Just won't start! - PeachParts Mercedes-Benz Forum

MountainBenz · #1 08-08-2007, 11:26 AM

I'm approaching the gurus of Deutche Diesel Dilemas for some direction.The love of my life, a '78 300D, last fall started getting more and more reluctant to fire up and finally just will not come to life. Prior to that, although compression obviously wasn't first-class, I didn't have excessive smoke and on the road could get an honest 25-26 mpg with reasonable power (about 210,000 miles on the speed clock).
The motor turns over fine; I've replaced all the glow plugs; I've replaced all the fuel filters; I've replaced all the pertinent hoses and lines; I loosened up the valves earlier in the fall ( I've only had the car a couple years). After changing the fuel filters, the in-line immediately refilled and the can was full when I loosened it up again.
After a session of cranking, I don't smell a faint buildup of diesel fuel (sorta like flooding a gasser) like I did when I first got the car. Also don't see much or any smoke out the back.
I'm literally a shade-tree wrencher; been reading over and over what printed material I have; have been poking around in your archives but haven't found anything that exactly matches what I'm experiencing. I really don't want to think my IP has gone south on me. Also am not excited about having the ol' gal towed 30-plus miles to whatever a "mechanic" might do for, to me.
Any thoughts?

vstech · #2 08-08-2007, 11:44 AM

pull the injectors and the lines, put the injectors on the lines out of the motor and crank. see if you are getting full spray patterns, or just dribbles... it sounds like IP is failing. I got a spare IP from my 78 if ya need it.

SD Blue · #3 08-08-2007, 11:48 AM

Sounds like a fuel problem to me. When you changed the fuel filters, did you clean the tank screen also? A clogged tank vent may be causing you headaches. Do you have any fuel leaks under the hood, such as return lines or primer pump? Were there black bits in the old primary filter?

The easiest way to narrow down part of the fuel system is to connect a portable fuel can under the hood, directly to the primary filter and cigar hose. If it starts, then you can see what is wrong with the tank end of the fuel system.

winmutt · #4 08-08-2007, 12:07 PM

Pull the #1 Injector from the engine and reattach it to the IP line, turn over engine. I you get einspritz you have fuel. You may want to verify all 5 injectors are doing their thing in the similar fashion (on their respective IP ports of course).

junqueyardjim · #5 08-08-2007, 12:10 PM

When you are talking about a diesel or diesels, the term gas is just plain wrong and should not be used. Fuel or diesel is correct and the only product to use. and if the stealer you were dealing with tried to start the beast on ether or starting fluid, he doesn't know what he is doing. Find a different car or a different stealer and to be fair to the writer of this thread, start a new thread for your problem.

MountainBenz · #6 08-08-2007, 01:29 PM

I will try the injector test. Also, I did not clean the tank strainer (wasn't sure about this whole procedure). I just now emptied out the old in-line filter and did observe some black flecks ( like coarse-ground black pepper) coming out?! Even if the filters appear to have fuel in them, could the strainer affect what's actually going to the cylinders?
From the first tank of fuel I ever put into this car, whether winter or summer, I've always used a diesel additive to "clean the injectors, prevent fuel gel, etc," I often also add a few ounces of Marvel's Mystery Oil to help keep things lubed up.

Phil · #7 08-08-2007, 01:47 PM

Just to start with the easiest things first try pulling out the fuse in the glow plug relay and then testing it. This fuse can look ok when it is in there and then when you pull it it comes out in two sections. If the fuse is ok then I agree with the idea of a fuel delivery problem.