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1975 Mercedes-Benz 300D
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Discussion Starter · #1 ·
at about 10:30 last night I was going down the highway in my '75 300 D and I suddenly lost power, when I pulled over and tried to start the engine the oil pressure gauge only went about halfway up (to 15) and the engine wouldn't start... I will post more info as I find out more about it, I've only had the car for about 3 weeks and have one week to get it running and registered, please help!
 

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1975 Mercedes-Benz 300D
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Discussion Starter · #2 ·
The engine didn't seem to overheat, the temp gauge stayed at 175 (what it has normally been at) when I attempted to start it there was a very loud knocking and the engine attempted to crank over but wouldn't... there was oil on the dipstick, but it looks like the P.O. hadn't changed the oil recently (it looked very thick, dark, and viscous...
 

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1996 E320, 2005 Toyota Camry
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oil pressure

Are there any warning signs of a head gasket about to blow? Or does it just "come out of the blue?" Thanks.
Hemersam
 

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1975 Mercedes-Benz 300D
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Discussion Starter · #5 ·
well, I went and looked at it in the light today, it happened out of the blue... a few long-time diesel owners told me to check the fuel filter, there is no obvious evidence of leakage anywhere but some diesel underneath the fuel filter, according to him this would cause a loss in compression and therefore in oil pressure, hence the low gauge... if nothing else I will change it and see what happens before moving on to more expensive/time consuming tests and repairs
 

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2001 Volvo V40
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A lack of power might be caused by a lack of diesel or air in the fuel system. How long do you have this 300D in your possession? Have you done any basic maintenance, like oil, fuel and air filter change? Have you looked at the valve clearance?

If the engine isn't running, but only cranking on the starter engine, it is normal that the oil pressure doesn't rise above 15 psi.
 

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1975 Mercedes-Benz 300D
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Discussion Starter · #7 ·
OK....

Well guys, I've tried replacing the duel and air filters, and even put fuel injector cleaner in my tank and tried to start it with starting fluid but the most I've gotten is rough running under its own power for about a minute. my hypothesis is that it's not getting enough fuel, and that the fuel pump is to blame. The chilton's manual says that the electric fuel pump is under the rear floor panel, but I can't find it.. Any ideas? is the fuel pump in the tank, or is there more than one? could it be my injection pump?
 

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2001 Volvo V40
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A 1975 300D does not have an electronic fuel pump.

On the side of the injection pump is a lift pump, which pumps the diesel out of the tank and to the high pressure area of the injection pump.

There should be a hand pump near the fuel filter, what happens if you use the hand pump and open the bleed screw on the fuel filter? Do you hear the valve opening on the injection pump if you use the hand pump?

How long ago did you adjust the valve clearance?
 

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1975 Mercedes-Benz 300D
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Discussion Starter · #9 ·
When I changed the secondary fuel filter, I used the hand pump to prime the engine, I get diesel coming out of the bleed screw mixed with air... after using the hand pump for a good 20 minutes I just got diesel, but when I would stop I heard a gurgling sound almost like a drain, and I would get air again... Good to know that I don't have an electronic fuel pump or one other than under the hood, the Chilton's manual lied! I've only had the car for about a month and haven't done much to it other than putting an new alternator in it and changing the filters, I don't know when the last valve clearance check was done, or even if it's ever been done, nor do I know how to check or do it (this is the 1st car I've spent any time working on)
 

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First buy a Factory Service Manual:
Classic Technical Literature
that will always tell the truth ;-)

It sounds that you have air in the system, if so, the engine will not start or run. Check all the rubber lines of the fuel system. There is one from the tank to the steel line, the other ones are in the engine bay. The lift pump could also have leaking valves, but it is not likely. 20 minutes of pumping doesn't sound right, it should be much less.

Check the valve clearance, it is important: it prevents burnt valves and it improves the compression.
 

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1976 300D
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where is the oil pump drive bushing located? how can i check if my oil pump is ok? i have the same problem. when i started the engine of my 1976 300D, the oil pressure gauge moves to the max. but it seems after 3 mins, there were no oil circulating the engine. i notice this when i oven the valve on the engine..help me also solve my problem.

actually this all started after i badly hit a potruding rock that almost pressed my lower oil pan. now, my 300D is on standby waiting for your advice please.

thank you.
 

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where is the oil pump drive bushing located? how can i check if my oil pump is ok? i have the same problem. when i started the engine of my 1976 300D, the oil pressure gauge moves to the max. but it seems after 3 mins, there were no oil circulating the engine. i notice this when i oven the valve on the engine..help me also solve my problem.



actually this all started after i badly hit a potruding rock that almost pressed my lower oil pan. now, my 300D is on standby waiting for your advice please.



thank you.

It's good practice to start a new thread, but maybe reference that you read everything in this one. It helps make sure people know who they are helping.

Unfortunately I don't know diddly about diesels. Sorry. Hopefully someone else will come along.
 

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where is the oil pump drive bushing located? how can i check if my oil pump is ok? i have the same problem. when i started the engine of my 1976 300D, the oil pressure gauge moves to the max. but it seems after 3 mins, there were no oil circulating the engine. i notice this when i oven the valve on the engine..help me also solve my problem.

actually this all started after i badly hit a potruding rock that almost pressed my lower oil pan. now, my 300D is on standby waiting for your advice please.

thank you.

The oil pump sucks oil from the oil pan. There is a rubber mouth so that oil is only sucked from the bottom of the oil pan (where the oil is coolest). When you hit something and the oil pan is hit, the rubber mouth can be damaged, so that no oil can be sucked. Replace oil pan (if it is dented) and the rubber mouth. You need a new gasket for the oil pan. Torque for the bolts is pretty low, not much more than 10 Nm (of the top of my head), but check the FSM for the correct figure.

See the picture. The rubber mouth is in the red circle. The mouth is under pressure against the bottom of the oil pan. The notches can get damaged when the oil pan is hit, so there will be no or little clearance, so no oil can get sucked.
 

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1972 220 D, 1974 450SL, 1995 E300D 2002 S430, 1976 300D, 1986 SDL, 1982 SD
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Could be vacuum pump failed. Not sure how that impacts the oil pump, but they are run off the same crank.

My sudden loss of pressure was due to the cam riser sheering off. The thing must have metal fatigued and the oil pipe inside it, now exposed, pumped oil with no effort, but no longer along the circuit.
 
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