I'm new here, so greetings fellow benders. I have just inherited a 79 300D 185k, but only 45k on a new crate motor from a friend that has given up on it. The car was used for everyday transportation until about 2 years ago when hot starts became an issue. It has 2k miles in two years. The fuel is fairly new. The car became a driveway queen. I brought it home about 3 weeks ago and it had no power, extreme difficulty in starting cold and hot- and have since tried a number of things. Reading this forum was the first step in my education. I found a hole in one of the fuel lines, replaced two engine compartment fuel filters, replaced air filter and radiator. Replaced old diesel return lines at injecters. I put a can of water remover in the tank. Car will now cold start- after some cranking, has regained power- if you want to call it that, and will run down the highway. (I ran it at 50 for about fifteen minutes. It idles nicely. It has a harmonic vibration in the cab that doesn't seem right, (It is louder in the cabin than next to the car.)and when I shut it off, it won't restart. I took a homemade stethescope and listened along the fuel lines and vacuum lines as best as I can and can hear no hissing. I am not a highly skilled mechanic, but am enjoying this car imensely- any ideas? Are there parts to throw at it or is it time for a mechanic?

 

Sounds to me like fuel delivery problem. A vacuum leak would cause it not to shut off, or slow to shut off. You might check that the fuel lines are not cloged. Also might check the vacuum shut off at the injector pump, maybe stuck.

 

Thanks, I completely agree with your logic. Shutting it off is not a problem. (Does that mean that the vacuum is ok?)I have been thinking that it is fuel, but I don't know how to narrow it down. It can be running fine, yet when I shut it off and try to restart it, even immediately, it cranks but won't run. In cold starts it seems to take a few minutes before the fuel gets to the engine. I have ordered a new hand primer pump, mine leaks a lot when I pump it. Would one bad injector cause this problem? How do I check the vacuum shut off?

 

If the car starts cold and runs OK and than wouldn't restart hot, that likely is indication, that injectors are dripping the fuel into cylinder.
Try to restart it hot with pedal on the floor?
For checking the performance do the 0-60 acceleration test. (after calibrating speedometer with GPS, or road marks).
From what I remember that engine suppose to make it in around 17 sec. If it takes longer, than you still have the problem.
Also check the glow plugs operation.

 

The vacuume is probably okay, but the shut off valve (on the back of the injector pump) might be sticking. I doubt the glow plugs are a problem, as it should start HOT with no problem. Check the shut off valve by putting a hand vacuume pump on the shut off valve vacuume line and pump it down, when the engine starts to quit, release the vacuume and the enigne should run smooth again. Repeat a couple times to insure the valve is operating.

I think you should check for proper fuel supply, or possibly a bad/clogged injector.

 

Timberfield, my friend, you are right on it! When hot, and not starting, I unplugged the vacuum hose to the shut-off valve, the line (brown, and coming through the fire wall) had vacuum on it, so I let it bleed off, plugged it back in and the car started right up. Then I repeated the procedure- no start- unplug and bleed off and blast -off. What the former owner told me was that when his wife came home one day the car wouldn't shut off, so she took it to the shop, where the mechanic side tracked the entire door lock circuit, returning vacuum to the shut off valve. Should there still be vacuum on the valve? or is that how a bad valve acts? If so, is this something that I can replace? thanks so much for the help!

 

Now I'm not sure the shut off valve is the problem.....the valve(on the pump) uses vacuum to shut off the fuel (controled at the ignition switch). Key on- no vacuum, key off- vacuum. If I understand you correctly, you have checked that the "fuel shut off valve" is operating correctly.

If you still have vacuum on the shut off side of the line with the key in the off position, you might have a problem w/ the vacuum valve on the ignition switch (rare). Pull the instrument cluster and lower panel to access (carefull of the oil pressure line)

Can you determine what line(s) the mechanic switched and correct them?? The doorlock circuit might somehow be feeding vacuum to the shut off circuit if something was crossed.

There are several things in the vaccum circuit that could be causing leaks, possibly the door locks. By isolating the door locks you can determine if that is the problem.


Just remember, vacuum to the fuel valve-the engine stops, no vacuum- the valve is open and the engine runs.

Good luck!

 

Cause sort of found- It was the fuel shut-off causing the problem. Actually, the vacuum to the IP was on all the time, making it difficult to start when cod and impossible when hot. I interupted the vacuum circuit and ran vacuum line through my firewall and put a ball stop valve in the interior so I could control the vacuum until I get a usable map of the vacuum line routing or a description of what goes where after it leaves the round disk on the firewall. I might have a bad start/stop valve at the ignition, but I am missing so many vacuum lines that I think I need to replace the lines, then find the leaks. It now starts with a touch of the key, hot or cold. Thanks for the guidance.

 

Problem fixed- I switched the two brown vac lines and the engine starts and stops as advertized! I am so humbled by easy fixes.