rough running, about to sputter out

I changed the fuel filters and there is no apparent change in the problem. I can only assume that the problem is not due to contaminated fuel.

When I dumped the fuel out of the used filters, it appeared clean. I have dumped fuel from filters in the past when the contamination in the fuel was very apparent.

I'm quite sure I have a different problem.

Perhaps a clue is that when I pull off the primary filter, I hear a gurgling sound. When I loosen the secondary filter, fuel gushes out. This makes it look like there is a lot of fuel pressure after the secondary filter but little pressure before the primary filter.

Any ideas?

 

How do you get 'em off.

It looks like they're welded in there.

 

I spoke too soon about the filters not helping.

It took about 20 minutes. I don't know why. I had shut 'er down tryin' to figure out what to do next. A fellow working on his Cummins told me it was probably the fuel line running from the secondary filter up to the head. He said, "Fuel ain't gettin' to the injectors."

When I saw how that line was routed, behind the starter motor, I realized there was nothing I was going to be able to do about it and still get the load delivered. I figured I'd bite the bullet and try and limp sputtering all the way to the receiver.

When I started 'er up, she was running like a champ. I don't understand, but I ain't complaining. She ran so good I took another load. I bought more fuel filters along the way. I bought 4 primaries and 3 secondaries. That was 450 miles ago and she's still runnin' great. I put in two fppf Fuel Power when I fueled up in Auburn, ME. The spot I'm in is I gotta keep runnin' if I can. Now it looks like I'll be alright as long as I have the spare filters, and I'll keep adding algae killer and fppf like you been doin'. I'll clean 'er up on the go. It's all I can do. She's gonna get all new fuel lines, too.

Thanks!

 

I don't think bad fuel or clogged fuel filters have anything to do with the problem.

Question: Why, after running hard, and experiencing symptoms of fuel starvation, does the secondary filter gush out fuel under pressure upon being loosened with the fuel filter wrench?

 

But the high pressure is there even after the engine is shut down. How is that possible?

About 20 years ago I installed a one-way check valve on the output of the fuel pump because I had a problem losing prime. It worked. That explains why the high pressure in the secondary filter cannot escape back through the main fuel line. But why doesn't the pressure escape through the cylinder head back through the return lines? I checked for flow in the return lines at idle. I opened the return lines at the top of the tanks, and there is plenty of smooth return flow.

What, then, exists inside the cylinder head that prevents the high pressure in the secondary filter from being released back through the return lines?