I know this subject has been discussed extensively, but I need additional illumination.

My ultra reliable 85 300sd wouldn't start. I deduced this condition was due to insufficient fuel. I had filled up with a tank of B-99; so, I assumed, that the filters were clogged and I replaced them. I primed the new filters by attaching my Mighty Vac to the return hose on the fuel filter housing and drawing a little fuel into a catch tube.

I was horrified that after it started it ran ragged. At full throttle, I could barely attain 2k rpm. Then it died. No black smoke, so apparently the problem was still insufficient fuel.

Stay with me now. I set up a "diesel purge" arrangement (with regular diesel fuel) to test if the Injection Pump was the problem. After a few tenuous moments the 5 cylinder was whirring away.

Here are the questions of the moment, "(1)Since the diesel started and ran when I set up a faux fuel tank, can I assume that the Injection Pump is fine?" I don't want to start a project until I am secure in that knowledge. If it means anything, the primer pump (new) draws little if any fuel into the secondary filter after numerous plunges

Next; I blew air back into the tank via the return hose but that did not help. "(2)This screen in the tank, can I clean it or does the job require a new part?"

Finally, getting this screen out on a 85 300sd tank, the posts are confusing. "(3)Will I need a gigantic allen wrench or a pipe wrench or channel locks?" I am prepared to drain the tank to minimize the mess.

Let me thank everyone for their patience, and thank specifically anyone who can answer my questions (3).

Joe Marroso

hello,1 if you could run the engine with purge and fuel the injection pump is working
2 the factory manual says to blow it out and check for damage, it looks like it has an o-ring or other rubber seal that may need repleced.
3 no mention of what tool to use in book, but it doesnt look to be allen wrench...hope this helps. Bill

__________________
Gretchen 1981 240D 4-spd 213,000 mi
1979 240D 4-spd 298,000 mi parts car

1994 BMW 325is
1991 Dodge turbo diesel
1997 ford expedition

BILL

Joe,

Im assuming it is similar to my 123.

Youll need a 46mm socket to loosen the tank screen. Of course you will need to drain the tank.

Once the tank is drained, its easy. Just unscrew, blow out, and re-install.

But, if you have a serious algae problem in the tank, you may want to remove and have it steam cleaned:

http://www.peachparts.com/Wikka/W123FuelTank

Good luck,
dd

__________________
-------------------------------
'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Metal fuel line pinched or somehow obstructed?

__________________
1980 300 TD

1997 Dodge Pickup/Cummins 5.9 12-valve

If you switch the supply and return lines temporarily and the car runs fine, you know it's the tank screen.

You shouldn't need a mighty vac to prime filters

__________________
Mark in MA
05 MB E320CDI 402k Granite Grey Metallic
05 MB E320CDI 267k Black
05 MB E320CDI 232k White
05 MB E320CDI 209k Tectite Grey
99 Dodge 2500 Cummins 5sp 148k
62 Jeep CJ-6 120k

This would be my thought. Another thought
would be the possabilty that it is sucking air somewhere

__________________
81 Mercedes 300SD 289k.......SOLD
82 Mercedes 300CD 252k......slow ride

82 mercedes 300 SD...mi Unknown
83 Mercedes 300D ????ksniff..gone too
84 Mercedes 300D 148k........SOLD
85 Mercedes 300TD 386k and holding some one elses project

one more quick thought - try running with the filler cap off the fuel tank. your vent line could be plugged resulting in a vacuum being pulled on the tank causing your symptoms.

worth a shot before doing any tank screen investigations...

__________________
-------------------------------
'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

I didn't see where you are located but if it is in a "cold climate" the B99 may be the problem. You say it started after you filled up with B99. If it was cold enough the fuel may be gelling. It would run fine on the purge setup but not be able to pump the fuel if it is gelled.

__________________
Darrell

1984 300SD "Ole Girl"
207K

Update:

Thank you Gentlemen, I have tried all of the suggestions and although I have not remedied the problem, many of the suggestions have helped me chart a course of action.

Clarification:

1) I live in sunny Las Vegas so the B-99 should not be the problem.

Results:

1) I forced compressed air back to the tank through both delivery and return lines. The obstruction in the line/tank is enough to distend the rubber fuel hose slightly when I apply pressure, though not enough to register much on the Mighty Vac when I draw fuel. The ever so slight back pressure in the delivery line is disconcerting, but, since there was not fuel leaking anywhere tells me that my lines are not sucking air or leaking. Good thing, yes?

2) Switching delivery and return lines, although a very good idea, did not help.

3) The filter is threaded into the tank on a 1985 300sd with a very large stamped nut. Looks like I could get it off with an adjustable wrench (dikes), but I will get a 46 mm socket from Harbor Freight as DieselDan44 recommends when I take out the screen.
I included this observation because there are a variety of tank screen pictures all over the net. The one for my 1985 300sd is different from most of the pictures I saw. Hope this prevents some anxiety for the next dieseler with an 85SD.

4) I put a full ounce of Raycor biocide in the 3/8 full tank. I sent air pressure back to agitate the mixture. I am letting the soup settle overnight.

5) As for the tank vent line being plugged, again props to DieselDan44, I notice a lot of back pressure when I applied air through the delivery line when the cap was on. Of course, that makes sense because I am introducing a lot of air into the fuel tank and the vent tube is narrow gauge. The clogged vent scenario does fit the baffling circumstances, because it wasn't 48 hours prior that I commented to myself how good she was running. I was making a fixture to blow out the vent line when domestic issues diverted my attention. Tomorrow.

Possible course(s) of action:

1) Blow vent line out and see if that was the problem.

2) I am going to siphon the fuel/biocide mix out of the tank and see if there are any floating pieces of debris in the fuel.

3) If the fuel is relatively clean then then I will try 2 gallons of ATF in the empty tank in an attempt to dissolve the goo. I can set up a draw and replenish system with my air compressor to run the same 2 gallons through the delivery line/tank several times.

4) As for taking the screen out; I am removing as fuel as possible as directed by the many postings. The aforementioned postings also warn that there will be fuel hiding in the recesses of the tank that will make a mess for even the most prepared. How bout this? Why don't I jack the car up on its passenger side thus sending all remaining fuel to the driver's side. Then take the 46mm nut/filter out? Or, am I missing something?

Any more help or suggestions is greatly appreciated.

Joe Marroso

Intermediate Update:

1) I decided to attempt removing the tank screen. On my 85 300sd, the tank screen fitting is 45mm. The axle is in the way and I couldn't get a clear shot with such a huge socket. The only way to get at the tank screen fitting is to take out the tank. Once clear of the obstructions, you won't need the expensive socket assembly. I chose NOT to take the tank out.

2) The previous owner was a biodieseler, so I was skeptical that the tank was compromised by crud. It wasn't. The failure to draw fuel from the tank was caused (so far as I can ascertain) by the crumbly fuel hoses entering the tank (Point of Order: many of the responders suggested this.) Anybody with original hoses should check them closely. I didn't see any leakage, but they were decrepit.

3) Hose fittings come out of the tank with a 19mm box wrench and much grunting.

4) I inspected the tank screen with a bright light. It was clean. As a precaution, I blew the screen out with an air nozzle and transmission fluid and let the fluid drain out from the return outlet. The tank is clean, biodiesel does keep a tank clean.

5) My parts arrive after the football weekend, I will conclude the thread and the job then.

Joe,
The PO of your car ran BD and that likely finished your old rubber lines.
I pulled the tank on my 123. pulled the strainer, washed, flushed and dried them both.
Replaced all fuel lines with viton and now run BD year round.
Get new lines anyway as the old rubber lines deteriorate

__________________
1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

Thanks Fruitcakesa,

You make a very good observation regarding the biodiesel use from the previous owner. He claimed to have replaced the fuel lines to make it biodiesel ready. He obviously didn't do these lines and who wouda thunk it except an expert? I am putting in factory replacements, I didn't see a vitron option. Nevertheless, I will not be using B-99 anymore, so the replacements should be fine.

I am keeping this thread coherent, so when I am finished, fellow unfortunates with fuel problems can search it up and read the collective wisdom from the "graduate school" that kindly responded.

By the by, Fruitcakes, after I back flushed the fuel tank (pressured ATF through the screen inlet and let it drain out the return) and saw no crud come out; I chose not to pull the tank. Is this a forgivable act of an old man, or am I to drummed out of the diesel brotherhood? Tank pulling seemed like such a *****. Truth, now.

In the 123 the tank is in the trunk and is held in by a few bolts. A little wiggling and it comes right out.

__________________
1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

You can also go to Napa or Autozone and get some generic Fuel injection hose line with the Blue tubing on the inside. I tried this and it works well for Biodiesel. I haven't been using biodiesel for awhile now, ever since diesel hit $1.73 a gallon since I can't make Bio for that! The pressure sleeve will have to come off the factory threaded fitting to slide in the fuel injection hose, but this does work!

So, I go into the trunk, not the interior, to remove this demon container (fuel tank)? Hmmm, that's makes the decision a lot easier. I am sufficiently humbled by this information and I will brave the cold and remove/clean the tank before my parts arrive.

Joe Marroso