I think all you need to do is turn the key and let the pump prime itself.
Try doing this a few times and see if it helps.

 

I've tried cranking it over several times, and cranking it for a long time each time.

 

Try cracking each injector line one at a time and crank over until it gets fuel.

Also, your fuel may have gunked up and clogged the filters. Try changing them and see if it helps.

 

There is no fuel pump. The injector pump is self priming.

 

So then it shouldn't have lost prime from sitting?

Try cracking each injector line one at a time and crank over until it gets fuel.

Also, your fuel may have gunked up and clogged the filters. Try changing them and see if it helps.

Filters? With an s? I know of the main fuel filter, where is the other. Stick with me, i'm new to these cars. Thanks!

 

There is usually an inline fuel filter below the air filter box. Not sure if it would be there on a 2.5 Turbo, but it would be a good place to start looking.

 

The conditions you describe don't sound like an injection pump that has lost it's prime. In my experience with the same engine in my 190D 2.5T, the only time it will lose it's prime is when changing the spin-on filter, or doing some mechanical work on the pump. When it has lost it's prime, it will not start & die. It simply won't start at all. Once it starts, it will remain running as the system purges itself of air. The trick is getting it started in the first place.

The best way (in my opinion) to bleed air out of the system is to crack the lines loose at the injectors, crank until diesel starts to weep out, then tighten the lines. This will save wear and tear on the starter, as compared to trying to crank it until it starts.

It sounds more like you may be having a fuel filter clogging problem, or possibly a vacuum shutoff valve/supply problem.

SteveM.

 

Since you mention that you just changed the "ignition" switch, the possibility exists that you may not have the vacuum lines attached properly at the rear of the switch. Double-check the vacuum lines to the back of the ignition switch. There are only 2. I can't remember if it makes a difference which way they are hooked up or not.

SteveM

 

You could have a clogged tank strainer, clogged filter, bad fuel or a clogged line or banjo bolt. You should drain your tank first, fill with fresh diesel (at least half a tank), and replace both filters. If you have compressed air, once you have the old fuel out, you can shoot compressed air in to the line that returns to the tank. That usually blows out the strainer and pressurizes the system. The you should hear your pressure relief valve hiss but should not see any fuel leaks. If you do not have compressed air, you can remove and clean the strainer with a 46mm bolt. The strainer can be found at the bottom of the gas tank, under the car, behind the rubber damn. There is a screw in fuel line going right up into it.

Once you have put fresh fuel in, replaced both filters (fill the filter with fresh fuel), cleaned the strainer, you can then pretty easily assess where your fuel issue is. I am sure it is bad or clogged fuel between the tank and the spin on filter. I recently had a no-start and I checked each inlet and outlet and return at the spin on filter while someone cranked the motor. Turned out it was a clogged banjo bolt from the filter to the IP.

If you have good fuel going in and out of the filter and returning to the tank, you should be able to start it. It will take about 45-60 seconds of cranking/priming.

Like mentioned above, also have a friend crank while you crack each of the five injector lines, one by one (crank for 10 secs, then close. Repeat.) Then, if you're glow plug system works, I am sure you will have a start.

Don't burn out your starter! It is a pain to replace.

 

There IS a lift pump in this car. It's driven off the injection pump, but it's a separate part.

The way I prime my '87 is to fill a new spin on filter with diesel. This will keep the car running for several seconds. Once it's dry, the engine will stall. Then one long crank and it will start up and keep running. The most common problem is that you worry so much about the starter motor that you don't crank it enough. Crank for 15 seconds, let it rest, crank again. No luck? Tighten the hose clamps on all the fuel feed lines. Try again.

If it still isn't starting it's possibly a problem with the lift pump. Inspect this by removing the feed line to the spin on, install a fuel pressure guage and measure while cranking. But more likely, it's the injector pump seals. Inspect the top of the injection pump for traces of fuel. If you see any, the pump is leaking. Here's a good photo tutorial on replacing them:

Mercedes Injection Pump O Ring R

.

 

My OM601 takes a good 30-45 seconds to self prime and start.