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Old 08-13-2004, 04:42 PM
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Join Date: Jun 2003
Location: Arkansas, USA
Posts: 4
under the hood fuel leak 300d

well, i havent been to the site since June and it looks like the search feature has changed a bit. even so, i can't get it to work properly, so i couldn't check the old posts for my question.
i have a 1987 300d turbo in pretty decent shape. usually runs fine, but a friend who was borrowing the car started having trouble on her 2 hour drive back to my place. it was "smelling funny" and driving sluggish. when she got it to my house, we popped the hood, and the funny smell was diesel gas spraying from somewhere in the vicinity of the vacuum hoses and the fuel lines. it was so wet under there, i couldnt spot the source of the leak, plus i had to get back to work, so i couldnt get too funny smelling myself. but poking around we also found one of the vacuum (or fuel) hoses totally disconnected and stuck between engine parts. lucky we didnt lose it. anyway, i can't tell where it is supposed to go just yet, or if it is even the cause of the leak. it is a 10" or so plastic tube, like a hard soda straw that has a rubber boot on the end. so my questions are: do some of these hard plastic tubes act as fuel lines, or are they all vacumm lines? are there many places where the fuel is going in and out? because that is where my obvious places for leaks might occur. and last, is there any link anyone can give me with a fuel hose/vacuum hose diagram for this model? maybe i can search down the missing tube if i had a picture.
any help on this would be appreciated. and again , i am sorry if this is available in an old post, but the search isnt working right today.
thanks ya'll.
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Old 08-13-2004, 07:23 PM
dieseldiehard's Avatar
Join Date: Oct 2002
Location: Bay Area No Calif.
Posts: 4,160
I wasn't aware the old posts were not available, are you sure on that?
As for the leaks, a diagram might be nice but I think with a littl poking and prodding you should be able to find whats leaking.
The small rigid lines are vacuum lines. They attach to various points with rubber elbows, you may have fun trying to find where that loose one goes, if you aren't familiar with the OM603 engine, but if its the leak that you are looking for don't worry about the vac line until you fix the fuel leak.

There are a couple of larger plastic lines that that carry fuel but they seldom break, they are clear when new but get yellowed or dark with age, these do carry fuel so if one cracked it would spew a LOT of fuel. BTW these are factory items, with a banjo bolt at each end. Look around the filters (primary and secondary) to see if they are leaking.

The fuel leaks you have may be (and hopefully are) coming from a injector fuel return hose, these are cloth covered and small diameter (3.2mm?), less than the OD of a pencil, and they run from one injector to another and down to the filter housing. There is I believe a plug at the last injector that may have blown off (It happened to me once) lastly there is a fuel heater that might have started leaking or blown a hose. Just run the engine at idle and look for where fuel is coming. I drove a 300TD about 50 miles with a fuel plug missing (fogged out anyone who tried to follow on my tail!) and it really stunk to high heaven.
You may be able to drive to a shop but hopefully you will spot the leak and be able to fix it on your own.
'00 E320 (wifes car), '95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!
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Old 08-13-2004, 10:27 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
There are hard plastic lines from the lift pump on the side of the injection pump (the thing with six steel lines on it) to the main fuel filter (canister type, up front) and from the fuel filter to the side of the injeciton pump. These are under about 30 psi, pulsating, so will spray fuel everywhere plus rob the IP of fuel if they crack while running.

If one is broken, as noted above, you must replace it complete, you cannot install new clear line. You can, however, replace the plastic with standard fuel line (5/16", I think) if you cut the plastic off the barbs and use some small hose clamps to hold the fuel line on. Certainly cheaper, and possibly the only option on a weekend.

Do not drive it til you fix the fuel leak, it's possible it may catch fire!

The return line from the fuel filter to a steel line on the fender can crack, too, and as the fuel tank is usually under some pressure, fuel will spray, usually forward, soaking everything.

The hoses are a bit complex since there is a fuel heater, too -- there should be a suction line (black fabric) with a small clear filter in it. It runs from the standpipe (steel) to the fuel heater thermostat (a small can bolted to the engine with four hoses on it). Two fabric hoses go up to and back from the fuel heater on the side of the block at the rear of the engine, and one goes to the injection pump.

From the IP, a clear hose goes to the fuel filter, and another one goes to the engine side of the IP. There is a black fabric (or often plain fuel line) hose that goes back to the other steel line.

There are small fabric lines that go from the injectors to the fuel return, plus another small line up there, I think.

You have several vac/pressure lines in that area, too. I suspect the hose section that connects the boost sensor line from the intake manifold to the big squarish can on the IP (the ALDA) is blown, leaving both ends intact but not connected. There are tiny hose clamps on this line, the plastic is white, rubber parts black. The rubber hose can be replaced with standard vacuum line, but it will be large enough to cause trouble with the tiny clamps. Must use the clamps, else the hose blows off. This line also connects to the vac amplifier (blue thing that looks like a horn on the fender) to control shift feel.

If the boost line is loose, you will have very poopy performance.

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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