Any Bosch CIS (K-Jetronic) Fuel injection experts here?

[alabbasi]

US export car using Bosch CIS fuel injection (not CIS-E) so it has a warm up regulator. The frequency valve has a problem and has long been disconnected so exclude this from the problem

Car recently had a head gasket replacement, everything went back together and it's been running fine but hardly driven. I recently pulled it out of the garage and everything was fine but when I went to restart it , it would barely run. It's blowing white smoke everywhere but it's not a sweet coolant smell. It smells like raw fuel. I'm not sure if the fuel distributor or warm up regulator is the problem but it's continuous in the sense that it does it when cold and hot.

How do I go about testing the system? The problem happened all of a sudden and not after it was driven hard. Injectors were recently replaced and the car ran well.

[stevieturbo]

Check your mixtures, no point taking wild guesses that you think it is over-fueling.


basics first.

[GreenV8S]

alabbasi said:

How do I go about testing the system?

Have you got even header temperatures? This might identify one cylinder over/under fuelling or with an ignition fault which is causing the misfire. In that case you'd pull that plug and check the spark in the usual way. Don't assume that just because you smell fuel, it's overfuelling - any misfire will put unburnt fuel in the exhaust.

If you conclude there's a problem in the fuelling, the plugs will tell you whether it's one cylinder or all cylinders and this gives you a clue about the nature of the problem. It's a mechanical system so you're looking for a mechanical problem. Maybe a stuck injector, stuck air flow sensor, failed or blocked CPR. If you still have a cold start injector, disconnect that to see if it helps (apparently they're not needed in this climate in any case).

https://tasteslikepetrol.net/2020/02/bosch-k-jetro... has a pretty good overview of how the system works if you end up trying to diagnose it yourself.

[Steve H]

Fuel distributors almost never failed on K jet so unless it’s been stood a long time and the shuttle is stuck it’s pretty unlikely to be that. The warmup regs could stick but it was also pretty rare. Most issues were just them being fussy on idle adjustments etc.

Unless you have fuel pressure testing kit it’s hard to get much further but if you post up a couple of pictures of the layout of the system there may be some manual testing you can do.

[alabbasi]

Thanks, I have a fuel pressure gauge that should have fittings for Bosch CIS. I'll take pressure readings from the WUR to the FD and from the FD to the fuel injector. I'll also take a compression test which I hope pans out. The reason I think it runs rich is that as soon as I crank the engine, I can hear the injectors howl. which I typically hear on CIS cars when the engine is running rich.

[Steve H]

Don’t bother with the pressure to the injectors, it’s not a helpful test. From the reg to the top of the fuel distributor will confirm if the reg is working correctly, make sure you have the pump running for this test even if the engine is static and I would suggest you disconnect the 2 pin plug off the reg so you have time to get a proper cold reading before the heater element changes the pressure. You should get a lowish pressure when cold, increasing as it warms up but you will need to find the specs, I think it will be a range of about 1-3 bar but they vary by application and it’s been over a decade since I last did that test .

The injectors should whine when you crank the engine but not when you turn the ignition on and the pump primes or if you keep the pump running.

But post pics, there are some manual tests that may help.

[stevieturbo]

alabbasi said:

Thanks, I have a fuel pressure gauge that should have fittings for Bosch CIS. I'll take pressure readings from the WUR to the FD and from the FD to the fuel injector. I'll also take a compression test which I hope pans out. The reason I think it runs rich is that as soon as I crank the engine, I can hear the injectors howl. which I typically hear on CIS cars when the engine is running rich.

Determine if it is rich or not. Guessing is not diagnosing a problem.

[GreenV8S]

alabbasi said:

I have a fuel pressure gauge ...

You're missing a lot of basic steps and likely to waste time, and potentially damage things along the way, chasing a problem you have assumed.

Do you have a misfire?

Which cylinders are affected?

Do the affected cylinders have fuel and a spark?

For all we know, it could be as simple as a plug lead come adrift.

[steveo3002]

white smoke isnt fuel imo ....mech problem and a misfire making it smell of fuel?

are the plugs fouled and wet

cant imagine you get far diagnosing kjet over the internet , get fuel pressure gauges on it and a book with the figures and see what you find

[alabbasi]

GreenV8S said:

You're missing a lot of basic steps and likely to waste time, and potentially damage things along the way, chasing a problem you have assumed.
Do you have a misfire? - Yes, the car barely runs

Which cylinders are affected? - Not sure, but it's a V8 and both banks are affected because they misfire is coming from both exhaust.

Do the affected cylinders have fuel and a spark? Yes , there's spark to all the plugs. Wires are newish, cap looks brand new and so does the rotor

For all we know, it could be as simple as a plug lead come adrift - I wish, you can hear a single dead cylinder. This is not it, the engine was glass smooth when i shut it off, an hour later, it ran like this

stevieturbo said:

Determine if it is rich or not. Guessing is not diagnosing a problem.

Unfortunately, It's a catalyst car so my tailpipe sniffer reads CO and not CO2. It is the kind of rich I can eyeball though.

[GreenV8S]

alabbasi said:

Do you have a misfire? - Yes, the car barely runs

Which cylinders are affected? - Not sure, but it's a V8 and both banks are affected because they misfire is coming from both exhaust.

Do you have separate exhausts from each bank to the tail pipe? Typically a V8 will run a single exhaust that splits at the tail. In that case you can't make any inference about which bank is causing the misfire.

You can tell which cylinders are affected by monitoring the header temperatures. Starting from cold you will have a few tens of seconds to feel the headers warmoing up before they get too hot to touch, and after that you can dab them with a cable tie to see how hot they are - or use an IR thermometer if you want a more precise answer.

If the problem is only affecting individual cylinders that leads to a completely different diagnosis.

Once you know which cylinders are affected you know which plugs to look at. Is it possible they've fouled and clean plugs will make the problem go away?

I don't remember whether you mentioned - how have you verified the spark?

[alabbasi]

Thanks. It's a true dual system all the way from the manifolds. I have an exhaust from a similar car sitting on the floor. I'll pull the plugs to inspect the condition and run a bore scope down there to see if I can see any coolant (worse case).

Someone mentioned that there's no sense checking pressures between the FD and the injectors but I'm wondering if the membrane between the two halves failed which would cause unmetered fuel as it's not going through the piston. It seems to be dumping a lot of fuel. I'll try to check the exhaust manifold temps with the IR but as you can see from the photo, it building fills up with smoke pretty quickly and to the point that working in there becomes unbearable if I leave the car on too long.

Edited by alabbasi on Monday 25th November 04:08

[stevieturbo]

Older cars like that with a cat used to have a test port pre-cat ?

CO2 is not overly important measurement anyway.

Get a wideband lambda so you can determine mixtures.

And as others have said, if it really is dumping so much fuel in as to cause smoke, the plugs must reflect this. So what are the plugs like ?

And have you confirmed a good strong spark at all cylinders ?

[Peter-jforf]

From EX Auto sparks.....retired now at 81 years.....make sure you have 12volt at the "Pressure warm up regulator" 2 pin plug with the engine running only.... this unit will be mounted on top of engine in a Hot position....so after switching off engine it still picks up heat...as it works on the "bi-metal" principly.....no 12v there will give excess fuel delivery.....2nd...there will be a extra electrical injector in the intake manafold some where...ive no idea what engine you have...but i know the Bosch "K & KE " systems very well...this extra injector is on the Full pressure Fuel line..ie 80 / 90 psi, so it only opens on cold start...but if its not closeing properly after starting then will give massive over fueling...to test it will have to be removed...and the fuel pressure relay bridged to give a constant running of fuel pump with no engine running...and you checking no fuel being released from injector...i dont know what car you have...so cant help re . fuel pump relay location...but for sure will have one...thats the main to items which can cause over fueling. Peter

[alabbasi]

stevieturbo said:

CO2 is not overly important measurement anyway.

Get a wideband lambda so you can determine mixtures.

While I appreciate your insistence to get accurate mixture readings and it's certainly important or fine tuning, Given that in this instance the car is smoking out a 7000SQ/FT shop in a matter of minutes to the point that I can't be in the building. Buying a wide band 02 sensor and welding it in would probably get me as much benefit as trying to a compression test on an engine with a hole in the side of the block.

The reason I suspect that it's over fueling is because it's drinking fuel like it's going out of fashion. I'm also smelling fuel in the oil which appears over full (I'll drain it today). I pulled the plugs on the passenger bank (LHD car) and they're all black. Inspection of the cylinder bores shows the pistons to be wet.

I cleaned the plugs and put them back in. I'll do the passenger side and then drain the oil and refill with fresh oil. If I can get to the pressure testing, I will do it today. Otherwise it needs to wait a couple of weeks.

This is how all the plugs look on the right bank



All cylinder bores look wet (bear in mind the heads were off not long ago)



Plugs cleaned with a spark plug cleaner before reinstalling

Edited by alabbasi on Sunday 24th November 20:32

[alabbasi]

Peter-jforf said:

From EX Auto sparks.....retired now at 81 years.....make sure you have 12volt at the "Pressure warm up regulator" 2 pin plug with the engine running only.... this unit will be mounted on top of engine in a Hot position....so after switching off engine it still picks up heat...as it works on the "bi-metal" principly.....no 12v there will give excess fuel delivery.....2nd...there will be a extra electrical injector in the intake manafold some where...ive no idea what engine you have...but i know the Bosch "K & KE " systems very well...this extra injector is on the Full pressure Fuel line..ie 80 / 90 psi, so it only opens on cold start...but if its not closeing properly after starting then will give massive over fueling...to test it will have to be removed...and the fuel pressure relay bridged to give a constant running of fuel pump with no engine running...and you checking no fuel being released from injector...i dont know what car you have...so cant help re . fuel pump relay location...but for sure will have one...thats the main to items which can cause over fueling. Peter

Thanks this is good info and I will test it. The WUR is under the AC compressor which is the most PITA place to out it but there you go.
I know where the relays are so I'll see if I can jump the pump at the relay or use my electrical probe. I appreciate the help. I'm in a mind freeze right now with this car even though I'm usually pretty good at waking CIS cars up.

[Steve H]

alabbasi said:

Someone mentioned that there's no sense checking pressures between the FD and the injectors but I'm wondering if the membrane between the two halves failed which would cause unmetered fuel as it's not going through the piston. It seems to be dumping a lot of fuel. I'll try to check the exhaust manifold temps with the IR but as you can see from the photo, it building fills up with smoke pretty quickly and to the point that working in there becomes unbearable if I leave the car on too long.

You are doing this the hard way. If the fuel distributor was just pumping straight to the injectors all you need to do to prove it is run the fuel pump while the engine is not running. If you hear the injectors whining then it is putting fuel to the cylinders when it shouldn’t be. But that’s unlikely.

If you then lift/press (layout depending) the air plate (that I asked you to post pictures of twice now) you would normally hear the injectors start to squeak.

If that happens the basics of the distributor are probably ok and it might be worth checking the control pressure coming from the warmup reg. Bear in mind that the heater element in the reg is often wired to the same circuit at the pump so if you have been hot wiring the pump the reg readings may be showing part warm by the time you do them, unless you disconnect the plug on the reg before starting all this.

If all that is ok then I would be agreeing with some of the other comments that you are probably looking in the wrong place.

[stevieturbo]

alabbasi said:

This is how all the plugs look on the right bank

They certainly do not look like plugs that are overfueling to the extent you seem to claim. With the smoke you mention, if it is even fuel, I'd expect them to be plain wet and likely to the extent they were no longer firing correctly...hence both mixtures need established and whether there is a proper good spark available at all cylinders

I can't even recall having any engine smoke so bad as you say yours is, even with crazy rich mixtures.

Again, establish some facts, not guesses.

[alabbasi]

All the plugs have been removed, cleaned and replaced The cylinders are all pretty wet. I just drained the oil and for 20W50, it was very thin and smelled of fuel so I'll replace the filter and put fresh oil in before I attempt to test pressures.

I connected my fuel pressure gauge between the WUR an the Fuel Distributor at the cop line connection. Upon start up, the fuel pressure gauge got up to 62psi and sat the there. On my test hose, there's a shut off valve on the hose that I connected the WUR to which if shut off , should isolate the WUR and prevent it from feeding the FD. Opening and closing this valve made no difference.

As there was a slight leak coming from the gauge, i didnt leave it running too long but enough to let it load up..
The car would smoke continuously but when the engine started running poorly, fuel pressure dropped to about 40 psi at that connection.

Edited by alabbasi on Sunday 24th November 23:41

[Steve H]

Over 4 bar cold on the line from the warmup reg sounds high to me, what does the spec say?

But if it was high that would give a weak mixture not rich……….