JimO

Quick question....

- When you turn the key and the starter is engaged (PRIOR TO PRIMARY IGNITION) does your tachometer "bounce"? My tach does NOT bounce and I'm suspecting a faulty reference sensor.

RT930turbo

Yes, the tach should bounce while cranking. Does your car still run?

JimO

No car doesn't start....
- have tried the 'wiggling' the wires trick
- the wiggle the speed/reference connectors
- unplug/plug the connectors
- i'm just going to wait until the morning and hope the cold/dew perhaps will play some magic so I can limp it to the garage a few miles away...

If you have any thoughts let me know. I'm assuming it's the reference sensor.... I can go read the Clark's write up.. but how is it to install a reference sensor? PITA or easy?

RT930turbo

I'd be willing to bet 100 to 1 it's the reference sensor. If you have already tried the wiggle trick, probably just need re-wired or replaced. It's not the worst job to install them, not very much room back there to work though. Read through the clark's write up and you should be able to handle it.

Good luck!

JimO

I'll give it a shot...

JimO

Well I popped the reference sensor.........
It didn't look too bad.... I replaced it.. plugged it in.. car still wouldn't start...

Decided to pop the speed sensor..... and the sun of a gun won't come out .. I'm wondering if the sensor is corroded or some is splayed out at the end... after an hour of playing with it.. threw liquid wench on and have come in the house to drink beer and watch deadliest catch..update in a few hours...

In the process ..decided to take out replacement reference sensor.... have lost bolt in the car/engine that restrains it... did the typical magnet sweep to no avail


How much money, time, and effort am I gonna have to expend to get this )(*&_(*^()*&%(&^% car to run ....

Musche

Use an ohm meter to measure the resistance on your new one and compare to your old ones. IIRC there should be about 600 ohms between two of the pins. I too had one frozen in the bracket and had to end up taking of the bracket and busting the original one to get it out. Good luck!

JimO

well replaced it.. tach 'bounces' darn car still won't start.. thinking of getting gun and shooting car... hehe.... well i'll figure it out eventually.. though thinking a tow maybe in the near future

carlege

DME relay? You getting spark?

quinnfiske

Did this problem crop up out of thin air? Or has it been hard to start off and on for a while? Has it ever stalled when running?

I would check for spark. I use a timing light to see if the plugs are firing. Then see if you have 12V between each of the small terminals on the coil and ground (ignition on). I have had no-start problems twice and both times turned out to be the ignition driver circuit in the DME. Replaced with a used one and that fixed it both times. But every car is different.

JimO

Are you able hear the fuel pump kick on if you are at the back of the car?

Willard Bridgham 3

If the DME relay is good, you will hear the fuel pump with the key on.

JimO

Yes you can hear the fuel pump...
I went to Clark's Garage.. There is a procedure for taking out the DME relay and temporarily replacing it with a 3-pronged connector which supplies DME power and power to the fuel pump. Once I plugged this in.. I could hear ... unmistakable sound of fuel coming into/flowing in the fuel rail. You can also listen prior to primary ignition and hear the fuel pump buzzing if you stick your head down close to one of the rear tires....
____

Well car started.. and ran which is a success... but it was incredibly rough...(dieseling) and I couldn't give the engine the least bit of gas or it would die instantly.. I'm thinking.... either the gas is perhaps is putrid or that I've fouled a plug in the process of so many attempted starts and during the rough running... thinking I may try adding octane enhancer/cleaner to the gas and taking the plugs out and cleaning them... we'll see...
If you have any thoughts on all this.. please feel free to chime in...
____

I'll let you guys know what happens.... perhaps this helps somebody sometime down the line...

quinnfiske

My last DME failure acted the same way. It seemed like some of the ignition impulses were missing and it was only running on a couple of cylinders. I am going to initiate a search for a cost effective oscilliscope so I can watch these signals real time. It is also possible to watch speed/ref sensor signals. Porsche's test plans have pictures of what these traces should look like.

JimO

As I really don't know what else to do.. decided to pull the plugs and put octane enhancer in the gas....

Once I pulled the plugs (starting from the nose cone moving towards the rear of the car)... Plug #1 was black/sooty: Plug #2 was black/sooty: Plug #3 COMPLETELY CLEAN: Plug #4 was black/sooty....hmm plot thickens..
Have sprayed carb cleaner on plugs to clean them up...

What is causing this.. back to the speed reference issue??? I don't think it's the distributor cap/wires .. have checked wires and pushed to make sure I have good connections.... hmmm Did I screw up the LR fuel injector wiring and mis-wire the knock sensor and the cylinder that had the completely clean spark plug.. More to come as I reveal my mechanical idiocy....