K-Jetronic experts?

[Onne]

Hello all,

Does anyone on here know their way around the K-Jetronic mechanical injection system?

My 300SE struggles to start up, takes about 10 secs of cranking to get her to run.

I am sick to the teeth of garages telling me that:
A, the diagnostics equipment is not compatible, here's a £50 bill
B, they say that there is nothing wrong.

Is there a way of ruling things out one by one? I have been told by my Merc "specialist" that it is definately NOT the cold start valve.

One isue I have is a leaky fuel pipe near the pump, replacement is being delivered on monday.

Have a Merc:

[The Transplanter]

If you have a leak in your fuel system then that is your problem. K-Jets require high pressures to run, and lack or loss of pressure will result in poor or non start.

My initial thought would be that the problem lies with the Pump, accumulator or WUR, but as you mention a leak then my money is on that

Only ever take a vehicle with mechanical injection to a garage who understand the system. Its beyond me how someone would even attempt to plug it into a diagnostics coms port. The only way to test mechanical systems is the old fashioned way, and thats by checking fuel pressure etc. as per the manufacturers spec.

[Onne]

Thanks, fingers crossed the pipe will solve the problem. Problem is finding a garage that does.

This one I used supposedly specialises in older mercs, so surely K-Jetronic would be a big part of that...
Apart from that I can't really fault this garage though, they are quite reasonable.

[TurboDieselWeasel]

Try the following:

Turn ignition to prime the pump. And off. Repeat 3-4 times and then start. If it starts quicker now, it might be a faulty fuel pressure reservoir. Part number A 000 476 06 21, 126€

Btw: a '90 car allready has the KE-Jetronic with electronically controlled fuel pressure regulator.

Do you have the factory service manual? Contains lots of diagnosis stuff for the KE. Can be tricky to track down a fault on these. I f you want to keep the car, might be a good idea to 'get into' the KE-Jetronic. Seems like people who know theyr way around the K/KE are getting scarce...

[Onne]

I do have a service manual on CD.

I'll give that a shot (after I've fixed the fuel pipe of course, no point now)
Whereabouts is this fuel pressure regulator/ reservoir?

It'd be good to get into this whole KE-Jetronic, as you rightly say not many people know about it.
Might have a look round to see if there are any resources/books on the subject.

Cheers!

[TurboDieselWeasel]

It's part of the fuel pump bundle [26]



But yeah, sort out any leaks first.

[Onne]

Aah, that is excellent, pipe 119 in that picture is leaking on mine, I've ordered all the fittings that go with it.
This is the situation on mine:

[TurboDieselWeasel]

From top to bottom: pressure reservoir, filter, pump. I'll give all pipes a good coat with wax on my W123 to prevent future headaches. Also check the fuel line where it goes over the subframe, you might want to put some wax or grease there; they'r usually quite rusty there

[Onne]

Will do! I don't mine looked bad when I was last under there. Hateful job though... Is there any way of stopping the tank draining?

[Onne]

Jan 27, 2012 11:02:13 GMT TurboDieselWeasel said:

Try the following:

Turn ignition to prime the pump. And off. Repeat 3-4 times and then start. If it starts quicker now, it might be a faulty fuel pressure reservoir. Part number A 000 476 06 21, 126€

Just tried the above, she fired up straight away (and started to pee out fuel from the filter banjo side)
Is there a way of testing the fuel pressure reservoir? I'll change the pipe and fittings first though, pressure might be dropping, confusing the FPR.

Found a good link about KE-Jetronic:
www.coming4you.net/downloads/KE-Jetronic_missing_pages_10_and_11.pdf

Also another photo of the above W126, one mighty parts hauler...
560SEL based:

[ChasR]

I would go with crud in the lines. My Volvo 740 (on a K-Jet system) became an awkward starter once it had ran dry of fuel, yet it was fine when warm.

Another thing is how dirty is your metering plate and is it free in movement? Cleaning them up does wonders on a K-Jet.

[Onne]

I'll have a go at the pipe first, and go from there. Fuel filter was replaced not long ago, so all should be clean (Filter is just above the pump on the picture)

[chrissyb]

does it idle low when first started?

I think these use KE jetronic which has some basic ECU control for cold start/fuel pressure. If the OVP relay fails/oxidised it can result in the car being in a default 'limp home' mode which takes some cranking....

on my 190e the relay was behind the battery, (behind black splash guard, relay is usually red with a clear plastic cover..) don't know if these have the same setup.....

[Onne]

Yes, they use the same setup, my OVP relay is fine though, she idles lovely. Just the starting bit that isn't (and that she sometimes stalls when running LPG, but that is fairly normal apparently when using a vapouriser)

[panelbeaterpeter]

I'm by no means an expert, but when my K-Jet Scirocco wasn't starting, I unplugged the 5th injector/cold start valve, and it started. I bought a new one from Germany for £90, and it made no difference. I've left it unplugged and it runs fine.

[carat 3.6]

Have you got anymore pictures of your car? I'm liking the estate conversion.

[Onne]

Sadly that's not my car...

Panelbeaterpeter; I think I'm getting nearer the solution thanks to mr Weasel of Diesel. The leak on the back seems to make a lot of difference, and she is a lot easier to start with the priming.
Pipe arrives today in all its gold platedness (£55 incl fittings) so hopefully fit it at the weekend!
If that doesn't make any difference it might be the FPR (which is connected to the pipe I'm replacing)

[scruff]

K Jet is very sensitive to fuel and vacuum leaks, even the tinyest leak can knacker hot or cold start as the pressures used in the metering head get out of kilter.

Fixed loads of 924 problems jsut by fixing vac and fuel leaks.

[Onne]

The big ones usually are the sensitive ones haha.

Got myself a lovely shiny new part today:



Now to get covered in fuel whilst fixing this. Good thing I don't smoke or cook on gas at home!

[Onne]

So, I broke down again last friday, heard a plop under the bonnet, and no way of starting again. Got towed home by the AA.

Next day (before the snow) I walked up to the car, turned the key, and after a few cranks (a fair few) she started up and ran like normal, on both fuels (but not at the same time obviously)

also changed the little pipe, old one was truly knackered, as were the copper washers. now all replaced.

Still doesn't start well, can anyone recommend anyone near Nottingham/Derby?