240d wont start, simple but I cant find it - PeachParts Mercedes-Benz Forum

Treeman · #1 10-31-2005, 12:06 AM

'77 240d, 288k
I have two problems here, one might fix the other. But yall are going to have to tell me. I cant figure this out. Once I get the car push started it runs fine. If car cools off say overnight. It will not start!
I cycle the New Glow plugs twice and on the second cycle I will let the plugs heat for more than 1 minute. Nothing. After the second try Im usually out of patience and push start the car. Starts everytime as if Im pushing or the key works as long as the motor is somewhat warm. I thought I had it figured out that I had air in the lines. So I replaced all the lines, from the rear tank to the IP and any others I could see. I also changed all filters. All fuel and air. Tightened all hose clamps and put a wrench on everything that the fuel would pass by or through. I then replaced the hand pump with a new one. Still nothing unless pushing or warm. I then ran a half of a can of 'Seafoam' through the crankcase and the other half through the fuel tank.
The only thing I have not done is replace the starter. The battery is brand new. (?) The other thing that may have something to contribute to the problem might be the vacumn lines coming thru the firewall seem to be leaking down as they squeal when you turn the engine off. If you disconnet them the motor will not turn off. So that is why I am thinking it might be part of the problem related to the hard start or not. Regardless I am asking for help and suggestions. I have the mechanical ability of a silverware drawer, so please ask questions if I left something out.
Thanks in advance, Treeman

t walgamuth · #2 10-31-2005, 12:21 AM

when you say won't crank do you mean won't start or won't turn the motor over?

tom w

Treeman · #3 10-31-2005, 12:23 AM

Quote:

Originally Posted by t walgamuth

when you say won't crank do you mean won't start or won't turn the motor over?

tom w

Sorry Tom, I mean it will not start.

Palangi · #4 10-31-2005, 12:28 AM

A 77 would have series glowplugs. Very simple, yet seems to baffle most people. Describe how you know the glowplugs are working.

Treeman · #5 10-31-2005, 12:31 AM

Quote:

Originally Posted by Palangi

A 77 would have series glowplugs. Very simple, yet seems to baffle most people. Describe how you know the glowplugs are working.

? Mechanic shop just replaced them? They seem to get very hot at they glow red. I have no other explanation. How can you know, I assumed?

Palangi · #6 10-31-2005, 12:35 AM

What glows red exactly? You can't see the tips of the glow plugs since they are in the head. Could Mr. Mechanic have installed parallel type plugs?

Treeman · #7 10-31-2005, 12:43 AM

Quote:

Originally Posted by Palangi

What glows red exactly? You can't see the tips of the glow plugs since they are in the head. Could Mr. Mechanic have installed parallel type plugs?

There ate 2 places that I for sure saw red. where the wire ties to the porcelan

Treeman · #8 10-31-2005, 09:16 PM

Quote:

Originally Posted by Palangi

What glows red exactly? You can't see the tips of the glow plugs since they are in the head. Could Mr. Mechanic have installed parallel type plugs?

I know that I should be able to answer this question but I cant. So how would I know. What do I look for? I guess maybe I need to buy new glow plugs and install myself! Is this the answer I am looking for?
Thanks,
Tree

Jim H · #9 10-31-2005, 09:46 PM

Quote:

Originally Posted by Treeman

What do I look for? I guess maybe I need to buy new glow plugs and install myself! Is this the answer I am looking for?

Well, not just yet...

You need to verify that the correct plug is installed. The older 'series' or 'loop' plug is different that the newer 'pencil' plug.

With an ohmmeter, loop plug should read open from electrical connector to chassis ground, pencil should read under 1.0 ohms.

If you want, undo the electrical connector and unscrew a plug to see what it would look like. Loop plug has a fat wire loop on the business end, pencil plug is one smooth tube.

Do a BuyParts lookup of your model and year. Loop plugs are under Glow Plugs, and the newer pencil plugs are under Glow Plug Kit.

Let us know.

Treeman · #10 10-31-2005, 10:36 PM

Quote:

Originally Posted by Jim H

Well, not just yet...

You need to verify that the correct plug is installed. The older 'series' or 'loop' plug is different that the newer 'pencil' plug.

With an ohmmeter, loop plug should read open from electrical connector to chassis ground, pencil should read under 1.0 ohms.

If you want, undo the electrical connector and unscrew a plug to see what it would look like. Loop plug has a fat wire loop on the business end, pencil plug is one smooth tube.

Do a BuyParts lookup of your model and year. Loop plugs are under Glow Plugs, and the newer pencil plugs are under Glow Plug Kit.

Let us know.

Ok it's raining, and the trick or treaters wont leave me alone. So I will have to pull one of the plugs Tuesday evening. But I did look at the Glow plugs to see if I could see anything unusual. "Bingo" When Mr Mechanic installed the last set. I noticed he had moved wires going to the plugs. Now under closer inspection I see the wires have been in contact with wire that heats the plugs. Looks to have cooked them pretty good. The wires are not broken but the plastic is hard and charred around the wires in two or three places. I guess I should have been more observant and I would have caught this sooner. I am hoping this will be the fix. Will post results, after the change has been made. Thanks, Tree

Jim H · #11 11-01-2005, 07:50 AM

Quote:

Originally Posted by Treeman

...Now under closer inspection I see the wires have been in contact with wire that heats the plugs. Looks to have cooked them pretty good...

The wires that you see don't actually heat the plugs, but they do glow... The wires are resistors, so they will heat up, but the loop of wire on the end of the plug is where the useful heating for the chamber occurs.

In an older 'series' or loop setup, the current runs through the first wire, through the first plug, through the second wire, the second plug, etc. Everybody glows!

The new plugs get 12V to each, in 'parallel' and the wires should not get hot at all.