Porsche Enthusiasts Club Forum

So I picked up my new-to-me '84 944 last weekend, thrashed it a hundred or more miles home with a huge grin on my face, until on the last leg the car just died. No spark, and if I take the end off the fuel rail, then petrol floods out, but only when cranking the engine; not just from turning on the ignition. First question : is that normal ?

I have 12v to pin 2/30 on the DME relay (ignition off) and 12v on pin 3/86 (ignition on). I have replaced both the coil and the relay with new ones. Still no joy. No discernible tacho bounce.

Taking a jumper from battery live to coil LT, still no joy. Second question : might simply doing that have damaged the ECU ? This car is somewhat more modern that those I am used to tinkering with, which have no electronics, but I haven't seen this step included in any of the "Dead 944" threads or discussions that I have so far encountered.

I have removed the last vestiges of an alarm that had been fitted but wasn't even connected.

There's a No Start Check List over on rennlist, but the relay pin numbers don't seem to agree - e.g. that has pin 4 as the start signal and pin 86 as the primary coil voltage. I have pin 4 as fuel pump feed and 86 (3) as ignition switched input. Maybe I've misunderstood something ?

So is it reference and speed sensors next, or dropping the ECU and inspecting that ? By the way, all the pictures I have seen of the ECU on '84 cars have shown it by the relay and fuse boards in the left-hand footwell, but they have all been in LHD cars. My relay and fuse boards are in the LH footwell, but the ECU is above the driver's right knee (RHD). Is that right ?

The car was largely rebuilt in 2011/12, having failed its MoT in Sept 09, but has done very few miles since then.

Crank sensors.

Mine spontaneously died over one winter. Not a terribly difficult job. Wiggle the wires and connecters before you buy new parts. they are located at the back of the engine bay.

Your locations for everything are right for an early square dash model. These cars are all 30+ years old now so a few gremlins are inevitable, they respond well to use and tlc

Interesting how many of these cars seem to hate starting.

My own 2.5 lux oval sometimes decides it wont go though it has a spark and once going never misses a beat.
When it wont start I take off no 1 spark lead and it will fire up on 3 cylinders happily
Why is this?
Good luck with you efforts to start it.

Thanks for the responses - tried wiggling the sensor connectors, tried removing a plug lead - no joy. Spent the best part of today with a mate going through what was going on. Found plenty of evidence of past bodges behind the dash (chocolate block connectors, insulation tape - even a 7.5 amp in-line blade fuse near the main lighting switch, which seems to only affect the lefthand fog light) ! There has been an after-market alarm fitted, and I think the wiring has suffered as a result - but that shouldn't explain sudden death after 100+ miles, surely ?

DME relay works as it should, getting 12v to pins 18 and 35 of the ECU plug, fuel gets pumped through to the rail (cannot check the actual pressure), resistances of the speed and position sensors are in spec, getting 12v to the coil LT lead, have 12v at one side of the injectors.

Dropped and opened the ECU and it looks good and clean, but I don't have the knowledge to run any diagnostics on it.

I think the next step is to try replacing the ECU with a known good one - if I can find such a thing !

Any other ideas ?

I've got a good ecu available - PM me if you need to

My money is still on the crank sensors though. I had to change mine after leaving the car standing for 6 months - it started perfectly before. Resistance is a red herring, i think they need to be checked with an oscilloscope - Clarks Garage website is your friend.

If you need any 8v parts PM me i've got loads of bits and no car anymore as I have a later S model now. Ive got engine looms and all sorts.

Snap! same symptoms, after a few runs up the road, it cut out and struggled to start again, then no start. Pump runs, have fuel,new leads,distributer, injectors pulse, 12v to coil, coil changed with two known good ones ,output from ecu to klr and back, new sensors checked with scope but no spark. Have even changed the engine loom incase of break in wiring, still no spark. Sent ecu and klr of to Tom barker which checked out ok.
Raising the white flag and taking car of to Tom's place to find fault as fueling needed to be set up correctly anyway. Will pass on outcome.

If yours has a KLR i take its a Turbo?

Dirtyhands' Turbo did this (No spark) and it was the KLR - check with a known good unit proved this. I don't know if the old unit was ever tested. I had an ECU that checked out on testing and turned out to be duff as well - that took some finding!!

For the OP the no tacho bounce is a big clue, provided that the tacho works of course

Chris - you have a PM.

And yes, the tacho was working before sudden death onset. And now no bounce.

There are two crank sensors on the bellhousing , the wiring for the both of these runs up to the back of the inlet manifold at the bulkhead where there are the two plugs that are the same.

If you have no tacho bounce when cranking, swap the plugs round and try cranking it again. Hopefully this will make the tacho bounce & pinpoints a faulty sensor.

replied

Sorted - a replacement ECU did the trick. The old one was still sealed and looked new both inside and out, but I think the car hadn't been used much which I guess might have contributed to the failure.

Now for an MoT to see what needs to be added to the extensive snag list which I've already drawn up.