Porsche Enthusiasts Club Forum

I have a 81 924 which has been the epitome of reliability over the years ,
I can leave it for some time throw a battery in it and it fires up.

now it is not playing ball and will not run,

stuff I have checked
plugs leads and distributor cap all cleaned and working, there is a spark at the plugs.

fuel pump is working, fuel filter new and flowing freely.
there is fuel at the injectors.

air filter is clean, I have stripped the air flow system to clean it as it was found to be dirty,
it has made no improvement.


the cars turns over on the key and appears to catch, as soon as the key is release from the start position it dies.

if I keep the starter turning the engine will fire and reluctantly rev with throttle use, but as soon as the key is released it dies .


I have had an ignition box (located behind the passenger light) fail and wonder if it could b this again ?

I really need to solve this issue as I was about to do the body work and give it a new paint job for getting it back on the road.

any help or ideas will be appreciated.

cheers roy


this was what I found inside the air metering system,

hi Roy

reading between the lines i think the first thing that i would do is drain the fuel and replace it with fresh, fuel has a shelf life and going by what you have described I bet the car doesn't get used that often and thus my first question would be, 'how old is the fuel'?

pete

hi pete,

should have said new fuel has been put in the tank, before any of the testing took place.

cheers roy

Did you remove the fuel dizzy from the air flap assembly(3 screws) and check the dizzy lift pin is free to drop under it's own weight, they gum up.

This might not be relevant to a 924, but on other cars that could have been a symptom of a problem with an ignition system using a ballast resistor (which allowed a higher voltage to the coil while cranking). Is there some similar function in the 924 system ?

Have you cleaned any gunk out of the fuel tank?? My 24's tank was full of all sorts of sh!te after being stood for a few years - mostly rust and a bit of baffling foam... That caused a major running issue with clogging the tiny filters in the fuel distribution head. If you've got the metering flap off then you should be able to get the filters out too ..

I posted a fairly comprehensive set of pictures on the 924 board a couple of years ago... if you're a member you might still be able to see them!

Greg

well the fuel metering head had crossed my mind, and I see that there are refurbishment kits available.

any one done a rebuild on the fuel metering head ?

also even if there is fuel at the injectors could low fuel pressure be enough to not open the injectors at tick over ?

fuel dizzy ? is this the metering head ?
sorry not aware of the part.

cheers roy

I've had these symptoms happen on a Golf, and it was the ballast resistor for the coil.

Fuel distributor =metering head. There often isn't any need to rebuild these, and it isn't always recommended, removing the unit completely from the assembly you have pictured, by removing the 3 cheesehead screws, won't disturb anything, but will reveal the centre pin which is operated by the air intake flap. The pin and flap must move freely as it is the movement of the flap by intake airflow that triggers fuel supply to the injectors. remove the pin(it should drop under it's own weight) and clean thoroughly with carb cleaner, spraying some up inside the unit, and work until it is free.

Air leaks and low fuel pressure are the cause of most K jetronic issues, and use of a fuel pressure test kit is recommended.

I think it is the pin in the fuel metering head,
I split it of the air flow housing and the pin does not move !

and given what little force the it takes the air flow system to move this, then I guess this looks like the issue.

so going to give this a thorough clean out to get the pin moving and refit to test if this is the issue.

thanks for the info ,

cheers roy

I've just been over to the '24 forum, but as my membership lapsed I can't see any of my 'interesting' posts.. But, if you're a member you might be able to ...

Look at this thread ... then if you can, follow the trail through the tech section... It also shows how clean your flap actually was!

https://porsche924.co.uk/forum/viewtopi ... =7&t=15542

Greg


..... and going back to the 24 junkyard reminded me of how bombastic some of the members there could be when it came to badgering you into paid membership...

I would prefer the term "persuasive" to "bombastic", and junkyard is a little dismissive?

If you want 924 help it is one of the most useful IMHO, but I am biased We are prepared to help anyone with a 924 problem.

I have the same Bosch fuel injection as you on my Quantum 2+2 that has a Ford RS turbo mill fitted and it is left all winter and expected to fire up in the spring, but this year it did what yours has, however I blamed the metering unit seizing as it cleared itself after the fuel pressure cleared whatever had jammed.
Does it run with carb cleaner sprayed in the intake while cranking?

wee update

with the fuel metering head off again I found the pin was free moving,
gave the part a blast throw with carb cleaner and refitted,
the result was the same fault remains.

before I retried the engine I removed the plugs and gave them a good clean,
trying the engine again after refitting the fuel unit, the plugs came out heavy dry black deposits.
which the manual says is over rich fuelling.

so going to get a rebuild kit and if it is the diaphragm that is faulty.

cheers roy

Before you start throwing time and money at it, I would strongly urge you to get a fuel pressure test kit and do a thorough test of the system. There are other components, AAV,WUR, which could cause mixture problems, or it could be a simple case of mixture adjustment out.