w108 injection pump - PeachParts Mercedes-Benz Forum

xaliscomex · #1 08-28-2012, 09:16 PM

Own a 1970 280 SEL and drove it to a reputable MB shop (whatever that means) to check out why my car has been running rich. I previously posted information on my car not having the original M130 engine or head. I currently have an M129 engine and head. I have the correct distributor(cap and rotor) that goes with my engine. I had previously checked the cold start valve and that seemed ok. The MB tech called me today and asked if anyone had played around with the screw at the back of the injection pump and I said "No way". I told him that my engine was rebuilt about 9 years ago and the shop owner had told me that they had only played around with the Air/Fuel mixture screw/knob.
The tech continued to tell me that someone had turned the screw all the way in and he was having trouble backing it out. Again, I repeated to him that as far as I knew, nobody had messed with it. I continued to tell him that I also knew that the screw can never be adjusted when the car is on. He said he had big hands and was a little blind (not kidding, could of been a sarcastic remark) and could not really see what else was going on behind the injection pump but it would be a great idea to remove it and see what was going on. He also said that he had worked at a shop that rebuilt the bosch pumps many years back and was familiar with what to do. He gave me 2 options:

1. Remove the injection pump and take it in to get it rebuilt or calibrated for 1,500 dollars with parts and labor, or

2. Remove it and see what was going on and then reinstall for 800 dollars.

I swore that I would never get ripped off again so now I'm posting this to get advice on what to do and what not to do. So far there is no charge for anything that they have done which is really only playing around with the cold start valve , WRD, throttle plate?, venturi air fuel mixture, distributor etc.

What easy test can be performed to check the injection pump. The mechanic did not mention anything being broken at the back of the injection pump but just said he could not back out the enrichment/leaning screw out.

I don't know much about injection, obviously, but it just seems like way too much money to just see if it works or to just remove and repair the injection pump. Where is Arthur Dalton?

Palolo · #2 08-28-2012, 11:57 PM

Quote:

Originally Posted by xaliscomex

Where is Arthur Dalton?

Florida, over close to the gulf coast side?

Hopefully safe and all well after Hurricane Isaac's passing showers that are now moistening New Orleans...

whunter · #3 08-29-2012, 12:04 AM

Quote:

Originally Posted by xaliscomex

Own a 1970 280 SEL and drove it to a reputable MB shop (whatever that means) to check out why my car has been running rich. I previously posted information on my car not having the original M130 engine or head. I currently have an M129 engine and head. I have the correct distributor(cap and rotor) that goes with my engine. I had previously checked the cold start valve and that seemed ok. The MB tech called me today and asked if anyone had played around with the screw at the back of the injection pump and I said "No way". I told him that my engine was rebuilt about 9 years ago and the shop owner had told me that they had only played around with the Air/Fuel mixture screw/knob.
The tech continued to tell me that someone had turned the screw all the way in and he was having trouble backing it out. Again, I repeated to him that as far as I knew, nobody had messed with it. I continued to tell him that I also knew that the screw can never be adjusted when the car is on. He said he had big hands and was a little blind (not kidding, could of been a sarcastic remark) and could not really see what else was going on behind the injection pump but it would be a great idea to remove it and see what was going on. He also said that he had worked at a shop that rebuilt the bosch pumps many years back and was familiar with what to do. He gave me 2 options:

1. Remove the injection pump and take it in to get it rebuilt or calibrated for 1,500 dollars with parts and labor, or

2. Remove it and see what was going on and then reinstall for 800 dollars.

I swore that I would never get ripped off again so now I'm posting this to get advice on what to do and what not to do. So far there is no charge for anything that they have done which is really only playing around with the cold start valve , WRD, throttle plate?, venturi air fuel mixture, distributor etc.

What easy test can be performed to check the injection pump. The mechanic did not mention anything being broken at the back of the injection pump but just said he could not back out the enrichment/leaning screw out.

I don't know much about injection, obviously, but it just seems like way too much money to just see if it works or to just remove and repair the injection pump. Where is Arthur Dalton?

Contact me directly.
A total rebuild should be $950.00 USD, and may be lower.
I have a Detroit Bosch certified shop that does them for me.

IMO: Remove reinstall for 800 dollars is to high..

.

wbain5280 · #4 08-29-2012, 10:52 AM

He probably needs less that a total rebuild, just an adjustment.

I have a 220SE with a 2 plunger pump on my engine and I think someone did the same idle adjustment. I also have a spare injection pump that I'm going to swap. One of the injection lines is rusted at the pump and I need to remove the complete assembly to swap it.

ctaylor738 · #5 08-29-2012, 05:43 PM

Someone probably messed with the idle mixture while the engine was running and jammed it all the way rich.

I bought a 230SL with this problem and was able to get it un-stuck by pushing the adjuster in to engage, putting Vise-Grips on the knob, and turning it CCW.

You can also remove the rear plate and get a screwdriver on the adjusting screw without too much trouble.

I wouldn't let this guy mess with it any more.

xaliscomex · #6 08-30-2012, 12:20 AM

Can the bolt be loosened (unstuck) without removing the pump. Anyone use mirrors?
I'm picking the car up tomorrow.

whunter · #7 08-30-2012, 01:12 AM

Quote:

Originally Posted by xaliscomex

Can the bolt be loosened (unstuck) without removing the pump. Anyone use mirrors?
I'm picking the car up tomorrow.

Frequently the answer is yes.

Some people can use mirrors.

I find these easier to use:

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.

ctaylor738 · #8 08-30-2012, 08:05 AM

This is very doable with the pump on the engine. Sometimes it's easIer to access the knob and The rear plate from under the car.

bwostosh · #9 08-30-2012, 01:39 PM

I can do this using brains and touch.

The blind guy,
secretary of San Diego Braille Club

mercmad6.3 · #10 09-01-2012, 08:51 AM

you should be able to see it from the side of the car,no need for mirrors etc. you need a 40 mm socket to loosen the big nut on the rear of the pump.
Borrow one ,is the best way to undo it.

When you get the large nut off, you will see a round thing with 5 screws,two white,two black and one hex bolt in the center with a slot in it.
the one in the center is the idle speed adjustment.
I am also of the opinion that some dummy has tried to adjust the idle by turning that screw with the engine running. I'll be he crapped him self when it zapped into the pump!.
Screw it counter clockwise aound 6 turns. thats about the mid point of the idle mixture.
Run the engine and give it a few hard revs to clear the plugs and check how it's running .No need to screw the nut back on straight away.
if it wont come undone,I'' post up the only remedy. But it's fixable by the home mechanic.

Benz Dr. · #11 09-01-2012, 01:20 PM

The easiest way to determine how rich or lean the mixture is would be to undo one end of the throttle linkage on the cross shaft. With the engine running, move the throttle linkage for the throttle valve. If it stalls it's probably in the range or too lean. If the engine begins to run better as you open the throttle it's too rich.
There's only two places where fuel enters the engine; through the CSV or the injectors. Check the CSV carefully to make sure it's not leaking.
If the engine is running rich across the whole range then you have a problem at the pump. I would check to see that the warm up system is operating correctly. You can remove the small air filter to see if the air is shutting off fully once warmed. Some repairs may be needed if it's still drawing a vacuum.

You can move the basic setting of the barometric compensator which will lean the pump across the whole range.

$1,500.00 to R&R the pump and have it rebuilt isn't too much at a retail level. The reason he wants $800.00 to R&R the pump is because when he gets it back on, it still won't work right, thus extra hours to figure it out.

There is a point where everything I try still won't make it run better and I pull the pump for a rebuild. Diagnostics is the key here. Sometimes you have to send it out and have it rebuilt.
On fresh engine rebuilds we generally have the pump rebuilt at the same time so that everything is set back to new specs. Injection pumps tend to wear rich which will lead to advanced cylinder wear if left unchecked.

xaliscomex · #12 09-01-2012, 11:42 PM

Quote:

Originally Posted by Benz Dr.

On fresh engine rebuilds we generally have the pump rebuilt at the same time so that everything is set back to new specs. Injection pumps tend to wear rich which will lead to advanced cylinder wear if left unchecked.

You might of hit the jackpot here. My engine head was rebuilt and nothing else was adjusted or calibrated afterwards. The car ran rough and rich since then. Looking back, the guy who rebuilt the engine head might have been the one who turned the injection pump adjuster while the car was running...I will get that 40mm socket ASAP. I wish more benz owners would upload video tutorials (you tube)on how to properly diagnose and check these older cars...I'm going to get a friend to video tape my injection pump adventure...

mercmad6.3 · #13 09-02-2012, 01:00 AM

Making a video would be a long job..ha ha, it takes me a day sometimes to sort out a MFi if someone else has had a go at it before me or the throttle plate is worn,or the ball ends are too loose or..or...

mercmad6.3 · #14 09-02-2012, 05:54 PM

Quote:

Originally Posted by xaliscomex

You might of hit the jackpot here. My engine head was rebuilt and nothing else was adjusted or calibrated afterwards. The car ran rough and rich since then. Looking back, the guy who rebuilt the engine head might have been the one who turned the injection pump adjuster while the car was running...I will get that 40mm socket ASAP. I wish more benz owners would upload video tutorials (you tube)on how to properly diagnose and check these older cars...I'm going to get a friend to video tape my injection pump adventure...

Hi CORRECTION

i should be a 41 mm socket! you only to borrow one, just loosen the nut with it and you can unscrew it by hand. Oil will come out too, a lot of oil means the pump is leaking internally and should be resealed. If that is the case ,get it rebuilt and your pump problems will be sorted. Gus Pfister at Pacific fuel injection,San Francisco, is one place I would reccomend. And Pelican parts has some on line information regarding the adjusting of MFi Systems. A lot of it was for porkers but it's the same set up on Mercedes.