1983 944 non starter,

[RTP01]

Hi , i have recently purchased a 1983 944, i have been reading lots on the net in various forums about non start issues. ie checking dme relays , changing sensors in bell housings etc, so not actually going in blind. i have checked the resistance on sensors , all seem fine , (No acess to oscilloscope), so changed tdc one any way.DME relay looks fine, Coil checked out, ok, My worry is it could be the actual DME gone , but before i commit to getting another one or sending mine to some one i just wanted a little advice.
My symptoms are
Non start, No tach bounce on cranking. cant hear fuel pump when cranking,no pulse voltage to/from coil
the DME is getting power.
I downloaded a checklist from ecu doctors and all connections on plug seems to be doing what they supposed to.
really at a loss now so a pointer in the right direction would be good , or the name and number of a good UK based ECU repairers, testers. in SW uk if poss
Thank you in advance
Rob

 

[pauljmcnulty]

Moved to the main 944 forum for you, hopefully some suggestions soon. []

 

[Diver944]

Have you tried making up a jumper lead to totally bypass the DME relay?

http://www.clarks-garage.com/shop-manual/fuel-05.htm

 

[RTP01]

Thank you, newbie and not acustomed to forums (lol)

 

[Mike_Pollock]

Hi and welcome
No tacho bounce points to crank sensors.
And we like pictures as nobody else has mentioned them!
Me and mine

 

[RTP01]

hi, made link cables as per clarkes garage. Fuel pump runs all the time but still no spark. looked at detailed drawing for DME and see that tach is connected to pin 11 on dme (computer), have changed sensors reckon dme is shot, as i assume sensors will pass signal through DME to tach
i bought the car in non running condition as a project, have spoken to previous owner and says he heard lots of clicking noises when connected brand new battery, since then non starter, so possibly spiked DME,


Tried taking photo, but car in garage and not very photogenic, keeping it dry as it has always been stored that way

 

[RTP01]

UPDATE, purchased S/H DME put it in still no start ' tried with relay , and bypass cables , back to the drawing board.
Is it possible for sensor pick up screws in fly wheel to be dislodged ?

 

[PSH]

ORIGINAL: RTP01

UPDATE, purchased S/H DME put it in still no start ' tried with relay , and bypass cables , back to the drawing board.
Is it possible for sensor pick up screws in fly wheel to be dislodged ?

Anything is possible but I can't say I've ever heard of such a problem. the screws are set using loctite so shouldn't move for any reason, although I guess it's possible to wear them down, certainly one of mine shows signs of being worn down a little. Have you checked the multi pin connectors that connects to the crank sensors? It's located at the back of the engine, held in a clip just below the camshaft tower, this is a well known problem as our cars get older. Try giving it a good clean, it's probably corroded, other things worth checking... coil, are you sure it's working? have you checked all involved wiring for continuity? Is the earth lead making proper contact, again try removing and cleaning the area that it makes contact with. Electrical problems can be one of the hardest things to diagnose but on a good note usually one of the easiest things to fix.

good luck

Pete

 

[eddieedmo]

ignition switch/module problem maybe , if faulty won't allow power to coil etc.

Nick

 

[tref]

Your method of working and analysis seems spot on to me, so I'm sure you'll get to the bottom of it! One thing worth checking, is I seem to recall that the height of the crankshaft sensors needs to be set in relation to the pin. When I had a similar problem (which did indeed turn out to be the DME brain), I seem to recall not being able to see the reference sensor pin - I think I ended up taking the starter motor out or something in order to have a proper look for it. Beware it is possible to set teh sensor too far down, and then it gets smahed to bits by said pin (for once, I didn't learn this the hard way!)

I also seem to recall it is possible to check the sensors with a moving coil meter - when the engine is cranking, the needle will swing briefly if connected across the sensor.

One other thing, is that the engine has to be cranking at a certain speed before it will send a spark or signal to the fuel pump relay.

Hope this helps,

Regards,

Tref.

 

[geoffbateman]

Just been having a load of problems with my 87 Lux which were very similar. Car actually cut out 50 miles from home and had to be recovered to home. Anyway suspected immobiliser and alarm so removed both. Engine fired up and ran thought great but then cut out and no start. DME relay and other 2 ignition relays changed - no result. No spark, no signal to injectors. No fuel pump with ignition on. Checked all wiring to DME all OK. Did resistance check on flywheel sensors - both replaced last year when I didi the clutch. All checked out OK. Downloaded DME schematic off net and worked out that fuel pump doesn't come on with ignition. Comes on when switch is moved to start position and then when engine speed is detected the DME overides the start based signal so that when the key returns to the ignition position the pump runs. The pump only runs if the ignition is on and the engine is running.
Thought that either DME or flywheel sensor U/S but resistance check said OK.
Got out old analogue bench meter and then checked pins 8-27 and 25-26 on the DME with the engine cranking. Good flick off the needle on 25-26 (reference sensor) but very weak on 8-27 (speed sensor - the one that detects off the teeth on the starter ring.
Interesting. Removed the speed sensor - fiddly - the rear one of the two and checked the gap. Well over spec. There was a shim fitted under the sensor for some reason that was a factory fit. If the shim was removed it would give me 0.8mm gap as per manual. Shim was 1.5mm so gap had been 2.3mm!!! and it had still worked for 3000 miles. Removed shim and all is fine again.
No signal or weak signal from the speed reference sensor will give no spark, no fuel injector signal and no fuel pump, so definitely worth a check. You don't need an oscilloscope just a good old fashioned analogue voltmeter about 5V full scale. Unplug the DME and check the 8-27 and 25-26 whist cranking the engine (as per clarkes garage website). Needle should flick up to around 2 to 2.5 volts if sensor distance set correct, both sensors should give same signal level - all on clarkes website.
Hope this helps - all the best.