This situation is happening with my 1980 International Scout, 4BT, ZF 5 speed (build thread here)
There are a lot of clues and bits of info in the story, I will include everything I think MIGHT be significant, even though some of it might end up not being significant.
After finishing the build, the 4BT Scout ran great with no problems for about 6-8 weeks.
About 10 days ago I replaced the fuel-level sending unit in the tank, which includes the pickup tube. I noticed the replacement unit had a strainer on the pickup tube, whereas the old unit had no strainer.
About one week ago, approximately 50 miles from home, the Scout rapidly began losing power. I drove about 2 or 3 miles with quickly diminishing power until I arrived at a gas station. After shutting down the engine and checking the oil level (good level) the engine would not start again. I replaced the fuel filter, and cranked the engine again, but still no start. I ended up towing it home.
One day later, I replaced the lift pump with a new NAPA pump, and the engine fired right up. When assembling the NPT barb fitting in the inlet port of the pump, I was careful not to over-tighten the fitting, as I have cracked the pump casting in the past by over-tightening.
(I destructively disassembled the old lift pump to find the problem. The small "flange" or "head" at the bottom of the diaphragm-plunger shaft had been worn off, or sheared off. Therefor the "rocker arm" which is moved at one end by the cam was not able to move the plunger shaft at the other end)
Now that the engine was running, I proceeded to use the Scout. However, after driving it only about 20 miles, I pulled into a parking lot in town and all of a sudden the engine idle became very rough and the exhaust became very smokey - white smoke that smelled of diesel. These symptoms improved a bit when I brought the idle up a few hundred revs. I drove it home with my girlfriend tailing me in our VW TDI, and she said it was smoky the whole time. Also, I noticed significantly reduced power on the way home.
Thinking these symptoms were consistent with either a restriction somewhere in the fuel line or air in the fuel, I did several things. I cracked and bled the injector lines, and although the rear three injector lines were not bubbly, the fuel coming out of the line nearest the front of the engine was very bubbly. I then A) replaced the filter again, B) tightened up the inlet and outlet fittings on the new lift pump, and C) removed the fuel-level sending unit from the tank and removed the strainer. I noticed that the pickup tube was shorter than the original one, so I bent it more straight down to better reach the bottom of the tank. Since the tank was only about half full, this led me to the theory that the short pickup tube had somehow sucked up some air from inside the tank. I installed the fuel line with two hose clamps. I then bled the lines at the injectors one or two more times.
At this point the engine idled much better, with no white smoke, but there was still a noticeable lack of power compared to before the lift pump went bad. I could get up to the same top speed, but it took a lot longer. Poor acceleration.
So today I went out to run errands in the Scout, even with its poor acceleration. I filled it up with diesel. About a half hour after filling it up, the exact same thing - the rough idle and thick-white-smoke-exhaust - happened again! I limped it home with very smokey exhaust and very poor power.
The pickup tube sucking air theory can't be true, because it is full of diesel. I have a hard time believing it is sucking air at the lift pump fittings, as they are pretty darned tight now.
The smokey exhaust and rough idle are intermittent, while the poor power and poor acceleration have been consistent since the new lift pump install.
Even though the lift pump is brand new, could it be bad? Could I have generally poor performance from an under-performing lift pump? Could air get into the fuel THROUGH the lift pump?
Could I have damaged the injection pump by driving three miles on a failed lift pump? (Seems unlikely)
I have been thinking about upgrading to one of Scott's piston pumps (this is the fourth time in 3 BT engines that a diaphragm lift pump has failed me) but it's just a shot in the dark that this might solve the problem.
I am not running bio-diesel or veggie. I do not have a pyrometer installed yet, is it in the mail.
Any other ideas? I am frustrated by this situation.
Thanks,
Christian
There are a lot of clues and bits of info in the story, I will include everything I think MIGHT be significant, even though some of it might end up not being significant.
After finishing the build, the 4BT Scout ran great with no problems for about 6-8 weeks.
About 10 days ago I replaced the fuel-level sending unit in the tank, which includes the pickup tube. I noticed the replacement unit had a strainer on the pickup tube, whereas the old unit had no strainer.
About one week ago, approximately 50 miles from home, the Scout rapidly began losing power. I drove about 2 or 3 miles with quickly diminishing power until I arrived at a gas station. After shutting down the engine and checking the oil level (good level) the engine would not start again. I replaced the fuel filter, and cranked the engine again, but still no start. I ended up towing it home.
One day later, I replaced the lift pump with a new NAPA pump, and the engine fired right up. When assembling the NPT barb fitting in the inlet port of the pump, I was careful not to over-tighten the fitting, as I have cracked the pump casting in the past by over-tightening.
(I destructively disassembled the old lift pump to find the problem. The small "flange" or "head" at the bottom of the diaphragm-plunger shaft had been worn off, or sheared off. Therefor the "rocker arm" which is moved at one end by the cam was not able to move the plunger shaft at the other end)
Now that the engine was running, I proceeded to use the Scout. However, after driving it only about 20 miles, I pulled into a parking lot in town and all of a sudden the engine idle became very rough and the exhaust became very smokey - white smoke that smelled of diesel. These symptoms improved a bit when I brought the idle up a few hundred revs. I drove it home with my girlfriend tailing me in our VW TDI, and she said it was smoky the whole time. Also, I noticed significantly reduced power on the way home.
Thinking these symptoms were consistent with either a restriction somewhere in the fuel line or air in the fuel, I did several things. I cracked and bled the injector lines, and although the rear three injector lines were not bubbly, the fuel coming out of the line nearest the front of the engine was very bubbly. I then A) replaced the filter again, B) tightened up the inlet and outlet fittings on the new lift pump, and C) removed the fuel-level sending unit from the tank and removed the strainer. I noticed that the pickup tube was shorter than the original one, so I bent it more straight down to better reach the bottom of the tank. Since the tank was only about half full, this led me to the theory that the short pickup tube had somehow sucked up some air from inside the tank. I installed the fuel line with two hose clamps. I then bled the lines at the injectors one or two more times.
At this point the engine idled much better, with no white smoke, but there was still a noticeable lack of power compared to before the lift pump went bad. I could get up to the same top speed, but it took a lot longer. Poor acceleration.
So today I went out to run errands in the Scout, even with its poor acceleration. I filled it up with diesel. About a half hour after filling it up, the exact same thing - the rough idle and thick-white-smoke-exhaust - happened again! I limped it home with very smokey exhaust and very poor power.
The pickup tube sucking air theory can't be true, because it is full of diesel. I have a hard time believing it is sucking air at the lift pump fittings, as they are pretty darned tight now.
The smokey exhaust and rough idle are intermittent, while the poor power and poor acceleration have been consistent since the new lift pump install.
Even though the lift pump is brand new, could it be bad? Could I have generally poor performance from an under-performing lift pump? Could air get into the fuel THROUGH the lift pump?
Could I have damaged the injection pump by driving three miles on a failed lift pump? (Seems unlikely)
I have been thinking about upgrading to one of Scott's piston pumps (this is the fourth time in 3 BT engines that a diaphragm lift pump has failed me) but it's just a shot in the dark that this might solve the problem.
I am not running bio-diesel or veggie. I do not have a pyrometer installed yet, is it in the mail.
Any other ideas? I am frustrated by this situation.
Thanks,
Christian
