V2Rocket

Hi,

The past few days I have been working on someone's 1987 944S to try to figure out why it is not starting. There is fuel in the rail, there is spark at the plugs, and the starter cranks and cranks and cranks.

He has tried swapping between various DME relays to no avail. I have looked through the relay box and swapped out relays and fuses to see if anything was bad...nothing.

He said the car used to sometimes die on him while driving and be especially hard to start on hot days. He took the car to the local Porsche dealer and after a week in their service center they had no idea what the problem was. For this reason, the car has been parked since about October.

I pulled the manifold and checked the reference sensor spacing and it should be correct. I did a voltage test on the sensor (multimeter attached to prongs, waving screwdriver in front of sensor end) and it worked as it should. The ohm test (as per Clark's) came out perfectly in spec. There is no tach bounce, but I believe the entire instrument cluster is dead because NO lights come on at all when the key is turned to the on position 1, 2, or cranking. Could a dead cluster somehow stop the car from starting? I can't imagine that being the case.

I put the car back together and now I can only think to swap clusters to see if it gives any tell-tale signs.

Thoughts?

Dougs951

Check the injector wiring

Edit-I should have read more, stick you head under the dash and sniff for electrical smoke smell

John_AZ

Nothing works?
Are the cluster harness connections in tight? Are they in the correct slot?

I am looking at Sheet 4 Instrument cluster and sensors USA Model 87 of the WSM Vol 4 .

Picture from Scott Levy:
http://tech.rennlist.com/924_944/por...stallation.pdf

Did the Porsche Dealer or anyone sway out the DME Motronic computer?

Pelican Cluster tuneup:
http://www.pelicanparts.com/techarti...e_problems.htm

I'll check more ideas...
John

doabarrelroll

The 16 valve models also have a cam position sensor on the back of the cam gear cover. Is it possible that a no-start could be the symptom of that sensor going bad?

I have a working S DME if you want to eliminate that as a possibility too.

John_AZ

Kerry Chadderton had a long term no start.
Here is his unique way of testing the DME.
Read on Post 178
https://rennlist.com/forums/924-931-...-start-12.html

GL
John

V2Rocket

The DME is definitely suspect. We are going to try swapping it with a nearby friend's DME, also from an 87S.

Regarding the cluster, there is NOTHING coming on. Not gas gauge, not parking brake light, no oil pressure when cranking, no ! light. To contrast, the guy's S2 lights up like a Christmas tree when the key is put to ON.

DarylJ

While the DME sounds like a reasonable suspect on this, several of the things on the cluster simply don't go through it. It sounds like you have some serious electrical gremlins going on. And you know what that means, right? Yes....check those grounds. And then replace the ignition switch, which is just creates a bunch of maddening random-looking issues when its bad.

John_AZ

+1 on the ignition switch. ^
http://www.clarks-garage.com/pdf-manual/elect-17.pdf

John

joonas

From Clark's

Fuel Pressure Too High Disconnect one fuel injector connector and attempt to start car. If the car starts and runs, where it would not before, then the Fuel Pressure Regulator (FPR) is most likely bad and should be replaced. Bascially when the FPR fails causing the fuel rail pressure to go high, the injectors have too high a differential pressure across them, they draw too much current, and the injector driver shuts down. Disconnecting one injector wire reduces the injector current enough to allow the engine to start. Realize that the car will run very rough as it's running on three cylinders

If you have spark and fuel something should happen. Fuel pressure too high or low? Did you measure fuel pressure?

V2Rocket

I did not measure fuel pressure, and did not know about the driver shutting down. I'm gone now, butI'll let the guy know and he can test it. Thanks!

homerj

for info i thought i would put it out there. this board helped solve some of my problems. i bought a 88 944 n/a from a porsche instructor at their training facility. the motor had been rebuilt, new clutch and mostly put back together. bought the car and put it back together. it would turn over but never start. called my friend whos a tech at porsche and he spent a little time each night for a week and still couldnt get it to start. he called the guy i bought it from since they were friends and he hadnt been able to get it going. long story short the alarm had to be bypassed and all the injectors were completely plugged. threw a set for my mustang on and it started up immediately. i learned about bypassing the alarm from this board. its funny both of them work on the carrera gt, but the 944 broke them

MacinTek

Check all the engine grounds... especially the ones at the rear of the engine. Clean them and make sure they're tight.

MM951

You dont need the cluster installed for the car to run.

I've had a crank sensor "test" (I say "test" because I didn't use an oscilloscope, only a multimeter) OK and still end up being the problem. The issue with hot starts would make me take a second look there.

Besides that, I'd take a look at the ignition switch as others have mentioned. If you have noid lights it wouldn't hurt to see if the injector harness is OK. Obviously I'm sure you know to check the grounds and to test the suspect DME in the running car.