Glo Plug Light Inconsistent
 

I am encountering a somewhat similar problem with my glo plug light as others who have posted recently with ONE difference.

My light comes on every other time or so and acts real inconsistent. When it does come on the car starts like it should. When it doesn't, it cranks forever and barely starts. I have tried turning it off and turning it on again. When I do so it stays the same as it was before.

My question is do the glo plugs go bad all at once or will they act inconsistent for awhile. I'm trying to determine which is failing intermittantly.....the glo plugs or the relay?

I've ordered plugs and will proceed to change the five, but wondered if any of you have had the problem with inconsistency.

Thanks,

Don

Did you check the 80 amp fuse in the relay box? It is a bar fuse, just a strip of metal. Screws on either side could be loose, or it may have a crack that you can't see unless you flex it a little bit.
And I would say a GP could go bad but still work some of the time. If the little coil inside that gets hot is broken vibration from the engine may make it make contact on the next start. One plug is not going to make for real hard starting anyway. I didn't notice mine were bad till 2 went, and then it would start OK, just idle pretty rough till all 5 were firing. When three went which included the number one plug and no light came on it was next to impossible to start below 45.

I had the same problems on my 82 240d.
I took the GP relay apart and found water in it. There are 4 small screws that you remove on the top of the relay & then the actual "relay" (circuit board thing-a-ma-dealie) comes out. In my case the water had corroded the solder on the circuit board - so I just soldered in a new wire to "jump" the corroded section.

Just a thought.

Aivars

Thanks guys for a couple of things to check out. Will keep you posted

Don

Don, before my glow light went off completely it was just like what you described "intermittently" on and off. It was the sign that one or two of your glow plugs are about to go dead.
I found my Plug#1 and #5 were bad. I ordered the parts and planning doing next weekend.


David
1985 300D

Thanks David.

I just went out in the garage and found the glo relay fuse. The two bolts holding that down were equally loose (slightly). I tightened both and have tried the car a couple of times since. The light has come on both times so far.

I did order 5 glo plugs anyway and will put them in when they arrive from fastlane since I believe that to be a part of the problem.

Don

had the exact same situation with my 83 300SD. I first tried replacing all the plugs, to no avail. Then, i took apart the relay and found that the relay connection points had carboned up. I cleaned them up with some sand paper and all is good. Oh yea, whenever you touch anything on the glow plug system you will think you have solved it until you pick up a friend or girlfriend etc, then, and ONLY then, will you realize you havn't solved the problem. And then you crank forever and make your car look bad. Must have done that 10 times, everytime thinking "YES! i fixed it, only to figure out i hadn't :( ) been a few months and several trips with my g/f and it hasn't re-appeared :D

I hear you on that one Ryan. Thought I had it fixed because the light was coming on 100%. Went out tonight with my wife to go to church and it just sat there and cranked. Got out and jumped in the 240.

I'm waiting for the 5 new glo plugs from fastlane and if that doesn't work, I'll be bummed.

Don

try the relay fix i mentioned while your waiting. Take the cover off, and slide a thin peice of sand paper in b/w the contact points on the relay, if i remember right there are two .One bigger one smaller. rub untill the contact points are clean again This solved my problem!
RYan

Finally got to the bottom of the problem. Replaced all 5 glo plugs and was smiling until I turned the key......no light. So I went back and re-read some posts. I noticed that on one post, a guy mentioned that the 80 amp strip fuse, even if slightly bent, might be the problem. I popped off the cover and sure enough it was somewhat bent. I swapped it out with the one in my 240 and whoa....glo plug light and a great start.

I don't know what i'd do without this forum. Thanks to all for the great assistance.

Don

Where can I find the glow plug relay & 80 amp fuse?
Somedays the gp light works others not.
I have an 81 300 SD
Also how much are a set of glow plugs?