bh05

Hey everyone, I have a 1984 944 that I’ve owned for roughly two weeks, had a ‘87 project before this. The car originally would stall during idle, however I replaced the engine temp sensor and it ran well after that. Other than that, I changed the battery/oil/sparkplugs but not much else because the car had been looked after fairly well by the previous owner. The other day I drove the car with no problems and the next day I started it to drive somewhere and I made it down the street before it stalled out like it had ran out of fuel. I tried restarting it and it runs for a second or so before shutting off, or if you apply any throttle it shuts off immediately. I figured it may be the fuel pump but it reads that it’s working, I replaced the DME Relay, emptied and refilled the fuel tank and there was no debris in the fuel, and then replaced the fuel filter. When I tried to run it, the same thing happened. Starts just fine, then runs for a second before it cuts off. Any ideas? Sorry for the essay.

Jfrahm

How do you know it has enough fuel, did you do a flow test or hook up a fuel pressure gauge and watch it under load?

A simple flow test, ideally while using a DME relay jumper wire, would be a good way to see if you have adequate fuel flow.
Take off the fuel rail nut
- Counterhold the fitting on the rail so you do not bend or break the fuel rail
- Do not lose the ball bearing under the nut
Fit a length of hose over the threads, and a hose clamp
Run the hose to a container like a 2L bottle or gas can
Connect the DME relay jumper and observe how long it takes to get 1L or a quart of fuel or so. It should be well under a minute.

You can also spray starting fluid into a vacuum line and see if it runs up off-idle a bit on starting fluid. This is not ideal, starting fluid is pretty rude, but it's a quick way to see if fuel is probably your problem (which it kinda sounds like).
A clogged tank sock or similar issue could be to blame.
-Joel.

Dan Martinic

Pull the ECU (DME) computer and check for little hairline cracks that look like this

bh05

Ill definitely check the DME out, I plan on doing a proper fuel pressure test sometime today so I’ll let you know if the pressure is iffy. Is there a chance that it could be the coil pack? I read somewhere that someone had a coil pack go and it shut off while driving and when they restarted it the same thing happened where it runs for a second and shuts off.
Thanks for the help, I’ll update after I check the rail and DME today.

Jfrahm

An 84 just has a coil, no coil "packs" and no ignition module (big silicon switch to trigger the coil). Coils do not go bad often and more commonly cause hard starting, poor higher-RPM operation, poor hot starting and stuff like that vs. a start but die off idle.
It's always sensible to get a spark checker and check your spark properly when diagnosing a problem, particularly if you are not sure what you are observing and things get confused when posting on the internet.
I suppose the trigger for the coil in the DME could be fading out when pressed above idle RPM, DME problems can be many and varied.

It's also great to check the spark plugs right when the problem is occurring as they will tell you a lot. Are they wet with fuel? Are they black with carbon?

Nowanker

It's big fun to DIY with a car. Satisfying, and actually pretty easy to change (most...) parts.
It's even bigger fun to trash automotive techs as greedy, ignorant thieves on the forums.
Until you run into a diagnostic problem. Maybe we don't all suck after all....

No substitute for step-by-step diagnosis.
First step:
Is it running out of fuel?
Or is running out of spark?
Since it starts and dies, you've already eliminated the other important data points.
It still has compression.
It has spark at the right time, at least sometimes.

Sorry to be blunt, and without any specific solution, but throwing parts at a problem, hoping for a score is no way to solve automotive mysteries.
If you're without any real diagnostic skills, it's often more cost-effective to pay for a pro.
Apologies for the rant, and good luck with the problem.
Let us know what you find...

Dr. 914

If you have fuel pressure when cranking then check spark. then check the two timing reference mark sensors

bh05

Ok I just tested the fuel pressure at 35psi, Ive heard the psi should be in the 40-60 range and I’ve also heard it should be in the 29-40 range so I’m not sure if 35 is enough pressure, let me know if it isn’t, I took the DME to an expert and they confirmed it was good, the injectors are working and so is the fuel pump, I tested the pump with a multimeter as well as the battery, both came to 12 volts. No vacuum leaks as far as I can tell, I took the J boot off and refitted it again. Someone was saying the speed and reference sensors could be at fault and I was wondering if it would start at all if it was one of the sensors because my ‘87 had a sensor problem and it just refused to even start until I replaced them, whereas with the ‘84 it starts and dies. The place I took my DME to said that it could be the damper because the FPR was replaced in March. Thanks for all the help I’ll update as I go.

papasmurf

Do a smoke test to check for vacuum leaks...the hoses under the intake manifold and connected to the idle valve are prone to failing especially.

bh05

Hey everyone I ended up replacing the DME/ECU. got the early DME from 944Online. That fixed my issue. In conclusion my car would start and shut off after a second or with throttle input, I checked the fuel pump and fuel pressure, replaced the DME Relay, then someone suggested the DME/ECU, I tried that, and it fixed it.

Nowanker

Congratulations on the repair, and thanks for posting your fix!