300D will not start - ideas? - PeachParts Mercedes-Benz Forum

Crowe · #1 04-17-2003, 11:17 AM

My son's '87 300D would not start this morning. He is in New Orleans and I am in Atlanta, so I am trying to help him diagnose the problem from a distance. The glow plugs appear to be working normally. The glow plug light cycles as normal and the engine will turn over also normally. But it will not even attempt to start up. There is approximatly a 1/4 tank of fuel. The car is parked on level ground (after all this is New Orleans). Fuel is present in the clear in-line fuel filter. The car was running fine when parked the night before.

This happened one other time for the prior owner, but after a while it eventually started. At the time the car was parked on a hill and he suspected that the fuel line may have had some air in it. He replaced the in-line fuel filter in case that was the problem. Now several months later, the problem has reoccurred. Any ideas what may be the problem?

I have also posted a request for a recommendation of a good independent shop in the New Orleans area in case he has to have it towed.

lrg · #2 04-17-2003, 01:07 PM

OM603 engines, like yours, are self priming but it takes a fair amount of cranking to get them primed. I'd replace the primary (clear plastic) fuel filter just on general principles and crank away. The filter should get about 90% full of fuel, if it's less than that you may have a bad fuel gauge and less fuel in the tank than you think (this actually happened to me...the car died showing 1/4 tank). You mention that the glow system is ok but just to be sure I'd remove the metal bar fuse for the plow plugs (it's on top of the left side wheel in the engine compartment) and check to see you are getting a good connection. Don't make a practice of it but it should be safe to crank the car for 30-40 secs at a time provided you let the starter cool for about a minute or two before you try again. Good luck.

P.E.Haiges · #3 04-17-2003, 10:56 PM

Crowe,

I think it is a GP problem. Fuel problems don't happen that quick. Just because the GD dash light comes on does not mean the GP are working.

A quick GP check is to turn key switch off and overhead cabin light on. Now turn key switch to GP popsition.

If the GP are working, the overhead light willl dim noticeably. If it does, GP are working. If not, the GP aren't working. Check the 80 amp fuse in the relay.

Also check if the GP relay is making a clicking sound when key switch is turned to GP position. If it doesn't, remove and replace 5 times the smaller of the 2 connectors on the relay. Listen for the relay clicking again. If it now clicks, engine should start. No click, it could be a bad relay.

P E H

Wallknight · #4 04-18-2003, 04:49 PM

You dont think even without the gp's it would try to start in New Orleans this time of year? Certainly waiting till afternoon would get the temp up to 80+ and even my 82 will start without plugs in that!

I say fuel.

dpbrowne · #5 04-19-2003, 04:30 AM

I had yhat problem last week and doing some research on this site I was told to check the neutral safty switch. Sure enough when moving the shifter through the gears a few times and trying to start it in neutral it worked. Worth a try.

Crowe · #6 04-19-2003, 11:05 PM

An update ..... when my son opened up one of the fuel lines and turned the engine over no fuel came out. So we decided to take the spin-on filter off and check it. He purchased new fuel filters. When he removed the old spin-on filter it had fuel in it, but it was not full. He filled the new filter with fuel and also replaced the clear in-line filter. Next he opened one of the fuel lines and turned the engine over several times to prime the system and purge any air. Once that was done the engine did start up. However now it is running rought and will "diesel" (continue to run) after the key is turned off. I suggested that he make sure that one of the vacuum lines had not been knocked off or disconnected. He report no vacuum lines out of place. The car ran fine before this no-start situation. Any ideas on what to check now?

Crowe · #7 04-21-2003, 10:39 AM

After further inspection a vacuum line was found to be the cause of the rough running and failure to turn off. So...he is back on the road. We are still not sure what caused the original no-start situation. It appears to be air getting into the fuel system. Any ideas how this is happening?

gsxr · #8 04-21-2003, 10:57 AM

It is possible the supply & return lines have been swapped at the metal lines on the chassis. When this happens, you will "run out of fuel" with about a 1/4 tank left. If he rarely lets it get low, that could be what happened - hard to tell. If not, your gauge could be off. The fuel system is self-priming and air in the system should not be a problem, and shouldn't really happen in the first place. Is the car running OK now?

Cardude · #9 04-21-2003, 01:12 PM

I'm having a similar situation today also.

But, I can not get it restarted at all. I have put more diesel in it already. I will check filters next but, not running right now. 1982 300TDT with 207000 miles.

Help, You are the diesel dudes My fuel gauge reads almost half a tank of fuel.

This is not fun, Stranded on the side of the road!

Cardude

gsxr · #10 04-21-2003, 01:20 PM

Check the 80A flat fuse in the glow plug relay first. If the car was warm and won't re-start, though, that's bad. I'm assuming it is stone cold and won't start - right?

Cardude · #11 04-21-2003, 09:12 PM

Nope, I was physically driving the car and it shut off. I had it pulled to my house by a friend. It just acts like it wants to start,,,,hmmmm as if it has a firing problem. Where is the fuel pump located on these babies maybe I should try there also. For some reason I'm still thinking fuel problem. I was running along at 50 mph and it shut off and never restarted.

Ackkkkkkcckkkkkkkccccckk!

Help, this is my super commuter car.

Cardude,

gsxr · #12 04-21-2003, 10:16 PM

Yup- if it died while driving it's almost guaranteed to be a fuel supply issue. Not sure where to start though... could be swapped supply & return lines, could be plugged filters or tank strainer, could be a bad lift pump, could be dead IP, could be bad ignition vac shutoff switch. Try unplugging the vacuum line to the IP for the shutoff, wouldn't hurt to rule that out up front...

BIGRED · #13 04-21-2003, 10:36 PM

On my boat (cummins diesels) I used spray start to isolate problems. Give it a shot in the intake, if she almost runs it is a fuel problem. In some cases its enough to solve some minor problems, because the motor starts and clears out the issue.

However, if it is a cam / value / chain issue then any cranking could / would / might - make matters worse.

Good Luck
Don

gsxr · #14 04-21-2003, 10:55 PM

WARNING!!! Do not use starting fluid/spray for Mercedes diesels. Big trucks and equipment (and probably boats) have low-compression, direct-injection diesel engines designed for that stuff. MB uses high compression, indirect injection. Starting fluid can destroy prechambers, which will in turn tear up pistons & cylinder walls. I'm not sure what you can safely shoot into the intake snorkel as a test... perhaps a little propane? Good idea, just need to find a safe "test fuel"!!

BIGRED · #15 04-21-2003, 11:28 PM

I bow to your expertise, but can't help wonder how a single 2 second shot could do all that damage.