Author Topic: Fuel Injection Pump Question (Read 2070 times)

YEOH250SL · « **on:** February 16, 2025, 02:28:33 »

Hello, is the fuel adjustment screw at the bottom of the FIP supposed to spin freely while engine is running? I know I'm not supposed to adjust it while running the engine, but you can't really adjust anyways it if it's spinning freely. Just want to know if mine's normal. Thanks

Cees Klumper · « **Reply #1 on:** February 16, 2025, 03:24:15 »

Yes that is normal. To adjust it (with engine off as you note) you need to press it inwards, until it engages with the slotted screw inside the pump. It is 'spring-loaded' to prevent people from turning the screw inadvertently with the engine running.

ja17 · « **Reply #2 on:** February 16, 2025, 03:34:41 »

The thumb adjustment must be pushed inward to engage the slotted adjustment screw. The slotted adjustment screw inside the pump housing is turning when the engine is running. Do not engage with the engine running. This adjustment changes the idle mixture up to 1700 rpms only! The adjustment knob remains in neutral until it is pushed inward and engaged in the slotted screw (engine not running). You should feel a click for each rotation of 60 degrees.

YEOH250SL · « **Reply #3 on:** February 17, 2025, 16:17:46 »

Just to be sure, turning it clockwise is allowing LESS fuel, and anti clockwise allowing more fuel, right?

Lori · « **Reply #4 on:** February 17, 2025, 18:57:51 »

It's the reverse

https://www.sl113.org/wiki/Restricted/Linkage-tour#Idle

YEOH250SL · « **Reply #5 on:** February 18, 2025, 01:14:47 »

Lori,

Appreciated the correction. Also, I think there's a leak on the adjusting screw. It is wet to the touch. I wipe it clean and it still become wet. I checked everywhere on the pump and the only spot that is wet with oil is the adjusting knob. Is there a seal in the knob? If so, how do I replace it? And what part numbers do I need for the job? Thanks

Pawel66 · « **Reply #6 on:** February 18, 2025, 06:52:30 »

There is an oring on this screw inside. You get to it when you remove the plate and screw. No part number for it, you need to use a generic one. I do not remember the dimensions…

WRe · « **Reply #7 on:** February 18, 2025, 07:23:35 »

sterntwiete.mparschau.de/html/einspritzung_2.html

Pawel66 · « **Reply #8 on:** February 18, 2025, 09:09:52 »

This is a comprehensive material from WRe - thank you!

I wanted to show where I had a leak and repair was a simple o-ring replacement. Not sure if you have this type of plate where the idle adjustment screw is or you have the big nut.

On the picture is my IP with marked where the o-ring is.

BobH · « **Reply #9 on:** February 18, 2025, 09:39:38 »

Quote from: WRe on February 18, 2025, 07:23:35

sterntwiete.mparschau.de/html/einspritzung_2.html

The translated version is on here

https://www.sl113.org/wiki/Fuel/Injection?action=download&upname=Fuel_Injection_Pump_English.pdf

YEOH250SL · « **Reply #10 on:** February 19, 2025, 00:05:19 »

Thank you guys. Really appreciated the information. Especially BobH for the translated version. Been reading the info on the pump. Felt a bit overwhelmed because I'm such a novice, but I'm gonna go over it and try to digest as much as I can. Once again, thank you guys for making this forum the best amongst Mercedes model's.

stickandrudderman · « **Reply #11 on:** February 19, 2025, 17:01:20 »

For clarity:
The adjuster should not be spinning when the engine is running. If it is then someone has turned it too far anti-clockwise so it has become permanently engaged.

YEOH250SL · « **Reply #12 on:** February 19, 2025, 17:23:15 »

Colin, how I do fix the adjusting knob free spinning problem? Also, I couldn't press in the knob as it feels stuck. From my understanding, you're supposed to be able to push in the knob and turn for "clicks" clockwise and counterclockwise, right? I can turn it but I can't push in the knob to engage. What seems to be the problem?

Cees Klumper · « **Reply #13 on:** February 20, 2025, 01:06:00 »

As Colin notes, it seems that someone has turned it too far clockwise so that the knob is now permanently engaged. Turn it counter clockwise until it starts to disengage and you have to press it inward to be able to keep turning it counter clockwise.

YEOH250SL · « **Reply #14 on:** February 20, 2025, 13:56:47 »

Thanks, I'll give it a go. Hopefully I don't have to take out the nut.

Pawel66 · « **Reply #15 on:** February 20, 2025, 14:17:36 »

If you have a leak there, you will have to undo the nut anyway, I am afraid. I did not do the nut myself (I have a plate there), but I would imagine, once you figure out with what to attack it, it may not be such a big deal... not sure.

I remember here on Forum Members were writing about removing these big nuts to get to screws.

In any case, when you get under the nut, do not mess with the black and white screws. The middle one is the idle screw that you want to unlock.

stickandrudderman · « **Reply #16 on:** February 20, 2025, 15:53:57 »

Quote from: Cees Klumper on February 20, 2025, 01:06:00

As Colin notes, it seems that someone has turned it too far clockwise so that the knob is now permanently engaged. Turn it counter clockwise until it starts to disengage and you have to press it inward to be able to keep turning it counter clockwise.

QUITE THE OPPOSITE!
Someone has turned it anti-clockwise too far such that the adjuster on the governor is now in permanent contact with the screw on the cover.
Anthony, turn the adjuster clockwise maybe 10 clicks (engine off) and see if it then stops spinning (engine on).
This in theory will richen the mixture a lot but since someone has already been playing with it I fear you are already comitted to opening pandora's box.

Cees Klumper · « **Reply #17 on:** February 21, 2025, 13:58:26 »

I was just repeating what you wrote Collin, did not double-think it for myself! See your reply #11:

Posted by: stickandrudderman
« on: February 19, 2025, 17:01:20 »Insert Quote
For clarity:
The adjuster should not be spinning when the engine is running. If it is then someone has turned it too far clockwise so it has become permanently engaged.

stickandrudderman · « **Reply #18 on:** February 21, 2025, 17:58:38 »

Thanks for pointing it out; now corrected.

YEOH250SL · « **Reply #19 on:** **Today** at 04:55:18 »

The 1 cup of oil that came out is petrol? Do I need to replenish any oil in the pump? Thanks

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Author Topic: Fuel Injection Pump Question (Read 2070 times)