'87 300TD Wont Start - PeachParts Mercedes-Benz Forum

djankov · #1 02-27-2004, 03:08 PM

I just tied to start my 1987 300TD and it catches, but wont start. I replaced both fuel filters about 1500 miles ago. I looked at the antifreeze and the level is OK with no oil in it. What should I try next to get it started?

1987 300D 186Km
1987 300TD 196Km
2001 CLK 430 Convertible 33Km

Fisherman · #2 02-27-2004, 04:18 PM

That's the order that I work from. If the GPs are cycling, then the battery has to be able to turn the engine fast enough to fire and if that is all working right then fuel delivery is the last thing. For that try pumping the hand primer a few hundred times...

HGV · #3 02-27-2004, 04:44 PM

One possiblity is the glow plugs. Does your glow plug lite act funny?
Henry

lrg · #4 02-27-2004, 04:47 PM

It sounds like you have air in the fuel system. Your car has a self priming fuel pump (there is no hand pump) so you just have to crank it for about 20-30 seconds to get it primed. Assuming you have a good battery and it is in a fairly warm garage, it should start even if the glow plugs are failing. You can crank for up to a minute without stopping but after that you should let the starter cool for a couple of minutes before trying again. I've gotten my '87 going from stone cold in 50 degree weather with no glow plugs but it took two tries on continuous cranking for close to a minute each. If the engine starts to go keep cranking until you are sure it's going. More often that not it won't start because you let go of the key too soon. If you get it going and the problem happens again look for a leak in your fuel system and/or bad glow plugs. A search here will get you to lots of info on fixing bothe those problems. Good luck.

djankov · #5 02-27-2004, 05:23 PM

Glow plug light works fine. I cranked it for about 45 sec and it finally started. It ussually starts immediately after the glow light light goes off.
I drove it around the block and the only thing I noticed that was unusual was the oil pressure was between 2.5 - 3 at idle instead of 1.5 - 2. Any ideas?

Thanks,

1987 300D 186Km
1987 300TD 196Km
2001 CLK 430 Convertible 32Km

#6 02-27-2004, 05:26 PM

I think the oil pressure is probably unrelated to your starting difficulties. It sounds like you have a few weak glowplugs. Based on your original description, it sounds like there are only a few good glowplugs on your engine, which will make it catch, but not want to start without continued cranking.

Check the resistance through each glowplug and report back. IIRC, resistance should be less than 0.4 Ohms.

When was the last time the glowplugs were replaced (if ever)?

edit: on the subject of your oil pressure, my car (same engine as yours) holds 3 Bar at idle until the engine reaches about 80°C. After I've driven for a few minutes, it will be down to 1.5 Bar at idle.

lrg · #7 02-27-2004, 05:28 PM

If the engine was not fully warmed up then the pressure at idle is normal. Cold/cool oil = thicker oil = more oil pressure. It should return to the the lower reading at idle after 10-20 minutes of constant driving.

djankov · #8 02-27-2004, 07:59 PM

I just tested the glowplugs for resistance and they were all between 0.72 and 0.76 Ohms. Like I said earlier, the engine always started right up on the first crank once the glow plug light went off. Anyway, I will keep you posted if the problem repeats.
The oil pressure is back to about 2 bars at idle.

Thanks,

1987 300 TD 196Km
1987 300D 186Km
2001 CLK 430 Convertible 31Km

#9 02-27-2004, 08:02 PM

The resistance through your glowplugs is a bit high. This is probably the cause of your difficult starting. Try replacing them and see if it makes a difference. I'm expecting that it will.

djankov · #10 02-27-2004, 08:22 PM

I just tested the glowplugs for resistance and they were all between 0.72 and 0.76 Ohms. Like I said earlier, the engine always started right up on the first crank once the glow plug light went off. Anyway, I will keep you posted if the problem repeats.
The oil pressure is back to about 2 bars at idle.

Thanks,

1987 300 TD 196Km
1987 300D 186Km
2001 CLK 430 Convertible 31Km

#11 02-27-2004, 08:34 PM

m'kay

Ken300D · #12 02-28-2004, 09:20 AM

Since you have a volt-ohm meter, my suggestion is for you to verify you are getting voltage at the glow plugs. Check as many as you can reasonably reach. More easily done if you have someone to turn the key for you.

To me it sounds mostly like you are not getting glow. These engines just don't like to start without a set of hot glow plugs.

Ken300D

djankov · #13 03-10-2004, 12:46 AM

OK, the problem repeated twice only when the car is parked on an incline overnight. When I park the car the other way (decline), no problem, it starts immediately! When I parked it on level ground, it took 2-3 tries of cranking.
?????

1987 300D 186Km
1987 300TD 197Km
2001 CLK 430 Convertible 34Km

lrg · #14 03-10-2004, 12:57 AM

Full tank of fuel? If it's low you might be getting some air in the line when you park it on a hill. Since it's so hilly here we have to be careful parking with a low fuel tank. Usually you find it's a problem in one direction but less so in the other.

TonyFromWestOz · #15 03-10-2004, 08:10 AM

Sounds like an air leak in the fuel line after the lift pump. On an incline, the fuel seeps back to the fuel tank thru the return line. Makes it difficult to start and might not leak when under pressure from the lift pump.