Been looking at the manual and becoming confused. What injection pump does my 1981/non turbo/automatic w123 have? It belches smoke occasionally and surges when going up a very shallow hill. Any ideas and is there anyone that rebuilds them if alas it's necessary.

Pat

Look at the top of the injection pump where the hard lines come out to the injectors. If the fittings have a flange with 2 bolts holding them down, it's a MW pump. If they have a spline and single screw that's shared by two hard lines, it's a M pump.

Most of these had the MW pump except for Euro non-turbo versions which had the M pump.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Does your Vacuum Pump have a tube that goes to the Intake Manifold?

Unfotunately we tend to blame things on the item that we do not under stand.

You could be having a Fuel Supply issue or air getting into the Fuel supply

Trance your Fuel Hoses to the Fuel Supply/Lift Pump (has the Hand Primer attached). That supplies the Fuel Injection Pump Housing with Fuel and the Fuel Pressure Relief/Overflow Valve regulates the Pressure of the Fuel as the Fuel Exites the Fuel Injection Pump Housing.
The above supplies Fuel to the Elements and the Elements are respoisible for the hight pressure Fuel for Injection. The Injectors act as sort of a spring loaded pressure Valve and control the the Fuel Injection Pressure.

If you have a Hand Primer that has a shiny Aluminum body that is the old style type. The are noted for being the cause of Air Leaks. They can be replaced with a New Sytyle Bosch one (don't get a copy of the Bosch).

Over time the Pressure Spring inside of the Fuel Pressure Relief/Overflow Valve becomes compressed and especially at the low Engine speeds does hold the pressure it is supposed to.
Ir you have a Relief/Overflow Valve that you can take apart you can stretch the spring to 27mm of length and that generally restores the pressure. Be careful not to lose the Ball Bearing that is used for a valve in it.
If your Relief/Overflow Valve has a big Ball Bearing pressed into the end you cannot take it apart and would need to get a new one or find one at the Junk Yard that you are able to take apart.

Anoter source of Air leaks can be the 2 sections of Fuel Inlet Hose. They are easily reaplced with 5/16" inside diameter Hose you can get from a regularFuel Hose from Auto Parts Store as that Hose is also rated for Diesel Fuel.

Partially plugged Fuel Filters can sometimes cause surging.
It is also possibe for the Fuel Supply/Lift Pump to need to have the valves inside replaced and the little 5mm O-ring.

__________________
84 300D, 82 Volvo 244Gl Diesel

What color smoke does it belch occasionally?

__________________
83 SD

84 CD

When the temp comes up a little I'll check ya'lls ideas. Thanks
Pat

I am not sure how one avoids the Chinese lift pumps. I got two out of China and the boxes looked like original bosh parts. This was maybe four years ago and things may have changed.

They were the newer style primer pumps. Maybe one should ask the supplier when buying but they might not tell the truth. Or think as I did that bosh may be manufacturing these because of the boxes..

I assume the primer pump is also called the lift pump?

Pat

No, the primer pump is attached to the top of the lift pump. It's what you pump by hand to help remove air from the fuel supply system after changing filters, for example.

The lift pump is underneath the primer pump. It is driven by the engine. It is what the small clear primary filter feeds in to. It's purpose is to draw fuel forward from the tank, through the spin-on filter before the fuel goes to the injection pump. It's a very simple pump.

It's generally rather durable, but there are springs inside that may weaken over time. They can be replaced and the seals refreshed, this is the extent of a rebuild.

For a visual, red circled item is the lift pump, blue arrow points to the primer pump.

__________________
1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

The Baja Arizona Oil Burners Send a message if you'd like to join the fun
Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130

Visit the W123 page on iFixit for over 70 helpful DIY guides!

Thanks ubber,
Wish I had a good mechanic here in the middle of Ozland/KS. Don't want to try and fix things if they aint broke if you know what I mean.

It's hard to go wrong by replacing the fuel filters. I know several folks who have suffered from fuel delivery issues and changing their spin on filter solved it.

__________________
1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

The Baja Arizona Oil Burners Send a message if you'd like to join the fun
Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130

Visit the W123 page on iFixit for over 70 helpful DIY guides!

Some clever Part Seller sell the Fuel Supply/Lift Pump with the Hand Primer Pump already mounted on it and if you look under Hand Primer you will find the whole thing at something like $165 each.

But, the Hand Primer is actually a seperate part and of course can be replaced as a seperate Part; they used to be aroung $22 each but I have not priced them lately.

__________________
84 300D, 82 Volvo 244Gl Diesel

Post a picture of your Fuel Injection Pump and the Hand Primer. The MW Fuel Injection Pump has a different Fuel Supply/Lift Pump than the M type Fuel Injection Pump.


Lift Pump, Fuel Supply Pump rebuild kit
Anybody know a good Fuel Pump replacement DIY page? - PeachParts Mercedes ShopForum
Lift Pump, Fuel Supply Pump about sanding the Valves has the small O-ring size
Lift Pump Rebuild... - PeachParts Mercedes ShopForum

__________________
84 300D, 82 Volvo 244Gl Diesel

It has MW pump (PES 5 MW 55/320 RS 20).

Salut!