Fuel plumbing revisited

Back in January, I mapped out my fuel plumbing according to emails from people with converted cars, diagrams and a series of posts on the Frybrid forum.

Well, everything worked fine except for a couple minor issues. Occasionally, when I was shutting the car off it would rev high for 2-3 seconds before shutting off. Then, when I restarted I would get a Check Engine light, triggered by code po215 (faulty shut off valve).

I thought I nixed the issue a couple weeks ago when I rewired the power supply for the valves and controller. No such luck, the CEL was back in a couple days.

I posted about it on the Mercedessop forum; they recommended changing the o-ring on fuel shutoff valve. Someone there had the same issue and cleared it up this way.

I also posted about it on the Frybrid forum; over there, "Greg" posted that he had the EXACT SAME symptoms after he plumbed his car according to the "unofficial" Frybrid method. He pointed me to a thread where he discussed his plumbing.

So, I replumbed it last night according to Greg's method. I also changed the o-ring on the shutoff valve, so it's hard to say which "procedure" cured the problem. I would have liked to do one at a time, but it's really hard to justify taking it all apart twice.

So, here is how it's now plumbed:


The diesel fuel flow:
1) fuel comes from tank, through fuel heater and into prefilter
2) prefilter to filter “in”
3) filter “out” to Supply valve
4) Supply to SOV
5) SOV to lift pump
6) lift pump to SOV – where the fuel is pumped into the injection pump & injectors
7) Excess fuel goes out the return line
8) Fuel flowing back from the injectors meets the excess fuel from th injection pump. This connection is made at a port on the fuel filter housing. The port in the housing is blocked off (indicated on diagram by the black lines) to prevent being drawn back into the diesel filter.
9) Excess fuel is sent back to the Return valve.
10) From the return valve back to the diesel tank

The Veggie fuel flow:
11) fuel comes from the veggie tank and tees into fuel from the Veg Return valve
12) into Supply valve
4) Supply to SOV
5) SOV to lift pump
6) lift pump to SOV – where the fuel is pumped into the injection pump & injectors
7) Excess fuel goes out the return line
8) Fuel flowing back from the injectors meets the excess fuel from th injection pump.
9) Excess fuel is sent back to the Return valve.
13) return valve to Veg Return Valve. Fuel is then either sent back to veggie tank (14) or looped back into fuel supply (11)

Anyway, the Check Engine light will stay on for a day or two until the code clears, but the car shuts off instantly when I turn the key, whether I'm on diesel or veggie. The car also has all its power back; the turbo boost is limited when the CEL is on. Now that it's working fine, the boost is back.