924Board.org

[fish62570]

Hello everyone! I am new to the discussion forum and have a fuel related question for my new toy. I had recently purchased a 1978 924 with an unknown fuel issue. The car looks to be in fantastic shape physically, and thought that this would be a learning experiance and a great start to the wonderful world of Porsche.
Here is what I know thus far. The engine starts but always seems to flood and cannot idle properly. I have recently drained the fuel and oil as well as replacing new injectors, cold start valve, and plugs. After purchasing the Haynes manual and conversing with another 924 owner, I had also checked the ohm's on the warm-start valve which was to read 20 ohms. I had also pulled the fuel pump relay to help rid any remaining gas.
The engine turns over well, and does start while the relay is out. This seems to tell me there is an issue with getting too much fuel. As I was checking the injectors, I had kept 2 injectors out, 3 & 4, and was able to idle without pressing the gas pedal. The engine idles with obvious exhaust issues.
Thoughts on system pressure being the issue or any other thoughts would be very helpful. I would love to get the car ready for summer fun!

Thanks in advance!!!!!!!
_________________
924 work in progress

[Smoothie]

[fish62570]

I didn't have a jumper attached while the fuel pump was removed. I had thought that this was the procedure to help get rid of any existing fuel. I had only attempted to run the fuel out and expected the engine to stop immediately without the pump adding more. Please excuse my ignorance if I am off on this, I am new. Regarding the car running continuously, it has only done so while the injectors were out. That is what is leading me to think it is getting too much fuel.I have always thought that there is an issue somewhere within the fuel distribution and it being way rich. Replacing the cold start valve was my first attempt after the injectors and plugs. I was then thinking next that it was somewhere in the warm-up valve or fuel distributor.

Is the WUR the relay for the warm-up valve?
_________________
924 work in progress

[Smoothie]

This for some reason led me to believe it was starting with the fuel pump relay removed -

[fish62570]

Thank you !!! I will look for further information in the locations you had suggested. I am sure I will be posting more in the near future.
_________________
924 work in progress

[Mike924]

One easy test you can do is to disconnect the electrical plug from the CSV (cold start valve - aka 5th injector) and see if the car start or runs any different.

If it starts better, that a sign that you're running too rich, if it runs (idles) better, that indicates your CSV isn't being turned off (unlikely).

Cars with the idle mixture set very rich are often a sign of a stuck WUR, where someone, unfamiliar with the secrets of the CIS system, has compensated by turning the mixture up.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[fish62570]

I will try the CSV test this evening, thank you. I had also ordered a couple books to read up a bit on the Bosch CIS. Should make for educational reading.
You had commented on adjusting the idle and turning the mixture up, is there a way to turn the mixture down? Is the screw on the intake manifold the one to adjust for the mixture? I had read something regarding the turning of this screw adjusts the idle. Am I way off? The reason I ask is that the person that had owned the car prior has more experience with GM/Ford off-road vehicles and I am trying to figure out what he might have tried before I purchased the car.
_________________
924 work in progress

[Mike924]

The mixture adjustment (up and down!) lives between the fuel distributor and the rubber boot on the air meter. It's easy to miss because it sit at the bottom of a thin tube (possibly with a bung in the end). You'll need a fairly long 3 mm Allen key to get to it. Turn it clockwise to richen the mixture, counter-clockwise to lean (I think). It can be stiff from fuel laquer deposits.

The simple screw on the intake manifold (throttle housing actually) is a throttle by-pass valve to adjust the isle speed. You may need to adjust this along with the mixture screw to keep the idle speed within range (~900 rpm).

You'll need a CO meter to set the mixture properly. Do you have the 924 Haynes manual? The whole procedure is in there in a fair amount of detail.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[fish62570]

Thank you for the education. I do have the Haynes manual and will read more upon it. I am one that learns more by having information, like what you have given, and now knowing what to look for in literature. I will pick up the CO tester to have on hand!!!!!!!

Thanks..........
_________________
924 work in progress

[fish62570]

I played a bit with the 924 last evening. Also in process of reading the Bosch books. Very informative I might add. Still the flued is very rich. I had tried adjusting the air/fuel mix, no luck yet. Seems like the fuel gage has dropped a little even though I have had the battery unplugged. Unplugged fuel lines from distributor and nuthin seems to leak. When I tried to unplug the feed line, it still seems much fuel is coming to the distributor though it isn't leaking. Can the diaphragm be considered good from that? Also, there seemed to be a bit of mixture that came out of the exhaust when it was started for a brief moment. Smelled like gas, looked like tar...ewwww though it smelled good. hahaha
Question...... did the 1978's have the frequency valve? My engine does but when searching the haynes, it seemed only related to the Lambda system.
Still smiling, just cuz I'm learning and looking forward to conquering the fuel problem and driving this baby!!!!
_________________
924 work in progress

[Paul]

No O2 sensor = no frequency valve.

You may be referring to the hot start solenoid.....
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Mike924]

Hot start solenoid was only fitted on '79 cars and later. Edit: and apparently supplied as a retro-fit kit to some earlier cars through a Technical Bulletin release (Thanks, Paul)

When you turn the pump off, the fuel accumulators maintain pressure in the fuel lines for some time. Is this what you refer to as 'the diaphagm'?

Will your cars actually start and run, or is it struggling even to do this?

If so, a back-to-basics approach might be required, i.e. setting everything up from scratch with the correct pressure testing guages.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

[Smoothie]

[fish62570]

I am starting to think the issue is in the fuel distributor. The leak I believe is internal. I haven't noticed any leakage of fuel from the distributor and always having a flooded engine leads me towards that. Mike924, I have only had the car running when injectors 3 and 4 were removed from the engine. It maintained idle, though bad, without having to press the gas pedal. Smoothie, the valve does have fuel lines and an electrical connector attached. I think I will remove the fuel distributor and inspect the diaphragm for damage. It might take some time, but what the heck. It is below freezing temperature outside(Minnesota), so I believe a warm garage will be my sanctuary from the wife and kids.
_________________
924 work in progress

[Mike924]

I believe the diaphragms in the fuel dist. are made of thin metal, so are unlikey to tear, but anything's possible. If one has gone, your best bet might be a second-hand replacement of the whole fuel dist.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org