We have an '82 300sd that will start great and run great when cold, after it warms up , if you try to restart it , no go. cranks over fine, just won't cough. and now it is also shutting down when going down the road after getting good and warmed up.

I had posted awhile back ( just got around to checking the thing ) and had some suggestions about possible residual vacuum going to the shutoff valve and possibly rack dampner screw too tight and binding rack.

Today I tested it for vacuum... no vacuum going to the fuel shut off while cranking, good vac to it when turned off.

Made sure the manual shut off wasn't binding.

Backed the rack dampner screw out .

No change, still wouldn't start warm.

Cracked a few injector lines loose to see if it was getting fuel while cranking. Some fuel drizzled out around the fittings, but not with the gusto that I would expect.

Could I be looking at a failing fuel shutoff valve, possibly the spring inside it so worn that it can't kick the thing open when warm??
Any other suggestions?
Thing runs great other than that. fuel filters are new and injectors all rebuilt within the last thousand miles by a very good Bosch injection shop.

Thanks---------Robert

Sure sounds like a fuel supply problem. I would check the fuel pump first. Warm up the engine and get it to its failure point. Then operate the hand pump and see if you get a "buzzing" sound that would indicate it is functioning. If it is working OK, your problem might be in the IP. You did say that the filters are new, but you might try back flushing the fuel supply lines to make sure they aren't plugged. If that solves the problem temporarily you should probably drain and clean the tank.

Just suggestions. Others will jump in with more I'm sure.

Tank was drained and cleaned and new screen installed about 2000 miles ago, along with new primer pump.
I wouldn't think the lines could be clogged if it's running great one second, then I turn it off and try to restart and nothing..

The next time it is warm and you want to start it try taking the fuel cap off the fuel tank.
If that does not work go to Alldata.com and check the TSB titles... one for your car may say ' problems restarting when warm' or to that effect....

From what I have observed on this site.I would just check to see if valves have too little clearance. Once engine warms very poor compression if valves not able to seat properly. Only should take a short time to do a check. especially if not done since heaven knows when. Just a thought.

Valves were adjusted about a thousand miles ago. and I set them a bit on the loose side, They *shouldn't* be tightening up .
I cleaned out the tank vent lines a couple of thousand miles ago, but it wouldn't hurt to try the cap trick.