Lift Pump/Prime pump
 

I finally had the minute to install the electric fuel pump before the primary filter. Is the lift pump essentially some sort of pump but at a low rate to feed the I? after I install the electric fuel pump the car seem to start faster even if the glow plug light still on and it accel better. The pump is 10-14 psi both for gas and diesel. did I just override the lift pump?

You may have increased the base pressure of the injection pump is my guess. Or the old lift pump was flowing poorly. Without a fuel pressure gauge for the base of the injection pump installed you have no ideal really except that things appear better.

The pressure in the base of the injection pump is determined by the supply pressure of the lift pump and the condition of the relief valve. Old semi obstructed filters can for example lower the operational pressure. Best for your vehicle is 19 pounds pressure but 14-16 is fine. Again you need a gauge to tell what you may have. Many have far less as the system has never been properly checked out.

barry, isn't 20-25 psi more like the target psi????

It is all in your mind. The injector stills opens at 135bar.

WOW, you mean to tell me that lift pump has the capability to provide that much pressure. If the lift was not working properly, can it be replace so the IP has the proper pressure? The 1985 300SD has what appears to be a newer version, will that help increase the pressure.

You can buy a new lift pump if you want, kind of pricy.

Here is a rebuild kit.

http://www.peachparts.com/shopforum/mercedes-parts-reference-library/327357-0000900210-om615-616-617-lift-pump-valve-kit.html

By newer version, are you refering to the black Primer Pump screwed into the Lift Pump?


Charlie

I can't tell which car you have WMO - can you (pretty please) stick some information about that in your posts or your signature? 'Cos I for one can't remember which car everyone here has!

If you want to see what a lift pump is like in bits then have a look here =>

http://www.peachparts.com/shopforum/diesel-discussion/294499-refreshing-fuel-pump-om617-european-spec-%96-non-turbo.html

It is unlikely to be the one on your car but it will be similar in many ways.

Do you have the part number for that tiny oring that goes within the lift pump? I had the link opened to jot down and shut down the PC by accident. :rolleyes:

My apologies to everyone, I am working on 1984 300D. Yes I was talking about the one with black prime pump screwed into the lift pump. The 1985 300SD I got from a friend has one, but I think I will get a new one and replace the one in my car. I am still new to these cars so re-building one at this point is not an option. Of course unless they are a pricy as you say they are. Anyone give me the price for one and maybe the P/N? Thank you

Pelican Parts; look there.
Often if you look up Primer Pump it takes you to the whole Fuel Supply/Lift Pump. They are somewhere between $100and $200 New.

I randomly grabbed the below stuff from My Notes; don't know if it all applys or not.
Lift Pump, Fuel Supply Pump rebuild kit
http://www.peachparts.com/shopforum/showthread.php?p=2284880#post2284880
Lift Pump, Fuel Supply Pump about sanding the Valves has the small O-ring size
http://www.peachparts.com/shopforum/showthread.php?t=266857&highlight=lift+pump+kit

Fuel Supply Lift Pump showing how I put it into the vice.
http://www.peachparts.com/shopforum/showthread.php?t=266857&highlight=lift+pump+kit

Fuel Supply Lift Pump Rebuild.
http://www.peachparts.com/shopforum/showthread.php?t=266857&highlight=lift+pump+kit

Lift/FUEL SUPPLY PUMP TINY o-ring
Bosch lists now 2 440 210 002 (MB 010 997 86 48) as replacement to the original black(perbunan?). And yes,the replacement is Viton.
The 5mmØ x 1.50mmØ 'O' ring is located in a groove in this bore and prevents engine oil in the IP from being sucked into the fuel re-circulation circuit. In most cases this O-ring has either hardened and broken up or completely disappeared.


If you get a Fuel Supply/Lift Pump kit from a Fuel Injection Shop it will likely be more complete (there is a model plate on yout Lift Pump with the Numbers):
Bosch Fuel Supply lift pump kits
http://www.peachparts.com/shopforum/showthread.php?t=215770
Bosch FP/K22MW22 Feed pump There is a repair kit for these pumps. Bosch part number DGK301 The kit covers FP?K KE and KS pumps includes more parts than you'll need to rebuild your pump includes springs, copper crush washers, piston seal and check valves. Also included in the kit is the mounting gasket. There is a sediment bowl and prefilter cartridge included in the kit for other applications. Some of these pumps are used in heavy equipment and in the aviation industry. I got my kit overnight from a diesel injection shop I used in the past. Hope this makes the parts easier to track down. Price wise I got it for under $22.00 including shipping and local sales tax.
ROBERT BOSCH DGK301 6123 REPAIR KIT FP/K.KE.KS.FEEDPUMP From Saco
DGK301-4 8408 SERVICE KIT FP/K.(4 VALVE)
DGK301-H 2362 REPAIR KIT FP/K...FEED PUMP

Lift pump reconditioning kit is in the ten dollar area. And they do normally produce more pressure than is required to open the relief valve. One problem is the older relief valves can open too early because the spring inside them has aged.

No the increased starting ability and increase in performamce is not in your head. Nineteen pounds pressure is the best for general use. That is in the base of the injection pump.

You can operate the base injection pump pressure at 20-25 pounds as was mentioned. The thing is then the amount of pump profile change if any is unknown. Some guys have been running about thirty pounds on the original lift pumps. They quote a really signifigant gain in power.

The lift pump on the normal aspired five cylinder and the 616 four cylinder are lesser in output pressure but the spring from the turbo lift pump can be simply incorporated in the lift pump to increase their output pressure.

You really do not want any substandard pressure present with any 123 diesel. It is almost certain that on the 616 four cylinder engine over a long period of time may cost you the engine. Not checking it out can be a costly error in my opinion.

Over time the fuel filter becomes more obstructed. This combined with a lower psi out of the weaker lift pump contributes to low base pressure in the injection pump on the 616.

Just remember the pressure in the base of the injection pump is controlled by a combination of the lift pumps output and the pressure release point of the fuel return relief valve.

Can you elaborate why? Why adding a pump to feed the IP would make a different in performance if the lift pump is working correctly. Starving the IP of fuel is a different issue, like a clog filter.

Barry has a point that under normal circumstances the Fuel Pressure Relief/Over Flow Valve controls the pressure; but, that is when it is working properly.

You may be making so much fuel flow volume now that the the relief valve is overcome to some extent. A good functional lift pump can make 30 pounds pressure available is common.

It takes a ten dollar fluid dampened 0-30 pound pressure gauge plumbed in to find out what is really going on. To me it makes a lot of sense to leave it in as both an early warning device for fuel filters getting too restrictive. Plus since most common problems on the 123s seem to be fuel supply related it will usually help you decide what is going on.

The engines idle better with the proper pressure and some report they are a little quieter on the highway. Some report better fuel milage but if so it is not much.

Much of the above depends on how low the pressure was before corrective measures where taken. Everyone that corrects from a very low base pressure reports a feeling of more apparent power in the seat of their pants. Some members have reported better performance on hills as well. This is a very inexpensive area of the car to at least check and restore if needed. In doing so you also become much more familiar with how it functions.

I got a new(old) lift pump from my local benz shop. They had a whole semi trailer full of parts. Charged me $10 for the lift pump! Fixed all my problems I've been chasing for a long time.