Fuel system common components
From Bytesmiths
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Fuel system: | Fuel system overview | Fuel system common components | Filling | Plumbing | Vegetable oil | Fuel system electrical |
These are components that are common to both biodiesel and vegetable oil systems. This includes the engine, lift pump, fuel heater, fuel monitor, and valve. Also mentioned here (for lack of a better place) are biodiesel-only components, including the stock fuel filter and tank. I wrap it up with a summary of fuel system issues and problems.
Click on an item or label for more information. This picture was taken before final assembly; all tubing was eventually covered with pipe insulation. This view is from near the center of the truck, looking toward the left front wheel.
Contents |
Biodiesel/vegoil valve
A motorized, six-port Pollak valve is used to switch between biodiesel and vegetable oil. This same model of valve is use to select between right and left tanks and to switch the auxiliary pump between filling the tanks and recirculating vegoil. This valve is available from JC Whitney, which is where I got mine.
In the normal position, fuel flows from the stock tank, through the stock filter, into the second port shown in the schematic out the common port, through the monitor, heater, and lift pump, into the engine.
Similarly, excess fuel is returned to the stock tank via the other section of this valve.
For the vegoil path, things are a bit different. Fuel comes from Pollak Valve 2, through the Vormax filter, and into the valve and then to the engine via the same path as with biodiesel.
However, excess fuel is not returned from the engine to the vegoil tanks, rather it is "looped" back to the input via a "T" in the plumbing. This helps keep the fuel nice and hot; if it were routed back to tanks, its heat would be dissipated in the large thermal mass of the tank's oil. This way, it retains heat it picks up from the engine, and makes it easier for the fuel heater to do its job.
Floscan fuel monitor
This was an extravagent luxury, but I wanted to have good information about my fuel consumption performance.
I chose the Floscan Series 9000 Fuel Monitoring Sysetm. Designed for demanding marine use, this system has two flow sensors that detect forward and return flow. The main panel then subtracts the two, and indicates real-time fuel flow in gallons per hour. It also has a tachometer input, and will indicate RPM and total running time, however, I have not hooked this up to date because I ran out of time. (I'll need to fabricate a bracket and a sensor. I'm planning to use a magnet epoxied to the crankshaft pulley and a Hall-effect sensor.)
But just measuring fuel consumption rate and RPM probably wouldn't have enticed me to spring for this expensive item, except it also has a standard NMEA interface for talking to common GPS devices, such as the Garmin GPS II+ I have mounted on my dash. By hooking it up to the GPS, it directly shows instantaneous fuel economy in miles per gallon! This has influenced my driving habits considerably!
Vegtherm fuel heater
Although I have gone to a lot of trouble to route engine heat all over the place, engine heat alone really cannot do the job in the Cummins 4BT, which has a 150 degree (F) thermostat. The darn engine is so efficient that it won't even hit 150 if it's below about 60 degrees outside! So I use an electric heater to boost the temperature to the 180 needed. I use the Vegtherm, from Neoteric Biofuels.
The Vegtherm is a quality product, and they respond to improvement suggestions. In my opinion, it's a great item with no parallel in the market. I've seen some discussion about making your own heater from Positive Temperature Coefficient (PTC) thermistors on biodiesel.infopop.cc but have not had the opportunity to play with it myself -- perhaps on my next conversion.
Neoteric says not to use the Vegtherm with diesel fuel. But I have a different opinion. One problem people often have is that they start up, drive until the engine temp gauge moves up a bit, then throw the switches to switch to vegoil. Some even wire their electric heater and valve to the same switch.
But I know that unless I'm working the Cummins 4BT real hard, the injection pump and injector lines are barely warm to the touch! So I turn my Vegtherm on as soon as I start the engine, hoping that the heated diesel fuel will warm the injection pump and lines enough so they won't cool the vegoil back down after switching over. So far, I've noted no ill effects to this practice, but Neoteric does strongly suggest that you shouldn't use the Vegtherm on petrodiesel fuel.
Early versions of the Vegtherm had spade connections that would loosen over time. I suggested to Ed Beggs that they use screw terminals instead, and new versions (since 2005) now have a much more secure wire connection system.
Lift pump
One thing nice about the Cummins is the separate lift pump. This is an inexpensive part that is often integrated with the precise, expensive injection pump. It's job is to supply the injection pump with a steady supply of fuel. I had to replace it within a few months of using biodiesel -- it appeared that the original pump (probably from 1989) had a rubber diaphram. I verified that the new one I bought (about $70) had biodiesel-safe Viton parts before purchasing it, and have not had a problem since.
I did make one change to the original fuel plumbing besides inserting the Pollak valve and Floscan sensors. Originally, the lift pump pushed fuel through the stock fuel filter before it got to the injection pump. I did not want to be putting vegoil and diesel fuel through the same filter! So I moved the stock filter to the other side of the Pollak valve. This has some implications, as pumps push better than they pull. I've had the stock filter clog several times since doing this conversion, and having it on the suction side may have something to do with it. I'm going to do some testing with a vacuum gauge to try to figure that out, and come up with a solution.
Cummins 4BT
Man, I love this engine! It's bomb-proof, starts easy (when I'm not having fuel filter problems), parts are cheap and available, and it's easy to work on. What more can I say?
It's rated 78kW (105 HP) which doesn't seem like much, but it gets the job done, hauling 4,500 kg (10,000 pounds) over the Rockies multiple times. The turbocharger means it works nearly as good at mountain passes as it does at sea level, unlike naturally-aspirated diesel engines.
Besides the lift pump and stock filter mods described above, I've done a bit of "elective surgery" on it. The air intake originally had three 90 degree bends, and went right across the top of the radiator. I wanted that space back, so I replaced a 90 with a 45 and ran the intake back over the valve covers. This gave me room for my cleanable oil filter and for a planned centrifugal bypass filter.
I hate disposable products, including oil filters. Sure, they're recycled (we hope), but recycling is the "R" of last resort, only when you cannot Reduce or Reuse first. So I got a cleanable Racor LFS-6428TT filter instead. An adaptor fits on the engine block where the original disposable spin-on filter mounted, and two hoses lead to the Racor filter, which is mounted in a convenient location. The filter comes apart, and the 28 micron element(8) is cleaned in a bath of mineral spirits. A sensor(5) lights a lamp on the dash if the filter becomes clogged before scheduled maintenance, which I do at 3,000 miles. The spin-on was mounted sideways, so this change also avoids the mess that always resulted from changing the spin-on.
Future plans are to add a centrifugal bypass filter. This spins the carbon soot out of the oil -- along with other contaminants -- and together with the cleanable Racor, should enable oil change intervals approaching 20,000 miles on synthetic oil. (I'm currently using Amsoil.)
I also changed the alternator out. The original was a Delco 60 amp, but the Vegtherm fuel heater alone can take up to 30 amps! And my fill/recirculate pump also takes 30 amps. Plus I've got lots of other power-hungry electrical goodies, so I replaced this with a 160 amp alternator.
Oh yes, did I mention that I completely re-wired the engine? It had a big cable bundle that was draped across the front with a coil of excess. It was in the way of where I wanted my lube oil filters, looked ugly, and the extra length simply violated my sence of efficiency! So I routed the main #10 charging wire, which ran up to the dash and back before hitting the battery, with a short length of #8 going directly to the batteries via an isolator, and trimmed and dressed the other cables nicely.
Stock fuel tank
There isn't much to say about this. It's listed here mainly as an anchor for the link on the schematic. It holds 30 gallons, and is pretty much a non-repairable unit. The fuel sender acts funny -- it won't go past 3/4 full -- but it can't be replaced, that I can see, anyway.
In January 2005, I'm going to drop the tank and add a separate feed for the Webasto coolant heater. I currently plumbed it into the main fuel line, but it has never worked, so I'm going to go back and do it "by the book."
Stock fuel filter
Again, this is here mainly as a reference from the schematic. It is mounted to the engine, and so it adds a bit of engine heat to the fuel.
Issues/problems
Stuff I need to work on:
- Need to include the Vormax filter in the looped return. When it is out of the loop, it has less fuel velocity, which is what makes it work. --Accomplished, spring 2005.
- It would be real nice to shorten the common fuel system loop somehow. It takes about a minute to switch between them at road speed; this means I'm dumping over a cup of vegoil into the diesel tank when I switch back. This seems to be causing diesel fuel filter clogging problems, especially when low on fuel. More investigation needed! -- Added a separate switch to manually delay switching return fuel, which seems to have solved this problem.
- The clogging diesel fuel filter may be due to putting it before the lift pump, whereas it was originally after it. More investigation needed!
- Need to solder wires onto the Vegtherm to keep the spade connectors from loosening due to thermal stress. --Ed Beggs sent me a new one with screw terminals -- no charge! Great support, Ed!
- (fuel gauge source needs to be put on the electrical page)
