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Trouble starting 1979 300sd that just ran fine the other day

1K views 10 replies 2 participants last post by  diametricalbenz 
#1 ·
Hello, have a 1979 300sd. Started up and ran just fine the other day. Replaced both fuel filters, transmission filter, and transmission fluid, as well as the fuel return lines. Now I can't get the engine to start anymore. It sputters, sounds like its going to start, but does not. Do I have to re-prime the fuel system or something? And if so how do I do this? Any help is greatly appreciated :D
 
#2 ·
So after doing some reading, it seemed I originally should of filled the fuel filter full of fuel before re-installing it. I took it off and at this point its already full so I just put it back on. Buddy of mine said that at work they will use starter fluid to try and get them started good enough so that the engine re-primes itself, but its not the greatest for the engine supposedly. Well I tried starting it with starter fluid with no luck...
 
#3 ·
Using starter fluid is probably one of the most damaging things you can do to it. DO NOT DO THAT.

Crack the fuel filter bleed screw at the top and pump the fuel from the manual plunger until it bubbles and then starts to leak. Retighten the bleed bolt. Start pumping the manual plunger rapidly while someone in the car depresses the throttle and cranks the motor. That should get fuel to the injectors and it will start. Make sure that they person on the throttle lifts off as soon as it catches so you don't rev the motor necessarily while cold. Try it and get back to us.
 
#4 ·
Thanks for the advice, after doing this repeatedly, over the course of a couple days it finally started, and would always start pretty much right up every time after that I tried (using the manual primer method).

I noticed that every now and then while driving, that the coil light starts to flash, I'm under the impression that that means the glow plugs are jacked? Or the relay? I expected it to maybe only flash directly after starting the car, not randomly while driving?

I also noticed that every now and then while driving over 40mph or so, the car starts to bog down, it almost feels like something is limiting fuel maybe? It gets worse and worse and speed constantly drops over the course of a couple minutes at which point the engine stalls. After a couple minutes of trying to start it starts up and runs fine temporarily, until the same problem repeats itself. The car always wants to die while stopped, so I have to give it slight gas to prevent it from dieing. Any advice on this? This is the last thing I need to do to get the car drivable from its previous conditions lol. Any help is greatly appreciated.
 
#5 ·
I am not sure about the GP relay issue but it definitely shouldn't come on while driving since the timer runs for 60 seconds or something like that to assist cold starts.

As for the power loss you have some issues with your fuel flow still. If the car has been sitting there may simply be a lot of junk being trapped by the spin on filter that may be passing the clear filter. I would check it very carefully with a flashlight to see if it's clogged up even though it may not appear to be with a quick glance. You may also be experiencing an air leak where you replaced the hoses. Make sure the connections are air tight but not crushed with hose clamps either.

Additionally there is a fuel tank strainer in the tank itself if you're not aware of that and it too can get crudded up. It has to be removed by emptying the tank so you have to drain the tank and then unscrew it from below. I haven't done it personally but the tank strainer can be plugged up. This happens more so in humid regions where the black fungus grows in the diesel fuel believe it or not.
 
#7 ·
Is it the white threaded knob or the black pushbutton type? If it's the white threaded knob and it's not screwed down it will leak and seep air as the mechanical pump takes over once it's started and that is a source for air seeping into the system.
 
#11 ·
Usually it's leaking fuel and unless it's completely dry then there may be no reason to replace it. Typically something plastic soaked in diesel for 30 years tends to degrade. It's also a $20 item and if everything else is repaired and or checked thoroughly you're running out of possible causes.
 
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