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K-jetronic vows

HansW

HansW

New member
Joined
Jul 25, 2004
Location
Ireland
Hi

I am wrestling with the K-jetronic. It is the type without Kat and comes from a B 230E.
the problem I am having is warm start:
After leaving the car sit for about 20 minutes it takes ages to get it back starting again, it could be 3 - 4 atempts.
What Have I done so far:
exchanged fuel pump: No betterment, When it did not start the next time I opened the fuel line to the cold start valve and found fuel under pressure there.
Changed the injectors with new seal rings: no improvement.
changed the complete unit to another: still the same
checked ignition, exchanged coil, power unit and measured currents -- all working OK.
Checked fuel pressure: OK
adjusted cold start air valve to open more: no betterment.
Checked everything for air leaks, none.
Adjusted co. still no betterment.
Valve and ignition setting perfect, good compression.

Maybe i am overlooking something --

any ideas?
 
maybe the accumulator

this is what prevents vapor lock. it keeps rest pressure up for quite a while, allowing quick warm starts.
 
howabout the accumulator next to the main pump? Retains fuel psi when the car isnt running, otherwise you have to restart pushing up all that fuel each time the car starts from rest
 
The accumulator was added in design to maintain a degree of pressure in the lines because of delayed starting after weeks of idle. It also is to help dampen the fuel line pulsations.

Two hours of idle will not drain the lines unless something else is wrong.

Check valve on the in-line pump?

As above, you have to have a pressure gauge on a k-jet..
 
Hi
Thanks for all the ideas.
I will have to fab a preasure gauge, as there is no Bosch workshop around. this problem is not new at all, tis been with the car ever since i got it. there is no seperate accumulator next to the fuel pump in this car, -- I may need to find something in that line and put it in.
I may use One from the late 940' which goes in line,-- I suppose worth a try.
The fuel pressure regulator has been checked and works perfect.
the fuel pressure relay works fine and comes on whenever I turn the key for a few seconds,-

I will see tomorrow, Hans
 
HansW said:
any ideas?
Click to expand...

What you are describing is often caused by the fuel pressure leaking down too fast. As has been mentioned, a fuel pressure gauge is essential to diagnosing this. If you get your hands on a maintenance and troubleshooting book (there is likely one online that you could find through this site- look at K-jet.org), it will give you a lot of useful info, such as, to start, the spec for rest pressure leakdown time. Then you can isolate various components, usually by pinching hoses off, and it will quickly become apparent where the leakage is happening. In my experience, the most common offender is the control pressure regulator. Other possible sites are the check valve on the fuel pump, and the o-ring on the piston in the fuel distributor.
 
Thanks Harry
I ordered a gauge with T-pieces on E-bay going up as far as 7 Bar. I will have it within a few days. then I can get around this One and find a solution.
I have the full instruction for the pressure test.

Greetings from ireland, Hans
 
But are u sure you dont have an accumulator next to the fuel pump under the front seat?

[we're talking 740 here, right?]

Which year is the car?

Since the issue have been there since you bought it, maybe some erk found the accumulator leaking and just replaced it with a fuel line instead?
 
JE Jr said:
But are u sure you dont have an accumulator next to the fuel pump under the front seat?

[we're talking 740 here, right?]

Which year is the car?

Since the issue have been there since you bought it, maybe some erk found the accumulator leaking and just replaced it with a fuel line instead?
Click to expand...

If we are speaking in 740 terms, i am not sure it ever got a fuel accumulator, since you are describing there is nothing next to the fuel pump.

Do you have a fuel filter on the engine firewall, or underneath the chassis in the fuel pump cage?

Usually cars that came with the filter on the firewall had a turbo accumulator next to the fuel pump, which was lovely in preventing vapor-lock and helping retain fuel pressure for k-jet warm starts.

I kept mine when I converted to megasquirt. (K-jet pumps are awesome on EFI systems)

It seems fuel pressure related. Do as they said - test for pressure drops when the car is off around various components. A fuel pressure gauge is critical to diagnosis of K-jetz.

good luck from texas,

Brett
 
Hi
That car is 1989 -- the car on the avatar and has the pump + filter in a crade under the car.
It's a NA car. i will have a look out for a accumulator from other cars and will mount it possibly on the firewall next to the main unit. We'l see tomorrow and thanks for everyones input.
 
Check here:

You should already have the accumulator, but yea, check the fuel pressure with a gauge first.

Fuelpump%20740%20B230E.jpg
 
problem solved

dear members

this morning I searched and found a complete pump assembley under the scrap 89 car which has the accumulator. It was in reasonable condition rusty though, so I dismantled the unit, cleaned up the components treated against rust and spray painted it. At the same time I fitted a new fuel filter -- put it into the car and started it.

Restart hot on the button !!!!!!!!

so here I go -- it never dawned on me, that the unit must have been replaced by a 940 One.

So thanks again to everyones input and I learn as I go by. I will have a look out for a spare unit now.
 
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