Need help with 83 Mercedes 300td
 

Hello,

My first post at Pelican so thanks in advance to any help you can offer.

We have an 83 Mercedes 300td. A few years ago it was in daily use and then one day just would not start. Due to a variety of reasons (one of which was a protracted stay in hospital) the car has been sitting, covered, until I decided to get it going again.

I will be undertaking replacing all the filters and will purge the fuel system and will also redo the valve clearances and clean the injectors and heater coils, but initially I tried turning it over.

It does this fine but no sign of starting. I have checked fuel delivery and discovered that the priming pump does leak when used, but not when locked in position. I cracked open slightly the fuel line just prior to the injector pump and fuel is flowing there when turned over, however, cracking open the hard line to No1 cylinder and there is no sign of fuel arriving.

I would assume that even a poorly balanced injector pump would still supply some fuel, but nothing happens. I am also assuming that this is the reason for the initial no start that caused the vehicle to be laid up in the first place.

Any thoughts/ideas where I might start to diagnose this problem?

Check your fuel filters and probably change them and the air filter. You can start and run a car with fuel problems by spraying wd40 into the intake too. If it ran when parked it should run now if it is getting fuel and has good compression. Purging and adjusting the valves should not be needed to start it...no harm of course.

while cranking, bury the pedal to the floor until it starts.

Hi,

Thanks for the suggestions. Tried the wd40 trick (and diesel easy start) and apart from the engine kicking once, nothing happened.

Just to reiterate, fuel seems to be getting to the injector pump but nothing is reaching the injectors. This car was laid up for a number of years BECAUSE it would not start one day even though it had been a daily driver before that.

Is there a cut off mechanism that may be faulty which is stopping the fuel flowing through the injector pump?

Thoughts anyone?

Thanks.

Hi, thanks.

Tried both of those suggestions and other than a quick "kick" of the engine nothing happened.
Just to reiterate, fuel does appear to be reaching the inlet of the injector pump, but nothing comes out the hard lines to the engine.

I have confirmed the shut off valve is working correctly (at least, it hold pressure when tested) so I am at a loss. I would assume that some fuel would arrive at the injectors even if the pump was faulty in some way.

Also the reason for laying up the vehicle several years ago was because it would not start despite having been a daily driver prior to that.

Any one else any thoughts?

you can loosen the hard line to injector nuts and crank the engine over. fuel should come out there after any air is bled out.

check the glow plugs are indeed glowing. you can bench test them or just remove and replace them with new.

check the air filter that there isnt something goofy in there like a mouse nest.

replacing the fuel filters is good practice. how does the tank smell? like diesel or kind of rotten? you may have an algae problem from the extended sitting.

once fuel, glow and air is there give the engine 10 rotations or so.

Have you checked the battery? You should have 12.6V on it cold before starting. It's possible it is marginal enough to bump the starter but not strong enough to start the car.

Dkr.

Hi,

Thanks for all the input.

Thus far I have checked and adjusted the fuel bypass valve (re set the spring length to spec), replaced primary and secondary fuel filters plus cleaned the filter in the tank.

Confirmed that the timing chain is intact.

I removed all the hardlines and cranked the engine and am only get a slight squirt from No5 port.

I then took out and carefully cleaned the delivery valves of both No2 port and No5 port (without touching the base plates at all) and swopped them, no difference (I appreciate that I should instal new copper washers but this is just to see if anything would change at this point), only a spurt of fuel from No5 port again.

This is a video link of what is happening......
https://vimeo.com/862976911 (battery slightly drained at this point in the game).

Until I get fuel to the injectors surely any talk of glow plugs is a bit mute (but correct me if I am wrong).

Thanks all for any help.