Engine randomly accelerates, but only on rear tank

John_piv

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Recently started running WMO in my 6.9 IDI. Truck ran like a top here for a while, but recently it started surging. I only put oil in the rear tank at about a 50/50 mix. While driving, the engine will randomly accelerate about 500 RPM before dropping back down, even on cruise. Switching to the front tank with pure diesel in it will solve the problem. I had originally thought that my WMO mix was too high, so I added some more diesel to the rear tank; to no avail. Some people say it sounds like air intrusion or a clogged filter, but I'd imagine that would have the same surging problem for both tanks right?

Any ideas on what I should check for / look for? Thanks!
 

Nero

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Sounds like you might have air intrusion on the rear tank. Check the lines for damage or leaks.
 

chillman88

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It's very possible the thicker viscosity of the oil is causing an air leak you wouldn't otherwise notice. My first thought would be the o rings in the quick disconnects on the sending unit.
 

Jesus Freak

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In my almost 2yr WMO experiment, the one thing I've determined is that you have to go over the fuel system from the tank to the engine. You don't need to replace the IP but I'd replace the mechanical fuel pump pretty soon. But the other guys are right your sucking air. I run @90% oil, but my system is TIGHT. If you look up my thread "Jesus Freaks WMO tow truck" and "Jesus Freaks WMO thread" there's my information and a handful of contributions from @kbenz and @NeverHave-I-Ether and @u2slow and several other guys....... there's also the nay sayers, but there's always the nay sayers.
 

John_piv

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It's very possible the thicker viscosity of the oil is causing an air leak you wouldn't otherwise notice. My first thought would be the o rings in the quick disconnects on the sending unit.
I did just recently pull the fuel tank selector valve to check it. Maybe I don't have the rear tank on all the way. On the other hand, the oil is use is from a farm, so the weight varies from 0-20w to 80-90w; so viscosity could also be to blame.
 

Jesus Freak

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I'm in NW Florida, I've ran 100% oil, so viscosity is a factor. The factory fuel selector valve is a pretty weak link.
I did just recently pull the fuel tank selector valve to check it. Maybe I don't have the rear tank on all the way. On the other hand, the oil is use is from a farm, so the weight varies from 0-20w to 80-90w; so viscosity could also be to blame.
Make sure you're filtering good, and keep some spare filters and a gallon of diesel to fill them up. You're going to sit on side of the road from time to time until you figure it out.
 

John_piv

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I'm in NW Florida, I've ran 100% oil, so viscosity is a factor. The factory fuel selector valve is a pretty weak link.

Make sure you're filtering good, and keep some spare filters and a gallon of diesel to fill them up. You're going to sit on side of the road from time to time until you figure it out.
I'm actually in central FL. I was banking on the warmer temps helping with viscosity. I keep the front tank full of just diesel, but it probably wouldn't hurt to keep some spare filters on hand. First priority is going to be to check my selector connections, but I appreciate the feedback!
 

Jesus Freak

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Once your system is set up and you have worked out the kinks, you will be able to run a 90 to 100 oil percentage all year down there. There's a thread about comparing single tank to a 2 tank system by @AcIdBuRn02ZTS he's got a sweet set up for eliminating the electric valve and doing manual 3way valves. It's kinda what I did.
 

chillman88

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I did just recently pull the fuel tank selector valve to check it. Maybe I don't have the rear tank on all the way. On the other hand, the oil is use is from a farm, so the weight varies from 0-20w to 80-90w; so viscosity could also be to blame.

My point being that it takes more pull to suck the oil through the lines than it would regular diesel. Extra suction will be more likely to pull air in through a potential weak point. Flip it around and think of it like pressure, something that doesn't leak at 5psi might leak at 20psi. Same basic principle.
 

Jesus Freak

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My point being that it takes more pull to suck the oil through the lines than it would regular diesel. Extra suction will be more likely to pull air in through a potential weak point. Flip it around and think of it like pressure, something that doesn't leak at 5psi might leak at 20psi. Same basic principle.
Chillman is right on.
 

Ferdy Mint

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I ran 50% SVO for years in France. Hard core WVO, WMO, and SVO guys over there swear by heaters in the fuel circuit. I didn't see any mention of that. Some heat the alternative oil tank too, run on diesel for a while until the waste oil tank heats up. FYI

Fun fact: Socialist France puts guys in jail for selling bulk SVO. You vote your way in, but have to shoot your way out.
 

Jesus Freak

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I ran 50% SVO for years in France. Hard core WVO, WMO, and SVO guys over there swear by heaters in the fuel circuit. I didn't see any mention of that. Some heat the alternative oil tank too, run on diesel for a while until the waste oil tank heats up. FYI

Fun fact: Socialist France puts guys in jail for selling bulk SVO. You vote your way in, but have to shoot your way out.
I've tried my best to get some local people interested in the WMO, maybe we could invest in a "community cenerfuge" or anything, just work together. But everyone stares at me like I'm an alien when I explain that my truck runs on waste oil........I think they're the weirdos.....
 

Ferdy Mint

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Let's face it, we really are aliens in this disposable, fallen culture. With our 30-40 year noisy old trucks that will survive an EMP or Carrington event. I'd feed 50 liters into my HDJ80 in a French supermarket parking lot so I could use their dumpster. Imagine the looks I got.
 

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