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

[rusty_vw_man]

3 hours ago, N Dentressangle said:

aaaand we now have a fuel leak on the fixed pipe:

Bollocks.

Pipe is long and NLA. It's also holed in the section that curves up next to the heelboard that you can see, then passes over the top of the rear axle, so a tricky shape.

Plan is now to buy a couple of these: https://www.screwfix.com/p/flomasta-brass-compression-equal-coupler-10mm/37293 and make up two stubs of 10mm copper pipe with flares on the end, then join to two with fuel hose and clips to remove the damaged section.

I have no flaring tool to do flares on the car, and the one I have is crap at the best of times. Not good enough for brakes, but should manage something which will stay fuel-tight here.

Was just catching up with this, saw big stillsons, bit of a fight and fixed fuel line all together in one post had a horrible feeling what was coming next - and it did. I always get the same issue with brake lines - touch it and poof, a hole appears  

Your plan looks fine though - can’t help with the diameter question, but if you do it in 8mm and you end up with poor  performance at high revs you’ll know what needs doing! 

[N Dentressangle]

I know! Although weirdly, nothing I was fighting with would have moved the bit of fixed pipe that's leaking, so 🤷‍♂️

Anyhow, much easier to do this now than have a fuel line explode on a rainy January evening somewhere horrible. That section is really rotten, so I knew it was coming sooner or later.

This is what the shakedown bit is for, after all.

Will try to replicate in copper, but got some 20 bar rated fuel hose ready for if it's beyond my limited skillz.

[N Dentressangle]

Knackered section of pipe chopped out in 3 pieces:

The break in the middle is where it passes over the axle and had started leaking. It was pretty crusty.

Started to have a go in copper, but even with a pipe bender it was obvious flow would be restricted further around the curves.

Decided to make up copper stubs and then put a flare on them with my crap Halfords kit, then 8mm fuel hose. Here's the end that goes to the accumulator all cleaned up and with the new hose fitted:

Time to get everything fitted up and see if it holds!

[N Dentressangle]

All now re-fitted and no leaks. Starts cold and idles, but still unwilling to hot start.

The guide says: Upon switching the pump/engine off, note the pressure reading on the gauge. It should settle at about 30psi ± 3psi. At the same time check your watch and write down the time. After at least 20-30 minutes the pressure should be no lower than around 25psi ± 3psi.

My pressure is down to zero after 10 min.

If I close the shut-off valve on the pressure tester, the pressure DOES hold.

Leaking injectors?

Monkey tennis?

[N Dentressangle]

All injectors spray when the pump runs, and don't dribble when the pump's turned off.

It's not the injectors.

[captain_70s]

My 740 has a similar K-Jet setup, a dead accumulator (pressure drops to 0 in under a minute) and an intermittent hot-start problem.

If the car is hot and left shut off for 20-40 mins or so it won't restart. An hour or so later it'll cough into life almost instantly.

 @juular and I spent way too long replacing parts and setting pressures to no avail. I'm sure at the time accumulators were silly money (like £350+) and only avaliable NOS from a couple of suppliers. I wonder if somebody has started knocking out less genuine ones...

I "solved" the hot start issue by buying a new battery so I could crank the engine over loads (like 30+ seconds) to bring fuel up to the injectors.

I've since found my crank position sensor also seems to be getting a bit reluctant to function when warm. So I may have had two issues on top of one another...

[N Dentressangle]

Definitely a genuine Bosch accumulator.

Starting to get sick of this ungrateful PoS to be honest.

[rusty_vw_man]

You seen this https://k-jet.biz/wp-content/uploads/2020/01/008-Hard-hot-start-problems.pdf

gives some additional tests to try and isolate where you precious fuel pressure is escaping to…. Need a fuel line clamp for most of them. 

[N Dentressangle]

18 minutes ago, rusty_vw_man said:

You seen this https://k-jet.biz/wp-content/uploads/2020/01/008-Hard-hot-start-problems.pdf

gives some additional tests to try and isolate where you precious fuel pressure is escaping to…. Need a fuel line clamp for most of them. 

Brilliant - thank you. I'll give those a go.

I have a new seal for the system pressure valve on order from Porsche, should be here next week.

[omegod]

I'm currently doing the Ke-jet tango too, new coolant temp switch, accumulator ( both Bosch)  and a new pump fitted and I am honestly dreading turning the key as the disappointment will be crushing 

[N Dentressangle]

25 minutes ago, omegod said:

I'm currently doing the Ke-jet tango too, new coolant temp switch, accumulator ( both Bosch)  and a new pump fitted and I am honestly dreading turning the key as the disappointment will be crushing 

That's EXACTLY how I'm feeling after every fix 😭

[omegod]

20 minutes ago, N Dentressangle said:

That's EXACTLY how I'm feeling after every fix 😭

We'll do the next one together via teams as a support strategy 😂

[rusty_vw_man]

15 hours ago, N Dentressangle said:

Starting to get sick of this ungrateful PoS to be honest.

Eyes on the prize - get this sorted and you’ll have a relaible* modern* sportscar* that will make you the envy* of your neighbours, and irresistibly* attractive (although possibly only to other middle aged men who have battled with k-jet!!)….

Depending on tests, I reckon it might be time to load up the parts cannon and any pressure holding rubber seals anywhere in the system gets replaced. I blame age and ethanol - reckon the combination might have seen off most of them….

Or I assume Euricarb will flog you a suitable set of carbs and manifolds for the same sort of cost of a new car! 

[juular]

22 hours ago, N Dentressangle said:

All now re-fitted and no leaks. Starts cold and idles, but still unwilling to hot start.

The guide says: Upon switching the pump/engine off, note the pressure reading on the gauge. It should settle at about 30psi ± 3psi. At the same time check your watch and write down the time. After at least 20-30 minutes the pressure should be no lower than around 25psi ± 3psi.

My pressure is down to zero after 10 min.

If I close the shut-off valve on the pressure tester, the pressure DOES hold.

Leaking injectors?

Monkey tennis?

FFS!

It has to be either the regulator or the WUR then.

It does sound like the accumulator was dead though so youd've had to replace it anyway. It's one less variable in the equation to think about.

Fingers crossed you get the answer.

As soon as it runs properly you'll forget about all the pain. 

[tooSavvy]

Who said 'S.U. sucks!'......

...... they were SO right 😉

YKIMS

🚙💨

[N Dentressangle]

33 minutes ago, tooSavvy said:

Who said 'S.U. sucks!'......

...... they were SO right 😉

YKIMS

🚙💨

I would LOVE to be able to just put a nice pair of HIF44s on this.

So much better.

[N Dentressangle]

17 hours ago, rusty_vw_man said:

You seen this https://k-jet.biz/wp-content/uploads/2020/01/008-Hard-hot-start-problems.pdf

gives some additional tests to try and isolate where you precious fuel pressure is escaping to…. Need a fuel line clamp for most of them. 

OK, test one - run engine then switch off and put a clamp on the fuel return:

and after 10min or so...

Fucking thing.

Next test

[N Dentressangle]

Run again. Switched off. Fuel feed line clamped.

Pressure drops quickly to zero.

Bollocks.

The weirdest thing is I unhooked the battery and the fucking thing kept running!!!:

WTAF?

[juular]

1 hour ago, N Dentressangle said:

I would LOVE to be able to just put a nice pair of HIF44s on this.

So much better.

Tempting isn't it 😄

The one positive I'll say about KJet is that once you have it sorted it'll stay sorted for the next 5-10 years. 

I feel like I'm always rebalancing SUs and wondering why one day they seem a bit rich and then fine the next.

But they do just work, I'll give you that.

The weird thing here is that you can't smell fuel. 

It's going somewhere.

[N Dentressangle]

Last ditch is to swap back in the old WUR.

If that doesn't work then I'll chuck it up on the field or break for spares.

Had enough now.

[rusty_vw_man]

For sanities sake are you sure the clamps are stopping all potential flow? 

If you are then it’s not going back to tank, or back through the pump, or from previous tests through the injectors. 

So the only place left is between the fuel distribution block and the injectors. But that doesn’t make sense as to lose that much pressure that quick I’d assume you’d be able to smell it, even if you can’t see it. 

Have you tried winding the screw in as suggested in the link just to rule out a dribble through the enrichment ? 

what an absolute arse! 

[rusty_vw_man]

Oh and run on is fine, alternator makes electrickery, with wire that joins to all major services and earthed through mounts, so it doesn’t need the battery to keep going.  More magical is if it then starts again with the battery disconnected…. 

[N Dentressangle]

35 minutes ago, rusty_vw_man said:

Oh and run on is fine, alternator makes electrickery, with wire that joins to all major services and earthed through mounts, so it doesn’t need the battery to keep going.  More magical is if it then starts again with the battery disconnected…. 

Yes, of course you're right.

Just found a fuel leak at the back somewhere, so that's the next thing to look into. I've swapped the old WUR back in anyway.

[N Dentressangle]

The leak is in the hose from the accumulator towards the engine, p/n 477209047B, and #14 here:

It comes in at around £100, so game over for the moment I think.

It clearly doesn't want to live.

[rusty_vw_man]

Upstream or downstream of where you clamped it though? Have you found £100 problem but also the source of the pressure bleed off? 

[N Dentressangle]

The thread on the accumulator is M14 x 1.5 DIN. If I can find a female pipe fitt

20 minutes ago, rusty_vw_man said:

Upstream or downstream of where you clamped it though? Have you found £100 problem but also the source of the pressure bleed off? 

Upstream. So it's not even where the pressure was bleeding off.

Union at the accumulator is M14 x 1.5 DIN female with a 90 deg elbow, so I guess I'll see if I can make something up.

 

[rusty_vw_man]

7 minutes ago, N Dentressangle said:

The thread on the accumulator is M14 x 1.5 DIN. If I can find a female pipe fitt

Upstream. So it's not even where the pressure was bleeding off.

Union at the accumulator is M14 x 1.5 DIN female with a 90 deg elbow, so I guess I'll see if I can make something up.

Oh FFS!!

[N Dentressangle]

Metal end stub that goes in the accumulator cut from the rest of the hose.

Heated and straightened slightly.

End heated and flared:

Ready to accept an 8mm / 3/16 fuel hose from the accumulator all the way around to the fixed line.

Can't see why it won't work.

Cost = 2m of fuel hose.

[dome]

Mine was an arse to start once it was warm and I'm pretty sure the solution that worked for me was to pull the air filter cover off and move the plate that goes to the metering head. 

Maybe @juular can remember better than me but I want to say that wear in the plunger meant that it was sticking in one position and needed the plate/ plunger to move and then it would fire straight up. 

 

 

[juular]

1 hour ago, N Dentressangle said:

Metal end stub that goes in the accumulator cut from the rest of the hose.

Heated and straightened slightly.

End heated and flared:

Ready to accept an 8mm / 3/16 fuel hose from the accumulator all the way around to the fixed line.

Can't see why it won't work.

Cost = 2m of fuel hose.

 

1 hour ago, N Dentressangle said:

Metal end stub that goes in the accumulator cut from the rest of the hose.

Heated and straightened slightly.

End heated and flared:

Ready to accept an 8mm / 3/16 fuel hose from the accumulator all the way around to the fixed line.

Can't see why it won't work.

Cost = 2m of fuel hose.

A couple of good hose clamps and that'll be reet.