Mercedes-Benz Forum banner

1 - 19 of 19 Posts

·
Registered
W107 W113
Joined
·
1,325 Posts
Discussion Starter #1
My '87 560 SL is not getting any fuel to the injectors.

I've disconnected the fuel line at the fuel distributor head, and no fuel is coming out (see picture) - there is plenty of fuel reaching the distributor head; I've disconnected the hose and a large amount of fuel flowed when I put the ignition ON.

I've also run the duty cycle test (ignition ON, engine not running obviously).

70%
13% when depressing the air plate
22% at WOT

Any idea what the issue could be?

Thanks



Sent from my MAR-LX1M using Tapatalk
 

·
Registered
1990 420 SEC
Joined
·
153 Posts
Does taco needle move as you crank? Fuel pumps are controlled on by fuel pump relay as ignition unit (EZL) tells engine is turning and also briefly as ignition is turned on. To do tests on non running engine you have to locate fuel pump relay and jump it. Search the forum for fuel pump relay jump. After jumping the relay you should hear fuel pump running all the time. Then you can repeat your test you posted picture of. Also you should hear injectors spraying as you deflect the plate. If you still do not get fuel you need to measure fuel pressures. Here is a link to W126 workshop manuals:

It explains some fuel pressure tests.
 

·
Registered
W107 W113
Joined
·
1,325 Posts
Discussion Starter #3
Does taco needle move as you crank? Fuel pumps are controlled on by fuel pump relay as ignition unit (EZL) tells engine is turning and also briefly as ignition is turned on. To do tests on non running engine you have to locate fuel pump relay and jump it. Search the forum for fuel pump relay jump. After jumping the relay you should hear fuel pump running all the time. Then you can repeat your test you posted picture of. Also you should hear injectors spraying as you deflect the plate. If you still do not get fuel you need to measure fuel pressures. Here is a link to W126 workshop manuals:

It explains some fuel pressure tests.
Thank you - I can definitely hear the pumps priming when I turn on the ignition.

Yes, the rpm gauge does move and I also have spark.

My question: with the ignition on, and deflecting the air plate, should fuel flow out of the distributor ports?

Another thing I noticed: when I push down on the plate, it has little to no resistance.

The mixture adjustment tower has been tampered with, could this affect it?

Sent from my MAR-LX1M using Tapatalk
 

·
Registered
1990 420 SEC
Joined
·
153 Posts
Fuel pumps have to run get sufficient fuel pressure. To get fuel pumps to run without engine running you have to jump the fuel pump relay. Resistance to the plate comes partly from fuel pressure. If the car ran with current "lamda" adjustment tampering is not likely causing the problem.
 

·
Registered
W107 W113
Joined
·
1,325 Posts
Discussion Starter #5
Thank you - should the pressure that is built up by priming (turning the ignition on/off many times) be enough to have some fuel come out of the port?

I was unable open the link.

Sent from my MAR-LX1M using Tapatalk
 

·
Registered
W107 W113
Joined
·
1,325 Posts
Discussion Starter #7
That would happen almost only when pumps are priming.
I can hear them priming, I guess I need to actually measure the fuel pressure.

What is the easiest way to jump the fuel pumps? I could also run 12V directly to the pumps under the car.

So just to confirm: with the pumps running, and the air plate depressed, there should be fuel coming out of the distributor head ports?

Sent from my MAR-LX1M using Tapatalk
 

·
Registered
1990 420 SEC
Joined
·
153 Posts
When pumps running and plate depressed fuel should flow out of the ports if lower camber pressure is low enough not to block the head ports and system pressure reaches the distributor. Finding fuel pump relay and jumping pins 7 and 8 is the easiest way to force pumps to run. Of course pumps run briefly as ignition is turned on as you can hear. If plate is deflected as ignition ia turned on fuel should flow out of ports for a moment.
 

·
Registered
W107 W113
Joined
·
1,325 Posts
Discussion Starter #9
When pumps running and plate depressed fuel should flow out of the ports if lower camber pressure is low enough not to block the head ports and system pressure reaches the distributor. Finding fuel pump relay and jumping pins 7 and 8 is the easiest way to force pumps to run. Of course pumps run briefly as ignition is turned on as you can hear. If plate is deflected as ignition ia turned on fuel should flow out of ports for a moment.
Great, then it would definitely seem I have a fuel pressure/supply issue.

Where do I find pins 7 and 8?

Sent from my MAR-LX1M using Tapatalk
 

·
Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
Joined
·
4,207 Posts
Thank you - I can definitely hear the pumps priming when I turn on the ignition.

Yes, the rpm gauge does move and I also have spark.

My question: with the ignition on, and deflecting the air plate, should fuel flow out of the distributor ports?

Another thing I noticed: when I push down on the plate, it has little to no resistance.

The mixture adjustment tower has been tampered with, could this affect it?
In addition to the advice & comments above, I think a bit more vehicle prior history would be helpful.

Your complaint/condition: "My '87 560 SL is not getting any fuel to the injectors." obviously can be caused by several variable/different conditions.

* Was your car running/driving reasonably well before this fuel flow condition occurred or are you starting with a non-running car?

Dirt or water can be a big problem in a CIS fuel system... Was a fuel filter changed recently? If a good running car, has some dirt been introduced accidentally into the main fuel feed from the fuel filter to the F/Distributor, possibly clogging the little filter screen in the fuel distributor inlet? Might it be that simple?

When you say: "the mixture adjustment tower has been tampered with" .. In what way do you mean please?

You are on the right track.. You'll get it working.

MBL
 

·
Registered
W107 W113
Joined
·
1,325 Posts
Discussion Starter #12
In addition to the advice & comments above, I think a bit more vehicle prior history would be helpful.

Your complaint/condition: "My '87 560 SL is not getting any fuel to the injectors." obviously can be caused by several variable/different conditions.

* Was your car running/driving reasonably well before this fuel flow condition occurred or are you starting with a non-running car?

Dirt or water can be a big problem in a CIS fuel system... Was a fuel filter changed recently? If a good running car, has some dirt been introduced accidentally into the main fuel feed from the fuel filter to the F/Distributor, possibly clogging the little filter screen in the fuel distributor inlet? Might it be that simple?

When you say: "the mixture adjustment tower has been tampered with" .. In what way do you mean please?

You are on the right track.. You'll get it working.

MBL
Thank you.

There is simply no fuel coming out of the fuel distributor ports - I removed all 8, ran the pump directly with a 12 volt supply, and pushed the air plate down: no fuel, no resistance at the air plate.

I have a suspicion it may simply be the fuel pumps/filter no supplying enough pressure.



Sent from my MAR-LX1M using Tapatalk
 

·
Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
Joined
·
4,207 Posts
Do you happen to know if the mixture screw has a "stop"? I'm afraid it is completely out of adjustment.
Dang! It's not at all like adjusting the idle mixture on a typical carburetor setup.
You know...running the mixture screw in lightly then opening a turn or two as a baseline to work from..

Below are some links in a post that Ian has placed in the DIY section. As you will see, H.D. is an absolute expert on our fuel injection.

KE-Jetronic Reference/technical Information

Inserting here links to threads by H.D. with his exceptional technical info on this fuel injection system.

https://www.benzworld.org/forums/w126-s-se-sec-sel-sd/2720049-ke-jetronic-lambda-control-duty-cycle.html

https://www.benzworld.org/forums/w126-s-se-sec-sel-sd/2906786-board-ke-jetronic-test-device.html
 

·
Registered
1990 420 SEC
Joined
·
153 Posts
Have you ever seen this engine running? If not or if you have been playing with that adjustment a lot then there may be a problem with that. If the engine was running and stopped doing that then leave that adjustment alone until it runs again or you find what really is wrong with it. To make progress with this you will have to be able to measure fuel pressures. System pressure is measured at cold start injector connection and lower camber pressure at the plug under the injector line you have disconnected at the pic. System pressure should be around 6.2 bar and lower chamber pressure 0.4 bar under system pressure when EHA cable is disconnected. The manual explains how to check different components.
 

·
Registered
1989 500SE
Joined
·
16 Posts
1 - Firstly ascertain that you you have correct fuel pressure to fuel divider(+/- 6bar)
2 - Check if inlet port(brass micro filter) is clear
3 - Check if Eha valve (black box on fuel divider) is functioning properly(not blocked internally)
You can check that the fuel is getting to and through the Eha valve by removing it and checking as ff:
Strategically place some old clean rags under the eha valve to catch the pressurised fuel leakage that will happen as you slowly and carefully open the two silver fasteners. Remove the eha and the two O'rings on the face of the fuel divider.Briefly start the pump to confirm if fuel is getting to the eha (fuel should squirt through the LEFT port. If you are getting strong squirt , it could mean that your eha inlet port micro filter is possibly blocked......,or....your eha adjustment screw o'ring has collapsed and is internally blocked.
Ps !!! Please observe all fire safety procedures and proper ventilation measures whenever carrying out fuel related d.i.y !!!!!
Good luck & keep us updated(unlike so many folks who solve their issues but don't report back with info that could help many fellow forum brothers and sisters)
 

·
Registered
W107 W113
Joined
·
1,325 Posts
Discussion Starter #18
1 - Firstly ascertain that you you have correct fuel pressure to fuel divider(+/- 6bar)
2 - Check if inlet port(brass micro filter) is clear
3 - Check if Eha valve (black box on fuel divider) is functioning properly(not blocked internally)
You can check that the fuel is getting to and through the Eha valve by removing it and checking as ff:
Strategically place some old clean rags under the eha valve to catch the pressurised fuel leakage that will happen as you slowly and carefully open the two silver fasteners. Remove the eha and the two O'rings on the face of the fuel divider.Briefly start the pump to confirm if fuel is getting to the eha (fuel should squirt through the LEFT port. If you are getting strong squirt , it could mean that your eha inlet port micro filter is possibly blocked......,or....your eha adjustment screw o'ring has collapsed and is internally blocked.
Ps !!! Please observe all fire safety procedures and proper ventilation measures whenever carrying out fuel related d.i.y !!!!!
Good luck & keep us updated(unlike so many folks who solve their issues but don't report back with info that could help many fellow forum brothers and sisters)
I sent the car to the shop, the car is running now!

It seems the problem was a large air leak, underneath the intake manifold, everything had to come off.

Now I am getting the fuel pumps, filters and fuel pipes replaced and should be good to go.

Thank you all for the suggestions.

Sent from my MAR-LX1M using Tapatalk
 
1 - 19 of 19 Posts
Top