SOLVED - No Spark, Coil Gets Power, Porsche 944.

1st, try changing the DME relay. A common problem with Porsche 944s. (And a cheap/easy fix).

I made up a 3 wire jumper and my DME relay is shagged. If I jump the relay board I do get the fuel pump prime, however still no start.

My ignition switch is faulty, if I turn the key it lights up the dash but does not actually turn the motor over, I have bypassed this with an ignition button. I am wondering if the no spark could be related to a faulty ignition switch?

I have asked my parts supplier for a price on a coil, but I'm not looking forward to hearing what it's going to be.

Hi, You have 12v to the coil, if you put a spark plug on the king lead and lay it on the engine then run a fly lead from the negative term on the coil to earth does the plug spark? If yes then move on to the dist, if no then it looks like the coil is faulty.

Colin

Thanks very much for the replies, I'm currently replying from bed after giving up for the evening so please forgive the shortness of this reply.

Injection system I seem to think is Kjet, similar to VW items. Ignition wise I have no idea, I shall investigate and report back.

Thanks for the tip on the coil and the negative, I will try that tomorrow evening once I am home from work. The dizzy when I got the car seemed to be incorrectly fitted and didn't look at its best, but I was putting the fault down to the coil and didn't investigate the dizzy set up with much passion.

Since my last reply I have installed a new ignition switch which seemed simple enough and now I get the engine cranking over on the key, I thought this may have been playing a part in the DME relay but still no difference.

With further investigations I have possibly found another avenue to persue. I get no taco bounce what so ever on cranking, needle is dead flat and it should supposedly bounce. This seems to suggest the problem is in the speed reference sensor or sensors on the rear of the engine. Annoyingly the sensors are super expensive but I've found the part numbers are the same as E30 crank sensors which are a lot more affordable.

Ah excellent mr Chasr! You are certainly right.

I was reading a thread about a 924 on here and Kjet was mentioned. However whilst trying to hunt down some sensors They're coming back as Bosche Motronic items

Just to add, my late night browsing seems to have turned up some fantastic sensor options!

Thanks for the help again welshpug.

The 944 has two sensors on the top of the bell housing. One is a speed sensor, one is a refference sensor. From my research they are the same as a E30 crank sensor and therefore I assumed did the same as a crank sensor and without that signal I guessed it wouldn't fire.

I ordered some new sensors last night and tonight I set about removing my current sensors so that I could Throw the new sensors straight in tomorrow.

Upon removing the speed sensor I found this...



I cleaned what appears to be a little bit of rust off the end of the sensor that the magnet has picked up and attracted and tested it, 1050 ohms across two pins, 1M across the other two. This falls almost bang in the middle of the recommended resistance.

With this in mind I then tested the resistance with the sensor pressed against the metal body work of my car, the resistance went way high, I then wondered if the magnetised bit of crud on the end of the sensor meant that the sensor was unable to relay the correct information back to the ecu and in turn ground the coil for a spark.

I refitted the sensor just out of curiosity really, cranked it over with a 3 way DME jumper in the relay and it started straight up!

The car has sat unused and has not been run for well over 3 years now, the DME relay was obviously a fault, as was a faulty ignition switch (which someone in the trade had diagnosed as a £330 starter motor, when in reality it was a £6 ignition switch) and I wonder if removal and testing of the starter motor has induced some sort of crud into the bell housing which has in turn been picked up by the sensor. Either way it now runs.

I did however manage to dodge the £145 charge for each sensor, I actually managed to get the pair for £20 through cross referencing part numbers. So if anyone comes across this via the search function please PM me and I'll gladly share the part numbers so you can save a few quid.

Thank you all very much for all of the help offered.

Please can I have these part numbers as I have the same problem on an'82 944 lux. We have just changed the coil and change too the spark. Much appreciated.
My email info@kentcarpenters.com