mhariush

Trying to trouble shoot my 944S.

The engine cranks but doesnt fire up. When I turn the key to "on" all instruments light up, lights work, everything. When i turn the key to start, it cranks but doesnt fire. Tachometer doesn't bounce.

The fuel pump doesnt start, listened for it and also unhooked the fuel lines to see if anything pumps out. nothing.

No sparks and don't hear the injectors click. The injectors are brand new OEM Bosch and the spark plugs are good.

Checked the coil, has 12V at + connector.

Checked the plug going into the Ignition Control Unit (Module), has 12V.

I've checked for loose wires and burned wires but can't see or find anything.

The DME relay is also good and working.

Any thoughts on what could cause the pump, spark and injectors to not fire up?

Thanks!

wesmc3

Sounds like DME plug didn't get seated well.

fireman02169

I think no tach bounce usually means reference sensors/speed sensors
I don't know how that affects the fuel pump though

pnbell

Ref sensors would stop the spark for sure...

Mine did a similiar thing a few months ago... turned out to the the Circuit Board inside the DME; there is a large transistor and the solder joints developed cracks.

Re-Soldered (very easy, first time ever soldering anything) and car starts perfect now.

this link explains the process and location perfectly... Grab this transistor and try to wiggle it while looking at each joint. It controls the ignition system; and will cause a no start.
https://rennlist.com/forums/924-931-...ed-w-pics.html

mhariush

Thanks pnbell, I'll look into that. I only drove the car one day after rebuilding it, i bought it with the destroyed head. It started up and ran great, started and stopped 6-7 times or more that day with out any hesitation. It wasn't until after the car wash that the trouble started.

pnbell

hmmm, Water has been known to leak down on to the DME and cause issues,,, so check for water marks while your in there.

peanut

did you get this car to start ? It would be useful to have some closure ....or not

mhariush

Nope. Still in the garage without starting. I haven't looked at it much since before X-Mas but I'm going to have to figure it out now shortly.

Suspecting that the car isn't registering the spinning flywheel, but the speed/ref sensor has been checked and is fairly new and the bracket has not been tampered with or moved. What can it be?

peanut

if you have no tach bounce then there is your problem right there!
Without that imput the ECU will not ground your DME relay so no fuel or ignition.

Your sensor and bracket might be fine . The most common problem is the cable, from the sensor to the first connector block, at the rear of the cyl head which gets brittle or the onnector contacts get oxidised.

Try cranking the engine whilst someone wiggles the CPS sensor wires and see if you get a tach bounce. Its a very tiny movement barely 1/8"

Oh forgot to ask was the tank nearly dry just before it stopped working ?

jayman1869

I had a buddy who couldnt get his car started after he ran out of gas.. Hasnt started since. Whats the deal.

mhariush

The connector is almost brand new, and the connector going into the harness is fine, not broken or brittle. I'll try to have it wiggled when i crank it when i get back. It's all so weird. All happened after the starter got stuck engaged while the engine was running and wouldn't stop, until it burned up and failed.

Filled the car up that day with Shell 91, so it was probably 96% full when it stopped.

peanut

and you never thought to mention that before ??????


I would say from the information that you have provided that you need to re-check that you have fitted the correct type of CPS , and that it has the correct gap and none of the flywheel teeth have been broken off.

peanut

you need to start a new thread about this really otherwise this thread will get a bit confusing. if you do I'll tell you how I managed to get my car started after the same problem

Basically if there is only a gallon or less of fuel in the tank some fuel pumps can struggle to maintain sufficient fuel pressure for the injectors to work properly. Its happened to my car twice and it looks like low gas levels can mean on some cars that there is insufficient 'head' of pressure for the pump to work efficiently or water/air gets drawn into fuel system from the bottom of the tank .



Welcome to the forum by the way.

mhariush

Hi Peanut,

Thanks for you reply. I have another thread in here that lists everything done to the car, as well as when it stopped working. I started this to have a clean thread without the back history in case that helped people think fresh or come up with a good reason based on the symptoms alone.

Here's what happened;

I got this car with a broken timing belt, i took out the head, had it rebuilt, put it in, new chain, new tensioner, new lifters, new seal, new pressure relief valve (head), new belts, water pump etc. After a year of rebuild (in my spare time) I started the car up, it fired right up, ran great (though i did hear a sound that i belived to be a stuck lifter). I drove the car around that day, from downtown LA to Santa Monica, then back to Hollywood with a couple of stops. No problems, the car ran great, started right up every time.
It was little dirty so i decided to run it through an automated car wash just to rinse it off before i did polish the next day. After the car wash the car started right up, I drove to my house about 2 minutes from the car wash and parked in my garage. But when i tried to turn the car off, it didn't, well the engine turned off, but the starter was still running and gentle turn with the key to the right fired the car right up again. It kept doing this for 6-10 minutes prob and i was just about to try and unplug the battery (but didn't have a wrench) when i heard a metallic clank. It sounded like someone dropped something somewhere in the garage (i was standing by the battery and i looked forward and to my left. Didn't see anything. After the clank the engine sound changed (assume it was the starter not running anymore) so I decided to try and turn the car off, and it did. I tried starting it up later but it didn't go. Battery was dead, and as it turns out, the starter was dead too. Bought a new rebuilt starter, put it in and now the engine cranks but doesn't fire.

I have looked at the flywheel, didn't see any missing teeth, the sensor looks fine when i pulled it. The sensor is Bosch and i took it from my running NA (and installed it in that car about 1 1/2-2 years earlier).

I also have another thread as I mentioned where all this is explained as well.

Thanks

peanut

I suspect that the various problems are probably unrelated.

I think the starter getting stuck was probably just due to lack of use and nothing to do with the car wash unless you pressure washed under the hood?

With the car being unused for so long it would have been wise to drain the fuel tank and refill with fresh gas but the problem now is your CPS crank position sensor.

There are 2x sensors fitted to the early 944 and only 1x on later cars .
if I were you I would buy a new CPS that is correct for your model and make sure that you set the gap exactly to spec and that it is fitted into the correct hole . Clarkes garage have a guide I believe.

Until you see that tach bounce the car will never start . Its the first crucial sensor that the ECU refers to before it earths the DME relay which enables the fuel pump and ignition.

If a new sensor doesn't get the tach needle to bounce you may have to run a bypass cable which i can explain if needed.

One other thing you need to do is to check the ECU and make sure no water got inside the ECU or the electrical connector during the car wash. Look for water stains.