Vacuum line mismatch?

[abgwin]

1985 300D sedan (California version) with 348K miles that I've had for about a month. At some time in the past, she was subjected to a Lovecraft veg oil 'conversion' but previous owner says no veg oil ran 'in years'.

Finally got the nerve to pull what I could, so yesterday out came the aux elec fuel pump and inline fuel heater. Disconnected the fuel supply to the Lovecraft and ran Diesel Purge, then an oil change.

Unfortunately the Lovecraft's heat supply line is a T in the radiator hose right above the oil filter, so wrestling the oil filter in and out knocked several vacuum lines off. Reattached as well as I could, but now engine not stopping with ignition switch

I know enough to know that this suggests the cutoff is the culprit, but I don't know enough to know which lines those are. There are no major leaks as the doors still lock quickly and the transmission shifts better than ever.

I've searched through all manner of diagrams but what would really help is a photo of the firewall port where the vacuum lines connect so I can be certain the right lines are in the right places.

I would be really grateful if someone could point me to one.

Thanks in advance -

[vstech]

there are two brown plastic lines that exit the firewall, one goes to vacuum source, and one goes to the shutoff diaphragm at the back of the IP.
Welcome to the forum, and glad you've rescued a lovecraft "converted" vehicle!

[toomany MBZ]

http://www.peachparts.com/shopforum/diesel-discussion/314017-vacuum-line-question.html
Post #3 has a pic from whunter showing the plumbing.

The pic here shows my CD, the lines go to a "bus" I think it's called, at the fire wall to enter the cabin.

A solid brown line from the vac pump and a brown/violet line going to the actuator.

[abgwin]

Thanks very much for the replies and photos. But now I'm even more confused, as the brown lines look just like mine. The brown/violet runs directly to ignition and brown runs to vacuum supply at brake booster.

[charmalu]

One brown line gets it`s vacuum supply from the large black vacuum line that goes between the vacuum pump on the front of the engine to the brake Booster.

This brown line goes into the cabin and connects to the vac switch on the steering lock assy.

From that vac switch the other brown line exits the cabin and connects to the vacuum fuel shutoff at the rear of the Injection Pump.

There is a small round can with a metal nupple the line connects to.

Charlie

[abgwin]

Ok, then it really looks like the vacuum circuit for the cutoff is in place correctly. If the other vacuum powered accessories work (climate control, door locks, transmission shifts well) where should I look for the problem?

Could the cutoff actuator die so suddenly and without warning? Any way to test the ignition switch to be sure it's doing its job? I am having some trouble with the switch - it's really finicky on turning all the way to START at times.

[vstech]

Originally Posted by abgwin

Ok, then it really looks like the vacuum circuit for the cutoff is in place correctly. If the other vacuum powered accessories work (climate control, door locks, transmission shifts well) where should I look for the problem?

Could the cutoff actuator die so suddenly and without warning? Any way to test the ignition switch to be sure it's doing its job? I am having some trouble with the switch - it's really finicky on turning all the way to START at times.

take 3 pictures of your engine bay, one closeup of the rear of the IP, one similar to the shot of the firewall above, and one with a wide angle showing where both brown lines connect.

[abgwin]

Will do. Work has me in Monterrey, Mexico for the week.

[abgwin]

Update: testing the cutoff switch with a vacuum hand pump. It does kill the engine, but doesn't seem to hold a vacuum on its own.

Also discovered that the door lock system isn't actually working: the vacuum reserve must be in good shape, as it held up for several days before slowly giving up.

A few (bad) pictures of the lines under the hood:

[MercPilot]

[QUOTE=abgwin;3117050]Update: testing the cutoff switch with a vacuum hand pump. It does kill the engine, but doesn't seem to hold a vacuum on its own.

Also discovered that the door lock system isn't actually working: the vacuum reserve must be in good shape, as it held up for several days before slowly giving up.

A few (bad) pictures of the lines under the hood:





What is the yellowish hose with the rubber connector going into the firewall in this pic? I have the black rubber connector with no hose coming out of it.
Zack

[toomany MBZ]

Yellow lines are usually for the lock system.

[MercPilot]

Thanks, I guess a better question is where is this line going to? I've looked for obvious signs of a missing line, but can't find where the other end of this line might go to. Any thoughts?

[abgwin]

Update: it wasn't a problem with the vacuum lines at all. It was a problem with the black rubber fittings and connectors. Simply replacing all the Ys and Xs - ordered from this site for a very reasonable price - and everything works once again.

Locks, climate control and - most importantly - the engine shuts off with the key.

So I would advise anyone to first replace those fittings. It can't hurt, it's cheap and a good thing to do anyway.

[charmalu]

Originally Posted by MercPilot

Thanks, I guess a better question is where is this line going to? I've looked for obvious signs of a missing line, but can't find where the other end of this line might go to. Any thoughts?

Are you refering to the yellowish line up by the Brake Booster in the above picture? it connects to the Switch over valve, and the other end to the ALDA, the square thing in the IP. there is a line from the rear of the intake manifold that goes to the same SO Valve. this is a boost line.

The yellow pod below the SO Valve is a check valve for the vacuum system for the door locks, fuel door and trunk locks. there are 2 yellow lines that go into the cabin, one goes to the Drivers door, and the master vac switch diverts the vac to the various door pods for lock and unlock. the other yellow line with grey stripe goes to the Vac Supply Tank in the trunk above the fuel tank. this is only for the door locks.

This thread explains it.
http://www.peachparts.com/shopforum/diesel-discussion/160169-w123-vacuum-interlock-diagram.html


Charlie

[toomany MBZ]

Glad to hear of a cheap and effective fix.