Tamed944

New to the forum. So my 1983 944 has been running great for me. Until I drove it to work, and then when trying to leave the engine won't stay on. It turns over and will fire up, but for no more than a second or 2. I saw some things about the AMF running out of sorts if any hoses are disconnected, and I noticed the timing belt vacuum S-hose is disconnected. Would this be the problem? Any other suggestions? Just not sure because it just won't stay on.

Thanks A Lot!

harveyf

I can't give you a specific recommendation on what to fix but in general, the ECU reads a couple of things, one being a certain minimum rpm, to continue with the starting sequence, which includes the fuel pump running and the ignition sparking. . When you literally have the starter engaged, all this "handshake" stuff is suspended. But the minute you let off the key from the starter position, you have to meet the criteria so to speak. The minimum rpm is a safety protocol to keep from pumping a bunch of fuel when the engine has died. Probably a bad DME relay is the most likely culpret. Clarks Garage has a troubleshooting guide. S hose is absollutely not your problem. AMF is low probability. Do you have a tach bounce?

curtisr

But if a hose from the lower side of #6 (air box/j boot) has come off, you'll get the condition you describe.

Gage

Could possibly be a faulty ignition switch losing contact in the run position. Try wiggling it to different areas of the run position after the car fires.

Tamed944

I am getting tach bounce. So that's what leads me to believe its a DME relay gone bad. And it is quite odd that it just all of the sudden decided to not start.... although it is a 944 lol. I ordered a new DME relay and will let you guys know how that works!

Tiger03447

GOOD LUCK AND WELCOME TO THE FORUM!!

pjs.oregan

Does it run at all if you have the throttle wide open or near wide open (as in rev up to 5000 or so immediately after starting). That was the condition I had and it was a large vacuum leak

Tamed944

nope! It doesn't do anything if I give it any throttle. Any thoughts on what that could be?

bonus12

This could be a lot of things but does sound like an enormous vacuum leak or clogged airflow. Busted catalytic converter? Rat in the airbox?

Tamed944

Not sure, everything about the car seems to be fine. Just got done with a 4 hour road trip last weekend with no problems. I also daily the car and have had no problems prior to this

bonus12

A bad dme relay really won't allow the car to start and then die like that as far as I understand. A bad dme relay will either cause the engine to turn and turn and turn, with no firing, or will just allow the car to start as if there is no problem at all. You can test the dme using Clarks garage as someone stated; it's called jumping the relay, and it essentially makes the fuel pump run full time.

How does the engine sound during those two seconds of running? Just fine? Chugging?

And what does it sound like when it dies? Sputters out? Cleanly cuts out?

have you been able to get it running at all since the problem started?

I think your road trip is a clue, but maybe not. Bad gas you got? Engine got properly hot and conditions are now new? How long after the trip did this occur?

need more info.

Tamed944

So the car turns off as soon as I release the key from turning it. And its a clean cut off. But the car has no trouble at all starting, the cylinders Fire a few times, but as soon as I stop turning the key it cleanly cuts out right away.

My road trip was on Saturday, and this just suddenly occurred yesterday(Thursday) and I was driving it everyday in between. I put in 89 octane but I don't believe my fuel should be the issue.

I have yet to get it running but will take a video later today and post it. I feel that should help you get an idea of what the problem may be

harveyf

I have had this problem in the past but cannot remember the fix. One thing I like to do is take my inductive timing light, clamp the sensor on the high tension lead to the coil, drag the "gun" into the cockpit, and watch what kind of flashes I do or don't get from the light. For a hard cut out as you describe, I will bet the light will stop flashing (no spark) as soon as you let off the key. Even if the fuel pump shuts down, there should be enough residual pressure to let the car idle for a few seconds. If it is the spark, and you can lay your hands on one, plugging in a known good dme is always a nice test. They don't typically fail like that but it is nice to rule that out. I've got no skin in the game but to my knowledge you can't damage someone elses dme unit when doing this test. Another check is to listen/feel one of the fuel injectors while attempting a start. It will be hard but you may be able to tell if there are/are not injector pulses after you let go of the key. Obviously this will take 2 people to do. It does not sound like a vacuum leak to me, since you say it sounds pretty good for the short time it is running with the starter engaged. The suggestion on the ignition key is a good one and can be checked pretty easily with a meter.

T&T Racing

Your observations would indicate a faulty ignition switch. To test that assumption, restart the engine and release the key.
If engine stops, do not touch the key. Try turning on the heater fan, the direction lights, or the radio. If none turned on, it is the ignition switch in run position. Then wiggle/rotate the 🔑 around the run position to see if there is a position that the heater fan, etc runs/on.

Tamed944

So I ran the suggested tests for the ignition switch. The lights came on so all the electrical components in my car work. I'm gonna attach a video to give everyone here a better idea of what I'm dealing with.