TIL that fuel return lines can cause more problems than the supply side

I had a Cummins ISX come in last month with a no-start condition. Fuel pressure was good at the pump, filters were fresh, but it would crank and crank without firing. Did all the usual stuff like checking injectors and wiring before a buddy told me to look at the return line. Turns out there was a restriction in the return line from a kinked hose. That build up of back pressure was keeping the check valves from seating right. Never would have thought a return line could cause that much trouble. Fixed the hose and it fired right up. Anyone else run into a weird return line issue before?

2 comments

2 Comments

olivia3984d ago

That kinked hose story convinced me I was wrong about return lines.

ryantorres4d ago

Whoa that brings back a memory. I remember reading a tech article a while back about return lines on some older Detroit Diesels that talked about how a collapsed return hose can create enough back pressure to actually push fuel out past the injector seals and cause a hydro lock situation. That always stuck with me because it's the opposite of what you'd expect. You figure the supply side is the only thing that matters for getting fuel into the cylinders but the return path is just as critical for the whole system to work right. Your kinked hose story just proves that point again. It's wild how something so simple can bring a whole engine to a halt.