Im going to continue to UTFSE but I thought id ask in case Ive missed something obvious. Even just saying 'go read about this topic' or 'search for so-and-so's thread on x' will help. I keep getting completely distracted by other interesting threads, i t never ends.

Ive got an 85 300d that will not start lately. I consistently get no glow plug light now (although this is something that has happened before, but intermittently).

It turns over strong but does not ever create any combustion. There is some small amount of the usual blow by , and some also wisps out of the tailpipe when i got out to look after the attempts. I'm not sure if this means a thing. This could just be unburnt fuel vapor or similar.

Here is a list of things Ive checked so far. compression, fuel, electrical.

1) compression -
- it builds 2.3+ after a 3-4 seconds and holds/increases from there. on a related not i also changed the air filter out (it was overdue). Up until the day before, it had started, but i usually had to give it a little extra fuel for the first couple seconds to keep it from dying (not always). id even need to do this when it was 50F-60F outside. i'm not sure if this was a related symptom or not.

2) ignition/electrical -
- the battery is in great shape. I've maintained it with a good charger, it tries hard.
- I ran through this guide and checked the relay wires, fuse, and glow plugs with a multimeter Dieselgiant glow plug repair guide.
- i pulled the Bosch glow plugs individually and each gave me about 0.6 ohms of resistance (after correcting for the multimeter's inherent probe resistance).
- via the guide, the glow plug relay fuse was good, as were the wires.
- Every glow plug tip was wet with a little diesel, so I'm pretty sure diesel is making it in from starting attempts. It hasn't sucessfully run in about a month so I think the fuel wouldnt be there from then (but i suppose a hot engine wouldnt encourage it to stay, either). I'm about ready to pull them all and do the 'red hot glow' check, just to be sure.

3) Fuel.
- I've looked over and felt the various fuel lines in the engine bay for any damage.
- replaced the return lines with new OEM lines (fabric on one ripped too easily, rubber ripped up some, so i considered that a sign, were otherwise ok looking, flexible). (If you are ever looking at doing this, a small amount of oil on the hose ends IS the difference between success and failure in getting the new one on..)
- replaced both filters was probably overdue, but i hadn't noticed symptoms such as loss of high end power that would indicate this was an issue.
- purged using the primer pump with the large filter barely loosened until fuel 'fizzed' out of the bolt head. ill cut the old filter the next time i go to work (i help a helicopter mechanic ).
- and even purged by cracking the fuel line/injector nut while the engine was turning over, until drops of fuel oozed or squirted out. i did every one on separate 10ish second start attempt. I could probably do this again to double check I bled every last bit out, but who knows.
- the tank is 3/4 full, id read on here that low fuel can become an exacerbating situation sometimes when there are other weak links in the fuel system.
-some clear plastic fuel lines are dark brown(?) is this just corrosion on the part of the diesel or something else?
-have the new style hand primer pump, it leaks a tiny bit when pumping but i think this is cause the system is already very pressurized and its the 'weakest' link (have pumped some with filters tightened to see if fuel comes out anywhere else.) it does not leak when the filter is loosened from what i've seen. The leak is at the base of the pump itself, or possibly at one of the other fittings. i think i can here a tiny, tiny hissing at the main fuel filter when i work the primer but its almost not there, never see any fuel drips..


So...
Do I need to read more about the relay? some other electircal aspect? Is the 'no glow plug light' situation a sign?
Could something still be wrong with the fuel system even though It was oozing/spurting from the fuel lines during start attempts?
Do do i need to pull the glow plugs and do a bench test, see if they glow hot just to be sure?
I suppose I could do a voltage or current test during a glow plug cycle to see what is actually going on, what current/voltage is making it to the plugs.




If i ever do get it started I'll be doing a Lubro Moly diesel purge immediately fwiw. I might go ahead and pour some in the fuel filter to see if it can help now. And then a compression test, hope the numbers are good


Thanks in advance.

I think you are complication things slightly. Have you checked for power at all 5 GP's? Sounds like your relay may not be doing its job since the dash light is not working properly.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Does your dome light light dim when the glow plugs turn on? If not, they're not working, which is the most likely cause of your problem.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

lol I'm sure I am at this point.. some some of this was overdue/in need of inspection anyway.. I used the multimeter to check the relay-to-plug wires for continuity and they all checked out.. it detected the inherent resistance of the multimeter/probes and showed a negligible change for the wires themselves. Continuity was there, but I really should check for voltage at the plug ends during the gp cycle, correct?

Clever! the bulb is removed at the moment but I think its rolling around in my dash compartment, I'll go try that in a minute.

yes, check for voltage at plugs

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

+1

__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

The above in Blue is part of the over complication the other member was speaking of. (Checking all of the stuff in blue was premature and with out a Wiring diagram or having knowledge of where all of the wires go probing around with the Multimeter is not a big help.)

What you really needed to know (as you indicated at the end) was if you were getting Voltage at the Glow Plugs and how much Voltage. That would give you and idea if the Glow Plug Relay was working or if the Ignition Switch is having a problem and not activating the Glow Plug Relay.

Also while the Glow Plugs were out it would have be a real good time to check the Glow Plugs individually to see if they. On the Battery as described in several of the DIY Threads.

You seem to be getting Fuel as evidenced by the wet Glow Plugs.
Wet Glow Plugs with fresh Fuel on them is a good indication that the Glow Plugs or the Glow Plug Relay system is not working.

If the Glow Plugs were hot the Fuel would evaporate off of them and would the would not be wet.

__________________
84 300D, 82 Volvo 244Gl Diesel

Simply, to have a fire you need:
Oxygen, fuel, a catalyst (ignition).

You have oxygen from the atmosphere.
You have fuel as indicated by the diesel on your glow plugs. I've heard board members use WD40 (which contains diesel like oil) for starting fluid.

That's two down.

The missing link is the catalyst: either compression (which squeezes the air and makes it hot so as to ignite the fuel) OR your glow plugs are not working.

As it was just running the other day and now your glow plug light isn't coming on... It seems to me that compression is probably not the problem.

I agree with the other guys: the Glow Plugs are not working. Now you have only to find out WHY.

You've tested those glow plugs for resistance but that doesn't mean they're any good. Some folks take them out individually and CAREFULLY test them to see if they turn red hot. THAT is the only real test of a glow plug's goodness.

Some glow plug circuits are series which means the wire from the relay goes to the first plug thence to the second then the third and so on ... If the wire is parted anywhere in the series circuit then they wont heat and you're indicator light wont light.

Other glow plug circuits are parallel where a separate wire goes to each plug from the relay.

These wires whether series or parallel must be in good shape and firmly connected to the glow plug and the relay with no corrosion.

Once the plugs themselves have been verified and you're sure you've checked the fuses and wires, the relay may be suspect.

If you have another known good relay then just try to swap them out.

__________________
Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

Glow plugs are cheap. I'd replace them. Keep the old set as spares if needbe. x2 on the checking the rest of the system though.

__________________
hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

If the glow plugs ohm properly they are capable of getting hot, though not always as hot as originally designed. The OP was talking about starting attempts above freezing. Even marginal glow plugs will get an engine in decent shape going in these conditions. I'm pretty sure something else in the glow plug system is failing to provide voltage to the plugs.

__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

I'll pile on a bit - I also think the pre-glow relay is suspect. The pre-glow light in the instrument panel working/not working is a major clue. The car was trying to tell you that the pre-glow system needed servicing way back then, but you missed it.

Check for voltage at a glow plug within 30 seconds of turning the key to the "glow" position. If no voltage, either the fuse is bad, the relay is bad, or the relay is not getting power or signal for some other reason (ignition switch).

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Thanks for all the input

I took a couple pics here, added arrows to 2nd pic to point to damage.

I'll go ahead and update and say its looking like the relay is toast. I went ahead and opened it up, and there is some burnt up wire at the end of the main coil on the right (arrow). It also looks like a connection on the left is a little cooked, too (arrow). There was even somewhat of a burnt smell when i first opened the sealed box. FWIW the fuse on top is intact, and I tested it with a multimeter using the previously mentioned guide.

I'll pull a relay from one of my friend's donor cars as a test later tonight.

Thanks for all the other suggestions/input, I will be following them when I have a minute. School, work, and another car i'm working on are leaving me short on time.