85 mercedes 300td wagon

Jezi, you may have "solved the veg oil problem" but the motor doesn't agree.

During the winter #1 diesel is added to #2 diesel in cold areas so the fuel will flow. (#1 contains some kerosene.) I suspect the veg oil is now Crisco inside the fuel filters etc. and that's why no fuel is at the injectors. So all must be set back to its "default" state.

First, if your "cables" are steel pipes, put the steel fuel pipes back on to the injectors and DON'T over tighten their nuts - these are compression fittings and over tightening will ruin them. Just firmly snug and if it leaks make it a bit snugger until it no longer leaks. Think, about 10 ft lbs, not more. But if your "cables" are, in fact, electric wires see paragraph about glow plug relay below.

There's a hand primer pump down at the small clear plastic, secondary fuel filter. It sticks up and has a black plastic cap that unscrews so you can pump it (wear latex gloves). Pump a bit and watch the clear plastic fuel lines for bubbles, or any movement of the fuel in them. The clear plastic secondary filter element ought to be the color of wet wood. If it's very dark it probably ought to be changed. The fuel also goes through a primary spin on metal filter that's behind (aft) of the power steering pump. Replace it too if the secondary filter is questionable. Then pump, pump, pump the hand primer to move fuel to and fill these two filters until all air bubbles have been expelled back to the fuel tank.

Alternatively, you may have to direct an electric space heater (not a torch) at the lower left side of the motor to liquefy the fuel inside the filters and injection pump. Plus hand priming.

Finally, on the left fender is the glow plug relay. It has a black plastic cover that slides UPward to reveal an 80 amp fuse a/k/a fusible link. It should be intact, if it's not the motor will not start, period. You ought to carry a spare link, they cost about $1 at M-B dealer or on line.

Starting diesels in very cold weather, especially worn ones, is difficult using diesel fuel so don't try to push the envelope with the veg unless you absolutely KNOW that it won't gel at your location's overnight temps. Base winter case ought to be diesel unless you KNOW the veg will flow.

OK, I understand the problem.

Don't mess with the injection pump!!! It's NOT the problem.

Your car exhibits a classic case of fuel starvation - replace both fuel filters and it should be fine. Bio100 loosens all the old deposits and dumps them into the fuel filters so your new fuel filters may now be clogged.

The secondary filter is the small clear plastic one down below the injection pump, next to the hand primer pump which you'll soon learn to use.

The primary filter is a metal "spin-on" filter aft of the power steering pump - follow the fuel line to it. Its open end is UP so we see its side and bottom.

Wear gloves, replace these two filters and prime the fuel system - that means pumping the hand pump until there are no air bubbles in the plastic fuel lines. The motor will start with some difficulty as you can't expel the air from the injectors only the motor can do that so FLOOR it while cranking to increase the fuel flow and let off once the motor fires and begins to run.

Buy two extra fuel filters, you may need to do this exercise again.

The way to check the fuel flow is to open the fuel connection to the injection pump - crack it loose, don't take it apart - and crank the motor. If reasonable amounts of fuel spill out of the loose connection the filters are OK and the problem is within the Injection Pump, if not investigate the fuel pump by loosening its connections before and after and the cursed filters etc. until you find the blockage.

One additional thought. Inside the Injection Pump is a vacuum powered shut down device (a bellows) that pulls the fuel rack to OFF when the key is so turned. Usually, the motor won't stop when these fail. It could be that this device is hanging and not allowing the motor to start. There's a brown vacuum line connected to the device (located on the aft end of the injection pump) - pull that vacuum line off and see if the motor will start. Note that you will then need to manually stop the motor by pressing the STOP lever on the throttle linkage.

Do you have a vege system installed? If so, I heard there was problem with earlier fuel switch valve that the seals fails and allow mixing. or simply plugs up...

Everyone is forgetting about the 3rd fuel filter!! It is screwed into the bottom of the fuel tank. Part number 110-470-04-86. It is as fine a mesh as the pre-filter. #56 here:

Early on -----

and on and we checked the strainer in the diesel tank and that was fine but then after that I was driving right out of my house and the car finally died

I don't know how one "checks" the strainer with fuel in the tank but they know there is one!

I have a 1982 300TDT (station wagon).

I have been having a hard time getting it to start in even slightly cool weather since our fuel dealers here in California were forced by regulation to switch to ultra low sulfur diesel. Everyone says that has nothing to do with my car not starting, but I have been going thorugh all the other possiblities with little success. I first noticed the problem last summer after parking the car overnight in the High Sierra at about 7,000 feet. In the morning I had to crank the motor for a long time, like it was 15 F, but it was only about 40 F. Now that it is winter and the morning temps are in the 20s F I can sometimes get the car to start if I had a block heater on all night, but today it would not start at all. The new fuel tends to flood the engine and then I need a tow to about 50 mph and drop it in low to get it to start.

I have replaced the filters. (but I had cracked a line and made sure that there were bursts of fuel when I turned the motor over. I have also replaced the glow plugs. I just ordered a new glow plug relay from Bosch that keeps the glow plugs energized for three minutes after the engine starts. Maybe that will help.

I use 2 oz of automatic transmission fluid and 3 oz of Power Service brand diesel additive for lubricity, centane boost and anti gelling.

I also bought a new Sears DieHard International battery, but I still have trouble getting the motor to start with the new fuel. I bought a tank of low sulfur, the old stuff, on the Navajo reservation last month and the next morning my started fine even with frost on the windows and the grass. That afternoon I filled up with ultra low sulfur diesel in Moab and the next morning it was 42 and I could not get my car to start. I had to have someone come from a serivice station and give me a jump start and run a hair dryer under the hood for two hours warming up the injection pump and lines.

I live in Easten California, and our fuel all comes from the L.A. basin and is mixed for their conditions.

snipped-for-privacy@yahoo.com wrote:

When is the last time you had your valves adjusted? This is most likely to be your cause...it must be done yearly. How is your compression readings?

You need new glow plugs.

Thanks for the link, Richard. Very helpful.

But crikey, where has that engine been?! It's filthy (if you don't mind my saying so) ; )

Euan CHCH NZ

We have salt on the roads here which makes them look awful. I wasn't going to clean it in Februrary when it was -30C. It cleans up fine.

Keep in mind it's got 500,000 miles on it too.

Ok when I did my TD I encountered some stuff that I want to ask y'all about.

1) The (CD-based) shop manual says to loosen the screw that connects the spin-on filter with the injectors (I guess that's where it's going), and then pump the pump 'til fuel comes out free of bubbles. Is loosening this screw necessary? (I did not loosen it.) 2) It seems like I had to pump it like 500,000 times. Literally, it was maybe a half-hour of pumping? 3) While pumping, fuel would spray out around the pump while I was pumping. Is this normal, or does this indicate that I need a new pump? Could I get by with just the hand pump part, or would I need to replace the whole fuel pump entirely, at 10x the cost (ugh)?

Car runs fine now, although I do have that persistent air-in-fuel problem that I'm now thinking that new fuel lines may solve.

thx,

-tom!

I've been running a ~30% mix of soybean oil in my '79, and it's been starting up every morning even with frost in the air and on the glass. I get the oil from Costco for about $13 for the 35# (~4.6 gallon) jug, and pour it in right before filling up at the pump, and I usually fill when I'm at 1/4 tank. Mind, if you go this route you'll need to change your fuel filters a couple times in the near-term.

-tom!