HELP- 300D fuel problem - PeachParts Mercedes-Benz Forum

cavaliers16 · #1 07-06-2006, 07:41 PM

The other day I went on a ride to the beach with my 83 300D. It ran 2/3 of the way there fine. The last leg of the trip, the car lost power on hills- it's never done this before. On the way back, the car became more and more sluggish, until the power dropped not only on hills, but on flat ground as well. I coaxed it all 122 miles home at 30 mph on 495 (speed limit is 65). I decided that this must be a fuel problem, because sometimes the car is quite peppy, and other times it loses power. If it were an engine cylinder blow by problem it would happen all the time. This happened most of the time. Occaisionally, I would put the accelerator to the floor and I would shoot up to 40 mph at record speeds before the car lost power. When I got home, I replaced the air filter, primary fuel filter, and secondary fuel filter. The DPO (dreaded previous owner) had obviously never done any maintenance on this car since the air filter was so corroded that the metal on the outside had rusted off

. The small clear plastic fuel filter was clogged to the brim (or ports I should say) with black gunk. After replacing both (and a small section of cracked rubber fuel line) I went to start the car.
Here's where the problem starts.
I primed the small white thing on the lift pump for at least 40 minutes but the small clear plastic fuel filter never filled up with fuel, and a whooshing air sound (I assume) kept coming out of the loosened banjo bolt. So after 40 minutes I got fed up with the whole thing and just started pouring diesel fuel down the lines with a funnel and into the filters to fill them up (manual priming). Since air kept coming out of the banjo bolt, I gave up, tightened the banjo bolt, and called it a night. When I went to take the car for a spin this morning, the car wouldn't start the first few times I tried, finally started, then died halfway down my street

. I mananged to get it home where it promptly died again. This afternoon, after priming the lift pump for a half hour, I took it out again. It accelerated onto my road at a blistering pace (one I have never experienced in this car) to 35 mph before losing power and dying. I restarted the car and tried again, this time the car's idle was very rough and it chugged along at about 2 mph before dying a few feet down the road. When I restarted, the car accelerated at it's breakneck speed again and died once it reached 25 mph.

What the h**l is the problem with this thing? I must have put 4-5 hours into fixing it's supposed fuel problem but it still runs weird. The acceleration is improved, but the car still dies after being run for a minute. It coughs, sputters, and dies every time. It seems as though fuel is not getting to the engine, though I may be wrong. I can see air in the clear plastic fuel filter but I can't get it out. Is there too much air in the lines? A leak? Dirty injectors? Can something like this come on so fast?
Please help

Diesel Giant · #2 07-06-2006, 07:45 PM

Sounds like the primer pump is no good. Was fuel gushing out while you were pumping it? It should only take about 20 strokes to fill up BOTH filters.

cavaliers16 · #3 07-06-2006, 07:47 PM

Gushing out of where? The primer pump?
I can't recall but I'll go check now.

cavaliers16 · #4 07-06-2006, 07:52 PM

I went and checked. No fuel is coming out of the primer pump. There is fuel coming out of the loosened banjo bolt with no air bubbles but there is still tons of air in the clear filter. It is probably 3/4 air 1/4 diesel.

Diesel Giant · #5 07-06-2006, 07:59 PM

Why is the banjo bolt loose? You are talking about the one on top of the spin on filter assembly?

cavaliers16 · #6 07-06-2006, 08:01 PM

No- the banjo bolt that has the three way hose connector coming out of it. The one with the cigar hose, the woven hose, and the hose to the injectors. To let the air out of the system you loosen the bolt because it is the highest point on the fuel system. The air that is pushed out by the diesel fuel by the primer pump escapes (because it rises) through the banjo bolt. I tighten it after I prime.

Diesel Giant · #7 07-06-2006, 08:05 PM

No you do not loosen it to prime! All you need to do is to use the primer pump, the air will escape back to the tank all by it self. That is the problem.

cavaliers16 · #8 07-06-2006, 08:06 PM

Ahhhh- I will go try this now.

Diesel Giant · #9 07-06-2006, 08:09 PM

Yes that is why you were getting lots of air in the system. The air will be forced out of the lines as you prime.

Don't feel bad, I have done much more stupid things in my life.

cavaliers16 · #10 07-06-2006, 08:11 PM

I tried it.
None of the air in the clear fuel filter went away after 40 pumps or so and no fuel gushed out anywhere. The filter is still 80% filled with air.

engatwork · #11 07-06-2006, 08:12 PM

Pull the tank screen and clean it and you should be fine.

cavaliers16 · #12 07-06-2006, 08:14 PM

Do I need to replace the filter/screen, or is it purely a clean it off sort of thing?

Diesel Giant · #13 07-06-2006, 08:16 PM

As engine said clean the screen in the tank. But to check the rest of the system out without the tank being in the equation, hook up a temporary tank like in this pictorial

http://dieselgiant.com/injectorcleaning.htm

If the screen is clogged, then everything should be normal and prime with the temporary tank.

cavaliers16 · #14 07-06-2006, 08:24 PM

Sure- I'll do it tomorrow
Thanks

Lostyankee · #15 07-07-2006, 10:35 PM

Chiltons manual or as I now call it C'sTP, calls for loosening the banjo bolt durring manual prime. It also states that ALL MBs have electric fuel pumps. My 300SD must not be a MB!
Garbage in garbage out.
Thanks Diesel Giant.
Good luck cavaliers16