juddspaintballs
my balls are painted!
1999 Burb with 24x,xxx miles on it.
I recently was down on power so after replacing injectors and filters, I moved on to the lift pump. I installed Leroy's Walbro pump and pre-filter kit and got most of my power back buy suspected the tank sock to be a bit plugged up. No issues up to this point as far as stalling or hiccuping.
Since I had to drop the tank to pull the tank sock, I decided to do the Metrum Rod Fuel Sending Unit upgrade for more accurate tank readings at the gauge. After a little bit of trimming and resoldering all was well with it and it works beautifully (Leroy was a pleasure to deal with).
While dropping the tank the first time, the return line at the tank broke on the steel line from rust. The supply line fitting spun off easily but the hard line was pretty rusty too. I cut the sending unit lines just beyond the nuts and slid rubber fuel hose over them and clamped them tight then did the same on the frame side of things. When I went for a drive the engine kept hiccuping and stalled out on my several times.
I dropped the tank again thinking my patch wasn't enough and replaced the factory hard line from the sending unit all the way to the new Walbro pump with rubber fuel hose. I also replaced that same length section of the return line in rubber. On the sending unit itself, the suction side has at least 1.5" of hose slipped over the steel line with two appropriately sized worm clamps on it and it terminates at the pump with a brass barbed fitting and a worm clamp. I also replaced the spin on filter and filter in the FFM between the first and second tank drop. At idle, the suction line shows no signs of collapsing and isn't even a bit soft.
The hiccups continue even after replacing the lines between tank and lift pump. I even stalled once today. Some things to note that I've discovered so far:
- At idle (or engine off and pump wired to run), I can hook up a clear hose to the T bleeder in the engine bay and see bubbles flow through along with the fuel. Sometimes it's light, other times it's more air than fuel. Sometimes it's only fuel with no air bubbles.
- I've got 42 gallons of fresh diesel in the tank
- Sometimes it runs great at all RPM/loads, other times it hiccups/stalls at very light throttle, and sometimes it's only hiccuping under heavy acceleration
- The tank sock is now removed. Prior to me dropping the tank, this issue did not exist. Tank was actually quite clean inside.
- When I replaced the pre-lift pump spin on filter as a trouble shooting measure, it was only about 1/2 full of fuel when I took it off.
Obviously air is getting in somehow. My best guess at this point is that the sending unit suction line on the outside of the tank (all about 2" of it before the rubber line starts) has a small hole in it and is sucking in air. It seems pretty silly to buy a new sending unit only to rip out the actual sending unit part to put my MRFSU in it's place, but if that's what I have to do, I will. Is there any way to build a pickup tube? It's got to be something between tank and lift pump. If there were a leak in the suction line, it would be spraying fuel out, not sucking air in. If the supply line leaked after the lift pump, it would also be spraying fuel not sucking air (since the lift pump pumps far more fuel than the engine can consume). Even if my rubber line was collapsing under suction, it would restrict flow, not introduce bubbles.
Any other ideas?
I recently was down on power so after replacing injectors and filters, I moved on to the lift pump. I installed Leroy's Walbro pump and pre-filter kit and got most of my power back buy suspected the tank sock to be a bit plugged up. No issues up to this point as far as stalling or hiccuping.
Since I had to drop the tank to pull the tank sock, I decided to do the Metrum Rod Fuel Sending Unit upgrade for more accurate tank readings at the gauge. After a little bit of trimming and resoldering all was well with it and it works beautifully (Leroy was a pleasure to deal with).
While dropping the tank the first time, the return line at the tank broke on the steel line from rust. The supply line fitting spun off easily but the hard line was pretty rusty too. I cut the sending unit lines just beyond the nuts and slid rubber fuel hose over them and clamped them tight then did the same on the frame side of things. When I went for a drive the engine kept hiccuping and stalled out on my several times.
I dropped the tank again thinking my patch wasn't enough and replaced the factory hard line from the sending unit all the way to the new Walbro pump with rubber fuel hose. I also replaced that same length section of the return line in rubber. On the sending unit itself, the suction side has at least 1.5" of hose slipped over the steel line with two appropriately sized worm clamps on it and it terminates at the pump with a brass barbed fitting and a worm clamp. I also replaced the spin on filter and filter in the FFM between the first and second tank drop. At idle, the suction line shows no signs of collapsing and isn't even a bit soft.
The hiccups continue even after replacing the lines between tank and lift pump. I even stalled once today. Some things to note that I've discovered so far:
- At idle (or engine off and pump wired to run), I can hook up a clear hose to the T bleeder in the engine bay and see bubbles flow through along with the fuel. Sometimes it's light, other times it's more air than fuel. Sometimes it's only fuel with no air bubbles.
- I've got 42 gallons of fresh diesel in the tank
- Sometimes it runs great at all RPM/loads, other times it hiccups/stalls at very light throttle, and sometimes it's only hiccuping under heavy acceleration
- The tank sock is now removed. Prior to me dropping the tank, this issue did not exist. Tank was actually quite clean inside.
- When I replaced the pre-lift pump spin on filter as a trouble shooting measure, it was only about 1/2 full of fuel when I took it off.
Obviously air is getting in somehow. My best guess at this point is that the sending unit suction line on the outside of the tank (all about 2" of it before the rubber line starts) has a small hole in it and is sucking in air. It seems pretty silly to buy a new sending unit only to rip out the actual sending unit part to put my MRFSU in it's place, but if that's what I have to do, I will. Is there any way to build a pickup tube? It's got to be something between tank and lift pump. If there were a leak in the suction line, it would be spraying fuel out, not sucking air in. If the supply line leaked after the lift pump, it would also be spraying fuel not sucking air (since the lift pump pumps far more fuel than the engine can consume). Even if my rubber line was collapsing under suction, it would restrict flow, not introduce bubbles.
Any other ideas?
