champagne944

The battery is almost new and has excellent output. I did a bunch of reading on the speed and reference sensors. Apparantly if you have tach bounce and the resistance checks out they're supposed to be ok? I have tach bounce while cranking but the only time it reads correctly is at idle. I've pulled the plugs apart a couple of times and they're really clean and solid. All the plugs and connections on the car don't seem to have the brittle issue that I've read about. I'll order a new dme temp sensor today. I still think the starter should at least engage? That's what really confuses me. Thanks

Humboldtgrin

So fuel pump works and no power to the starter... Make sure the battery is charged. It may be bad also. Check the connection on the battery terminals for any looseness. The DME temp sensor wouldn't creat the starter not to engage. Nor a bad sensor. That would be a low battery, the ignition switch itself, the wires coming from the battery to the starter or to the ignition to the starter, bad (corroded)electrical connection. Check your starter to make sure it's still in one piece or not coming apart also. I had that issue on a rebiult unit. The starter doesn't have any fuses to check, it's a pretty simple system. You'll find what is wrong. You may have just enough power for the fuel pump but not the starter. If you battery is swollen on the sides it is sulfated and needs to be replaced. Auto manufactures purposely don't charge the battery to 14.8v on a low amp to fully charge the battery so that battery companies can still sell batteries every 3 to 8 years depending on the conditions and quality. At 13.6 v the battery always has a little sulfer left on the lead plates making the battery sulfate over the years and swell on the sides loosing its ability to hold a charge.. If you want to have your battery last a lot longer (like 30+ years) put a low amp 15v solar panel in the rear hatch and wire it to the battery which ever means necessary, or use a 14.8v trickle charger hooked right to the battery if it's in a garage while the car sits.

Humboldtgrin

Check the voltage at the starter solenoid and the starter. And the wires.

Humboldtgrin

Check your votage directly on the battery when you try and start. If it drops below 10v replace it. It may read 12.6 with no load but have little amps. I've seen bad new batteries too. I'm know others have too if they have worked as a technician long enough. Also check to see if someone had tried to put in a security system and cut the big yellow wire off the ignition switch's wire harness under the steering colum. A security system could mess things up if it's still installed or if it was removed and the wire splices are in bad shape. Also check your alternator as it can go bad and create electrical problems on the starting/charging system. You ignition switch is realy old too, I would replace it. There easy to do. Once the car is started I'm betting the wires fixed the bad running issues. I've seen your initial symptom way to many times as a tech. Although if I was there it would be so much easier to fix! Think how many times that ignition switch has turned in its life. And the starter turning. And how old they are. Welcome to slowly replacing everything on your 85 944. But it is a super nice car so don't get discraged. You will get it running. And you will like how it drives. A little TLC and you'll be good to go.

champagne944

Ok, first I have to apologize, clearly I don't know as much about batteries as I thought. The output while cranking was not enough. I mistakenly thought even a low battery will attempt to crank. So the car now starts fine. Thanks for the faith Humboldtgrin. New plug wires installed and it still has the same symptoms. New DME temp sensor will be in tomorrow. Will update then. Thanks

champagne944

New plug wires and new dme temp sensor. No changes. Any other ideas?

champagne944

Ok. So I managed to take the car on a little drive. About 1 mile. Found out that I can bring it to 1300rpm on the nose. Any more and the missing starts. At that point the tach begins to read incorrectly as well, it will drop even though the engine increases rpm (very rough hesitant gain of rpm). From idle to 1300 rpm the engine runs very smooth. If I'm gentle and careful I can shift through all gears and pick up speed but only if I stay below 1300. Could this be caused by the speed/reference sensors? Are those sensors the only thing the tach reads from? Do they have an effect on ignition and/or timing? What else do the sensors control? As usual any input is appreciated. Thanks

odonnell

The tach itself triggers off the coil.

The coil is controlled by the DME, which knows where the engine is in the cycle based on the speed/reference sensors. I have a good used coil if you want it for cheap. The sensors are notorious for running issues on these cars, definitely worth replacing with new parts if you suspect they are original.

champagne944

I believe they are original even though they appear to be in great shape. I'll order a set and see what that does. The coil in my car is a new Bosch unit, replaced by the previous owner. Thanks for the offer though.

Humboldtgrin

Yes that could happen with the speed/ref sensor. Also do a ohms check on your wires from the sensors to the DME, and do a "pull test" by wiggling on the wires to see if there is a break that is inside the wire insulation or if the wire totally seperates. Sorry for the misdiagnosis on the spark plug wires but that really what the symptoms described sounded like the problem being. I had a speed sensor go bad on me while driving on the freeway. It would be hit and miss. Then nothing. The braided sheath had separated as the wire harness pulled out the back of the connector.

F18Rep

I wonder if you've lost one of those pesky flywheel set screws. ...Bruce