87 300TD OM603 power loss issues.
 

Hello all.

For the last month I have been chasing a 'loss of power' issue that has gone as far as repeated stalling and 'no start'. The last couple weeks, there has been no stalling and even on cold mornings it starts right up with out being plugged in.

I have replaced the fuel filters and am about to do so again.

A little history.

I acquired this car from my Aunt in April of this year. I did a precursory once over and replaced filters, fluids, brake pads, rotors, brake fluid flush, air filter, and new tires. A couple electrical items repaired and I have a reasonably functioning commuter car sans a/c. :(

Shortly into the summer a hard starting issue occurred that found me replacing the delivery valves. Problem solved. This was followed shortly after with new return hoses as there were leaks from the injectors.

Fast forward to early October and now I find it difficult to keep up with highway traffic at 70-80mph. What required part throttle this summer is now FULL throttle. This is now moved onto "barely able to go 60mph" and quite dangerous on I95 where traffic goes 80-85mph.

I have replaced all the fuel lines under the hood thinking I had an air leak issue. (*edit) In doing so, I bypassed the fuel t-stat. I will later reconnect it. (* end edit). Next I drained the tank and pulled the in tank prefilter/screen. How the heck this thing screens anything is beyond me. I cant see the pick up tube through the hole in the bottom of the tank, and there is no place for anything to attach to the screen assembly. (will update with photo later).

Draining the tank:
The fuel coming out of the tank looks as clean as I would expect fuel to be. 100% clean. no dirt, no little bits, nothing.

Just for kicks, I am putting the screen back in, returning the drained fuel back to the tank, and putting in another new filter set.

My fear is that all of this is pointing to a new lift pump. Is there anyway to test the lift pump? I hate to purchase a new one and have this not be the problem.

Thanks in advance for any help.


Note: I am also soon looking for a thread describing tranny service. I am assuming I just drop the pan, unbolt the filter, reassemble and then add DexIII to the dipstick tube. (?)
I need to also do this for our W210, but the dipstick is locked. :confused:

step one unscrew the alda
drive and report back.
as far as trans drain there is a drain plug in the torque converter and the drain pan. drin both then drop the pan and inspect for metal bits then clean and replace gasket on pan. change filter and reassemble and refill

^^^^^What he said about the ALDA!! Unscrew & put on a shelf...

sounds like a issue I had

Check the fuel Pre heater thermostat thingy. mine sucked air which threw the whole system off.

Check all the clamps for the fuel too,

Are there any pictures? What tool do I need? Perhaps an "idiots guide to removing the Alda" ? "reporting back" I can handle.

Thanks for the reply.


Thank you. This is helpful. Any comment on the W210 trans service?

Aqua: Thank you for the comment, I will update the first post as I forgot to mention that in my quest to eliminate possible air issues, I by-passed the fuel t-stat. My plan is to reconnect it (with new o-ring) once I have this issue licked.


Update: In tank screen reinstalled. I tried to view inside the tank from the opening, but the small hole doesn't afford much of a view. I am concerned if there is perhaps a pick up issue. (?). I filled the tank this evening, so if all is grand and once it reaches 1/2 full and below, issues return, I will suspect something else in tank.

New fuel filters installed.

I am able to get decent acceleration, and even see mild black smoke in my mirror. Typically I would experience power loss after 30-40 minutes on the highway and at full throttle see no black smoke from the exhaust. I was only able to get about 20 minutes highway driving in this evening. Tomorrow will see a longer drive.

Not sure about the harder starts, but you may want to connect a boost guage to see what is hapening with your turbo boost. No power without it! May also need to check/clean the little port (forgot the name) on the drivers side of the intake manifold . It has a vacuum hose on it going to drivers side fender wall. you can unscrew it and clean it out. It often plugs up with gunk in the intake. That is the vacuum line that you can "T" into with a boost guage also

Get about 6 feet of vac line and pull it through the drivers window temporarily

I had a annoying loss of power issue that was worst when heading uphill or at full load. Took me forever to figure out what the issue was. It turned out to be a damaged and improperly installed vacuum shutoff actuator on the injection pump. Under load the actuator was choking off fuel delivery. Probably not what your issue is, but it is easy to check. Watch the shutoff lever while the engine is running. If it sticks pretty much straight up and does not bob up and down you are probably fine. If it bobs up and down and moves down when the accelerator is pressed then it could be an issue.

If all else fails it could be a plugged catalytic converter. I have a 1987 300TD that had this problem. If you cannot get the rpm's up when parked, try removing the exhaust crossover pipe. If the rpm's suddenly jump up, the exhaust system is plugged.

A few years ago I also had a fuel thermostat that sucked air. I bypassed it and it runs fine in cold weather.

Good luck.

good idea. And you can disconnect the vacuum hose to it to be sure its not getting vacuum.

also when you open your gas cap, does it have a big whoosh sound like sucking in air? if so you fuel tank vent might be clogged.

Trying to think what is happening after a 30 minutes of driving causing the low power. Extra suction on shut off valve sounds plausible but that would mean your ignition switch is allowing vacuum through to the shutoff valve or something like that.

First thing i do with low power issues on these is pull the alda and throw it away in the tool box (anybody need an alda , pm me :) ) . But usually the low power is when cold and gets better when warm if it is the alda. That was case on my 87 wagon. It was a slug when it first started up in the morning then a minute down the road it was better. Now with the alda off it takes off right after it starts.