[Swoboda]

Hello: I have a 1985 911 that was running great, then just stopped working.

Quick story: The car was running fine. I recently drove it to work, came home, and parked it in the garage. When I went to start it up a couple days later, it just cranked.

It doesn't start and it doesn't "catch" or "stumble".

I switched the DME relay with a new one. No change.

I switched the ECU with a known good one. No change.

I jumped the fuel pump at the fuse box and it runs.

I still have to check for spark--I'm running solo so I can't turn the key and be at the engine to check (but I will get some help soon).

Any thoughts on what it could be?

What I last had it out it was on one of those blazing hot days a couple weeks ago.

Thanks very much for any thoughts!

[Jazzbass]

No start problems are usually flywheel sensors or DME relay. Try jumping the fuel pump so that you hear it running, then try to start. The fuel is a closed loop system so it’s fine to jump it for the tests.

If it starts and runs well, you probably have DME relay problem. If it tries to run but does so badly probably the flywheel sensors.

[Swoboda]

Thank you! I'll give that a shot.

[Swoboda]

I tried jumping the fuel pump, and could hear it running. I tried starting the car, but still no start or even a “catch”.

I tried cranking for a good bit several times to ensure that the gas made it to the engine and I gave it a chance fire up.

Does this indicate the sensors?

Can I get access to the sensors with minimal jacking? The car’s in the garage with little space to maneuver?

Thanks for the advice!

[VaSteve]

I always see the sensors tagged as a source of failure, but how often do they just fail? Did you swap in another DME relay?

[Richard Curtis]

old coils have been known to generate a weak spark over time, too weak to ignite the fuel mixture. Spark color should be blue. If any shade of yellow, orange or red, replace the coil.

[86911TLCAB]

If you can get under the rear of the car you can get to the flywheel sensor.

[Swoboda]

I did swap the DME relay with a new one and, when that didn't work, I also swapped in a known good ECU.

I may have a spare coil to try.

I've have the car for 10 years and have been doing regular maintenance to it, but I've never looked at the sensors.

I'll see if I can play around with it more today.

I appreciate the suggestions and help!

[Len 911]

I have an 85 also...had the same problem and it was the sensors on the flywheel..wasn't to bad of a job...I used the BMW sensors way cheaper and are the same..
Good luck

[86911TLCAB]

I recently swapped out the camshaft sensor in my e36...I decided to strip the wire to see what it looked like inside...and basically the covering on the individual wires was crumbling and wires were shorted in spots...so these things live in a hot environment and like anything else can eventually cease to function...