Lack of glow plug light & no start - Page 2 - PeachParts Mercedes-Benz Forum

mobetta · #16 10-03-2008, 12:16 AM

Quote:

Originally Posted by johnathan1

Can I get the updated pencil type retrofit plugs at Autozone?

autozone stopped carrying glow plugs. at least in MN.

back when they did, they carried Bosch dura-terms.(french made) I now get them at Napa for $3 more.

oreilly and CSK carry autolie crap.

barry123400 · #17 10-03-2008, 12:52 AM

Okay, since they are series plugs they do not ground in the head. Instead the element is across the threaded portion to the next conductive layer below. So you will find the continuity from the threaded tip to the next conductive layer on the glow plug. This is separated by the porcelian bushing normally. When you originally went from the battery ground to the series string and got an open or infinite reading you proved as you say that you have an open ground or at least one suspect open plug.

Retest each plug again using the proper checking points. Any further concerns post again with them. At this point it does sound like you have an open plug probably.

It is not unusual for those older glow pluig relays to call it a day with time and usage. It is somewhat of an upside you seem to have missed that bullet at this time. At least since removing the plugs you will understand their other name used occasionally is loop type plugs.

I still have the series or loop plugs myself in my 77 300d and they perform fairly well. This might depend on how solid the engine is. Mine is still pretty sound.

I agree the pencil plugs are superior without a doubt. Just for starters there is no external heating effect that is created by the squiggly resistance wires. Also one plug open will not stop the engine from starting as the others will still work. On a working series system you can see those wires turn reddish in the dark.

Another possible cause of your initial no resistance indication might be the glow plug terminals connection oxidation. If the car sat a long while so clean up all your terminals in the glow plug system in the engine compartment.

When checking loop plugs it only takes a minute to also read for any resistance between the threaded portion and the mounting threads at the base of the plug. If there is any continuity then the plug is shorted internally. You have already done this test by reading infinity the way you checked them so you do not have a shorted plug.

Just one further comment. If you stay with the loop plugs carry a jumper wire with two good size alligator clips in your trunk. A spare glow plug does not hurt either. That way if a plug burns out on the road the jumper will find it by you bridging one glow plug at a time. This way the other glow plugs will work until you get a chance to change the open one out that is shutting them all down.

There is not much chance of finding a parts place on the road with this obsolite style of plug in stock. Thats the main reason to carry a spare. Mercedes used the loop plugs in series from 1939 till about 1980 by the way. Hope all the above helps you a little. It is not a complex system.

johnathan1 · #18 10-03-2008, 05:44 AM

Alright, I feel like a 'tard...lol.

I tested the glow plugs properly, and they are all within spec, and they all look fine. I used a steel brush and cleaned ALL the contact points everywhere. The glow plugs now seem to be functioning. The glow light still doesn't come on, but the squiggly wires get very hot to the touch, and I hear the relay click.

There is, however, one more problem. The engine still won't start!! :[

It just cranks and cranks. Since the glow plug system seems to now be working, I decided to turn to the fuel system. I tried pumping using the primer pump, and I hear lots of gurgling noises coming from somewhere when I pump, and the pump leaked diesel all over my hand... Maybe I have air in the lines? lol. I held a flashlight to the primary filter, and it seems clear, with no air bubbles...I also saw some fuel dribbling out of a leaking fuel return line, not sure what that means...

Maybe I should also note that I thought you were supposed to pump the hand primer until it became firm, and hard to pump...well it seems like I can't get it to get firm, I just pump and pump and pump, and never really feel any pressure...

Any ideas?

johnathan1 · #19 10-03-2008, 04:24 PM

Someone? Anyone?

TylerH860 · #20 10-03-2008, 04:27 PM

Perhaps you could attach your fuel line to another small tank. If it starts, you know that's the problem.

That tank has to be really nasty after sitting for so long.

johnathan1 · #21 10-03-2008, 04:56 PM

Well, the fuel in the fuel filter looks fine...no dark color or debris to be seen...but I should add that the car was sitting with NO fuel cap on. I have no idea for how long. And it also looks like an aftermarket fuel tank was installed at some point...It's much bigger than the stock tank, and protrudes into the trunk space. I'll try to get some pics of it up.

TylerH860 · #22 10-03-2008, 04:58 PM

I hope you're not trying to start it with the fuel that came with the car. I know diesel ages better, but its no French Wine, yikes.

johnathan1 · #23 10-03-2008, 05:00 PM

Was never a problem in the other two diesels I have started in the past that had been sitting for about 10 years. The fuel was actually just fine, and the cars ran perfect.

barry123400 · #24 10-03-2008, 06:10 PM

You have some experience with these cars and thats good. I would do a compression check to see what I have. This avoids spending money and effort with no real hope.

Conversly if the compresion is reasonable or good you know your efforts will work out before you spend any money and time. Right now it sounds like you need a new primer pump for starters.

Again in my opinion with unknowns I always like to establish a baseline. A compression check does that. For example if you had one dead cylinder and it was not valve related but a serious piston/bore problem would you want to spend any money and time? Most the time it is only minor issues on these cars yet there will always be the exceptions as well. I am not trying to burst anyones bubble here. It's just a logical approch can ease the mental burdens somewhat and sometimes save money.

Part of this approach is owners have reported very low compression readings when they eventually got there after trying everything else first. This seems to occur on some cars sitting a long time. Occasionally a tow gets them started once they are sure fuel is getting to the engine.

johnathan1 · #25 10-03-2008, 08:18 PM

Success! Apparently I wasn't allowing the plugs to glow for long enough...WOW they really take a long time! O_O

I cranked it for a while, and it finally started. Ran really well, too. :] Too bad I can't drive it, since someone took apart the throttle linkage, and it's missing a couple bars. Why anyone would do that, I have no clue. -_-

barry123400 · #26 10-04-2008, 12:24 AM

Well if it sat a long time and started the engine may be pretty good.

chetwesley · #27 10-04-2008, 01:17 AM

Did you say that when you pumped the primer pump that it got diesel all over your hands? From my recent experience, that means that the pump is failing.

As it was stated to me, if your pump is leaking fuel out, then air can leak in.

I would change the pump, even if you got it started for now. It could be intermittently letting air into the system.

I just got a 79 240d that wouldn't start for the exact reason that this pump was faulty (wouldn't draw fuel and was leaking air into the system. I got it started, but it would die because it was leaking air in and then wouldn't start again. I replaced it and it now runs and stays running.