944 not starting

shunt_jps · Aug 15, 2013

Hi guys, I have been having problem with the 944. The other day after replacing the battery after removing the wiper motor, the car would not fire.

It turns over fine, I have replaced the coil, dizzy cap, rotor, DME relay, checked the HT leads and yet no luck. I inspected the spark plugs and it seems as though they have an intermittent spark, when I took them out the plugs were wet so I know its getting fuel.

Also I cleaned the contacts on the speed refference sensor (I think) and the one underneath, it told me to do that on the internet somewhere, 2 connectors at the back of the engine.

But now I am running out of ideas...... :/

Any help would be highly appreciated. Thank you.

924nutter · Aug 15, 2013

Without wishing to cast aspersions of questioning your ability check that the plug leads are connected to the correct plugs and that number one is in the right place. It is easy to get it 180 crank degrees out. It is worth bearing in mind that if you line up the timing marks it could be either no1 or no 4 at the top of its compression stroke. I have a question, did you manage to unscrew the bolt from the rotor and get it off the end of the crankshaft? If so did you put it back on corectly and not 180 camshaft degres out? I changed the rotor and stub shaft on mine so I don't know whether the bolt hole goes all the way through or if there is a keyway which only allows the rotor to go on one way. In practise 944s either spark or don't, if it is the crankshart and speed reference sensors. The 944 needs to crank at 200 rpm or the fuel pump wont run so you know you are getting that. If a crack sensor stops working it generally fails permanently. On a separate topic I hope you don't mind me pointing out as politley as I can that unless it is intentional, you would be the third person recently to think that the 914 script is a heavily stylised 944 badge.

zcacogp · Aug 15, 2013

Erm, all good points John but I presume (although this is guessing) that it worked fine until he removed the battery and the wiper motor. Assuming that the wiper motor is incidental and can be ruled out then what about removing and replacing the battery would make it fail to start. (I don't doubt that the subsequent attempted fault-finding may have made the situation worse.) Oli.

924nutter · Aug 16, 2013

Many items have been replaced now Oli so the car is not exactly as it was when the battery was reconnected the first time, so I am trying to get the owner to double check his work so that this remedial work is as it should be, and thus eliminate it from the equation; then we can get down to finding the original fault, otherwise we will be chasiing our tails. With fuel reaching the cylinders we can rule out the fuel pump part of the dme relay, and anyway the gentleman says he has changed it, so we have dme, we have 200 rpm cranking, so all we need is something to light the fire at the right time. It has been mentioned that there seems to be an intermittent spark. We both know 944 well enough to know that if there is a spark it will fire up if it is at the right time, but there is not any mention of it even coughing on the intermittent spark, which it should do if the spark is there, unless in changing the wiper motor something else has been disturbed, but given the location of the motor behind the bulkhead it is well out of the way of engine management systems. This is one of those that I would like to get under the bonnet to with a nice fresh spare battery. It could be too rich but how would changing the wiper motor effect the motronic's ability to meter the fuel. There is of course the possibility of it being FPR which has failed totally conincidentally, or maybe a required ancillary fuse has been shorted out by the removal of the wiper motor, but the thing I come across most is the misconnecting of plug leads so I have used my Occam's razor principle. "easiest to go wrong, easiest to fix." Let's wait and see what the gentleman says to our comments.

zcacogp · Aug 16, 2013

John, Hmmm. From your post it sounds like we are in danger of being in violent agreement. Given that you and I are meant to disagree permanently then I think I'll bow out. [

] (I need to add that I am most impressed by your fault-finding logic there. Very, very logical. I now am quite curious to know what is/was wrong!) Oli.

ChasR · Aug 16, 2013

I would also be tempted to go with a fuel regulator issue (will it start with an injector lead disconnected?) or the HT leads being wired in wrong. Where exactly are you in the country?

924nutter · Aug 16, 2013

We can have a man hug on the garage day.

shunt_jps · Aug 17, 2013

Sorry for the late reply, I have been extremely busy this week so not had much time to use the computer. Thank you for the replys. Yes the new parts are set up right in the correct order and the rotor was replaced with the little bolt in the right place, however if it was in the wrong place 180 degrees out then in theory it should still create a spark (which I checked with all the plugs out and grounded them to the inlet manifold). From what I have gathered, the car is turning over and injecting fuel just fine. The spark problem is intermittent, during cranking it wont spark at all but then you will see 1 or 2 spark and then it will stop, the only way I can describe it is if there was bad contacts on an old points type distributor. I havent had a huge amount of time to get into it and I need to get a wiring diagram at some point, but to me it sounds as though something has gone wrong in the electrics like an ignition amplifier or maybe some part of the ECU, it has been sitting outside for a while before this problem and there does seem to be a leak somewhere which has caused moisture in the cabin, so I have invested in a car cover for now but the car isn't moving.

924nutter · Aug 18, 2013

Thanks for clearing that up I wasn't sure how you had checked for the intermittent spark. As you will have read the crank speed sensor needs to read 200 rpm before the DME relay is enabled; the DME really two relays in one; it enables fuel pump and igniton and as it is brand new and enabling fuel it is a fair assumption that it is enabling spark but there have been cases mentioned on this forum where a new dme was duff, so dont automatically assume it is working correctly. You've changed the coil haven't you?

zcacogp · Aug 18, 2013

ORIGINAL: 924nutter You've changed the coil haven't you?

My thoughts exactly. Oli.

924nutter · Aug 18, 2013

Checking back to his original post I see that he has changed the coil. I am begining to think that there is a problem with the the other flywheel sensor, if not then it is either a duff new component or part of the motronic unit that deals with the ballasted supply to the coil when cranking, or indeed the ballast wire or resistor (I don't have a 944 wiring diagram so don't know if the 944 has one in circuit) I wonder if the gentleman is getting that intermittent spark just as he relases the key? What you could also do is pop up the false floor in the passenger footwell to expose the motronic (moronic lol) unit and check the connector plug for corrosion if moisture has entered the cabin, but again as it is enabling the dme relay it is a straw clutcher. Have you tried craking with a plug lead stuck in the coil to elliminate distributor? If you get a good spark here then please also check for a good connection of the carbon brush to the centre of the rotor arm. After Tref's experiences we know that pattern rotor arms aren't always a good fit.