Doesnt start on Deisel but dies on WVO???

[NC Benz]

**EDIT** Dies was supposed to be DOES. My typing skills SUCK.

OK riddle me this batman.......

We run WVO during the summer on our 300Ds. They run just fine, combined have put on about 30,000 on wvo.

During the winter, we change over to diesel. No surprise here.

But we find when we are straight diesel, we cannot start one of the 300s, and the other one starts hard.

The one that doesnt start doesnt even fire at all. I have changed out filters, did a valve adjustment on both. Changed out bad glow plugs, changed out a few return fuel lines that were leaking...

With the one that doesnt fire, when we go out and buy a bottle of Canola oil and put it in. After a little priming, the car starts up.

One would think with the much lower flash point of diesel, compared to canoloa oil, that the diesel would start in a (eh hem) flash. But it appears both cars like to have a little oil in them to run well or even start.

Is this strange or what?

[Astroman]

I've seen this problem a couple times before, and what it indicates is worn out plungers in the injection pump. The more viscous VO helps seal between the plungers and the barrels in the IP, but the much thinner diesel doesn't and really exposes the problem, especially when the engine is hot and it's even thinner. This is why adding in the VO to the mix and priming it up helps solve the problem. The result is that due to the "blow by" in the IP, you're not getting much fuel into the cylinder. Probably doesn't even blow any smoke or unburnt fuel when cranking. When it does start, the higher rpm masks the problem, just like low compression in the engine cylinders.
I won't speculate as to the cause of the wear, but inadequately filtered fuel (whatever that fuel may be) and/or water can and has done it.
Swap the IP on the problem car with one from the yard, and scrutinize for air leaks in the system.

[NC Benz]

Originally Posted by Astroman

I've seen this problem a couple times before, and what it indicates is worn out plungers in the injection pump. The more viscous VO helps seal between the plungers and the barrels in the IP, but the much thinner diesel doesn't and really exposes the problem, especially when the engine is hot and it's even thinner. This is why adding in the VO to the mix and priming it up helps solve the problem. The result is that due to the "blow by" in the IP, you're not getting much fuel into the cylinder. Probably doesn't even blow any smoke or unburnt fuel when cranking. When it does start, the higher rpm masks the problem, just like low compression in the engine cylinders.
I won't speculate as to the cause of the wear, but inadequately filtered fuel (whatever that fuel may be) and/or water can and has done it.
Swap the IP on the problem car with one from the yard, and scrutinize for air leaks in the system.

We actually have a problem with the RPM being LOWER, where we need to keep our foot on the accelerator until it warms up.

I am still barking up the air leaks tree with this too.

[Biodiesel300TD]

Have you cleaned the tank strainer? If you can run on a bottle of VO but not the diesel from your tank, the only thing different other than that fuels themselves is the tank strainer.

[Astroman]

He has to mix in a bottle of VO and prime to get it to start. He's not running from the separate VO bottle.

[Astroman]

Originally Posted by NC Benz

We actually have a problem with the RPM being LOWER, where we need to keep our foot on the accelerator until it warms up.

I am still barking up the air leaks tree with this too.

Right, until the car warms up enough for the idle to be high enough. I stand by my diagnosis.

[NC Benz]

Originally Posted by Biodiesel300TD

Have you cleaned the tank strainer? If you can run on a bottle of VO but not the diesel from your tank, the only thing different other than that fuels themselves is the tank strainer.

Pulled the tank strainer. It was spotless.

[NC Benz]

Originally Posted by Astroman

Right, until the car warms up enough for the idle to be high enough. I stand by my diagnosis.

The only problem is that it will start WARM on Diesel. It will not start COLD with diesel. But will start cold when we add a little VO.

Wouldnt that negate the plunger issue then?

Just to make sure.... I am NOT arguing, just trying to understand.

[turbobenz]

I agree to the second poster, you probably destroyed your plungers with the VO.




Or your timings off and the slower combustion or flash point gets it started

[jross]

Your symptoms are pretty close to what happened with my car when the IP burned out because of WVO (whoever did the install before I bought it didn't install a sufficient WVO heater).

Bummer, man. The good news is IPs are pretty easy to do if you don't mind getting a bit oily. The hard part is finding one that doesn't cost an arm and a leg...

[Astroman]

Have you tried just priming the heck out of it before you attempt the first cold start? Just on plain diesel fuel, prime it like crazy, then try starting. The only other thing I can think of is air leaks in the system. Then when that doesn't work, replace the IP..

[NC Benz]

I am able to finalize this issue.

It turned out it was not the plunger, but it was a hairline crack on one of the return lines that was sucking in air. Once it was found and replace (we replaced all of the lines) it started just fine.

[Alastair]

Originally Posted by jross

Your symptoms are pretty close to what happened with my car when the IP burned out because of WVO (whoever did the install before I bought it didn't install a sufficient WVO heater).
leg...

Nah, Heat-Exchangers or the Lack of them will NOT cause issues with the pump when using veggy-oil...

What does, is cruddy, dirty, moisture laden, FFA Loaded, over-used and poorly prepared Used/Waste Vegetable-oil, or WVO....

The biggest killer in Used VO is the Moisture which Cant be filtered out and the second is the FFA which turns the moisture Acidic...

(FFA is, Free-Fatty-Acid. This is an oil just like the veggy its dissolved in. It Cannot be Filtered out. It is not a heavier component like fats)

Leaving the WVO to stand will NOT remove all the moisture from it. It MUST be Dried Properly, by heating up to 120 deg C with lots of air contact regardless of what others say....

The metal of the elements (plunger/barrel assy.) inside the pump is hardened Steel. Acidic moisture in WVO just Loves to munch on those precision parts making them a dull grey 'pickled' appearance and increasing clearances. They are normally a Mirror-finish, just like the needles of new injectors....

My Diag, FWIW is the I.P. Elements destroyed by cruddy, and damp WVO.....

[WD8CDH]

Originally Posted by turbobenz

I agree to the second poster, you probably destroyed your plungers with the VO.

More likely, you damaged your IP with water. VO lubricates better than diesel.

How are you de-wattering your oil?