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| Looped systems (where the return line is connected back to the vegy line or the front of the pump) are superior to Return-To-Tank systems because they allow earlier switchover to vegetable oil and (if done right) backflush of the vegy fuel filter on shutdown. One of the main drawbacks to looped systems is they trap air and grunge. I've tried a few things to relieve this problem, a RTT system as well as removeing air from the loop, has the added benefits of warming the tank and letting oil out of the loop to be refiltered. The system I use now is a blend of the two systems so I've been calling it the Hybrid system. I rarely need to energise the RTT solenoid other than long trips or if air appears in my clear return line. |
| The BLUE LINE goes to the output of the fuel filter. The BRICK RED lines goes back to the vegy tank. The SEMI-CLEAR line is from the injection pump. This fuel solenoid decides between looped or RTT |
| The lower solenoid (picture to the right) sends fuel, from the return line, to the diesel tank (black cloth-cover hose) or the vegy line (semi-clear PEX). I didn't know what would happen if I tried to send fuel back to the vegytank when it was clogged with cold oil. I connected a pressure guage to the return line to see what kind of pressure would build up. I eventually just crimped the return line and watched what would happen. The small fuel lines between the injectors popped off and fuel sprayed everywhere. This would not be a good thing to happen if I was traveling down the road. A pressure override switch would shut this solenoid down if pressure got too high. |
| Below is a closeup of how the fuel lines are connected to the front of the pump. The YELLOW-GREEN tubing is the diesel fuel line. The BLUE line goes from the fuel select solenoid to the injection pump. The BLACK line, in my hand, goes to the vacuum guage. |
| HEATED FUEL LINE |
| HEATED TANK |
| TO PRESSURE GUAGE |