vacuum / shutoff troubles vex 300td
 

this, "new to me" 83 300td has a few problems, and now that the dust is settling after my relocation to the Buckeye, I have started to address them.

First was the "not shutting off syndrome" ... Step 1. Bought Mityvac vacuum tester and began chasing lines. ( Brown ) Not knowing what the specs should be, I found that the main line vac was 22-23 in., measured at the Tee infront of the brake booster. Testing brown line heading into the firewall, I found 16 in. Testing the line returning to the "thing-a-mabob" atop the injector pump, I found that line to have 10 in. vac. I also found that that line, as it connected to the "thing-a-mabob" was loose, so I trimmed the end and reconnected it.

The "not shutting off" syndrome is now solved, but with one consiquence and a few questions.

Consiquence... the red manual shut off no longer stops the engine.

Questions...
Were my vacuum readings anywhere near normal spec's?
What is the "thing-a-mabob" really called?
What should the other lines exiting the "thing-a-mabob" be reading for vacuum? ( currently, none of the lines exiting it read anything at all )

Last question for this post...

Did I spell "thing-a-mabob" correctly?

Thanks to all...love this site

Frank

PS.... be warned, I will have a few more questions about this 300TD as the reconstruction proceeds.

It's the vacuum shutoff solenoid for the IP. Vac is a little low at the solenoid, but if it stops, it's working. Check the rubber bits on all the vac lines, they are all probably bad and can be replaced with vac line from the autoparts store.

Check the restriction at the main line where the brown line is attached, it may be partly plugged. Don't ream the plastic out, just clean it, the hole is farily small.

You have the LEAN down on the shutoff lever to kill the engine, just pushing down won't work. The newer (60x) engines are easier, but he 617 takes some pressure.

You have several things attached at the vac pump -- the brown with blue stripe line is the shutoff, works off a switch on the key switch, supplied by the brown line.

On top of the IP is the ALDA (or alititude compensator) with a white line attached. This line is a pressure line from the intake manifold, causes the IP to add fuel as the intake pressure comes up from the turbo.

Also on the IP is a vac leakdown switch that oprates the teh EGR and the vac system for the tranny. On the 83 I think this is one switch set, but I could be wrong. Don't remember the colors, either, but you can trace the lines.

On the transmission line (to the modulator) you should have something like 16" vac with the throttle completely closed, a drop of 1-2" when you just open the throttle, and then a progressive drop to 0 at wide open. If you don't have any vac, you will get HARD shifts, make the rear end bang.

Check the supply line (should come from the main vac line) for blockages or cracked or torn rubber connectors and cracked hard plastic lines. They are brittle by now, and can crack fairly easily. Fix with a short bit of rubber vac hose over the break.

I'll bet you have hard shifts, and will find some more dead rubber hose bits, replacing them will fix the tranny shifts and make the EGR work again.

Peter

Thanks for the reply....actually, I have sloppy shifts ..slight flare between 1st and 2nd and a much more pronounced one between 2nd and 3rd....I will follow your suggestions and do some more investigating and repair and report back in tomorrow, Captian..

Frank

Transmission tuning
 

These tuning tips may help - the tranmsission in your 83 300TD should be similar to that in my 83 300SD.