Fuel delivery problem
 

I recently ran out of fuel and then ran into a few other problems along the way.

I am getting air into the system from somewhere.

After running out of fuel I have replaced the following:

Secondary fuel filter, primary fuel filter, fuel line to and from primary filter, primer pump, tecalan line from primer pump area to secondary filter(with 5/16 rubber fuel line).

I have bled this thing till it won't bleed any more but I still have rough running conditions.

It is 27F right now and it wouldn't start at all. I put the charger on it, used the 50A engine start selection on charger and it still wouldn't start.

I get an idea to pump the primer pump a dozen or so times and VOILA, she starts.

What gives?

With all my mucking around in there I have noticed that I managed to cause one of the rubber fuel lines on the rear injector to spring a minor leak but other than that I can't detect any leaks.

What would be the problem if I can start the engine after a few pumps on the primer pump but it won't start otherwise?

It also runs pretty poorly right now in general and it got this bad after I ran out of fuel. I will say that it is basically a worse version of how it was running before so I may have just magnified an existing problem somehow.

At stop lights it will lug badly if I leave it in gear with the brakes on and will also run pretty badly when I put it in neutral.

It does this warm and cold.

I will replace the tank screen as soon as it warms up a bit. Could that cause this problem?

Yeah, when you ran it down, all the critters that live in your tank tried to clog up the strainer. You may want to use a biocide.
Sounds like you've got most items covered.

Try swapping the inlet and outlet fuel hoses down by the Fender well. This will back flush you Tank Screen (this is just a temp fix not a cure) with return fuel and will draw fuel from a higher position in the than as the normal return return for fuel goes into the tank at a higher position.
This will also means that you need to keep your tank filled with more fuel as you will run out of fuel and you gauge will still show that you have some
I do not know what the minimum amout of fuel you can get away with is when you swap the hoses.

Right now the tank only has about 3-5 gallons in it so I plan on changing the strainer out tomorrow anyway. If memory serves it definitely looks like the original strainer. I replaced the rubber fuel line there last year and the strainer nut had undercoating on it.

I am pretty sure that several of my injectors are bad or weak.

When I was bleeding the system I noticed that when I cracked the front two injector lines the engine performance barely changed. When I cracked #4 it really died down. This leads me to believe that #4 may be the only one doing it's full job.

The car has 250K on it now but I'm not the original owner so I don't know if they have ever been changed before.

I found some on Ebay that have already been pop tested and are within spec.

The tank strainer is spotless. It's just covered in a thin layer of dark scum.

No debris detected in the strainer or in the fuel.

I think that when I ran out of fuel and ran motor oil and transmission fluid in the secondary filter to try to get me to a station I exacerbated an existing problem with the injectors.

I am pretty sure that my problem is bad injectors.

Anybody have a good deal on rebuilt/new injectors for a non-turbo '81 300D?

Any good pump shop in your local area that could test them? Recondition them as well if required?

That way for a small overall charge you know they do need repairing. Then the cost of the repair is justified as well.

Ah diesel, when we clean fuel tanks we get anything from black stringy scum to tar. When we clean gas fuel tanks we get stuff that looks like oatmeal. The new fuel blends of today are not very favorable for setting around. We clean, marine vessels, construction & farm equipment to name a few. They all share a common problem, bad fuel. A good fuel additive will not re-new bad fuel, but if added when the fuel is fresh an additive will help.


Good Luck,

Luther Carrier

Believe it or not my problem turned out to be loose glow plug wires.

Instead of a nut, three of them have a knurled chrome wheel designed to be tightened by hand. All three were very loose.

I tightened them up with a pair of pliers and I have had no starting problems since.

Glad is was something simple. You might want to get the proper nuts on there. So you can tighten them properly and so they'll stay tight.

Is it still idling rough when warm?

Yes, it still idles rough when warm and I was premature to assume that the loose GP wires were my problem.

My starting problem was caused by using oil that was too thick for the cold weather.

I was using Motorcraft 15W40 and I switched to Rotella Synthetic 5W40.

It spins like a champ and starts now even at 19 degrees so far.

I do still have an injector problem.

I plan on replacing them in the next month or so.

I am still having rough running issues, fuel in the exhaust and poor fuel economy.