car starts great cold.

When warm, it will crank over forever without starting till I pull the top vacuum line off of the whitish-yellowed plastic transmission switchover valve shown below.


Further, if I start the engine this way, it seems to lack full fuel flow.
If I wait 15 minutes or so, it will warm start without having to pull this vacuum line off and then it gets full fuel flow.

My question: Is this because of a sticky fuel shut off valve that lays underneath the trans switchover valve?

Or is it a problem with the ignition switch, or both, or something else?
could it be low air pressure in the left front tire?

__________________
The modern conservative is engaged in one of man''s oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.
-John Kenneth Galbraith

oh yeah, it does take a few seconds for the engine to shut down after I turn off the key.

__________________
The modern conservative is engaged in one of man''s oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.
-John Kenneth Galbraith

I'd suspect a problem in the vacuum portion of the ignition switch. Put a mity vac directly on the shut off vacuum line and get some readings to figure out what is happening.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

So a reading with the engine running and one with it off? Maybe watch to see if it bleeds down? I am not sure what I am looking for but I will post what I find with the mity vac.

So the vacuum is supposed to neutralize to release the valve when I turn on the key right?
but when I pull off the line and start it, the fuel shut off doesn't seem to open all the way, could be both issues eh?, and leak and a bad fuel cut off valve?

I obviously have a leak because it doesn't shut down right away.

__________________
The modern conservative is engaged in one of man''s oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.
-John Kenneth Galbraith

Perhaps you have a shut off valve that is sticking in both directions but I've never heard of that problem on this forum before.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

thanks kerry, I'll start with the ignition switch.

__________________
The modern conservative is engaged in one of man''s oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.
-John Kenneth Galbraith

'Put the MV's hose on the fuel shut off actuator on the IP (with the engine
running)...Apply vacuum...engine should shut off immediately.If it does not
you have a bad shut off valve/actuator.

Start engine... take vacuum line from the fuel shutoff valve/actuator and plug
it into your Mighty Vac...Watching the Mighty Vac (You may need a helper to
turn off the key) turn the ignition key to "OFF." What Vacuum reading do you
get on the MV?[HINT,HINT...This will tell you if there's problems with the
vacuum portion of the ignition switch AND/OR if there's something amiss twixt
the ignition switch and the Vacuum Pump...AND/OR if the vacuum pump itself
is FUBAR.)

The fact that you've figured out how to un-plug a Transmission portion of the
vacuum system tells us you're pretty Diagnosis inclined(Although,having to do
that to start the engine sounds like the Dreaded "P.O. Hack Job on the Vacuum System")


Report Back.

(To Whom?)

__________________
'84 300SD sold
124.128

right-on man

MV to fuel shut off valve: with engine running, got up to 15 Hg while vigorously pumping, resulting in no engine shut down = bad valve.

MV to hose: turned off key and almost immediately, with little delay, got engine shut down and 20 inches on mity vac.

Thanks for the procedure man.

Now, wheres a good place to buy another valve?

__________________
The modern conservative is engaged in one of man''s oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.
-John Kenneth Galbraith

The Second procedure was to take the vacuum hose OFF the Fuel ShutOff valve and plug it onto the MV
(Which leaves NO hose to the Fuel Shut-Off,unless you "T"ed into the vacuum hose to the Fuel Shut-Off).
You were testing the integrity of the vacuum portion of the Ignition Switch (and all the components from there to the Vacuum Pump itself)

Please explain this:
"MV to hose: turned off key and almost immediately, with little delay, got engine shut down and 20 inches on mity vac."

O.K. If you got the engine to shut off with the key...The ONLY WAY to do that
is if the Fuel Shut-Off Valve/Actuator is working.

AND according to the results you posted on test#1 the Fuel Shut-Off is BAD?

It's always possible the the rubber diaphragm inside the fuel shut-off is
BAD on an Intermittent Basis...
(AND I'm the Next Comptroller of the Currency)?

OR MAYBE the Vacuum hose from the Vacuum portion of the Ignition Key
to the Fuel Shut-Off is BAD ...SOMETIMES?

Please Advise...I do not want you to buy a new shut off if it's good.

Try test #2 again (and this time leave the Fuel Shut-Off out of the Loop)

(I still like Kerry's idea about the Ignition Switch.) Being the Culprit.

EDIT:
O.K. What year and Model Mercedes are we talking about?
We need to get a Vacuum diagram here...I suspect your hoses have
been routed incorrectly (Maybe)?

__________________
'84 300SD sold
124.128

I understood, and to clairify, I unplugged the line to the fuel shut-off valve, plugged in the MV into the line tha t I had unplugged, and did NOT use a tee to reconnect it to the fuel shut off valve. the result of turning off the key was engine shut down, and 20 hg on the line, where as before shutdown there was 0hg on the line.

So with 20hg on shutdown, does that mean my ignition valve is ok?
and how does the engine shut off without putting vac on the fuel shutoff valve?

On a side note, I noticed some fuel lightly seeping around the round black thingy on top of the ALDA top cover plate to the injection pump, shown in this pic.

I don't know if it is relative or a problem.

I do think my vac lines have been messed with because two have been cut and plugged that go into the passenger compartment, one yellow, and one yellow with black stripe.

Also in this next pic, there is a lower vac line coming out of the side of the transmission switchover valve, it splits and one goes toward the front of the car, I believe to the pump, and one goes toward the back of the car and is just hanging wild. where should that wild one be attached?

__________________
The modern conservative is engaged in one of man''s oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.
-John Kenneth Galbraith

Sounds like your ignition switch is ok, but I also am very confused.
How can your engine shut down (which you wrote that it did) if the fuel shut off valve is bad? And how can the engine shut down if you disconnected the line to the shut off valve, connected the Mity Vac to the line, but didn't T it back into the shut off valve?

I think what we have here is a failure to communicate.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I wrote it correctly, I disconnected the top vac line on the transmission switchover valve, that apearently draws vac from the fuel shut off valve to kill the motor. I did NOT reconnect it with a tee. I then turned the key off and the engine stopped. read the previous post because I added something about my vac lines, maybe that will shed some light. and thanks for working with me.

__________________
The modern conservative is engaged in one of man''s oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.
-John Kenneth Galbraith

VCV for transmission should not be getting vacuum from the shut off valve. If it does, it means that the VCV is not getting vacuum when the engine is running.

The brown line in the picture in a recent post, closer to the engine than the VCV running down the oil filter housing and to the back of the IP is the line for the shut off valve. You need to conduct your shut off experiments using that line.

The yellow lines are your door locks. I bet none of your door locks work.

There is a vent on the VCV. The disconnected line to which you refer, could be that vent.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

well punch my fat gut.
13 posts to get me to test the right line.
sorry about that.

So, I just did both test on the little brown line citcuit.

First test shut the engine down with one pump of mightyvac; only 5Hg to get shut down, so I think the fuel shutoff valve is good.

Second test, on the brown line only, did NOT shut the engine down but did produce 15 Hg with a turn of the key to the off position.

Note: upon removal and inspection of the 7mm rubber hose that coupled the brown vac line to the fuel shutoff valve, I noticed it was in bad shape with cracks. I replaced it before the tests.

after the test I took the car down the hill and got the temp up to 80c.
I then messed around with starting the car warm as per my original complaints.

Now if I shut it off and try to restart it will still turnover forever without combustion on the first try, but second try always starts it with little effort.

I tried a bunch of ways, all I have to do is bump it once, turn the key off, and then bump it again and it starts. but it never starts on the first try.
I can live with this, but would like to fix it if I can.

also, your right, the only door lock that works automatically is the driver door. I assume another door had a leak and someone "fixed" it this way.

thanks for all the help.
I know I will need more as I get more into this car.

__________________
The modern conservative is engaged in one of man''s oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness.
-John Kenneth Galbraith

I think If you, WVOJOE,can get your hands on the correct Vacuum diagram
...You can re-route the hoses and connections correctly.(Someone HAS
Altered the routing of your system)

I still have No Idea what kind of vehicle we were discussing.

Let me know if I can be of any more assistance.

__________________
'84 300SD sold
124.128