Heated WVO system run on diesel - PeachParts Mercedes-Benz Forum

Skinflint · #1 03-20-2013, 01:41 PM

Hey all, longtime reader, first time poster.

Question re: heated WVO setup on straight diesel.

I have a 350SD with a single tank WVO setup. Aux pusher fuel pump at the base of the tank, and a hose-in-hose 3/8 fuel line heating the fuel from the tank to the engine bay. I've plumbed the fuel line into the fuel heat exchanger already on the engine, bypassing the fuel thermostat, and then through a vegetherm inline "stick" heater prior to the lift pump/injection pump. I also keep the return looped.

I recently installed a rebuilt injection pump, lift pump, turbo, injection hard lines, and glow plugs. At the same time, I had all the injectors bench tested. They were all right according to the mechanic that did the work, and re-installed.

I was out of town and ran low on WVO and added diesel to the tank.

About the same time, I started having an issue in which the car idled very rough--seems like a cylinder isnt' firing at low rpm--and putting out pretty significant white smoke at idle. Once you convince the engine to rev past 2000 rpm, it seems normal, with normal power and no smoke, although getting there is a real challenge. It starts cold, if you crank it with your foot to the floor, but if you let it stall hot it won't refire until it cools down.

Filters are all clear. I even took the tank out and cleaned it--including the "pot" in it and the screen in the pickup.

I've always heard white smoke was indicative of fuel starvation.

Any thoughts what I'm looking at? Injectors? Faulty Injection Pump? Did perhaps running the heated diesel through the system cause damage through lack of lubricity?

I can't point to a direct cause and effect with the addition of diesel to the tank--don't really remember what happened when, and the symptoms came and went a couple times...

Would love to hear your thoughts.

Should add I live in south Florida--heat isn't a huge issue. 50k plus miles on WVO--no idea how many miles on the car--well over 250k minimum.

Thanks
Nathan

ytmtnman · #2 03-20-2013, 08:58 PM

Is it overheating?
Worst case scenario: 350SDL Engine Problems

GregMN · #3 03-20-2013, 08:58 PM

Start with a compression test. Report the results.

The next time it will not start "hot", pour a gallon of water on the injection pump to cool it down. Report back if that helped or not.

Without that information, anything you do could be a waste of time and money.

Skinflint · #4 03-20-2013, 11:11 PM

At the mechanic's place. I ran out of my wife's patience for spending time in the garage working on the thing. I'll report the findings. I have the cylinder pressure test numbers from a couple years back somewhere to compare with. And no--it's not overheating.

Only problem with the mechanic is he's slow as molasses, so it might take a few days.

And thanks for linking me to the rod bender thread. I am aware of those issues, but not terribly concerned with them because a) I am not using any appreciable oil between changes, b) there's no real pressure blowback if you take off the oil fill cap, and c) the diesel knocking is not noticeably louder. But time will tell.

Nathan

Phillytwotank · #5 03-21-2013, 07:20 AM

Running hot diesel is not good but I don't think that it could cause problems in such a short time.

fender_bender · #6 03-21-2013, 08:41 AM

Quote:

Originally Posted by Skinflint

I ran out of my wife's patience for spending time in the garage working on the thing.

This made me laugh for some reason.

Skinflint · #7 03-21-2013, 04:44 PM

Quote:

Originally Posted by fender_bender

This made me laugh for some reason.

Yeah. Wish my wife felt the same way!

Skinflint · #8 03-27-2013, 03:52 PM

For those of you who posted, please know I will update with info as to what went wrong--when my mechanic gets around to figuring it out...%@!#*^!

Skinflint · #9 03-28-2013, 12:22 PM

Ok. Well. Bad news--one of the cylinders is checking in at just over 200psi.

Not sure if it's rings or valves...

So...short of rebuilding the engine, or buying a rebuilt 603...what can I try? I am short on time AND money for the next six months--building an addition on the house.

Soak the cylinders with MMO?

Mist some water into the intake tube while running?

Add some Sea Foam to the crank case oil?

Any thoughts appreciated.

GregMN · #10 03-28-2013, 01:52 PM

Cheap water injection system may loosen the rings and bring back the compression. I helped my SIL do this to a '95 W124 with a 606 to bring it back from the dead.

Water Injection for cleaning

The injectors will spray 160 degree F WVO in the same pattern as diesel.
Cold WVO will dribble out, get on the piston and cylinder walls, down into the rings and carbonize the rings to their grooves in the piston. When I encounter this, I have to use a hammer and chisel to get them out, in pieces.

I have never had this happen on one of the WVO powered vehicles that I own and operate.

Starting on cold WVO, as single tank systems do, the injectors are not spraying a good pattern until the engine/fuel is warmed up. Not purging a 2 tank system will have the same effect. Depending on the number of cold starts, a single tank, unblended, WVO system can last for years before damage is terminal. In your case, it seems about 50k miles.

It is possible that a cheap water injection system used periodically would mitigate any problems caused by injecting cold WVO. But, as you can guess, I prefer a 2 tank system for the long haul.

Good luck. If you try water injection, please report back with the results.

Skinflint · #11 03-28-2013, 05:09 PM

Will do. Assuming the rings didn't break, perhaps something simple will give me a few more miles.

If it doesn't work, I'll either a) sell the car as a parts car or b) hold onto it for a year and then find someone to rebuild the engine and add a second tank and move to a two tank system.

Have a buddy with a 2001 F350 that does cross country hauling. He's run a two tank system on his rig for years, and has never had a problem resulting from running oil other than the inevitable clogged filter from time to time.

Any other thoughts?

Phillytwotank · #12 03-28-2013, 07:08 PM

Quote:

Originally Posted by Skinflint

I recently installed a rebuilt injection pump, lift pump, turbo, injection hard lines, and glow plugs. At the same time, I had all the injectors bench tested. They were all right according to the mechanic that did the work, and re-installed.

doing many jobs at the same time like this makes it harder to isolate what could be wrong to one particular system or component.

when ever some thing crops up in my benz i always use the last job performed as a starting point in diagnosis. seem like you have done a lot of "big" projects recently and that can open up the door for problems to arise.

injectors, GPs, turbo, lift pump, IP... anything off with any of those individual things could cause you some trouble.

GregMN · #13 03-28-2013, 07:47 PM

Quote:

Originally Posted by Skinflint

It starts cold, if you crank it with your foot to the floor, but if you let it stall hot it won't refire until it cools down.

I had a similar problem that was diagnosed by pouring water on the IP when it was up to temp: MB 2.2 will not re-start when warm - Forums

So you have one cylinder with low compression. Hopefully water injection will fix that. If you still have the no-restart when warm, see if cooling the IP helps this issue.

Let me know if you are going to sell it for parts.

Skinflint · #14 03-29-2013, 10:53 AM

Quote:

Originally Posted by GregMN

So you have one cylinder with low compression. Hopefully water injection will fix that. If you still have the no-restart when warm, see if cooling the IP helps this issue.

Let me know if you are going to sell it for parts.

Greg,

Trying to diagnose the effectiveness of water injection without spending the $200+ on an actual injection system...Having seen them installed but never actually handled one, can you tell me via rough comparison how much water is injected? For instance, I have garden misters on my biodiesel processor for mist washing--more water volume or less? I have a steamer--If I inserted the steam probe in the intake post turbo would it be enough fluid to make a significant difference in your opinion? Or should I actually use a mister?

Definitely going to try cooling the IP--hopefully after I have flushed out enough carbon via water injection to get the cylinder firing again...

If I decide to let it go for parts, I'll let you know.

Thanks for all y'all's advice. Appreciate you.

GregMN · #15 03-29-2013, 12:47 PM

The nozzle costs about $6. One of your misting nozzles might work.
Then you need a 12v pump that will push the water at about 50psi.
The hose I used is cheap polly, a few cents a foot.
I used the windshield washer tank. I stopped every 20 minutes to refill.
The wiring was all temp. with a cig. lighter plug on then end. I ran the wires out the hood and in the door.

RV water pumps are 12v and have enough pressure. If you can scrounge this part, the rest of it is almost free.

This is not for a permanent install, just one day temporary. After running 4 to 8 gallons through it, it is either getting better or it's not.