For the forth of July weekend, my wife Ann and I decided to go camping outside of Asheville, NC. For the 800mile trip, I ran a batch of oil through my trusty Raw Power Centrifuge and filled up my 90Gallon tank. I had not been doing much driving lately and had a little less that a quarter of fuel in the diesel tank. As always, I brought along a light tool box however normaly it contains a replacement filter; I had used my last filter coming home from the Keys and had neglected to get a replacement. (ominous foreshadowing)

 

We hit the road out of Charleston, SC Thursday in the midst of the 5pm rush (as usual) but made good time to Spartanburg where we started for a quick dinner. Then things got interesting: When I started the, now hot, truck back up and flipped the veggie system back on. The veggie pump came on as per normal but the diesel pump did not turn off. After a few moments of flipping things on and off to no avail, we completed the final 100 miles with both pumps running. Because my design works on check valve at the engine, the diesel pump should simply circulate fuel through the filter housing back to the tank as it would in normal operation given that the veggie pump is producing more pressure (as it should). None the less, my mind was doing the usual system tear-down deducing the problem. My conclusion was that the pressure switch was failing.

Over the weekend, we drove into town a few times and did a drive down the Blue Ridge Parkway to a hike where the system operated as it should about 75% of the time, the remaining 25% with the pressure switch stuck open and both pumps running. One of us had a good time driving a 6000lb vehicle like a sport car. In any case we burnt a lot of veggie and I could tell, when the pressure switch was working that I was getting to the end of the filter life. Of course there was no chance to get a replacement filter on the long weekend so I just let it do what it could and suplimented with the 1/8 tank of diesel that I had.

Then things got more interesting; I am pretty sure that my diesel fuel gauge had actually increasing slightly. I know that I should have been consuming diesel but I was reading almost a ¼ of a tank by Sunday and the truck was not starting as quickly as usual. One or both of the check valves on the diesel side were allowing veggie to be pushed into the diesel tank. Since I was quite low on diesel this was noticeable on the gauge and produced mixture of veggie/diesel significantly high enough to affect starting performance. Average temperature was 70-80F.

While I could have shut the veggie system down and driven on diesel, we made the 350mile drive home with both pumps running, an expiring filter, and probably leaky check valves. This consumed the ¼ tank of fuel (mix) in the diesel tank. I put 15 gallons of diesel in the diesel tank as we pulled back into Charleston, ensuring that I had now a high percentage of diesel to flush the engine with.

In retrospect, it has burned me every time I have gone on a trip without a filter. Better to have one and not use it; kinda like my experience with umbrellas. As for the veggie system, it has been running for almost two years but I would have liked to see better life from the pressure switch. I am going to replace it along with a filter asap. The check valves are a pain in the ass to replace but I will get some of the stainless ones ordered for when I get worked up enough to change them.

My final word on this is: Its not about IF a failure will happen, its WHEN and you need to plan and design accordingly. Three things failed on the veggie system during this trip and I was never at risk of being stranded. In the end we drove about 800 miles on 7 gallons of diesel...not bad mileage per dollar for a 6000lb vehicle....