Another 7.3 IDI "No Start"

[Tommy_B]

I have been reading the other similar posts about non-starting 7.3 diesels and seem to have a similar but a little different situation. First of all, the engine has always started and run very well until recently. While on the road pulling a 5th wheel RV in 100+ degree temperatures last week I pulled off the freeway for fuel. The truck was running fine. After topping off the tanks, I pulled onto the highway, drove about 100 yards, and it suddenly died. I have a clear section of fuel line between the filter and the IP and I could see that no fuel was flowing while my wife cranked the engine.
After getting towed off the highway, I bought a new lift pump and installed it. When the old pump came out, I manually operated it and found that it was good but installed the new one just the same. While my wife cranked the engine I removed and replaced the wires on top of the IP and it (reluctantly) started. It ran fine for the next 6 hours. We spent the night at an RV park and the next morning the truck started up normally but died suddenly after about 20 seconds. I messed with the wires again and then it restarted. This same thing has happened 3 more times this week when I start it cold (ambient temp about 70) but NOT EVERY time. Once it starts it keeps running. Also, it seems to lack some power but otherwise runs smooth. Sorry for the long post but I felt the details were important. The truck has 160K miles on it. Time for a new IP??

[Mr_Roboto]

The only thing the wire on the top of the IP does is energize the FSS (Fuel Shutoff Solenoid) so that it opens and allows fuel to flow through the IP.

I have a couple guesses.

One is that you have a bad connection to the FSS or resistance in the circuit to the FSS. Even low voltage will make it hard for the solenoid to open. But once it is open it takes less power / voltage to keep it open. Check your battery voltage, then check the voltage at the FSS wire. It should be within a few tenths of a volt.

Second possibility is that the fuel you picked up had some crud in it that has gummed up the IP and FSS.

I don't believe the IP itself is the problem as playing with the wires wouldn't change the IP internal clearances etc.