74 240D Glow Plug Problems

[Jas2on]

I jsut had to replace the glow plugs on my 74 240d for the second time this year. Im no expert, but that dont seem right. Whats going on?

[Jas2on]

I had to replace one in January, then all four in February and just this weekend replaced all four. Total failure.. Its in a series so if one goes out, they all go out...

[Lycoming-8]

It is correct that if one plug goes out on a series system, all of the rest quit glowing. However it is generally not because they have failed. It is because the open one has caused an open circuit and the other three can no longer get power!!! Those other plugs should be tested not thrown out!!

[Jas2on]

All four were burnt out for the second time this year... Checked everything else and it seems fine... So I think its probobly me, Im letting them burn too long. Its a 115 so it doesn't have a timed realy...

[t walgamuth]

yes, i think you are glowing too long. is the engine hard to start? also the carbon build up could be causing a problem, perhaps you are damaging them on installation. you are using the original loop type? the fast glow retro fits on the 115 i had found to not last very long... perhaps from glowing too long.

[diametricalbenz]

Originally Posted by t walgamuth

yes, i think you are glowing too long. is the engine hard to start? also the carbon build up could be causing a problem, perhaps you are damaging them on installation. you are using the original loop type? the fast glow retro fits on the 115 i had found to not last very long... perhaps from glowing too long.

When doing the conversion, is the 5th dashboard glow plug replaced with a pencil plug as well? If the loop type is left in place there would be a heating time difference between the glow plug types right? Would that account for the extra glow plug time leading to early burnout? or are the pencil plugs just not as robust as the loop type?

[watsone91]

Replaced my glow plugs on my 1994 c220 six months ago with NGK ones having a problem starting now and may go back to merc ones

[Palangi]

Bad injectors can cause the loop type plugs to burn out. Excessive carbon buildup is another possiblity. There is a special reamer tool for removing the carbon buildup, but it's a bit expensive. In either case, most likely the problem would repeat itself on one cylinder. It doesn't seem likely that all 4 plugs could actually burn out at the same time.