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Discussion Starter #1
My '93 6.5 5-speed is barely running now that we've had over a week of temps between -18 and +10 F. This is my first full winter with a diesel truck, so I'm looking for guidance. Hope I haven't done anything dumb.


Truck started losing power this last Monday, and stalled once. On Tuesday, I limped home with less & less power and speed on my 23-mile commute that night with temp around 5 degrees. If I kept the revs up around 2500 RPM, I could keep rolling but felt like it'd stall out if I didn't feather the throttle. 45-50 MPH max in 4th gear. No acceleration or torque. It was going in for an oil change the next day so I had the garage change the fuel filter as a first step. It sat for a couple of days, then they kept it inside overnight last night before changing oil and filter. I picked it up tonight cold, with temp. around 10 degrees. I cycled the glow plugs twice and it started OK, running a little rough but smoothing out. After 4 - 5 minute warm-up, I started home. Again, no power. Needed creeper gear to get the truck moving. It stalled a couple of times. I warmed it up for 10 more minutes and limped home, with some power but not much. Does this sound like gelling in the tank or lines?


The big unknown to seems to be fuel. I was running biodiesel over the summer into the fall, with no apparent problems. At the beginning of December, I'd switched over to around 50% biodiesel / 50% regular fuel, plus Power Service Arctic Express. By late December, I'd gone to 100% regular diesel, with additives. During this time I'd had the "Water in Fuel" light come on about 6 to 8 times. Each time that happened, I drained the fuel system with the water valve at the front of the engine. I've kept the tank full and changed the fuel filter once in December. The truck ran OK until the cold weather hit the Northeast. I'm wondering if I have mystery gunk in the bottom of my tank that's causing problems. Any remaining biodiesel (or petro-diesel sludge) that didn't mix into the fuel would be at the bottom of the tank because it's heavier than regular diesel. Is the truck's fuel pickup at the bottom of the tank or is it a floating pickup? Could it be something else?


What do you suggest?


John
 

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King Nuzz


I just got my 95 Burb 6.5 back yesterday from the shop and, I had a similar problem as you describe. In my case it was an oil pressure switch that enables the lifter pump and, fuel that was jelling up on me. This took me by surprise as this is my 5th winter with no prior fuel jelling problems. Have the fuel checked to see if it's winter graded. example; Summer fuel will normally read 30 on the instrument. (it's a glass gage affair, much like the ones you use to take a reading on your battery..but, not the one~!) Proper winterized fuel will read between 39 to 44 on the instrument. A note here: I mixed my fuel yesterday with 50/50 K1 with diesel plus poured in some anti-jelling mixture. So far it's running like a top~! There could be other causes for your problem besides the o/p switch..I wish you luck~!


ciao
 

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KN,


Change fuel filt again, cold weather and cold bio fuel residue may be clogging it to point of restriction, from what I've read on topic of biofuel I think it needs heated fuel to run best. I'd change fuel filt 1st then if you still have trouble start troubleshooting fuel lift pump circuit. My truck had similar symptoms on a partially blocked filt, limped under load.


On re-read of your post youv'e changed filt once since problem started, I've no experience with bio-fuel does it sludge in winter, put a gauge on the fuel filt drain line with the truck at idle should be 4-6 psi, hiway speed should be 3-4 psi, under heavy load may drop to 2, if lower than that either the lift pump has a problem or power to the pumps. I also don't know if residual biofuel lowers gelling point of fuel. IIRC Diesel starts waxing @ 60F I don't know if bio changes this. Does the 93 have a heater in it's fuel filt. bowl the 98 does may be a problem there.Edited by: Turbine Doc
 

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Discussion Starter #4
Thanks Towner7 & Turbine Doc.


I think I'm going to get the tank and fuel lines cleaned out as a baseline before checking the lift pump. The biodiesel can lower the gel point bigtime if it's not mixing well with the regular diesel; Bio on its own gels solid around 32 F. I suspect the diesel / bio mix settles into layers enough if the truck isn't driven constantly and the fuel mix circulated and kept warm. I don't know how much heat the truck puts into the fuel as it recirculates it, or if the fuel filter has a heater. [TD: How does the fuel filter heater on the '98 work and where is it?] With the cooling upgrades I had done, the truck runs cool; temp. gage stays around 160 degrees. This may contribute to the situation.


Also, additives and kero may not penetrate or dissolve gelled bio when it's really cold. Think it's safe to say that the fuel at the fuel pickup is not winter grade at this point....
 

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KN


heater element located in base of fuel manager/filter bowl energizes when sensor in bowl sees temp < 46F (8C) for your problems though I don't think you are getting fuel to or through the filter
 

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Hi King Nuzz,


I too used to have a 93 6.5 and it was a good motor ran it all the time with no pump or injector problems.


It's easy to check if your lift pump is working just crawl under and touch it when motor is running you will feel if it's pumping or not.


I had mine go bad twice on me in ten years. The truck will still run but you will feel the loss of power.


And I dont believe there is a fuel heater in the 93's and I don't think the fuel recirculates so it stays cold all the time.


Maybe your biodiesel is causing you problems, if none of the additives will clean it out, personally I like Standadyne additives, you might have to drain the tank completely to clean it out. Either undo the fuel line at the lift pump and turn it on so it pumps the tank dry or drop the tank all together to clean it out better.


And although mixing some kerosene with diesl is ok. Mixing a lot is no good because kerosene dosent do well at lubricating the pumps and injectors like diesel does. Better stick with the additives.


Good luck and try to get the truck in a heated garage overnight till it warms up well and then try driving it and see if the problem comes back or not.


Bye Diesel Dragon
 

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Discussion Starter #7
Took the truck in last Thursday night to get the fuel tank & lines cleaned out for a fresh start. Ambient temp was around 20 degrees. Truck started right up and ran fine. I think the lift pump is OK, but will check it. I'm looking into adding a coolant-loop fuel tank heater, like they use for big trucks. [See my post under the Biodiesel forum here.] This should offset the gelling problems that additives and kerosine couldn't fix when the temp got and stayed below zero. I'm figuring that biodiesel raises the temp threshold for "artic conditions" equipment to around zero. I don't have a warm garage to put the truck in, so have to bring the heat to the truck. If the frost-plug heater does not put enough heat into the coolant, I'll try adding a canister coolant heater.


Anyone here have experience with coolant-loop fuel tank heaters on light trucks?


KN
 

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If you want to run mixed diesels in the winter perhaps you should pass your fuel line through a heater before the lift pump. Also if you add solvents and stablerizers to the mix it should help. I mix diesel,biodiesel,kero and a cetane addative(total 25 gal.) then to that I add 2 gallons Ethanol and 1 liter THF(solvent) mixed. This runs hot and shouldn't gel due to the solvents. your power restriction is because your injector system can't move the higher viscosity fuel, mixing solvents/jelling agents lowers viscosity, improves flowability. lubricity shouldn't be a factor at 2%biodiesel or higher.
 
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