300td cold compression check - Page 2 - PeachParts Mercedes-Benz Forum

riethoven · #16 02-12-2007, 02:55 PM

I never saw what year the car is but saw you replaced 5 glow plugs so it must be a 1978-1985 chassis W123 with an OM617 turbo or non turbo motor depending on what year the car is.

These engines are some of the best engines ever made. Because they last so long there are many out there that have outlasted the chassis they came in. You should be able to find a used car with a good engine for under $1,000. At this point you have nothing to lose so check the compression again and see if it came up. Although the initial test is really low. Keep in mind that you need another engine out of a wagon because of the auto leveling suspension, or you will have to swap heads with the replacement engine if it is out of a sedan or coupe.

If you are in it for the long haul with this car, spring for the factory service manual. It is on 2 CDs and goes for $19.95 from MB plus freight.

Johnhef · #17 02-12-2007, 02:55 PM

if you dont have a good battery and thin oil in it, do that first.

vstech · #18 02-12-2007, 04:13 PM

Quote:

Originally Posted by guru

the update...
soaked it a week and adjusted the valves, they were waay off, and I now get a smoky shaky sputter. still will not start. I haven't checked the compression since soak and valve adjust. Getting discouraged and spoke to a few people who said that motor is very hard to find and $5000 to rebuild. ouch

anyone know any details on pull starting this beast?

sounds better. how cold is it where you are? is the block heater working? does the motor crank quickly or does it sound like it's dragging? now that the valves are up to par, redo the comp check, and report the numbers. if it is still below 250 or so, it's not going to start until it warms up.
basically, a pull start is you get it on the road behind someone pulling the car with a tow vehicle, preferably a pickup or something heavier than your car. have the Key in glow position and the shifter in N, when you get the car above 15 or so, drop the thing in low, and let the motor crank. give the throttle about 1/4 pressure, and she should fire up soon. if it will not fire after about 1 mile, it probably will not fire. Keep the car under 30 mph.
John

guru · #19 02-12-2007, 04:48 PM

its a 1980 300td (non-turbo).
block heater works well, motor feels like 90 degrees F currently 60 degrees F outside in San Francisco.
I'll report new compression #s asap
thanks for the encouragement...

barry123400 · #20 02-12-2007, 08:51 PM

Do not loose the faith yet. I think it will fire off with the tow. Good used engine prices and availability just depend on where you live and how you go about it. A useless car or wreck with a good engine might be had pretty cheap.

t walgamuth · #21 02-12-2007, 11:11 PM

i wouldn't put thin oil in it.

use the 30w or 15w40 rotella adn get it started by pulling it. drive it around for a couple of hours at least and see if it will start back up.

the non turbo 617 is about indestructable and unless it has been run with very dirty oil it is probably not worn out.

good luck

tom w

guru · #22 02-12-2007, 11:49 PM

checked the compression after a while with the block heater plugged in, 4/5 cylinders up to 300 lbs/inch, the other is 180 dry and 220 with oil down the glow plug. That is with all glow plugs removed. This is up from 150-170 for all 5! Still shaking, and sputtering and seems close to starting after 6 cycles of the plugs. I'll tow start it per the owners manual. and drive her a fair bit if/ when she fires.

one question, After bleeding the fuel lines, I'm curious how much fuel is normal to come out of fuel lines at the injector. I'm getting a dribble but not the spray I expect. I'll update as events progress.
thanks,
Matt

barry123400 · #23 02-13-2007, 12:21 AM

Since the amount of fuel actually injected into the engine is almost nil for practical purposes per stroke do not expect much out of a backed off line connection. Some people possibly expect squirts. I would not want to guess how many strokes of the pump it would take to process an ounce of fuel but it would be up there.
It sounds like you have enough compression to start now except the cylinders are probably fouled pretty bad. Certainly enough compression exists to easily start with a pull tow. Thats if there is not something else wrong of course and there probably is not.
It does really look like your soak down has done some real good. hopefully it has been the solvent oil or do you have another explanation. How far where those valves out of adjustment for example? You at least give me faith that these situations are reversable now. I was not sure of how difficult the coking would be to overcome.
I also hope driving and another soak if required is going to get you a serviceable engine out of this. I am also not there but I would run the engine for a few hours and check the compression of the weak cylinder especially. If it is coming up in compression just drive more. If it wants to stay down I would intensly re soak only that cylinder as long as the others are above 300 lbs.
I personally thank you for continuing to post on your thread. You are developing the background material for dealing with a situation that I suspect is going to come up more in the future. . Great going.
Also consider putting marvel oil into the tank after you get it running and it is going to run. Thats only if you are a believer in the stuff of course.

I feel it might aid in cleaning out the prechamber area at least. Someone quoted a quart a tank.
I fully expect to be looking for suggestions for my engine from you before too much longer now. I also would warm the block up with the block heater before the tow as well. I think you have already thought of that.

guru · #24 02-13-2007, 01:02 AM

I'll be glad if this helps you and others down the line, I'm sure grateful for the advice that has gotten me this far.

I can only attribute the change in compression to the Marvel oil, the valve adjustment and the 25+ gain in temp from the block heater. I'm told ATF can achieveve similar results as MMO. I keep hearing stories of "stuck" motors or "left for dead" motors being brought back with patience and a cleansing. Many years ago a buddy dropped a stuck turbo charger in a carb tank for a few days, it worked perfectly afterwards.

ATF and Marvel look the same but MMO smells like it has a minty freshness... (and it leaves my moter running minty fresh) It does not list any special ingredients on the bottle.

I have long ago pledged to name her the Marvel Mystery Mobile if this works, sounds better than ATF anyway.

vstech · #25 02-13-2007, 09:50 AM

Quote:

Originally Posted by guru

checked the compression after a while with the block heater plugged in, 4/5 cylinders up to 300 lbs/inch, the other is 180 dry and 220 with oil down the glow plug. That is with all glow plugs removed. This is up from 150-170 for all 5! Still shaking, and sputtering and seems close to starting after 6 cycles of the plugs. I'll tow start it per the owners manual. and drive her a fair bit if/ when she fires.

one question, After bleeding the fuel lines, I'm curious how much fuel is normal to come out of fuel lines at the injector. I'm getting a dribble but not the spray I expect. I'll update as events progress.
thanks,
Matt

uht oh... I have tested many injectors on my cars, and they all spray pretty good during cranking... if yours are just dribbling, test them all. if all are just dribbling, you may have an IP problem... but to be sure, make sure all filters have good fuel flow through them. and a plugged tank screen can cause this too. do you have access to a parts car to swap some injectors from it? perhaps a junk yard? (sometimes I wonder about my yard

)
keep us posted.
John

guru · #26 03-04-2007, 04:29 AM

I replaced the SLS hose with a hose made by a heavy equipment shop in SoSF and filled res with febi fluid like a good boy should. No leaks.

Pulled the wagon all around the neighborhood, through multiple stop signs, with a buddy blocking intersections on a motorcyle, but failed to get her started. SFPD cruiser didn't seem to care. Towed it as per manual but it never spun the motor. Key on II, shifted to D S and L and it all felt like neutral. Tried it a number of times to no avail 20 mph up to 35 without engaging the motor WTF? Slight vibration felt at shifter, automatic of course, ATF shows full on dipstick, But it never engaged the motor. later tried cranking the starter and verrrry close to starting but still no go.

What am I missing?

barry123400 · #27 03-04-2007, 11:58 AM

I have a couple of ideals on how to try to start it but would preffer for you to wait a little and see if better are available. Sorry the pull start did not work as the manual says it should but perhaps not many have tried it.That was useful information that it does not always work at spinning the engine up. I suspect for whatever reason your speed was not high enough by the way. Yet I could not feel comforatable with much higher speed myself unless perhaps anchored to a tow truck front wheel dolly.
Well time to list some of my desperate ploys for consideration. First would be to separate the starter circuit and apply 24 volts to the starter with two good batteries. Most starters will take this abuse but no garantees. Another would be to get the block and head as hot as possible by sharing the cooling circuit with another car. Or any other method you can think of to get the block temperature above 150 degrees. Disable your glow plugs and try a touch of ether. Again this is not a recommended approach but you are approaching desperation. You do seem to now have enough compression to start so if all else is well it should go.
I only hope the last owner did not hurt the injection pump with his unheated vegatable oil but if all injector lines are producing output it is probably okay.
We want to hear this engine run as well. Just stay safety minded. . I think the engine would have started normally unless there is another issue. Your issue might just be badly fouled cylinders that need cleared out by the first start.

240Joe · #28 03-04-2007, 12:12 PM

You never had a compression issue. The guy said it was running fine after he went back to dino diesel. What on Earth would make you think compression would drop all of a sudden? Forget compression testing.

You have a fuel issue. Simple as that.

240Joe

kerry · #29 03-04-2007, 12:28 PM

Try an alternative fuel source. Using a soda bottle filled with diesel or diesel purge, put one line to the primary filter and stick the return line in the bottle. This will rule out any fuel problems from the engine back to the tank. You should get a pretty good flow from the fuel return hose backinto the bottle.

barry123400 · #30 03-04-2007, 01:23 PM

This car like one of mine was on unheated vegatable oil. The one I purchased not running obviously has stuck rings. We had quite a time to get it started. Evidence the previous owner had gone through several starters. It now has massive blowby and is a low milage car. I estimate if driven a few thousand miles more on unheated vegatable oil it would have no longer been capable of self start. Still have a gummed up /carbonized ring problem by the amount of blowby.
This gentleman does no longer have a big compression issue. He has modified that. Joe on this point you are right. His car now has enough to start. Yes he could have a fuel issue. I suspect the previous owner of it used the car until the last gasp. Vendors do tend to not always tell the truth. I just want to hear that he has got his engine running again.