Ah crap.
Problems are back. I drove the truck all weekend, probably 150 miles, lots of highway, not a hiccup. Fired right up even after sitting overnight, and ran great.
This morning it cranked right up after sitting overnight. Drove it about an hour to a junkyard to pick up some parts for another project. Shut the truck down for about 10 mins, fired it up and it acts like it had air bleed back into the fuel lines. Stumbles around for a bit and then smoothed out. Drove from there to work. Ran fine on the way, about an hour. Shut down at work.
Start up after sitting for a few hours to go to lunch. Cranks up but quickly coughs and sputters like its getting the air out of the lines. After 20-30 seconds it smooths out some and I back out of the parking spot. Take off in 2nd, running fine, go around the corner, hit a straight-away, push in the clutch to shift to 3rd, and the engine dies, a new symptom.
Now, when on the gas under load, it runs absolutely fine. I would think there might be a fuel delivery issue, but it pulls great through the gears. However if you are in neutral and give it some gas, it will not go straight to a constant RPM, but wander around a bit.
When driving, if you rev to 2000 RPM, then push in the clutch and let the RPM drop, it will straight up die. Cranks right back up and idles smoothly like nothing ever happened. It died about 5 times on a 2 mile trip to lunch.
New mechanical lift pump
New hard fuel supply line from the FSV forward.
No leaks observed from mechanical pump to filter head. No leaks observed on filter head or filter to IP line, no leaks observed on injection or return lines on top of the engine.
Right now i'm thinking it could be one of a few things.
Sucking a lot of air from somewhere between the FSV and the front tank. I have never run it on the rear tank as the previous owner told me that the return lines will pressurize if you select the rear tank. I have not had a chance to troubleshoot that yet. I have a replacement FSV but I have been fixing other stuff on the truck and just dealing with the reduced fuel capacity for now.
A vent problem on the front tank
This could explain some things if the vent is clogged. I'm going to pull the fuel cap off and see if that does anything
Clogged fuel pickup from showerhead parts
Could explain why the truck dies after being revved up. The fuel pressure gets low due to a restriction and it does not have time to "catch up" as the RPM's fall, when the RPM's get down to idle the IP has low lift pressure and it stalls.
I am ordering a fuel pressure gauge so i'll have that in a day or two. I also have an old Filter to IP hard line that I cut and spliced in a few inches of clear fuel line, so I can see if air is getting to the injection pump.
I'll post a video of it running here in a sec.
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