81 300td lost power... now won't start
 

Hi everyone!
My new car was too good to be true :confused: It was in need of fuel and air filters and oil change when I bought it and I drove it a little while until I saved the money for the tune-up. On a highway trip I stopped to add oil, (it was registering, but low at a fuel stop) and then it began to exhibit symptoms of a clogged fuel filter, losing power, until it gradually stopped running as I pulled to the offramp. I replaced both filters, filled the secondary with diesel, my roommate lost the washer on the top, I pushed the primer (black rubber) about 30 times and the car won't start. It cranks, but seems weak. How do I know if the engine was ruined from lack of oil, if the IP is ruined from clogging filters, or if I just need to keep priming the pump... crack the lines... etc? Do I crack each injector line to test and see if they are working?

Thank you!

You mentioned you pushed the primer pump "black rubber" the old style is white plastic that needs to be unscrewed and pulled up and then pumped. The newer style has a metal top that you just push down and it recoils and then you push again. Check that you have used the primer pump correctly. If your battery is questionable I would suggest cracking the hard fuel lines at the injectors, push primer until you see fuel from each then retighten and attempt to start.

Ok, thanks. It has no knob, just a sort of rounded black cylinder that travels up and down. I have pumped it A LOT but won't build any pressure. I will crack the lines now. How many times will I need to pump it to see fuel? A few or a hundred?

After a typical fuel filter change, or glow plug change (where hard lines are removed) I don't remember pumping more than about fifteen. This may sound like a stupid question, but does your fuel gague read properly? Maybe try getting three gallons of diesel, and pouring it in the tank. Then use the primer pump as you have in the past. There is a screen in the fuel tank that if clogged could have the same effects as being on an empty tank while there is still a quarter tank or more.

That is SO not a stupid question. I wish I had read your post before I had paid $300 to tow my car home from Seattle. The tow driver told me to bang on the fuel tank with a hammer. I was so depressed I didn't think to ask why and just dismissed it. Last night, after my fingers ached from pushing the primer pump a half million times, jumping it for two hours, unable to crack the hard fuel line nuts (can't turn a wrench with the lines in the way!) and was ready to give up and take it to the shop, I remembered about banging on the tank. What the hell? I did, and when I turned the key to try to start it for the last time, the fuel gauge dropped from full to empty!!! I put in 4 gallons of biodiesel, the pump primed right up in about 20 pumps and after 10 or so more cranks she started right up... running smooth! Thanks for your help!

Now I would suggest keeping around three primary filters (the clear ones) on hand in the vehicle as you more than likely have some quantity of crud that will be going through the system. To do the job properly have the tank removed and cleaned, and a new strainer installed. And I do not want to knock someone for any advise but someone telling you to knock on your tank is not a fix but at least it got you in the right direction.

I have just reread your previous post and didn't comprehend at first that you stated the tank was depressed. That is a clear sign that the fuel tank vent is not operating. Try filling the tank and running it down to around three quarter full and remove the fuel cap. If you notice air rushing in or a vacuum situation you have a bad fuel tank vent and not the tank strainer. An easy fix if it is the tank vent.

ok! interesting! I will do that, thank you :)

If you drive long enough at some time you are going find you simply ran out of Fuel; so that happens to everyone.

When you own an old Cars like this it really is more economical to have an Auto Club or other Membership where you get some free Towing and other Roadside assistance.

A few Months after I first got My Mercedes I got in the Car and it was cranking well and the Glow Plugs were working but no start. I called the Auto Club and as the Guy was hooking up to tow Me I went in side to get the Shifter out of Park.
Guess what. I had left the Shifter in Drive. And, being in Drive was the reason My Car would not start.
I kept My Mouth shut and let the Guy Tow Me Home. After He dropped Me off and was out of site I put the Shifter in Park and of course it started normally.

A Crows Foot Wrench like the one in the Pic (a Flare Nut Crows Foot Wrench) on the end of a Socket Wrench Extension works really well on the Fuel Injection Hard Line Nuts at the Injectors and also down on the Fuel Injection Pump.

A regular Crows Foot Wrench will also work.

Size 17mm