mark Harper

My 1983 944 will not start, i have check the fuel pressure with a gauge and it seem correct, also i have replaced speed sensor, and i have tachometer bounce
i have tried everything, i can find in manuals, and still i cannot find the problem.
I have managed to get the car started a few times, when i close the return fuel line, and it will sometime fired up, after a few moments i removed the clamp and the car runs, my fuel pressure gauge reads 2 bar,

and the car will restart if i stop the engine, but once it's left for a while it will not start, please can someone point me in the right direction to fix this issue.

walfreyydo

Have you read through Clarks Garage Engine Troubleshooting? https://www.clarks-garage.com/shop-manual/ts-01.htm

1) Are you getting spark? Yes or no?

2) What was your actual fuel pressure reading (while cranking) without clamping the fuel return line?
3) What is the rail pressure after you let it sit for 20 minutes after cranking? (see: https://www.clarks-garage.com/shop-manual/fuel-01.htm)

My initial guess is this, based on the fact you need to clamp your return line and the car wont restart after sitting (but would be confirmed if you could give us the actual fuel pressure readings while cranking and then after sitting for 20 minutes):

mark Harper

crank car over and it fire up, but stop and would not fire again, Fuel rail Pressure just under 3 bar, and it took 14 seconds to drop to O.
I check for spark there was a spark, but it looked very weak, then there was no spark. until i start car again, but aging the spark look very weak.

walfreyydo

Fuel pressure too high (it should be closer to 2 bar) - possibly bad FPR (check for fuel in the vacuum line-that would indicate a torn diaphram)
Fuel pump check valve not functioning (rail should hold pressure for longer than 14 seconds)

You also need to determine why you have no spark/weak spark - run through the checks of the cap/rotor/plugs/plug wires and ignition coil.

Review the links I posted from Clarks Engine Troubleshooting - its all there for you.

mark Harper

Thank for getting back to me, i have suspected the FPR for a while, as for the spark issue, i have replaced plug cables distributor cap have a new rotor i can place
check specification of coil and test out Ok.
For your information when the car runs the pressure is around 2 bar, and increases when i remove the Vacuum line, which i think is correct.
what else can cause a weak spark?

walfreyydo

Im not going to regurgitate the same info that is easily found/read on clarks garage (which I have pointed you to numerous times now). Youll have to take some initiative yourself and do some reading and testing.

Read through the engine troubleshooting section on "lack of spark" and then run through the tests listed therein - here is the ignition troubleshooting subsection:
https://www.clarks-garage.com/shop-manual/ign-04.htm.

If you have specific questions, let us know.

mark Harper

Hi I've downloaded all the Clarks tests and preformed most of them, I finally can get the car started but I have to clamp the fuel return hose and spray easy start in the air filter, the car will then fire and run, I remove the clamp and car still runs, once car has warmed up, it can be stopped and it will restart but if I leave it for a long period, I have to, go back to the clamping and spraying easy start, then car will start again.
I noticed that when car is running I have around 2,5 bar, once I stop the car pressure drops to 0 bar very fast, please can someone help.

931guru

You have either a leaking fuel pressure regulator or a leaking fuel injector (or more).

mark Harper

I have check the injectors, and they test good, and with the return line clamped the pressure does not drop, i thought that the FPR was normally closed and only release when the pressure reachers the set limit of around 2,5 bar, it's very strange that when the car is running the pressure stay around the 2,5 bar, if it not the FPR and not the injectors where do i investigate further?

931guru

There are three things in the fuel system that can cause a failure to hold the leakdown pressure:

1) The injectors (which you say are good).
2) The FPR
3) The check valve on the fuel pump.

It's got to be one of those three, so start with the cheapest and try something else. The factory workshop manual does not list the causes for a leakdown failure, just states how to test and the desired results of the test.

mark Harper

When i crank engine, fuel rail pressure is around 2,5 bar on the gauge not sure how accurate the gauge is, i also tried the disconnecting one injector, but still car did not start.
I tried just to spray easy start into filter without clamping the return line and the car fires, but stalls, most likely if i could keep spraying the easy start, it would run, but without clamping the return line the car is very sluggish, and if i touch the gas it sometime dies, but as i said previously with the return line clamped and easy start, the car starts and run , after a short period i remove the clamp and car remains running perfectly, and will restart without clamping and without easy start, it a strange problem, and frustrating, as the car run perfectly when it starts.
another thing that maybe relevant, is the car has been standing for a while, i have put fresh fuel, in tank, and the fact that the car will run i think bad fuel is not the problem.
I will replace the fuel filter and the FPR, and see what this does, then i'm out of ideas.

walfreyydo

I agree with 931guru. Have you also looked for vacuum leaks? Especially the port on the bottom side of the intake, AOS line and brake booster line.

Here are the fuel pressure specifications - you should verify these (without the fuel line clamped)
https://www.clarks-garage.com/shop-manual/fuel-01.htm

Report back what you found, especially the 20 minute leakdown pressure.