startup and maintains a pressure of 40 psi after and then slowly goes to zero.
Any suggestions?

rpaulish,

Welcome to the forum!!!!! Before we entertain to answer some of your inquiries, it is a protocol for new member/poster to show his/her car to the reading public. For the moment, you are excused but we expect you to post the picture of your car next time around (just kidding).

Why on earth did you replace all these CIS components (FP, FA, WUR, FD, FI)? Due to bad gasoline????? Whose suggestion? Your mechanic? Then you are not alone. I was in similar situation when I bought a '78 SC two decades ago.

For starter, give us the control and system fuel pressures. When did this problem first showed up? Was the car running OK before? Have you check for vacuum leak in the system? These 90 psi and 40 psi fuel pressures were measured where? What are these pressures? Get back to us and we'll get it sorted in no time at all.

Tony

[rayporsche]

hahahaha ..............

[rpaulish]

The car was not running before changing out the CIS components. I have not checked for vacuum leaks. The pressures are measured from the fuel distributor to the WUR.

[boyt911sc]

Originally Posted by rpaulish

The car was not running before changing out the CIS components. I have not checked for vacuum leaks. The pressures are measured from the fuel distributor to the WUR.

rpaulish,

Since we (readers) don't know much about the background of your car's history, let's start from the beginning. Who replaced and installed these CIS components? You or your mechanic? For what reasons? Were they defective?

The fuel pressures you have given above were too HIGH!!!!! I am assuming those were the system and control fuel pressures. If they are, your CIS engine won't even get to idle for several seconds!!! Your current problem could be compounded by fuel pressures (out of spec) including residual pressure, vacuum leak, and ignition timing. This is just to name a few mostly culprits to be determined and confirmed.

Do you have a reference manual like Bentley to use? Could you post some pictures of the engine with the fuel gauge reading (FP pump running). Keep us posted.

Tony

[Peter Seow]

maybe you can read my post on diagnosing the CIS. I did a one by one test and tracked the problem down

[rpaulish]

The car has been sitting idle for almost a year which caused the fuel problem. The injectors were fouled and the fuel distributor was a mess. I replaced and installed all of the parts.
I have the Bentley service manual.

[RSTarga]

Did you check the fuel filter at the tank? You may need to flush the tank out after sitting for a year. When you pul the filter at the bottom of the tank it should give you a good idea if you have additional crud in there.

[ossiblue]

From the picture you posted and without an explanation of what you're trying to show, we must assume it's a shot of control pressure as the valve to the WUR is in the open position. But is it warm or cold control pressure? We have know way of knowing--is the electrical connector to the WUR unplugged? Is the engine running? Regardless, as Tony said, it is way too high. You appear to have the gauge set up correctly and though the numbers are not clear, it looks to show about 5.7 bars which would be about right for a system pressure reading. You may have a blockage in the fuel return line from the WUR, or the inlet to your WUR may be plugged, or the WUR itself may be way out of adjustment. At this point, a bit more information will help and there are many here that can give guidance. You have replaced a lot of components so you have narrowed down the variables. Provide some more information and more focused answers will follow.

BTW, now might be a good time to install a pop-off valve in the air box. Dealing with CIS problems can lead to backfires that could destroy the box and that's a headache you don't want.

[rpaulish]

The gauge shows the cold pressure (5.7 bars) with the pump on and engine not running. When the engine starts it will run for three seconds and quit.

[jinos]

Have you checked the fuel frequency valve? Had the same problem and replaced all the parts like you. Ended up replacing the freq. valve and worked fine after.

[boyt911sc]

Originally Posted by rpaulish

The gauge shows the cold pressure (5.7 bars) with the pump on and engine not running. When the engine starts it will run for three seconds and quit.

rpaulish,

The cold pressure (5.7) is too high!!!!! This is even higher than system pressure (spec) for your engine. One way you could achieve this very high control pressure is a flow restriction somewhere between WUR and the return line to the tank.

Check the inlet screen for the WUR. A quick check for this type of problem is bleeding the pressurize fuel line section by section up to the main fuel return line to the tank.

If I were to do the troubleshooting for your car, this is what I will do:
1). Pressurize the fuel line by running the FP like what you did before for a few seconds just to build the pressure up. The pressure gauge installed and set to read control pressure. Take note of the pressure reading.
2). Does your pressure gauge kit have a pressure bleeder? Use it to bleed the fuel pressure down to zero.
3). Disconnect the WUR's return line and place the end of the line in a container. Find a way to plug the fitting where you removed this line. The goal is to prevent gasoline flowing out during the next test.
4). With fitting properly plugged and the WUR's return line end in a suitable container, you are ready for the next test.
5). Clean the WUR inlet screen. Repeat step #1. The control pressure reading should drop down dramatically compared to the previous test.
6). However, if the restriction occurs after the WUR, further investigation at the FD return valve and return fuel line to follow.

Keep us posted.

Tony

[rpaulish]

As best as I can tell the fuel return line from the WUR goes back to the FD. It makes it difficult to remove the line. I'll work on it.
As a side note, when I turn the key to the on position the fuel pump starts. I notice the manual shows connecting a jumper to the relay terminals to start the pump.

[Peter Seow]

Originally Posted by rpaulish

As best as I can tell the fuel return line from the WUR goes back to the FD. It makes it difficult to remove the line. I'll work on it.
As a side note, when I turn the key to the on position the fuel pump starts. I notice the manual shows connecting a jumper to the relay terminals to start the pump.

TRY this trick, just to get your engine to run, here your picture, shows the line from the fuel gauge returning to the WUR, disconnect that line, let it go free flow to a bucket chances are it will start, it happened to me, what you were going was exactly what happen to me before i started any replacement are you dead sure your replacement wur is working is it new or used or rebuilt?

[rr262]

per an earlier post, I strongly recommend you install a pop off before you do too much troubleshooting. When I was sorting out starting issues on my 83 SC the valve popped several times and I was glad I had it.

There are a lot of experiences guys on this site and they truly want to help. Everyone will tell you to first get the fuel pressures so follow the bently manual and get everything you can get and then report back your numbers. per bently, you should run the fuel pump by jumpering the relay.

I would also check your fuses, When I was working through my starting / running problems one of the problems was due to a 5A fuse that not only fed the clock but the ECM under the passenger seat.

Based on a bad experience with Permatune, you may also want to provide info on your ignition, original Bosch, Permatune or MSD.

Your fuel filter should also be clear as well as the little check valve that is attached to the fuel pump.

[boyt911sc]

Originally Posted by Peter Seow

TRY this trick, just to get your engine to run, here your picture, shows the line from the fuel gauge returning to the WUR, disconnect that line, let it go free flow to a bucket chances are it will start, it happened to me, what you were going was exactly what happen to me before i started any replacement are you dead sure your replacement wur is working is it new or used or rebuilt?

Peter,

Sorry to disagree with your suggestion. This is a very bad advise!!!! For what ever reason it may START which I doubt, and could cause an engine FIRE!!!! Resulting to some catastropic losses. Running a motor with an open-end fuel line under pressure and hanging on top of the motor is surely looking for trouble IMHO.

I believe in your interest to help, you probably overlooked the safety issue that could result from your ill conceived advise. I hope he has a better judgement not to take the unnecessary risk involved. You could try to start the engine but never with an open pressurized fuel line over the motor. Just my two-cents.

Tony

[Peter Seow]

Originally Posted by boyt911sc

Peter,

Sorry to disagree with your suggestion. This is a very bad advise!!!! For what ever reason it may START which I doubt, and could cause an engine FIRE!!!! Resulting to some catastropic losses. Running a motor with an open-end fuel line under pressure and hanging on top of the motor is surely looking for trouble IMHO.

I believe in your interest to help, you probably overlooked the safety issue that could result from your ill conceived advise. I hope he has a better judgement not to take the unnecessary risk involved. You could try to start the engine but never with an open pressurized fuel line over the motor. Just my two-cents.

Tony

With the fuel line all properly flow to a bucket i think i would start, but have someone to start the engine and you keep a close looks out well. That's the only way now to drop the control pressure without replacing or taking out any components.

Keep all your safety measure with you a fire extinguisher if you screw up. By adjusting the flow tap from the fuel gauge you can adjust the control pressure "manually"

I am pretty sure something is wrong with your fuel pressure i had the exact same problem. Mine would start when the last time round till i isolate components one by one to trace down why the control ptressure is high well at least you know it's your control pressure that is too high that stops its from starting.