87 300 DT No Start
 

1987 300DT 195K
Problems began after replacing metal and rubber fuel lines at tank. At first the car ran ok after replacing fuel lines, maybe 100 miles, then it had little to no acceleration, then I could not get the RPM’s over 1500 while in park, (idled well at this time) replaced fuel filters,Then it was slowly down hill with it running for a few seconds then would die and now does not start. Turns over nicely, and almost starts. I had the ALDA off and put it back ( did a 1 turn CCW) on and replaced plastic and rubber connections to and from the switchover valve. Doors open and lock per normal. There is a little air in the pre filter about as much when the car was running well. Can one test the fuel pump somehow if it is ok, or do they simply just quit and that’s it??? I probably had a lot of crap come out of the fuel tank when I emptied it. It flowed out very well and when I just did the pre filter fuel was coming out of the feed line as per normal. I also changed over the feed and return lines but I did that before I installed another pre filter, no change, put it back to original way. Pre filter had some dirt but I just replaced it. No leaks to be seen anywhere. I have not again replaced the spin on as it has maybe 4 miles on it…Still no start. Any ideas from someone…It is cool today here about 40F.

You may be having the same problem as me, the way I have been getting my car to start is to purge air out of the lines by loosening the injection lines (6 14mm blocks on the rail), cranking the engine, and tightening them back as you see fuel bubble out. I will have my mechanic check for leaks in the fuel system when I have it in for routine maintenance at some point next week..

Also, make sure if you do this not to knock out the hose that connects to the engine cutoff, mine has a green fitting end, if it pops out the motor won't stop. Very easy to pop out when loosening the fuel lines closest to the firewall.

Is the trap oxidizer on that car? They have been known to plug up. BTDT
There is a port on the front of the exhaust manifold that is where a back pressure test is performed. Iin my case just removing it allowed the car to run better than it was (essentially it would not run with that port on!) Just a possibility! still if you crank the engine with the lines loosened the air ought to be displaced to the point the car will start and run after stumbling and sputtering a while after the lines are retightened

Trap is off the car. Where exactly is the port on the front of the manifold?
I will try the loosen the lines part once the weather gets a bit warmer here...at least a few degrees and I have a helper. What PIA at the moment...Good thing the wife is gone for another week!! Thanks

The port is a metal plug with a large hex head right at the front of the exhaust manifold. There is a procedure in the 603 manual for testing backpressure. I've seen gauges sold for that purpose (must be a problem in gassers too, as I recall they have a rubbher tip that seals against the O2 sensor).
The Cat oxidizer may be there, downstream under the car, if they did the Open Campaign, and those also have been known to plug up. A mechanic I know had a case where the under body Cat was plugged so bad the car was overheating and ran very poorly.
You may just have a fuel problem but if the Trap is plugged up like the one on my 603 was, it is a situation that prevented the car from starting. This problem can mislead some mechanics, if they haven't seen a plugged Cat they aren't experienced!

From PM it seems like that Wolfsburg has a plugged Cat (being the thing that replaced the Trap and located under the car)
He will post some follow up on this later, right now he is barely running with the plug removed form the front of the exhaust manifold.
Since this was a problem I have experienced I thought it worth keeping this thread alive. The problem seems to be related to a car that not been run very often or driven very far, that set of conditions causes the matrix in the Cat or Trap oxidixer to plug up and no exhaust will flow and the engine is starved for air to flow and the result is a non running diesel.
my experience lies in this thread: http://www.peachparts.com/shopforum/diesel-discussion/137241-603-engine-problem-has-got-me-stumped-help.html

Wait - you replaced the fuel filters? Did you fill the new spin-on filter before installing it? If the engine has run since then, at least unscrew it and make sure it is FULL. The fuel lift pump rarely fails. If you disconnect the hoses in the engine compartment, where the hard lines switch to rubber at the frame rail, it should pour out nicely due to gravity feed from the tank. If not, you may have a blockage further back.

No way a plugged cat would do this... that would let the engine start & run, but reduce power and/or limit RPM.

:o

I know it may sound simple but here it goes. What type of fuel line did you use? Are you certain that it is not kinked? Could it be collapsing? I would do a volume test @ IP inlet. Plugged TO will almost always have some up top hissing in the engine compartment, same for anything downstream from there. Sounds to me like it is a fuel starvation issue.

I have found the problem, at least it looks like it. There is a plug on the exhaust manifold as mentioned earlier in the post by Dieseldiehard. I checked the fuel pump, fuel came pouring out when engine was turned over, then cracked all the injector lines and all were getting wet fairly quickly, and then I removed the exhaust port plug. It starts like normal now without the plug. The engine just will not go above 1700 RPM's or so, but this would seem normal to me if the exhaust hole is maybe 1/2 inch. Diesels need a lot of air coming in and also going out. I will have the middle muffler/cat removed tomorrow and replaced by a straight piece. As soon as I even put the plug in only loose, it would not start. I used all original MB metal fuel line direct from the dealer thru Phil, who supports this site. Believe me it does look like a toatally plugged cat. PO drove the car to work when it rained, maybe 300 yards! Thanks for all your help especially Dieseldiehard. Things get scary when one runs out of ideas as to what is wrong with the car. Fortunately there are people on this site that gives one almost endless ideas as to solutions to problems. I will post again as to the result of removing the Cat.

Don't expect that engine to run down the road with the plug out, the fact it runs now is proof the exhaust is blocked.
Well, history repeats itself, only this time its the Cat not the Trap (both are stupid things that don't belong on a diesel!)
I have to credit Dave, WANT '71 280SEL, for the suggestion last year when I was faced with the same problem.
Now when I get a long drill bit I can fix the Cat on my car :rolleyes:

Fixed
 

Well I had the cat removed, plugged completely. It now drives better than ever. Never had so much pickup as I do now. The shop took a 2 1/8 inch pipe expanded the ends a bit and then welded into place. The new pipe fits inside the existing pipe on the car. I drove the car to the shop about 3 miles, never got the car above 20 mph. Now it goes great. Thanks to all on this site and to Dieseldiehard for making me aware of the plug. Onto the next repairs! Well now it drives well! Thanks

Good going! With that plug out you were able to run at 20 MPH? Great! Didn't it sound sorta like a cross between a diesel and a jet aircraft?
If you haven't driven an '87 300D turbo before you are in for some fun!

Oh yes, can I order a bypass pipe from that shop? Hmmm, maybe a Group Buy? I think the pipe is 2.75 in actually. Oh well, anything is better than a plugged Cat!

The fellow has a muffler shop and took a 2 1/8 (that's what he told me) straight exhaust pipe cut it about 5 inches longer than the now missing cat, expanded the ends most likely to about 2.4 inches and the welded the pipe in. Yes you are most likely correct that the original outside is 2.75 inches but the inside is most likely about 2.5 inches and to get the new piece into the old he expanded it to 2.4 probably and welded all the way around. He has one of those exhaust pipe expander machines that he used. He asked if it has to go thru emissions tests, and here in Onatrio no tests for diesels or for cars that are older than 1988 model year.

That is BIZARRE... I've never heard of a cat plugging so quickly like that, and right after messing with the fuel system. Oh well, at least it's fixed! Congrats!

:cool:

I think it was a slow plugging up, that just happened by chance to be fully plugged after replacing the fuel lines etc. I have a very steep driveway, maybe that moved the junk around in the cat??? Until yesterday I could never figure out the 0-60 times that people were posting...how did their MB do that I thought to myself??? Now I realize that these 300DT actually move pretty fast. I hope now to have a cycle of no problems on this car...Car runs great now.