A couple issues, please help a brother out
 

Hello, I have an '84 300SD. I am having several issues with it, one that recently started happening and I am not sure what the culprit is.

The most recent one is when I am driving for a long period of time, say more than one hour, and I stop to get gas or something, I turn the engine off, and when I go to start it again, it won't start. Nothing happens. There is a single click and then nothing. Eventually it will start again, but it takes anywhere from one to ten minutes and several to a bunch of tries turning it over. Driving around the city this never happens, only longer cross country trips. I am at a loss as to the culprit. Any help would be much appreciated.

The other thing happening is my engine does not turn off with the key. I have tried trouble shooting all of the normal culprits. The vacuum motor seems to be working fine as all of my other vacuum components are working. I vacuum tested the lines to the shut off valve and they are fine. And I applied vacuum pressure to the shut off valve directly and it shuts the engine off perfectly. I have noticed that there are two vacuum lines going to the ignition switch, so I am wondering if there is an issue with that, possibly that it is not giving the signal that the motor needs to apply vacuum to the shut off valve. I also wonder if this might also be the culprit to my trouble restarting after long trips.

Again, any information you can provide would be very helpful. If you have any other questions, please let me know and I will answer them as I am able.

Thanks in advance.

When that happened to me it was inside my starter..... the three little screws which hold the ' cage ' for the brushes had backed out....after ONLY 25 years of use !!! lol
I saw the starter as they opened it up and showed me the problem... the advantage of going to a small agricultural town alternator/starter shop...

As for the shut off - doesn't the ignition switch have a nipple and vac tube attached for shut off? Could this be the problem?

Leatermang, did they pull the starter off and then open it up, or can you access those bolts with the starter still attached to the car?

Spokenapp, I pulled the starter and took it to their shop.... it is the screws which go into the end of the starter..from the inside.... so you have to open it up to deal with them...
The brushes in these starters are massive... and it was only the lack of steady holding that was wrong with the starter...but they had one not picked up by someone sitting there so I took that one and kept my old one....for $108 I was really pleased... also saved me a trip back to pick it up..

Probably not the vacuum shut-down valve. To be sure, just pull the vac tube to it before trying to start next time. The tube runs beside the VCV on top of the injection pump.

I agree it is most likely in the starter motor, perhaps the solenoid that is integral with it. But, could also be a voltage supply issue to the starter. Remove and clean the battery terminals. Some older U.S. V-8 engines had issues where the starter was over-heated by the exhaust, so insure all your heat shields are in place. In 1984, I recall that is just one bolted under the exhaust rear and a little one to protect the battery. 1985 CA engines have many more.

The starter isn't trivial to remove. I would insure it is getting >8 V right at the starter before condemning it. That is measured from the case (blk lead) to the big stud on the starter (red lead). You could have a voltage drop from block to frame, so don't put the blk lead on BAT- and assume that is a valid measurement.

You can bypass all switches by bridging the correct 2 contacts in the junction box on the passenger side in the engine compartment. I for got exactly which 2 contacts. I think the 2 toward the rear. That is how I turn the engine over for a valve adjustment using a remote starter switch. Pliers or a wire work also. You may need the ignition switch to be in the run position.

Be sure that the trans is in neutral or park.

Pulling the starter is more trouble than testing for voltage and voltage drop through out the system. At least be sure that you have a charged battery and full battery voltage at the starter before you tear into pulling the starter.

It may be the solenoid or starter but it could also be bad connections or a combination of all of the above.

When this same starting problem happened to me, it turned out to be a loose engine to chassis ground wire.

Separate issues... Shut down is not related to startup...

For shut down, you FIRST need to verify vacuum is present at the pump... Then follow it until you no longer have vacuum...
Stating per vacuum devices work fine, has little to do with your problem too, as the SD has a separate vacuum system for several things in the car.

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