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