LLSkier23

So I recently purchased an '86 944 (NA)...my first Porsche! Check one off the bucket list. I was so proud of it until about three days later when it refused to start one morning. The battery was strong and the engine turned over fine, but it simply refused to fire.

I did my research and tried a few things including new spark plugs, examining the speed/reference sensor plugs, and popping in a new DME relay. Nothing. So eventually I had it towed to the nearest shop to have it looked at. They managed to start it in their parking lot right away and after a quick look through the engine, found no smoking gun. Something during the towing process must have set things right again.

Here I am three weeks later and it's starting to do the same thing again. It doesn't always happen, but many times after sitting for a short while (10+ minutes) it just refuses to fire. Eventually if I keep trying and trying, it usually fires and it also fires up immediately after shutoff without issue. Pushing the car a few feet sometimes seems to help I think, though I have no idea why it would. As a side note, the car runs great when it actually runs, and it's a blast to drive.

At this point I'm at a total loss. I'm thinking perhaps an issue with getting fuel to the engine, but that's just a wild guess. If I can get it fired, I'm driving it straight to the shop again.

Any ideas as to what might be the problem? I'm in love with this car, but can't afford to deal with gremlins like this. Please toss any thoughts you might have my way.

-Andrew-

Ben951S

Welcome to Rennlist.

The search feature works pretty well and this is a very common and usually easy to fix issue.

First and foremost. Does your tach bounce (twitch, move at all) when you try and start the car? That's a biggy. Good job on the new DME relay though...

John_AZ

I would begin with the suggestion from Porsche when the 944 has these symptoms:

Clean every electrical connection on top of the engine.
Clean every ground. Cover the TDC hole on the bell housing with tape or do a clutch job when a bolt drops down.
Check the reference sensor wires for cracks-if the stall happens again wiggle the reference sensor wires and connector.

While you are doing the cleaning, check the vacuum hoses for leaks and tight connections.

Charge the battery disconnected from the car with a slow charger overnight.

When you get this far, read more at Clarks:

http://www.clarks-garage.com/shop-manual/ts-01.htm

GL & welcome,
John

ZR8ED

Fuel pressure bleeding down? Throw a gauge on the fuel rail.

szabon

I have the exact same issue. I am pretty sure mine is the reference/speed sensor, because if I wiggle them when I have the problem it fixes it. I just haven't replaced them yet....Next time it happens try wiggling these wires.

LLSkier23

Thanks for all the responses everyone. Much appreciated.

Ben: I'm pretty sure the tach bounces on startup, but I'm not clear about how much it's supposed to move. I've read about this detail before and checked previously. Maybe just the vibration of turning the engine over is what I'm seeing as bouncing.

Overall, I'm leaning toward it being a fuel pressure issue right now, based on what's been said above and in Clark's. However, since I don't have a gauge (or many other specialized tools for that matter), it might just have to go into the shop. I'll keep you all posted when I find out more.

szabon

it will be cheaper to buy a gauge than pay a shop to fix it. Plus you get to keep the gauge....

Jamesr6967

Just a quick thought. When it doesn't start, have you checked for power at the fuel pump? Possibly poor connection at one of the fuel pump power connections or bad contact at fuse/ fuse panel.

Jamesr6967

I had same issue. After replacing the old pump and swapping DME relay, still same issue. Replaced fuse, which LOOKED fine, problem gone.

spanky

I wld jumper the DME relay which starts the fuel pump no matter what position the key is in. It really wld help to have a guage. Wait for 2/3 mi and then give it a try.If it starts up the fuel rail is draining either back to the tank ( fuel pump check valve),a faulty fuel dampner or a fuel injector is leaking into a cylinder. Remove the relay wire jumper when testing has been completed Good luck!!!

LLSkier23

So I'm now 99% sure it's the speed/reference sensor. I found some black electrical tape wrapped around one of the wires and upon undoing it, found some bare wires intermingling in there. Not sure what damaged it in the first place, but redoing the wiring helped the car fire right up. It's still not perfect, but going under the hood and jiggling it around makes the car start every time now. I need to do a better job splicing the wires together and getting some heat shrink around them for protections.

Thanks again everyone for all your input. You guys are the best.