Porsche 924 Scheiße - understanding why people fit carbs...

[inconsistant]

Not sure about the running either but sound like something the 924oc peeps will know about. Good to see it’s on all four wheels and running, at least a bit. 

 I suspect the sunroof will be manual, so just 4 clips to undo/snap/replace. I think only the later 924S only had the electric roof.

Love those estates too. The first bunch were based on the 944, the later red one is 924 based. I think there are 2 different versions, types, manufacturers. Very rare. I’ll dig out some photos. 

[N Dentressangle]

1 hour ago, inconsistant said:

Not sure about the running either but sound like something the 924oc peeps will know about.

No answers so far. Let's hope they come up with something - I have no idea.

[N Dentressangle]

10 hours ago, N Dentressangle said:

No answers so far. Let's hope they come up with something - I have no idea.

We have some suggestions from the 924OC forum, so will have a play around and report back.

[N Dentressangle]

Cleaning the Hall sensor connection at the dizzy and replacing the king HT lead has made no difference.

I have re-made the vac pipe connections to the WUR and inlet manifold, and removed all the trunking to check connections and find any splits:

On top is the vac pipe from the crankcase to the inlet tract - not keen on the bodgy tape repair and cobbled together part at the engine end, so will be replacing this with new* 3/4" hose. Here's where that crankcase end plugs into:

There was a fair amount of debris - snail shells, chewed nutshells, leaves and cobwebs - collected behind the engine mount. I went magnet fishing and found a little treasure trove of lost things 🤣:

Next job is to re-make that pipe and put it all back together.

[N Dentressangle]

One very small split found and repaired:

This is a relatively cheap bit of pipe (£50ish) so can be replaced in time.

Just got to wait for the glue to set and then all can be re-fitted

[Zelandeth]

If you have changed anything ignition wise in terms of cap/rotor - try swapping back just in case when the fault is there.

I got sent on a merry old dance that wasted me a month on a K-Jet fitted Saab 900 about 15 years back by the fact that the wrong rotor arm turned out to be listed in the Intermotor catalogue.

Car ran absolutely fine from cold, would run for about 10 minutes then start to exhibit symptoms which seemed all the world like fuel starvation.

I must have rebuilt about 3/4 of the injection system before I found the old rotor (I'd changed about a week before the fault appeared) rolling around in the boot and figured "what the hell, I'm out of rational ideas at this point..."

At which point the car ran absolutely perfectly again.

I still had a spark at the plugs when I checked - but it was apparently too weak to work under cylinder compression once the engine warmed up (leaner mixture needs a hotter spark to ignite apparently).

Suffice to say a note in big capital letters telling me to only use a Bosch rotor of the correct number not equivalents went in the service notes.

Wouldn't surprise me if a lot of the fuelling and ignition bits are identical between the two cars, and it's a quick and easy thing to try at least.

[N Dentressangle]

All now back together, and guess what? It still won't run properly.

I do have enough petrol left to set fire to it 🤔

[N Dentressangle]

Just now, Zelandeth said:

If you have changed anything ignition wise in terms of cap/rotor - try swapping back just in case when the fault is there.

I got sent on a merry old dance that wasted me a month on a K-Jet fitted Saab 900 about 15 years back by the fact that the wrong rotor arm turned out to be listed in the Intermotor catalogue.

Car ran absolutely fine from cold, would run for about 10 minutes then start to exhibit symptoms which seemed all the world like fuel starvation.

I must have rebuilt about 3/4 of the injection system before I found the old rotor (I'd changed about a week before the fault appeared) rolling around in the boot and figured "what the hell, I'm out of rational ideas at this point..."

At which point the car ran absolutely perfectly again.

I still had a spark at the plugs when I checked - but it was apparently too weak to work under cylinder compression once the engine warmed up (leaner mixture needs a hotter spark to ignite apparently).

Suffice to say a note in big capital letters telling me to only use a Bosch rotor of the correct number not equivalents went in the service notes.

Wouldn't surprise me if a lot of the fuelling and ignition bits are identical between the two cars, and it's a quick and easy thing to try at least.

Thanks. I think I will do just that. Bear with me...

[N Dentressangle]

29 minutes ago, N Dentressangle said:

Thanks. I think I will do just that. Bear with me...

Nope. Makes no difference.

Bollocks

[Zelandeth]

Bugger.  Was worth a try at least!

Worth sniffing around (carefully!) with a cab of brake clean or similar to see if there is a vacuum leak somewhere I guess.

Making sure the warmup regulator isn't full of crap (and is getting power) would probably be my next port of call.  Beyond that though you probably really need a pressure gauge so you can see what's going on.  As everything K-Jet does is pressure controlled you're kind of flying blind for anything beyond the most basic troubleshooting without one.

Something I never ended up needing as for my part I've never had a bit of trouble with it beyond the metering head being a bit gummed up, the odd vacuum leak and the aforementioned rotor arm incident where the injection system was eventually proven to be innocent.

[N Dentressangle]

Coil resistances tested and are within range, but swapped out for a spare 6v one anyway:

Makes no difference.

[N Dentressangle]

BTW the previous owner did mess with and clean the WUR:

So given his mechanical ability* I might end up pulling this and having another go at it...

[inconsistant]

What @Zelandeth said happened with my 924 earlier in the year when trying to start it after HGF. Put the old rotor arm & cap & spare distributor back and it finally started, but I think you've discounted that as a problem, but just wanted to agree.

I’m a bit crap at all this mechanical diagnosing stuff, so I’m not in a position to advise, but I wanted to share what I tend to do which is think along non-mechanical problem solving lines.
First thing I would be thinking is along the lines of what have I done since it didn’t do this, to make it do this now. Anything that can be swapped back over? like put old sparkle plugs back in or something? Try old HT leads, etc, sorry can’t recall what bits and bobs you’ve changed. 
Second, I’d be thinking along the lines of if it starts and runs for 10-15mins and then stalls, what sort of things change after 10-15 minutes? The K jet warm up gubbins should have all settled down by then, and coolant and engine should be up to temp so I’d be looking at stuff like metal heating up and expanding so it might make a lose connection somewhere? On my previous 924 one of the HT leads was damaged and when the engine was warm from running for a while it stopped making a good connection with the sparkle plug (the HT leads are under the inclined hot side of the engine so they take a bit of a beating and can go wring) so I had an occasional misfire, took ages to diagnose, a replacement ht lead sorted it. 
Have you unscrewed/removed the caps from the top of the spark plugs before fitting leads?

Sorry just some random thoughts…  and a bit of an insight into how I pretend to be good at keeping an old car running. 
 

Also, the rear spoiler on yours is off a 944 and to my eye looks too big. Assume the hatch/spoiler has been changed at some point? The 924 spoiler was smaller and I think is better proportioned for the narrower body. Probably not a priority though, but replacement hatches with spoilers are cheap, if you care enough!

[inconsistant]

Also, it might not make any difference but that left hand rubber bit needs to be pushed more fully onto the hard plastic bit so that the partially visible ridge circled in red is completely covered and the jubilee clip forms a seal behind it. 
Just in case air is getting in via that joint. 

Edit to add: here’s mine, in case it helps to see how far they should overlap:

[Zelandeth]

I did have a dig around in the box of stuff from back that far to see if I still had a spare one floating around, sadly looks like it was passed on to someone at some point.

Other possible thermal thought - ignition amplifier.  Square metal thing with an 8(?) pin connector on it.  Looks something vaguely like this.

They rely on good thermal contact to the metal they're attached to for heatsinking.  They also can play up when hot as a failure mode.  I always used to keep a spare in the car...of course never needed it!

No idea where it would be on the Porsche, was on the inner wing on the Saab.  About 7 o clock below.

For all it has it's foibles, K-Jet works incredibly well for what it is once sorted out.  I've definitely had less issues with it across all of my Saabs (and the first one was an utter nail) than a friend had with their 16v ones with conventional electronic systems.  Must have done nearly 40K miles in the last one too in all conditions and aside from a couple of idle stumbles which were quickly tracked to vacuum leaks it Just Worked.

Biggest gripe with it was that getting the big intake hose back onto the metering head was fscking awkward!

...I really miss that car.

[N Dentressangle]

11 hours ago, inconsistant said:

Also, it might not make any difference but that left hand rubber bit needs to be pushed more fully onto the hard plastic bit so that the partially visible ridge circled in red is completely covered and the jubilee clip forms a seal behind it. 
Just in case air is getting in via that joint. 

Edit to add: here’s mine, in case it helps to see how far they should overlap:

Thank you - yes, I spotted that when I took everything apart and made sure it's all in the right place.

It would not amaze me if this is WUR related, given the PO's meddling.

[N Dentressangle]

7 hours ago, Zelandeth said:

I did have a dig around in the box of stuff from back that far to see if I still had a spare one floating around, sadly looks like it was passed on to someone at some point.

Other possible thermal thought - ignition amplifier.  Square metal thing with an 8(?) pin connector on it.  Looks something vaguely like this.

They rely on good thermal contact to the metal they're attached to for heatsinking.  They also can play up when hot as a failure mode.  I always used to keep a spare in the car...of course never needed it!

No idea where it would be on the Porsche, was on the inner wing on the Saab.  About 7 o clock below.

For all it has it's foibles, K-Jet works incredibly well for what it is once sorted out.  I've definitely had less issues with it across all of my Saabs (and the first one was an utter nail) than a friend had with their 16v ones with conventional electronic systems.  Must have done nearly 40K miles in the last one too in all conditions and aside from a couple of idle stumbles which were quickly tracked to vacuum leaks it Just Worked.

Biggest gripe with it was that getting the big intake hose back onto the metering head was fscking awkward!

...I really miss that car.

Good thought. I'll give that a check.

It would be my first port of call on a 14CUX hotwire injection Land Rover product, so could well be worth a look here.

[EyesWeldedShut]

If you rule out heatsink/heatsoak problems on the amplifier - how about checking the fuel filler cap is correct? 924 (iirc) use a vented one and if yours isn't then there could be a vacuum led fuel-starvation problem?
Someplace in the degs of my brain there's an idea that a 944 cap on a 924 can also cause this

[N Dentressangle]

11 hours ago, inconsistant said:

Also, the rear spoiler on yours is off a 944 and to my eye looks too big. Assume the hatch/spoiler has been changed at some point? The 924 spoiler was smaller and I think is better proportioned for the narrower body. Probably not a priority though, but replacement hatches with spoilers are cheap, if you care enough!

The PO put that on.

I rather like it 🫢

[N Dentressangle]

1 hour ago, N Dentressangle said:

Good thought. I'll give that a check.

It would be my first port of call on a 14CUX hotwire injection Land Rover product, so could well be worth a look here.

Now all cleaned up:

Plenty of corrosion and white dust all over the earth contact, so I thought we might have a culprit.

But.... no dice.

Bollocks

[N Dentressangle]

924OC thinks there have been some shennanigans going on with the way the WUR is piped up, so I'm checking that.

Whilst we get a consensus. I drained the tank and pulled the outlet:

It came out like this, in two pieces. I had to fish the filter part out. FFS.

Someone has deleted the in-tank pump (not needed anyway) then bodged the remains back together. It should look like this:

🤣

It's not impossible that the loose filter part had been sucked at an angle against the outlet, blocking the flow 🤔

[N Dentressangle]

I knew this already, but the in-tank fuel pump isn't actually needed. Porsche replaced it with a simple strainer, but being a Porsche part it's #omghowmuch and that's not the shite way.

THIS is the shite way:

Obvs I've cleaned and blasted the filter as much as poss, and it should now be OK. I'll pop it back in and 🤞

[N Dentressangle]

All back together and somewhat predictably, no difference.

Bollocks again.

[N Dentressangle]

OK, I'm going to call this as an ignition problem. This is a BIG step forward, as it now limits the possible issues.

Here's what happens when you try to start the car now:

This is worse than it was 2 days ago.

I just tried a really generous amount of carb cleaner into the inlet manifold and had another go at starting it with the throttle pressed to the floor. The result was exactly the same as the above video. No different at all for the addition of tons of volatile fuel.

So, the coil ohms out OK. That's all I know so far. What to check next?

[Talbot]

Definitely ignition.  I've sort of skim read through the rest of the thread, but first things to check:

Timing.

New plugs.

It sounds like it's running massively out of time and on 1.5 cylinders. 

[N Dentressangle]

9 minutes ago, Talbot said:

Definitely ignition.  I've sort of skim read through the rest of the thread, but first things to check:

Timing.

New plugs.

It sounds like it's running massively out of time and on 1.5 cylinders. 

When it cut out, it did so suddenly.

For the next day, it got harder to start but would stay running ok and rev for up to 10min before eventually stumbling and dying. It wouldn't idle.

It will now barely start as you can see in that latest video.

I think the timing is OK, but part of the ignition system - either the electronic ignition in the distributor, or the ignition module I cleaned up earlier - is dying / dead. It's not the coil as it (a) tests OK and (b) has been swapped with a different one to no effect. Same goes for the HT leads, cap and rotor arm, and the plugs are brand new correctly gapped NGKs.

[EyesWeldedShut]

3 minutes ago, Talbot said:

Timing.

I think this was already mentioned  - is the dizzy inserted right? I screwed our 924 up by (iirc) refitting the thing about 180 degrees out (may have been 90) - after faffing about for about a week I rang Dave Berlyn who (politely) suggested I'd got the dizzy in wrong and should either  reseat it properly or try moving the plugs around the dizzy cap and see what happened. Moving the HT leads got it running.
This was all pretty much pre-internet days, Haynes was either wrong or just useless. Bound to be better info out there these days - probably even colour photos  

[N Dentressangle]

1 minute ago, EyesWeldedShut said:

I think this was already mentioned  - is the dizzy inserted right? I screwed our 924 up by (iirc) refitting the thing about 180 degrees out (may have been 90) - after faffing about for about a week I rang Dave Berlyn who (politely) suggested I'd got the dizzy in wrong and should either  reseat it properly or try moving the plugs around the dizzy cap and see what happened. Moving the HT leads got it running.
This was all pretty much pre-internet days, Haynes was either wrong or just useless. Bound to be better info out there these days - probably even colour photos  

Yes,timing is fine.

The fact that it started and ran smoothly for a while again after it first cut out proves the timing is still good.

[stuboy]

4 hours ago, N Dentressangle said:

Yes,timing is fine.

The fact that it started and ran smoothly for a while again after it first cut out proves the timing is still good.

daft suggestion time............. is fuel coming up?

[N Dentressangle]

8 minutes ago, stuboy said:

daft suggestion time............. is fuel coming up?

Yes it is.

But even if it weren't, the engine should have fired on the carb cleaner if the ignition system was good.