85 300SD Prob. - PeachParts Mercedes-Benz Forum

Beastie · #1 08-07-2006, 12:13 PM

I am fairly new to the Diesel threads but here goes. I am now the proud owner of my Fathers 85 300SD which he bought new. Long story short I loaned the vehicle to my brother who has been driving it for 2 months. Last night when he was coming home the car would not start so he had it towed home. He said the fuel was low so he went and got 2-3 gallons and poured it in and the car started. He said it idled rough and that when he tried to rev the engine the car would die. I am going over this afternoon to take a look and will look through my shop manual but any suggestions would be appreciated. I do not believe him when he says that he did not run out of fuel. He "SAYS" the low fuel light never came on. This is my brother who has owned 8 cars and all have either been totaled, donated etc. I have not worked on a Diesel for about 25 years and the things you forget !. HELP !!

Alan

TX76513 · #2 08-07-2006, 12:22 PM

Throw two new filters on and make assurances there is fuel.

Beastie · #3 08-07-2006, 12:37 PM

Thanks , I will give it a shot. I am going over this afternoon or tuesday a.m.. Any other ideas appreciated. My brother is a bonehead !.
Thanks again.
Alan

Brian Carlton · #4 08-07-2006, 01:12 PM

TX is right on the money.

Make sure you have a can of fresh fuel to fill the secondary filter before you tighten back up..........otherwise you'll never start it.

And, pump the primer pump about 30 times after you secure the secondary filter.

sixto · #5 08-07-2006, 01:13 PM

If ran low on fuel meant ran out of fuel, try the primer pump on the driver side of the injection pump. It'll either have a flat plastic button that you press repeatedly or a finger loop that you release by unscrewing then pull out-push in prepeatedly. Loosen the big bolt (17mm wrench?) that goes through the spin-on fuel filter ahead of the injection pump. You're primed when fuel leaks out of the fitting.

Check that the stop lever isn't stuck in the 'down' position. The lever should rest against an internal hard stop in the vertical position. If you can move the lever upwards with the key in the run position, there is likely a problem with the vacuum switch actuated by the key. Remove the vacuum hose connected to the injection pump to until you can sort it out but note that you will not be able to shut-off the engine from the cabin.

Could be tired glow plugs or a bad glow plug relay but the problem will be getting the engine to fire, not keeping it running... certainly not after a few seconds.

Sixto
... stay tuned

Beastie · #6 08-07-2006, 01:35 PM

Thanks to all, I am picking up the filters this afternoon and I talked to a buddy of mine who has owned 3-4 diesel benz's and he basicaly said the same things. This is why I love this forum. I will update. As soon as my brother gets another car he will not even have his a%#& touch the seat in this one again.

Alan

psfred · #7 08-07-2006, 11:37 PM

Check the suction side hoses from the standpipe in the engine compartment to the lift pump. If damp with fuel or original, I'd bet they are leaking and you are pulling air into the IP.

If you have the original red capped screw in type hand pump, replace it, it's likely shot. If you use it and it leaks fuel, definitely replace it, it's leaking air in as well.

Crack the big screw on top of the fuel filter and operate the hand pump -- if lots of air comes out, but never fuel only, you have an intake leak. If you can't operate the pump easily, like the filters are clogged with crap from bad fuel -- I would change them "on spec" -- your symptoms are typical of air leaks or clogged filters.

If you cannot purge the air out of the filters or the hand pump won't lift or return by itself (new type with internal spring), the tank screen in plugged with algae and you need to remove and replace it. Algicide in fuel treatment will kill any remaining in the tank.

Clogged screen is much more likely with low fuel by the way.

Peter

Beastie · #8 08-09-2006, 03:42 PM

I just got home and after looking at the great and very helpfull responsesI got the car started. I loosened the 17MM on top of the filter and primed the pump. It only took one pump and fuel came out so I tightened everything back up and cranked the car. It took about 35 seconds before it caught and ran fine. The glow plug light does come on so I will follow up on that as well as all the filters in the next few days. Over the last few years this car has been driven less and less due to my fathers health. He gave me the car but wanted the keys at his house ( this was a dream of his to own a Mercedes , so after he did his 31 years in the marine corps and got inot the private sector he bought this one ) Thanks again for everyones input . I am certain I will be requesting help again since this is the first Diesel I haveowned in over 20 years and for my Dad I want to keep rolling down the road to pass on to my son someday.

Alan