1978 300D won't start NEED HELP!! - PeachParts Mercedes-Benz Forum

deferr · #1 11-25-2006, 06:15 PM

I am having trouble starting my 1978 300D. I tried to start the car the other morning and it was about 25 deg. After about 3 glow cycles, It would not start. It was firing every once in awhile but not cranking fast enough to start. I do not have a block heater and was running 15w 40 (a mistake I know).

I pushed the car into the gargage and put it on the battery charger. The next afternoon it was about 60 deg in the garage and the battery had a full charge. I tried to start it and although it was now cranking plenty fast, it did not fire any more often than before.

I have converted to the newer pencil syle glow plugs, but I suspected a glow cycle issue so I pulled all the plugs and checked them with the jumper cable method. Each plug glowed yellow hot very quickly. I then checked to see if the inline fuse was blown. It was not. I measured voltage getting to the fuse and voltage going into the plugs.

I then thought that maybe the fuel had gelled when it was 25 deg so I changed the fuel filters and tried to start it. NOTHING.

At this point I am stuck and need some more diagnostic help. The only starting problems that I have recently had other than this is from a vacuum leak. My door locks are completely shot so the car would not shut off due to the large vacuum leak in the cabin of the car. I simply plugged the line that goes to the cabin of the car and the car would shut off fine. This caused one problem. If I would shut the car off wait anywhere from 1 to 10 min. the car does not start again unless I bleed all of the vacuum from the system.

I know that the shutoff valve is vacuum operated and was wondering if it's possible that this valve has stuck closed.

If anyone could help that would be great.

Stevo · #2 11-25-2006, 06:25 PM

Your starter must turn 100 RPM so when these engines get a few miles on them you really need a good battery and a good starter motor. The new style GPs were a smart investment.

Pull the brown vacuum line from the shut off switch on the IP and see if that helps.

deferr · #3 11-25-2006, 06:51 PM

I just went out and tried that and this did not solve the problem. I thought my problem was cranking speed but I now have a fully charged battery and it's 60 deg and the car is cranking as fast as ever and is not firing.

Stevo · #4 11-25-2006, 07:03 PM

trouble is at this point after cranking for a while the cylinder walls get washed down with fuel and you lose compression. You can tow start these cars if your in a place where that would be practical. I'd be getting the tow strap out bout now. Instructions are in the owners manual, essentially you have to be going about 30 mph as I remember.

Brian Carlton · #5 11-25-2006, 07:22 PM

We're all making the assumption that you've got fuel and it's not starting due to the cold.

But, the warmer temps didn't make a difference.

So, back to the basics.

Pull the secondary filter and change it (refill with fresh fuel before you tighten it down).

Pull the outlet line from the fuel pump and see if you get decent fuel to the secondary filter during cranking. It should easily put out one ounce of fuel in 10 seconds or so.

It may be a basic fuel problem. If so, you can tow it for miles and it won't run.

Motorhead · #6 11-25-2006, 08:11 PM

When did you last adjust the valves??? It doesn't take but a few tight valves to prevent them from starting in the cold.

deferr · #7 11-26-2006, 01:56 AM

I cracked the hard fuel lines where they go into the injectors like I was bleeding the lines to see if I was getting fuel. There is fuel coming to the injectors. I replaced the spin on filter and had the valves adjusted about 2 months ago. The car ran great right up until it wouldn't start that cold morning.

What does towing do for me? You mean tow it to the mechanic or tow it to fix it somehow?

sodapop6620 · #8 11-26-2006, 07:53 AM

I think he means that you can tow start the car just like a manual. I know I could do this with my 66 Chevy, it had a powerglide. But check the owners manual first. If it is in there the book will tell you how fast you need to be going when you drop it in gear.

Motorhead · #9 11-26-2006, 01:02 PM

Tow the car for a 1/4 mile or so at about 25-30 mph. Turn the key on to run/glow position. After the glow light goes out, put the shift selector in to "S" position. This should start the engine. Signal off the tow vehicle and let it idle until the glow circuit cancels on its own.
The non turbo engines, in my opinion, seem to have a harder time at cold starting.
My 240 with only 143,000 miles is getting harder to start in the mornings and I live in Calif. It gets into the mid 20's at night.
I have learned to lightly "feather" the throttle while trying to start it. I also hold the starter a little longer while it is trying to start.

Stevo · #10 11-26-2006, 03:20 PM

Quote:

Originally Posted by deferr

What does towing do for me? You mean tow it to the mechanic or tow it to fix it somehow?

Yah, you could do that too. Just leave it at the machnics if it doesn't start by the time you get there

Another trick if you cant tow it due to a conjusted neighborhood, or no tow vehicle, is a few "squerts" of lub oil in each cylinder to improve compression.

deferr · #11 11-26-2006, 04:45 PM

by lube oil you mean motor oil? Would 15W 40 work? What's the easiest way to get it in the cylinder.

Stevo · #12 11-26-2006, 05:05 PM

Quote:

Originally Posted by deferr

by lube oil you mean motor oil? Would 15W 40 work? What's the easiest way to get it in the cylinder.

Lube oil, lubrication oil, as opposed to fuel oil..."diesel speak"

I 've used the GP hole and thinned the oil down a little with ATF. Don't know if thats necessary but it worked for me. Just a couple of "squirts" as you don't want to hydra lock the engine, not much room above those pistons. You cant tow it, huh?

deferr · #13 11-27-2006, 12:35 AM

I tried the lub oil in each cylinder and this gave much more stumbling, if that makes sense. The engine still did not start but it seemed like it was on the verge. I know that you cannot EVER use starter fluid with these but can you use anything similar?

Thanks for all the help

deferr · #14 11-27-2006, 08:11 AM

I got up this morning and went to start the car and it started. I guess letting the oil sit in the cylinders all night helped. Thanks everyone for your help.

arkie · #15 11-27-2006, 08:26 AM

You probably still have a glow plug issue. You managed to "flood" the engine with diesel which washed away the oil and you lost compression. I have a 79 240D with 217K on the dial and the old style glow plugs. It will start with 2 cycles of the glow plugs without any trouble at 25 degrees (the coldest it has been here so far this season).