Gilmore27

I have an 83 944 NA that's been sitting for a few years. I've been dealing with a no start issue. it would turn over, just wouldn't start. I finally got it to a point where it will run only when the ignition is in the start position. As soon as I let it back off the start positions it dies. If I keep it in the start position the engine sounds good. It responds well with the throttle. I don't do that for long fearing damage to the starter, less that 20 seconds.

Here's what I did so far to get it to this point.

replaced fuel pump and filter
fuel pressure checks good at the rail with a gauge
cleaned, rebuild, and checked the fuel injectors
replaced coil and spark plugs
reference sensors checked good with an oscilloscope at the DME connector
I pulled the ignition switch, the resistance checked ok in the different key positions.

also, the tach's not working, Im guessing it's unrelated, but thought id add it in case it is.

I couldn't find an issue like this in this in this or any other forums.

any help is much appreciated.

thanks,
Dave

odonnell

1) Replace ignition switch

2) Clean electrical grounds

Gilmore27

I'll try another ignition switch.

I'll clean up the contacts connecting the neg battery cables. Where else can I find the gound points to clean?

Thanks for the response

odonnell

Grounds:

travisgreen

I'm having the same issue with a turbo, I swapped ignition switches and didn't fix it. If I figure it out I will be sure to let you know. Please do the same!

william_b_noble

I would hazard a guess that the ignition switch is bad, as others said - but you can tell right away - put a lamp on the +12 input to the DME and see if it goes on and off as you expect.

Gilmore27

I replaced the ignition switch and cleaned the ground point a the battery and the one behind the fuse and relay box (MPII i think).

It still wont run unless you keep the ignition in the start position.
I'll clean the rest of the ground points. I'll also check the voltage at the DME.

Thanks

william_b_noble

I think, but you can verify with some reading, that when cranking certain sensors are ignored - read up on what they are and that will help you localize the problem. Do you have the troubleshooting chart from the shop manual?

Gilmore27

Im getting 12V at the DME input (pins 18 and 35 to GND). Wouldn't the fact that the car runs (when ignition is the start position) suggest that the DME is getting power and reference sensors are good?

I cant find anything on any sensors being ignored, still trying to find info on that. I think I found a troubleshooting chart that pointed to testing the air flow sensor, temp sensor. Im not sure if its the same one you're thinking. If not, is there a place I can find it (other than the actual shop manual that I don't have).

I'm still in the process of cleaning the ground points.

thanks,
Dave

Gilmore27

I found that if I disconnect the temperature sensor, the engine runs. As soon as I reconnect it the engine stops. The resistance looks ok at pin 13 to GND on the DME connector (2K ohms). Has anyone heard of a temp sensor causing it not to start?

Thanks,
Dave

Gilmore27

I got it. At least its better. The AFM was disconnected. It still runs rough and cuts off especially at low rpms, but I think thats due to a vacuum leak. The AFM tested good (using Clarks Garage's procedure). At least now it will run with the key in the ON position and Temperature sensor connected.

now to replace the badly needed vacuum hoses.

thanks for your replies,
Dave

william_b_noble

good work, you are on a roll - the car is very sensitive to vacuum leaks, check the J-tube carefully as well as the usual vac lines.