loop style glow plug question - PeachParts Mercedes-Benz Forum

johninva · #1 09-07-2007, 07:47 PM

this should be simple for you guys, 78300d quit starting, from the #5 plug to #4 plug the resistor wire glows red, same for #4 to #3, the remaining resistor wires do not glow red, but they do get hot. i pulled plugs 1,2,&3 and they look ok, no broken loop, and resistance testing seems to indicate that they are ok. Bad resistor wire ? plugs bad anyway ?, any suggestions would be appreciated.

#2 09-07-2007, 08:21 PM

If the resistor wires are glowing at all that means it's a complete circuit.

Narrow down "quit starting" for us. How did it quit starting? Did it fun fine then decide to not start the next day?

Is there any exhaust smoke while it's cranking?

Does it try to start at all? Coughing, sputtering, etc?

johninva · #3 09-07-2007, 08:38 PM

started getting harder to start, would have to let glow longer and longer, then one day it wouldnt start, after trying for some time the batteryseemed to go down, so i hooked up the jumper cables to my truck, the mercedes started up pretty quick with the cables attached. ran and started good for a week and now no start period, cables or no, i plugged in the block heater for a couple days - no start, not really coughing or sputtering when cranking maybe a tiny bit just for a second. no smoke that ive noticed while cranking.

#4 09-07-2007, 08:44 PM

Have you tried changing the fuel filters? Take off the fuel tank cap and listen for a rush of air which could mean a plugged tank vent.

Pump the primer handle a bunch (Like 50+ times) and see if it makes it any easier to start.

vstech · #5 09-07-2007, 09:27 PM

with the jumper hooked up, does it sound like the crank speed is the same as last week when it was starting? a bad battery will make it very difficult to crank these 22:1 CR motors. it sounds like either your starter has gotten weak, or your battery is failing. another possibility is that the loops are inadequate to heat the PC enough to aid ignition. new loops could get the band aid going a bit longer, but conversion to pencil plugs will make a MUCH bigger difference. is it worth 100.00 to find out? your call. get a fully charged type 49 battery in there and see if the plugs and starter work better. if no change, you might wanna look into conversion...

Stevo · #6 09-07-2007, 09:42 PM

I suggestion you take this opportunity too switch to the new style GPs, you wont regret it.

pdxwaker · #7 09-07-2007, 09:51 PM

Quote:

Originally Posted by Stevo

I suggestion you take this opportunity too switch to the new style GPs, you wont regret it.

This is excellent advice... do it!

KCM · #8 09-07-2007, 10:38 PM

Your problem may be simpler than you think, and cheaper than retrofitting to the new style plugs. Take off all the wires between the glow plugs and at each end (even the end that grounds to the engine itself) and give them a good cleaning with a wire brush until they are nice and shiney. Do the same with the glow plugs themselves. Clean any metal connection that makes electrical contact. Then reattach everything and give it a try.

Recently bought a car that would not start. Tried everything, including ether. Wouldn't even hit. Turned out one of the connections on the glow plugs had corrosion and excessive resistance. Once the connections were cleaned, the engine started right up. I would never have thought that could make so much of a difference, but it did.

vstech · #9 09-07-2007, 11:29 PM

good point KCM, but he has pulled the plugs, and reinstalled them, it's unlikely there is still some resistance from corrosion or whatnot... still, not a bad idea. a wire brush, or some sandpaper wouldn't hurt.

johninva · #10 09-08-2007, 07:35 AM

i only pulled the plugs out after the point where the resistor wires werent glowing, the first three, cleaned everythinh real good. starter sounds like it always did when the cables are attached. im pretty sure its getting fuel, but i will crack the nuts at the tops of the injectors and crank to see if fuel comes out. I have hand primed a bunch - no help. Should all of the resistor wires be glowing red ? I would think so, and they are not leading me to think glow plug issue. I think i will upgrade to the dieselgiants plugs that do not require any changing of the relays or any of the other related jazz. but i was hoping to get the car started this weekend.

johninva · #11 09-08-2007, 08:54 AM

can i just go buy some pencil type plugs from the napa and wire them up like on the diesel giants site http://www.dieselgiant.com/mercedesdieselloopglowplugrepair.htm, or are those some kind of special plug.

kerry · #12 09-08-2007, 10:13 AM

They're a special plug. The series plugs have larger diameter threads so it's a pencil plug with series threads. They are available invidividually but you'll need the exact part number, a standard pencil plug for later engines will not fit.

JimmyL · #13 09-08-2007, 10:24 AM

Quote:

Originally Posted by johninva

i plugged in the block heater for a couple days - no start........

While it does sound like symptoms of glow plug issues, he did plug in the block heater. {providing it works.....}
That makes it sound more like the weak battery, slow starer scenario.......
I agree about upgrading the glow plugs, as that needs to happen whether it's the problem or not.

johninva · #14 09-08-2007, 10:38 AM

anybody got a part number for those pencil type with series threads plugs ?

johninva · #15 09-08-2007, 11:16 AM

jimmyL, ought it to start when it's being jumped. cranking sounds right. block heater seems to be working, the valve cover was hot to the touch. what about these non glowing resistor wires ?