Problems with 80' 300sd
 

I have returned to ask a couple of questions about problems I am having.

A) The first thing is that the engine does not want to cut off unless the climate control is set to "BILEVEL". Which I have heard was a vaccum realted function. But I cannot find a leak.
B) Also when the air compressor is engaged, it makes this horrible rattle; it dissappears when the engine is idled @ 1000 rpm. The AC still blows cool air.
C) My fuel return lines are leaking, and I am about to go buy a replacement, could this have some effect on shutting down.
D) The vehicle shakes really really bad unless kept at about a steady 900-1000 rpms.

I am sorry this is so long, but it's hard to find a mechanic who is willing to work on my car. So hopefully, I can find some help here.
Thanks,

Ty

Ty,

The engine is shut off by stopping the supply of fuel, which is controlled by vacuum. Do a search on the subject of not shutting off or vacuum leaks and you will get a ton of information on the subject. It is a common event with old Diesels as the vacuum bits and pieces begin to age and crack, and then leak.

The fuel leakage is not linked to difficulty shutting off the engine. But they need to be replaced so buy a meter or so of the hose and pull the old ones off, then cut new ones using the old ones as templates for length. I use needle nose pliers to pull the old ones off and push the new ones back on the nipples on the injecgtors.

Shaking at low rpm is possibly linked to engine mounts. As they age they get stiff and can develop a resonance at the forcing frequency of the engine at idle, leading to rougher idle. Rough idle can also be related to an injection pump feature on the 5 cylinder models, and possibly the 6 cylinder units called the injector rack bolt. Do a search on that to see if the bolt could be part of the problem.

Mounts and the rack bolt are changed out regularly by guys on the site, so don't be afraid to get the information you need to do each job, then get the parts and give it a shot.

Good luck, and I believe all the problems you listed are reasonably well within the DIY'er range of difficulty. Jim

As far as your A/C goes. Your compressor is on its way out. Plan on a replacement soon. Compressor failure while running can contaminate the system and cost you a bundle to have everything flushed out. Although if you have the GM R-4 compressor, that doesn't happen too often.

Vacuum Connection
 

I have done some inspection of the vacumm components and may have found my problem. Beside the fuse panel there are two little 4 way connectors. The first one with a green vac line it has a golf tee stuck in one of the ports. The second one has a little inline filter looking thing with no hose coming out of it. This particular 4 way has two yellow lines on it. Can anyone tell me thr original hook up for this little connection.

Ps. Thanks for the above advice billrok and Jim Smith

I think you should check for tech bulletins concerning your car.... I think there have been some related to a couple of your symptoms.... Greg

tech bulletins
 

I've searched the site and at google and so far none of the bulletins that I have looked at have helped. Any suggestions for a site I may have overlooked.

Ty

The A/C rattle you hear may be the clutch. Will rattle more when A/C is not running. When the clutch kicks in noise should stop or at least be much less. It will run quite awhile before it goes out most of the time. When it does it will not hurt the inner workings of the A/C. Clutch replacement is a pretty easy job.

Did you try alldata.com ? You can see a free list of the titles of the tsb's and recalls....directed at your car .... Greg

MB service information No. 07.1/21 deals with the engine vibration dampner on your car...

Service Bullitens
 

Ty,

Have you tried this one?

http://www.nhtsa.dot.gov/cars/problems/tsb/service1.cfm?SearchTopic=Vehicle

Bill

Hey,
Bill I have looked at the site you reccomended, the had some information but nothign that i could find about the vacuum system. Its great for brake diagnostics

Greg- I think i might have to get a subscription to the one you gave me looks like their might be some possible info.

If the A/C clutch is supposed to rattle only when disengaged, then its definately not my cluch. The whole car smooths out a little when the a/c is off. (OFF on climate control + AIRCOND switch off.) When ever the system gets turned on is when it starts to rattle.

:confused:

Trial and error.
 

Welll I got under the hood and started playing around with the connections. I hooked up one of the two yellow hoses to the first 4 way. All of a sudden all my doors unlocked. Could this be my gateway for find my problem.?