Diesel engine "GURU!"

[machmeter62]

I have a 2.4 liter MB diesel engine that has been overhauled, but still lacks normal power, and is well past break-in mileage.

Here's what was done: cylinders honed, (re-boring not required) new rings, bearings, valve job, and new filters, timing set properly, compression normal, excellent oil pressure, and starts instantly after glowed. But the engine is sluggish in performance. I have reduced the equation to either a weak fuel injection pump, bad, worn, or wrong fuel injectors, but the engine runs smooth, (maybe partially plugged injectors?). With everything else checking out; I assume it has to be lack of fuel delivery to the cylinders?? The transmission/drivetrain is normal also!

I have two of these same vehicles, and the other one has normal power!

Thanx in advance for your suggestions. The actual mileage at overhaul is unknown.

 

[Rebel]

I agree it sounds like a problem in the fuel system. A good diesel shop should be able to "pop test" your injectors to check the pop off pressure and spray pattern. If the injectors check out ok then you'll have to bite the bullet and have your injection pump rebuilt or tuned up.

 

[Skyco]

How hard would it be to swap injectors and/or pump from the good vehicle to determine what the problem is?

 

[SnowRidge]

Recheck injection pump timing.
Fuel restriction.
-- Bad lift pump.
-- Clogged fuel line.
-- Clogged screen (tank pickup, pump or filter inlet).
-- Collapsed/crimped fuel line.
-- Fuel tank not venting properly.
Exhaust restriction.

Any chance someone has added an additional fuel filter or water separator underneath the vehicle?

If it starts easily and runs smoothly, but lacks power, I would first suspect fuel flow problems. If possible, T a vacuum gauge into the line at or near the lift pump inlet. Compare the two vehicles. If the problem vehicle has a higher vacuum, it will confirm a downstream fuel flow issue.

These a generic ideas. I have no experience with your particular engine/vehicle.

Good luck.

 

[number two]

I'm still running a '77 MB 240D in the summer months. Don't ask me why-just runs cheap and keeps on ticking. Have you checked that rather complex throttle linkage system to see if you're getting full throttle at the pump? Sure sounds like a real possibility to me. Those ball ends wear on those linkage arms and they may need replacing or adjusting. Seems like I've adjusted mine some many years ago. I've also repaired the foot pedal assembly connection at the floor,and those pedal bottom round bushings wear also.
I guess have someone sit in the car and floor the pedal while you watch the linkage under the hood for travel. Heck,you may even feel free travel in the linkage from the seat if the pedal moves a ways before it starts moving the lever at the pump. It seems like you can look between the pump and engine and see the throttle lever and if it's hitting the stop. Or after seeing how much the linkage moves from the pedal,disconnect the linkage and see if you can move it more manually.
Just some thoughts-sounds like you've ruled an awful lot of things out. Good luck. I'd like to hear what you find.

 

[machmeter62]

Thank you gentlemen for all the replies. You have given me a lot of additional things to checkout, think about, and that is what I will focus on; I started to get tunnel vision. My wife calls it a "slug," and refuses to drive it period! I will report back if I find the problem; but it will take me awhile.

 

[art]

One of the main reasons for the need of a rebuild is from cylinder glazing which is caused from excess fuel. IT will give a general lack of power and more then likely oil consumption. It doesn't mean that an injector is leaking, that would be continual smoke but it could be one that is putting excess fuel into one area of the cylinder possibly from a blocked orfice on the injector.

 

[gemini5362]

I am not a mechanic so I am just making a swag here. If your air filter was blocked would that affect a diesel. I had a gas engine I had completely rebuilt that would flood out every time you gave it gas. After three days in the shop on a dynamometer they found that someone had put the wrong breather on it and it was not getting enough air. Since you dont meter the air on a diesel would a clog in the air filter or snorkel cause a problem ?

 

[RobJ]

Make sure other parts on the vehicle are in order. brakes dragging? Etc.

My mom had a 76 or 77 240d, that thing ran like a slug brand new!!

 

[wolfneck]

Some good ideas already, if you can post the vehicle year model and mileage, that would be helpful. I operate an independent German auto repair shop, and 2 of my techs drive older Benz diesels. They may be able to provide some vehicle specific info or further diagnostic ideas.

Wolfneck

 

[machmeter62]

Some good ideas already, if you can post the vehicle year model and mileage, that would be helpful. I operate an independent German auto repair shop, and 2 of my techs drive older Benz diesels. They may be able to provide some vehicle specific info or further diagnostic ideas.

Wolfneck

It's a '79 MB 240D with an INOP speedometer, (187,000) but the vehicle has "many- many" more miles, and the front wheels were severely out of alignment, because of inside tire wear, and the brake discs are out of limits too! The engine ran out of compression shortly after purchase! It was purchased by my son, ($900) for distant commuting, but I got involved in the rebuild of the engine! The front seats also show a lot of wear with sagging too. It may have 500,000 miles (?) + It has been a challenging project, but they are a quality vehicle. The German engineering amazes me also! Thanx in advance.

 

[machmeter62]

Make sure other parts on the vehicle are in order. brakes dragging? Etc.

My mom had a 76 or 77 240d, that thing ran like a slug brand new!!

When I drive this vehicle, I anticipate hills, and "floor it" in advance to prevent a "traffic jam!!" But I usually still get "lip service" while their passing me too!! I take alternate routes to avoid hills, because the engine is only rated at 62 HP.; but will maintain good speed on level roads!

 

[wolfneck]

It's a '79 MB 240D with an INOP speedometer, (187,000) but the vehicle has "many- many" more miles, and the front wheels were severely out of alignment, because of inside tire wear, and the brake discs are out of limits too! The engine ran out of compression shortly after purchase! It was purchased by my son, ($900) for distant commuting, but I got involved in the rebuild of the engine! The front seats also show a lot of wear with sagging too. It may have 500,000 miles (?) + It has been a challenging project, but they are a quality vehicle. The German engineering amazes me also! Thanx in advance.

My head Benz honcho says the following:
1. Recheck the pump timing, and if this is correct

2. Raise the fuel volume on the pump. Since this is a non turbo model the adjustment is a strange looking bolt with a 13mm locknut on it, on the back of the pump. This increases fuel volume to the internal pump rack. He says that if it running smoothly, he doesn't think you have injector problems.

Hope this helps! If'n it doesn't, let me know, and we'll reassess the situation.

Wolfneck

ps. yes, German engineering is fascinating, BUT, ultimately the Japanese reverse engineer it and make it RELIABLE.The German automakers have fallen way short in that regard in the last decade, from what I'm seeing in the field.

 

[machmeter62]

My head Benz honcho says the following:
1. Recheck the pump timing, and if this is correct

2. Raise the fuel volume on the pump. Since this is a non turbo model the adjustment is a strange looking bolt with a 13mm locknut on it, on the back of the pump. This increases fuel volume to the internal pump rack. He says that if it running smoothly, he doesn't think you have injector problems.

Hope this helps! If'n it doesn't, let me know, and we'll reassess the situation.

Wolfneck
Thank you, would that be a clockwise/counter clockwise to increase the fuel flow?
ps. yes, German engineering is fascinating, BUT, ultimately the Japanese reverse engineer it and make it RELIABLE.The German automakers have fallen way short in that regard in the last decade, from what I'm seeing in the field.

Thanks again for the reply, I will raise the fuel level.
This is subject to debate:

I will always feel that Japan take others ideas and advance to a higher level; and save millions because of less research required? Cameras is another, (35MM) came from Germany I think(?) But Japan advanced it?

This has happened to England also; the English invented the jet engne, but the Germans perfected it, and figured out how to use it on aircraft.

The British are great designers of automobiles, with all their beautiful classic history, but reliability, or mechanical challenges, is a different matter. I once owned a '52 MG TD with a LUCAS ignition system!! I probably towed and pushed it equal to the miles I drove it!! Jaguars also come to mind; just look at the resale values for proof? These are just my opinions only, and I don't want to hurt any owners of these vehicles.

 

[FULLPULL]

If it has a cable to kill the fuel flow check that it is letting the shut off lever on the injector pump open all of the way to get the full flow of fuel.

 

[machmeter62]

If it has a cable to kill the fuel flow check that it is letting the shut off lever on the injector pump open all of the way to get the full flow of fuel.

Once again, I thank all of you for your time and suggestions; I have learned a lot from your information. I checked and tinkered with things that were suspect including linkage, cables, additional filters, and any fuel blockage, and increased the flow of fuel in the injection pump, with the elongated bolt! The vehicle seems to have more power now, but haven't given it any hill tests yet! That will come this weekend on some grades over several miles long.

I have no idea what the true basic weight of these vehicles are, but it feels and drives like a car > than 3500#? I have been carrying about 100# of tools in the trunk in case there needed!

 

[number two]

I seem to recall the title weight on my 240D being about 3300#. A lot for 62 HP. Believe me,I understand the meaning of rolling roadblock! Hope you got her fixed.