willie59
Administrator
First of all, I'd be careful about running the machine very long as it is with the problem you've described, as in, the hot vapor in the tank. Liquid diesel fuel doesn't ignite easily, but vapor is much more combustible.
As for what to do first, doesn't matter to me, this is all theory at the moment since no one has come forward and said "I've seen this before...here's what you do...". You could check the fuel return hose if you want, I'm near certain the problem does come via return hose because if it was from the only other hose, the supply, then the pressure going to tank would interupt supply, engine would quit. Also, the lift pump has check valves in it. If the pressure went through these valves, I would think it would kill the lift pump. As for the injectors, if you don't have one that has a miss, it would be difficult to find the bad one. About the best you could do is test the fuel return rail from the injectors. All the injectors share a common fuel return and one of the injectors has the return to tank connected to it. You could disconnect the injector return hose, run it to a bucket, and see if the pressure is coming from the injectors that way. But you have to have the engine rev's up as you described no pressure problem at idle. I think testing the injector return line would give better info than testing the tank return hose. We still have that other hose from intake to injection pump you described, that's another line you could disconnect and plug off to check. So there's three items for you to check; the fuel return from the injector return line, the Thermostart, and the intake to injection pump line.
As for what to do first, doesn't matter to me, this is all theory at the moment since no one has come forward and said "I've seen this before...here's what you do...". You could check the fuel return hose if you want, I'm near certain the problem does come via return hose because if it was from the only other hose, the supply, then the pressure going to tank would interupt supply, engine would quit. Also, the lift pump has check valves in it. If the pressure went through these valves, I would think it would kill the lift pump. As for the injectors, if you don't have one that has a miss, it would be difficult to find the bad one. About the best you could do is test the fuel return rail from the injectors. All the injectors share a common fuel return and one of the injectors has the return to tank connected to it. You could disconnect the injector return hose, run it to a bucket, and see if the pressure is coming from the injectors that way. But you have to have the engine rev's up as you described no pressure problem at idle. I think testing the injector return line would give better info than testing the tank return hose. We still have that other hose from intake to injection pump you described, that's another line you could disconnect and plug off to check. So there's three items for you to check; the fuel return from the injector return line, the Thermostart, and the intake to injection pump line.
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