W123 230E 1982 misfiring

[optimusprime]

Yes i did see your post - And i can see that you have been running before you could walk. Sill i need to know what plugs you have fitted ?. I recon thiose are wrong ones for a start Dont even know your engine type . is it 110 or 115 You say you have set valve clearances ,,that are set by oil presure .[how] .. you might have checked clearances only .
And check ECU along with EZL One place you said you had not replaced the rotor,then you had .
You need a good mechanic to sort out your puzzle.

 

[bikeman]

Yes i did see your post - And i can see that you have been running before you could walk. Sill i need to know what plugs you have fitted ?. I recon thiose are wrong ones for a start Dont even know your engine type . is it 110 or 115 You say you have set valve clearances ,,that are set by oil presure .[how] .. you might have checked clearances only .
And check ECU along with EZL One place you said you had not replaced the rotor,then you had .
You need a good mechanic to sort out your puzzle.

It's a 1983 230E, engine is 102.980.
Valve clearances are manual.
Plugs are correct. I have the service manual.
Rotor arm was cleaned then subsequently changed when I could source.

What I've done is pretty logical:

1. I serviced and replaced all service items, plugs, filters etc.
2. Replaced obvious suspects eg fuel pump, injectors
3. Cleaned fuel system and checked fuel system electrical components.
4. Checked for vacuum leaks
5. Took it to a Mercedes Specialist and had him check the ht side with a scope, the fuel pump delivery and the Kjet fuel pressures.

Cant see what else I could have done.

If you know any good mechanics in Buckinghamshire, and I mean ones that wont just chuck parts at it that have already been changed and one that actually knows something about Kjet beyond twiddling the mixture screw, let me know and I'd be happy to use them.

 

[optimusprime]

As for adjustment in the fuel distributor did you adjust the mixture screw ?

 

[optimusprime]

Throttle position sensor check -

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[bikeman]

Throttle position sensor check -

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This is not the same car. Mine doesnt have those parts.

 

[DITTRICH]

I find this thread absolutely fascinating - kind for like a frustratingly good whodunnit!
Knowing sod all about this subject I did dredge up this (to educate myself).

Bosch K-Jetronic – Part 1, The Basics

Bosch K-Jetronic seems to be a bit of a black art these days. Almost anyone you mention it to backs off and cringes. Hopefully this series of posts clears up some of that misinformation and scaremo…

tasteslikepetrol.net

The person who wrote this up might be contactable?
There is also parts 2 : testing and 3 : tuning and fixing on the blog - some commenters seem to have shared their insights too.
Apologies if you found this already yourself.

 

[optimusprime]

Bikerman Yes your right, looking in to this more i can see it not the same engine in your car . I had W201 in mind -190E ..Do uou have a rubber boot under fuel distributor ? if so check it out for leaks. I have one of those manuals above and parts dont marry up to the ones fitted now .

 

[optimusprime]

We will try again

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[bikeman]

I'm coming back round to something affecting the fuel pump.

To recap:

The car starts and runs fine for about 10miles/20 mins. Then it violently misfires on even gentle acceleration but can be driven on a light throttle and will idle perfectly. The fuel pump also gets noisy.

I've removed the FP relay, jumpered it, same as above so relay is good.

I've left the fuel pump jumpered and running, engine not running and it remains quiet. I've done this for 5 minutes. Would it be ok to leave it for 20 minutes running like this?

So it looks like there's something in the fuel circuit putting a strain of the fuel pump after being driven a while. I surmised that maybe the fuel pressure is rising so high that the pump struggles against it. But I did pay a specialist to measure the pressure and was told it was ok. I've ordered a gauge so I can check for myself.

I figured the pressure regulator valve on the fuel distributor might be stuck closed but it seems ok ie no dirt etc.

 

[alabbasi]

Sounds like you need to take it somewhere to get diagnosed. Nobody here is in front of your car and it seems like plenty have chimed in with free advice. It's time to open your wallet.

 

[bikeman]

Sounds like you need to take it somewhere to get diagnosed. Nobody here is in front of your car and it seems like plenty have chimed in with free advice. It's time to open your wallet.

Yes very helpful mate. You obviously didnt read the OP where I said that I'd already had a Mercedes specialist look at it for 2 weeks and then started suggesting changing parts that had already been changed. There isnt another nearby that knows these old cars.

 

[Bellow]

The fuel pump also gets noisy.

Cavitation? Starved on the suction side?
Expect dry plugs with the above, wet with over-pressurisation.

 

[alabbasi]

Yes very helpful mate. You obviously didnt read the OP where I said that I'd already had a Mercedes specialist look at it for 2 weeks and then started suggesting changing parts that had already been changed. There isnt another nearby that knows these old cars.

Then you need to look further

 

[bikeman]

Cavitation? Starved on the suction side?
Expect dry plugs with the above, wet with over-pressurisation.

Tank filter and feed pipe to pump have been checked. Not sure what else would cause cavitation.

Wouldnt it also cavitate when running the pump with the engne not running? Why would it only happen after 10minutes/20miles?

Plugs look normal.

 

[Jobsworth]

Take a look at the banjo bolt where the fuel supply line from the pump joins to the K Jet fuel distributor. If its head has a raised circle on it the banjo bolt contains a tiny gauze filter. Seen them blocked many a time

 

[Bellow]

Plugs look normal.

Are you pulling them at the point of misfire, ie, a 'plug chop'?

 

[bikeman]

Take a look at the banjo bolt where the fuel supply line from the pump joins to the K Jet fuel distributor. If its head has a raised circle on it the banjo bolt contains a tiny gauze filter. Seen them blocked many a time

OP said that this had been changed.

 

[Jobsworth]

OP said that this had been changed.

Fair enough. Was just a thought.

 

[Jobsworth]

Rereading everything you’ve written I’m moving away from a fueling fault. In my experience if it’s a lack of fuel when you open the throttle hard you get a smooth constipated groan from the intake and it goes away the moment you shut the throttle again. If it jerks violently when you open the throttle it’s much more likely to be an ignition problem.

 

[Flyinspanner]

If it happens after 20mins it may well point to an electrical heat soak issue affecting a part ( which is ok when tested ‘cold’)

Hope you track it down