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280SE K-Jet no idle

Started by Franbom, 07 June 2024, 03:56 PM

Franbom

Hello,

I have bought 280SE (manual with air condition) in wonderful condition in Spain and went in it across whole Europe to Poland, where I live (about 3000km).
After few weeks of using it daily the car has broken down.
I need your help because I do not have idea what to do.

Symptoms: the car has no idle, meaning: when I push accelerator engine works OK, the more power the more evenly it works. But when I move my leg from accelerator engine immediately stops.
I start it again, there is no problem with start and again: I need to push leg on the accelerator. When I release it engine stops.

The same day but few kilometers before the engine han broken down there was one symptom that may be connected or may be not: the control of handbrake started to flash when I was stopping. It flashed at the beginig dimly but after the engine broken down it was flashing really hard. I do not know if this to symptoms are connected or not.

Just before the engine broke down I spent a 30 minutes in traffic jam moving about 2-3km. And just before it happeden i think I heard sth form clutch pedal, like squeeze. Maybe also not connected.

Thanks for your help.



daantjie

Before you bought the car did it perhaps sit for a long time?  Could be that you have some dirt in the fuel line but if you ran so many km already then likely you have run clean fuel through already but still good idea to confirm for example age of the fuel filter?

Kjet is also very sensitive to any vacuum leaks so also check all your plastic hard lines and rubber connectors for brittle areas and replace any suspicious ones.

Does the car pull strong in all gears up to red line without hesitation?
Daniel
1977 450 SEL 6.9 - Astralsilber

Franbom

Hello,

car was usually used once a month. It was stored in a very clean garage.

Yes, the car pull strong in all gears without hestitation. Actually there is not even work below 2000 rpm but then there is no hestitation.

My friend told me that there may be two fuel pumps in the tank: one for low revs and one for high revs. Is it true?

Jan S

Hi,

you probably have a standard kjet fuel assembly at the back under your car. You see it next to the rear axle, on the right side. One fuel pump, one filter, one accumulator, one pressure damper and a few hoses.

I'm far from an expert, but I have done some tests and solved a few problems on my car (6.9). I recommend doing a step-by-step diagnosis. Usually there are more than one problem with the system. I believe there is a manual describing the process in detail, maybe on this site. There are tons of material on this Forum regarding kjet.

Pressure testing are probably the most important tests on the system (e.g. system and control pressures under various conditions). Return fuel flow to tank is important. Leaks in the system must be identified. Idling valve must open and close ... etc.

It can be a nerve-racking process but you will learn a lot.

Good luck!
1975-mod W116 450 SE with 6.9 engine

raueda1

Quote from: Jan S on 08 June 2024, 01:52 PMHi,

you probably have a standard kjet fuel assembly at the back under your car. You see it next to the rear axle, on the right side. One fuel pump, one filter, one accumulator, one pressure damper and a few hoses.

I'm far from an expert, but I have done some tests and solved a few problems on my car (6.9). I recommend doing a step-by-step diagnosis. Usually there are more than one problem with the system. I believe there is a manual describing the process in detail, maybe on this site. There are tons of material on this Forum regarding kjet.

Pressure testing are probably the most important tests on the system (e.g. system and control pressures under various conditions). Return fuel flow to tank is important. Leaks in the system must be identified. Idling valve must open and close ... etc.

It can be a nerve-racking process but you will learn a lot.

Good luck!
There is, in the tech section.  It's probably the best way to attack it.  Cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

rumb

Start simple and check disti and timing. Then find idle screw and turn up a bit so it idles.

When you start cold engine does the rpm go up and the slowdown after a few minutes? That is what it should do. If not The idle air valve may need cleaning.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

ptashek

#6
Cześć,

I'm not going to be much help with troubleshooting. But you're in good hands here, plenty of people who know their way around K-jet. But at least I can help on the fuel pump and tank-side setup question.

This is what it should look like on your car:


- #371 is the pressure accumulator - it's responsible for keeping the fuel system pressurised when the fuel pump is not running; if failed, you would have severe issues with hot-starting the engine

- #210 is the fuel filter
- #423 is the fuel pressure dampener
- #189 if the fuel pump, there's only one

This whole package is located in front of the left-rear wheel, looking from front of car.


1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

raueda1

Can we clarify the problem a bit more?  My understanding is that the car worked fine for a long trip.  Then, abruptly, something changed such that it stallsfine  when your foot is off the gas but runs as long as the gas pedal is pressed?
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

raueda1

Quote from: raueda1 on 09 June 2024, 08:36 PMCan we clarify the problem a bit more?  My understanding is that the car worked fine for a long trip.  Then, abruptly, something changed such that it stallsfine  when your foot is off the gas but runs as long as the gas pedal is pressed?
Taking a step back, you say car runs when your foot is depressing the gas pedal.  That means that the car is capable of running, so there's not some total failure of electrical/ignition system or fuel delivery.  AND, the problem happened abruptly, right?  I'm guessing that something broke on the throttle linkage.  This can happen.  There are a number of small plastic bushings and bits that can fail.  Take a look at the CIS manual.  The manual is organized sequentially, that is, you can't jump to chapter 5 before you're sure that the previous steps are all OK.  Jumping around has made many people crazy. And the first step is..........  checking the throttle linkage!  I would start there.  Maybe get somebody to start the car while you are looking at the linkage so you can see what is happening with the linkage and go from there.  Cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0