924 won't start, cough or anything.

[Guest]

I'm after more help. My brother has purchased an 80 924. The thing will not start or anything. The story so far =
Checked TDC lines up with rotor 1 and dot on cam wheel = Yes
Checked spark from new plugs = Yes
Checked fuel pump and relay = Replaced with New
Checked air regulator valve = Yes
Checked injectors are getting fuel from fuel meter unit = Yes

We have fuel, air and a spark but the beast is dormant. We have tried everything we can think of. I refuse to believe it won't start. Please help.

Cheers

Alan

 

[SteveSJS]

Perhaps stating the obvious if so I apologise in advance, but does it have any sort of imobiliser fitted? Old ones have been known to cause problems...

SteveS

 

[Guest]

A valid question. I have an 81 924 and an 86 944 turbo and both have the alarm lock by the drivers door, but this car does not have that. It does however have a switch mounted on the dash between the clock and oil pressure (or volt meter, can't remember) and a metal switch mounted inside the ash tray. Very strange. If an imobilier was fitted (and working) would that not stop the spark or the engine turning over ?

 

[usermjg]

I have only ever had one starting problem with my car, my pump was fine, i had spark and for a split second it would fire and then stop but only ir you left if for some time. The AA said it was the fuel pump relay, but it turned out to be the fuel pressure regulator and was fixed in 3 minutes flat, but it took a week or two to figure it out. The Fuel pump produces to much pressure and the engine has to regulate it down and thats all it was. Not sure its the same for your car but its worht a look.

Marc

 

[usermjg]

an immobliser will stop the spark but not the engine turning over.

 

[Guest]

We have tested the fuel is getting back to the tank, but not the fuel pressure itself. We have a spare fuel meter unit. Is it just a case of unscrewing the old fuel pressure switch and screwing in the spare or can the current fuel pressure switch be adjusted, and if so to what pressure ?

Thanks for all the help so far. This is great.

Cheers

Alan.

 

[924nutter]

This is an ignition module fault without question. Been there done that. Had the same situation, did all the checks you have done. Adjusted the mixture through the range until the engine was almost hydrualic-locking with fuel. You may get a spark, as I did, but is it occuring when it should? Is it the correct voltage. How can you check? Maybe a strobe light will show that the spark is nowhere near where it should be, but what about the voltage. My engine even tried to run backwards on the accumulated fuel. Then I changed the ignition module....... What was that gold blur Wilbur?

 

[Guest]

My 84 924 was always a real problem started when cold, but having just (last night) fitted a new warm up regulator (about £135 from Porschshop or £350 from Porsche dealer but possibly cheaper elsewhere) and she fires into life better than "my other car" (R plate!)

Might be worth a try

I also have a new thermo time switch, but haven't (and probably wont now given by how difficult it looks) fitted it as just the regulator has solved the problem.

Not sure how you can check out whether it is working properly before trying a change, but don't doubt some of the guys on here can help with that dilemma.

Andy

 

[924nutter]

Replacing the warm up regulator will greatly improve the cold-start performance of a car whose engine fires, then cuts out, and I am pleased to see that someone has provided some feedback for other members, as this now confirms some suggestions made in the 924 faq. about cold starting.

I am not discounting anh's suggestion, but here we are looking at an engine that wont even cough. I have in the past, stood in the drive with jump leads attached trying to start a dead engine, slowly richening (and leaning out) the mixture an eighth of a turn at a time, until the engine starts to struggle over tdc due to the volume of fuel in the cylinder. This would suggest that at some point I would have passed through the ideal stoichiometric ratio for perfect cold starting irrespective of the status of the w.u.r. but alas "de nada". The fact that a spark is present is decieving. Arthur Conan Doyle, as the creator of Sherlock Holmes, said whenever you have removed the impossible, what ever remains is the truth, no mater how improbable. So in the context of the non-starter, we need three thing to be present, just as in the triangle of fire; Fuel, air, source of ignition.

Let us examine what has changed.
Have we got fuel? Yes. Has the mixture been altered? No.
Air and fuel available.

Is the cam rotating? Yes.
Is the cam timing correct? Yes.
Air and fuel present.

We have elliminated two of the three things we need as being unchanged, therefore however unlikely, the source of ignition must be different somehow. The spark is controlled by the igniton module, and from bitter experience I know that they can fail but still produce a spark. What I cant say is whether the failure is due to the spark being too feeble
or occuring at the wrong time. I can say that on one occasion my engine did indeed run backwards with exhaust smoke coming from the air filter, which seems to suggest a spark occuring way too soon. The signal to the module is from an induction coil in the bottom of the distributor energised when the cruciform shape passes between two magnets. It could actually
be worth checking to see if the cruciform is in the right place on the distributor shaft, as I have seen that alter postion too, but only once.

 

[944Turbo]

Has it got any compression? Are there any air/vacuum leaks?

Tony

 

[Hannu]

Just a short note to say dont go replacing the warm up regulater too quickly!.
At £98+ there not cheap. Mine had the problem of starting then cutting out, had to start it 4 or 5 times before it would run and then only with skillful work with the throttle.
I removed the warm up regulater and stripped it down, found a very small peice of dirt blocking the fuel path to the diaphram. It runs like a dream now and starts first time.

 

[924nutter]

I haven't got any problems 944 turbo, I am if you like expanding on a theory for another gentleman who's car wont cough splutter or anything.
I have taken it as a given that the non cougher was an engine that, prior to failure of whatever component, was a good runner.

I offered my situation an example from long ago; my module failed in the car park while stationary. I had driven to work, no problems. Went out to jump start a colleague's car and mine wouldn't cough or splutter. On inspection it had a spark. I had just driven it to work, so mechanically it was ok. Good compression, no vacuum leaks. It took me about three days before I finally changed the module in desperation. Woosh. The replacement (brand new from an OPC) lasted about six years. When the problem manfested itself again, I rebuilt the distributor internals, never thinking that the six year old module would give up the ghost so soon when the original had lasted 17 years. The second time I bought a second hand one from Lodge Sport, so you can understand why I think the thread starter has an ignition problem.

 

[944Turbo]

Hi Mr 924nutter,
Yes I can see where you are coming from with that, however the first post says we have fuel, air and a spark and also mentions a (recent possibly) purchase that won't start, was it bought as a non runner?
Assuming the sparks are at the right time, then missing compression would also cause a lack of running. Vacuum leaks could also cause incorrect mixture and difficult starting. Whilst your knowledge of the 924 is undoubtedly superior to mine, I just threw in a couple of other options.
Gadgetmaster how is it going?
Tony

 

[924nutter]

Thats the thing, the spark. I know it is difficult to believe, that if you have a spark the engine must start. Somehow the ignition module gets screwed up and sends the spark out at the wrong time. I am no electronices expert, so I can only guess at the failure of one of the little timing chips in the module. I have to admit that I made the assumption that the engine had, up to the point of failure, been ok in all other respects, so you could be right with the loss of compression or vacuum leak. The 924 is totally reliant on air passage through the metering unit to regulate fuel flow, so any air leaks would lean out the mixture. To lose compression on all 4 pots is however very unusual.

Merry christmas one and all

 

[jamie_aero]

Hi, just saying that I agree with 924nutter. Im building a 924 race car and had the exact same problem with mine (just as the car was about to go on the rolling road of all times). If your listening gadgetsmaster, have a look at the igintion module, it will probably look/smell fried. I ended up replacing mine with one I found in an old Volvo 740 (same bosch part number, yet a more 'solid state electronics' item), the car now runs fine.

 

[Guest]

Hello people.

I can now put an end to this problem. Sorry for not getting back sooner, my brother and I have spent a great deal of time swearing at this car. The problem is that the car was setup using the timing dot on the front of the cam wheel and not the dot on the back. This made the timing so far out that it would not start. After finding a post referring to a back dot, we cleaned the cam wheel and under the grit and grim there it was. After adjusting the timing the car starting but sounded a bit noisy. We took the cam cover off to find 2 snapped cam bearings and the studs bent out. We have been rebuilding another head.

What I would be interested in is what the front dot on the cam is for ?

Thanks for all your help.

I have learnt a lot from all your suggestions.

Alan.

 

[danmason]

Are you talking about the red dot? (it's red on mine, anyway). It should be lined up with the pointer on the top of the camshaft cover when removing and replacing your belts, and indicates that cylinder 1 is at top dead centre.

 

[924nutter]

Well don't I look stupid. Remember that the engine was in the Audi 100 coupe before it even found its way into the LT28, and heaven knows how old the cam wheel design is. It could be for anything. Once you have installed the cam correctly, have a look to see if it lines up with the machined face of the head with the cover off, as it could be for timing the cam with the cam cover off, something you might want to do if setting the engine up to test run it on a stand or something.
The Haynes manual clearly shows that the BACK MARK shoub be aligned with the pointer cast on to the cam cover as Dan says, but first, you should look for the tdc mark on the flywheel through the inspection hole. To get you close, use the timing mark on the crankshaft pulley, then use a nice bright torch to look into the square hole in the bell housing. Oriented from the front looking at the engine, it is at about the 1 o'clock position. If it is not there you should rotate the engine by hand until you see it, then get both marks aligned with their respective pointers. If the distributor has been removed, there is a mark on the body of the 'strib to align with the rotor arm, for No.1 tdc but when refitting remember that the skew gear will move one tooth as it slides in, so offset it by one tooth, but I can remember for the life of me wether it moves advanced or retarded.