617 Engine- Strange Combination of Problems

[aldaeron]

I have a 1980 300TD Wagon with the 617 engine (non-turbo).

While I have been researching some of the problems I am having on the forums, I am posting just in case these three problems have some overlapping single fix.

My three problems are:

1) It does not start easily. It requires quite a bit of cranking (2-3 thirty second cranking sessions at full throttle). When it finally starts there is a large cloud of black smoke.
2) The engine temperature is significantly hotter. It is typically at 60-80 C and now it at 100+ C after 15 ish minutes of driving
3) The transmission shifts very late and very hard.

Some vehicle history (it is a little hazy - I got married 2 weeks ago and the Benz has been sitting for a little while)

I have been running the car on SVO. This is clean, new (expensive) Soybean oil from Costco. When it first was having trouble starting, I filled it up with Dino diesel. I estimate the tank still has ~ 25% SVO.

I live in Colorado. The summer was nice and hot and it has cooled down a bit recently. I don't think it is enough to affect starting the car.

I have done an "Italian Tune Up" within the past 6 months with 2 cans of Lubro Moly.

I have a number of filters in place for the SVO. They are all new.

The oil and filter were changed recently and the oil level is ok.

I had a local diesel shop do my valves about 3 years ago, but only 1500 driving miles ago. They also adjusted my transmission to make it shift smoother. I am hoping to not have to pay them for their expertise again.

I have a rear boost pump and heater to help with the SVO. (https://**************.com/node/2133 & https://**************.com/node/6310)

The glow plugs are new and the chamber were reamed with https://**************.com/node/2842. After replacing them the car was still running fine.

Around the time things started going downhill I made a few upgrades that I believe may have caused my problems:

1) I replaced the two fuel lines that attach to the fuel filter housing. One is from the manual lift pump to the fuel filter and the other is from the fuel filter to the injection pump. I also replaced the stock manual lift pump with a beefier metal one (https://**************.com/node/4773). I did not change the soft washers when I changed these components. I did not over tighten them - I was carefully increasing the torque with a crow's foot wrench until the leaking stopped. I fear that dirt may have gotten into the fuel line. I have seen other postings for cleaning the filter and pressure relief spring in the injection pump so I will look into that next. I have a CD with all the original factory manuals so I hope I find the correct procedure in there.

2) I was worried that the water pump belt was slipping so I checked the belts. Turned out the compressor belt was missing! I replaced and tightened all three belts per the manual. Like many old W123s I have a fault Climate Control Module. It is next on my list! I fear that the compressor/climate circuit may be causing some starting or overheating issues.

I am also aware that tight valves can cause difficulty starting so I am adding that to the list as well.

Thanks for reading such a long post. I appreciate any advice. The car was really working great about 2 months ago and I miss driving it.

-matto-

[t walgamuth]

Sounds like non operating glow plugs to me.

[sixto]

2) Could be a lazy thermostat. It should go to 80*C within a few miles and stay above 80*C. Seems like it's stuck partially open delaying reaching operating temperature but not opening enough to allow proper flow under load. Are you using SVO as coolant as well?

For kicks, remove one injector and have it tested for opening pressure and spray pattern. That will tell you if you're heating the SVO to an acceptable temperature.

Sixto
87 300D

[aldaeron]

Thanks for the super quick response!!!!

I am using regular coolant.

I have special injectors from Elsbett designed specifically for SVO and they were working beautifully. I have not had any problems

I have noticed the Glow Plug light does not go on at all. The plugs are new, but perhaps the wiring or circuit is faulty. I will look into that.

Also I was unaware that this forum blocks URLs. The above links are all from ************** DOT com.

-matto-

[Zacharias]

If the glow light on the dash isn't coming on, that suggests your glow relay isn't functioning. No glow relay means no juice to the glowplugs.

Take off the cover on the relay and make sure the plug for the injector wiring harness is still in place. It would be possible that you yanked on it while doing other work on the car. If the plug is okay, make sure the metal strip fuse is intact. If these check out, then I would assume the relay has failed internally. They don't last forever.

Fix it as soon as possible, as you aren't doing any favours to your starter with all that cranking.

This forum is sponsored by PeachParts/PelicanParts. It blocks URLs to competing suppliers.

If by 'regular coolant' you mean prestone or the equivalent, you should plan to drain that out, flush the system then use either Mercedes coolant or Zerex G-05. Prestone isn't formulated for these cars.

[Stretch]

The three numbered problems in your first post do not seem to be connected.

For number one (as stated) check glow plugs

For number two (as stated) check coolant system - if you have a snazzy IR non contact thermometer these can help big time but even a thermocouple connected to a common DVM will help

For number three this is probably a vacuum related problem - do you have the vacuum only 722.118 transmission fitted?


Uhmmm what else?

Oh yeah

1) Welcome to the forum
2) Congratulations (for the wedding)

[aldaeron]

All,

Many thanks for the help!

Regarding coolant - appreciate the advice and specifics on the brands! I have not yet replaced it since I bought it. I am installing a coolant heater for my SVO so it will be changed soon!

The glow plug relay is shot there is a sizeable bulge where it melted. Unfortunately I have a 1980 with the large box relay (Mercedes PN 1235401545). They are hard to find and appear to all come from Mercedes for $450+ new. I have seen a kit where a BIG manual solenoid is used in place of the relay. Any thoughts about this MUCH CHEAPER option?

Thanks again!

-matto-

[Zacharias]

You can find that style of relay used, they are just in shorter supply than the later models. Someone else may disagree but I don't think you need to match that exact part number as long as it looks the same.

(As a matter of fact I have one, original Mercedes P/N 001 545 5332 sitting on the desk in front of me.) PM me if you want it, but I am in Canada so finding one stateside will be easier/cheaper for you, shipping wise.

Here is one new on eBay for $295 or best offer: http://www.ebay.ca/itm/OEM-Mercedes-W123-Preglow-Time-Relay-300SD-300TD-300CD-/290636200888?pt=Motors_Car_Truck_Parts_Accessories&hash=item43ab447bb8

As for the manual option you mention, I have that kit on my CD and it works very well, does take a bit of time to install versus just plugging in a replacement relay. If you have basic 12v electrical skills and understanding you can source the relay (or a similar unit) by itself at a decent auto supply store, or on eBay, and wire it up yourself. The relay used is just a Ford starter solenoid:
http://www.ebay.ca/itm/STARTER-SOLENOID-RELAY-Ford-Tractor-2000-3000-4000-2600-2610-3500-3550-3600-3610-/300727993946?pt=LH_DefaultDomain_0&hash=item4604c9065a

Whunter did a thread on conversion from the older style of glowplugs (not what you have) and it has info that will be useful if you go the complete DIY route:
Homemade: Loop to pencil style glow plug conversion

[Phil_F_NM]

If you're at all handy, you can install your own glow plug bypass using a switch rated for 60+ amps, some 8ga wire and splice/solder the high-amp supply to serve as the relay. The only issue is that you have to pay close attention to the time your glow plugs are on.

I used a tractor pull-starter rated for 80 amps and just spliced then soldered the high-amp lines to the ones going to the relay and the plugs, respectively.

If you have the big aluminum blox type relay, there is a possibility of fixing it. On mine, I had both 220 microFarad 16v capacitors heat up too hot when the relay gap stuck closed once and overheated the unit. The electrolyte in the capacitors melted out and I just soldered in new capacitors only an hour or so ago. I'll be reinstalling the relay on saturday and checking to see if it works properly. (The whole thing failed because the previous owner bypassed the 80amp fuse box and had the high-am glow plug supply wired directly to the relay. Had it been fused, I'd still have a good relay.)

Good luck!

Phil Forrest

[aldaeron]

Mine is melted on the side and there is a noticeable bulge where the plastic is melted thru. My guess is some major damage happened in there, most likely after I replaced my plugs. They were pretty dirty before and may have drawn less current. The ebay link above is the part I need, but $300 seems a bit steep.

I appreciate the offer for a new one, but personally I want something I can control especially because it gets cold in Colorado and I run SVO. I may want to leave the plugs on a bit longer.

I am pretty handy and already have an Arduino microprocessor on board. I was planning to wire in to the factory glow plug temp sensor and use a low level signal to drive the appropriate electronics to control the solenoid and heat it up.

My only question is how much does it matter what solenoid I use? My guess is any automotive one rated for 80A will work fine since 60-70A is drawn during normal use (per the Mercedes Manual). I would also add an 80A fuse. Any advice here is much appreciated.

-matto-

[aldaeron]

Also, I have been having trouble finding the current required to open a standard starter solenoid. I was going to use a low level signal to open a ?? Amp relay to open the Solenoid to get the plugs to start, but I am unsure what current the relay needs to source.

Thanks!

-matto-