1972 220D doesn't start anymore - Page 3 - PeachParts Mercedes-Benz Forum

t walgamuth · #31 07-20-2005, 09:00 PM

thinking that you dont know if you have working glow plugs. you need to run them and see if there getting hot. or take them out and test them with jumper cables. if you arent getting glow it wont start if it is worn much, which is likely is considering the age.

if you dont know about the glow plugs, you are just not going to make any progress if they're bad.

Palangi · #32 07-20-2005, 10:57 PM

DANGER DANGER DANGER

You would NOT want to test serial glow plugs using jumper cables off a 12 volt source.

Palangi · #33 07-20-2005, 11:00 PM

Is there any possibility that this car could have been misfueled or otherwise have bad fuel in it? Any alternative fuel experiments, etc?

t walgamuth · #34 07-20-2005, 11:01 PM

of testing the plugs out of the vehicle. with reasonable care this is not dangerous.

Palangi · #35 07-20-2005, 11:16 PM

Serial glow plugs are low voltage devices. If you're gonna test them out of the car, use really long cables so you can stand waaaay back.

fshacker · #36 07-20-2005, 11:43 PM

Had same discussion with Mattdave offline and I don't think I'm going to test these glow plugs live outside. I will measure voltage across them in the car, and perhaps take them out and compare their open circuit resistance plus visual inspection.

Well, it is 100% Diesel fuel to answer your question re:fuel. However, it could be a bad tank of Diesel for sure. I need to work on that assumption a little to see how I can switch the supply temporarily to another tank.

Thanks!

Palangi · #37 07-21-2005, 12:00 AM

Actually not a bad idea to measure the voltage on each glow plug. It is conceivable that one could be shorted or miswired, such that only 2 or 3 plugs are actually in the circuit. Glow light would still work if a short existed in the middle of the circuit somewhere.

There should be about 2 to 2.5 volts on the #1 plug, twice that on the #2 plug, 6 to 8 volts on the #3 plug, etc. Voltages stated are approximate, but should increase as you work your way towards the rear of the engine.

We really need to make a DIY post on troubleshooting series glow plugs, as this subject comes up several times a year and seems to baffle people.

#38 07-21-2005, 12:31 AM

I can’t get the scanner to work I will keep trying but here is a start
Set voltmeter to 0 to 16 volts DC connect plus cable of voltmeter to input (threaded stud) of 4th cylinder and minus cable to ground Actuate glow plug system and read voltage on meter. If reading is 12 volts the interruption is located at glow plugs or there connection. If voltmeter reads 0 volts look for interruption at pre-glow starter switch or on glow plug resistance control
Checking glow plug for resistance.
Connect minus cable of volt meter to ground check voltage at current input and out put of 4 glow plugs using the plus voltmeter cable if a glow plug shows 12 volts at input but 0 volts at out put the respective glow plug is bad and must be replaced
Dave S

#39 07-21-2005, 03:02 AM

If you remove the glow plugs crank the engine for 30 seconds with the glow plug relay fuse removed. You should get a nice clouds of diesel out the glow plug holes this tells you your injectors are getting fuel and at least working to some degree surly enough to rule them out as the cause of a no start problem.
DHS

fshacker · #40 07-23-2005, 07:19 PM

Okay... Mattdave helped me eliminate glo plugs and fuel problems. We did the compression test last and we had Cyl # 1 @ 190~210psi, and the rest ranged from 240~290psi..... so this is likely it! - Have no idea how to proceed from this point.

Thanks for all the help folks!

P.E.Haiges · #41 07-23-2005, 07:59 PM

fshacker,

Do you have a big hill with little traffic near your place? If you do, tow the car to the top of the hill and let it roll down. When it is going about 40 MPH, glow the plugs, put it in 3rd gear and let the clutch out to try to start the engine. If its an automatic, put shift lever in 2nd gear. If it is going to run at all, this will start it.

Then when the engine is warm, try to start it with the starter using the GP normally. You should drive back to the top of the hill before you shut off the engine just in case it still won't start. Then you can roll start it again.

If the engine runs after the roll start but still won't start using the starter, maybe your starter isn't cranking the engine fast enough. Otherwise the compression isn't high enough and the engine needs an overhaul or a valve job.

P E H

t walgamuth · #42 07-23-2005, 09:05 PM

the compression is on the low side it should run and start with that much. imho.

fshacker · #43 07-23-2005, 10:09 PM

I don't know..., but it might have started by push start as few have recommended here. Just not easy for me to do the push start where I live.

The shop manual lists the compression at 22 - 24 bars with no more than 3 bars variation b/w cyls. This translates to 319 - 348 psi, and 44 psi respectively. I think our measurements are well below these nums.

Thanks!

#44 07-23-2005, 11:15 PM

The compression test we did was on a cold engine since we could not start it up. Any ideas on how much difference there is doing the test on cold engine verses a hot engine like it should be. The out side temperature was at least 90 degrees and we had turned the engine a lot with the starter using another battery to jump his freshly charged battery. The engine was defiantly rotating fast enough on the one battery with both there is no doubt it is not a starter related problem. We hooked up a spare metal fuel line with an injector out of the car there was some minor pee nothing major it is defiantly not a fuel problem. It is so close to starting you can smell burned fuel from the exhaust it goes right up to the edge of going but won’t quite kick over. My 220d engine would start after about 30 seconds of cranking on three cylinders you could even drive it very slowly but it would move. This is a car that looks like it was transported from 1975 to today it is just in fantastic shape. I guess at 146K miles a valve job might be excepted but it ran so well just a few weeks ago is there any chance one of the valves retaining nuts came loose? There is a wide variation between cylinder compression But I am sure the gauge is accurate I have compared readings on it with another gauge on a different car and they both read the sane compression. We went back 3 times and read the first cylinder and got the same readings all three times. If it had been a gas car I would have put some oil in the cylinder to see if it was the rings or valves but I was reluctant to try this on a diesel because of the risk of hydro locking are my fears there justified? The other anomaly was the last cylinder the injector cane out soaked in oil just covered in the stuff dripping off the injector cause of this? A valve job on a 220d is not so bad except the darn air conditioning is a nightmare to remove and this is a perfect classic with cold AC so you would have to reinstall it no fun at all. Any thoughts?
Dave S

t walgamuth · #45 07-23-2005, 11:20 PM

definately squirt in some fairly thick motor oil. all the cranking has probably washed it all out and your seal is not as good as it should be. just keep the amount of oil under say, .5 cu in. to avoid hydrolock.

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