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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
 

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the smoke was probably air in the line.The new lift pump was probably able to suck through the screen thats breaking down in the fuel pickup.If youve changed your filter then i would susspect pickup or an air leak.If the pickup was meant for gas will will most certainly congeal.
 

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I have had trouble with rubber hoses and hose clamps in the past and changed everything out for nylon and compression fittings, the nylon is also see through so bubbles can be seen. Did you buy your diesel from the same place? maybe the diesel you bought was bad? Can you put a can of fresh diesel bought from a truck stop on and connect directly to the lift pump? this will eliminate some things out of the equation. Gauges are a good idea even on a sock motor as they are a good fault finding tool, fuel pressure, boost and EGT will tell you a lot. I am a big fan of piston lift pumps and if I had a VE pump I would definitely buy one. Does the lift pump have a mesh screen on the input? I have had this trouble on a piston lift pump in the past being blocked. If it is you need to clean your tank out and put a filter before the pump. If the lift pump gets blocked it creates a vacuum and sucks alot of air.
You need to work through in a methodical fashion and you will eventually find the problem.

Gaza
 

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This situation is happening with my 1980 International Scout, 4BT, ZF 5 speed (build thread here)


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.


Any other ideas? I am frustrated by this situation.

Thanks,
Christian
Did you remove this gasoline strainer? If not I'm betting this is your problem. Gasoline is so highly refined it will pass through a Styrofoam cup where diesel will not.
 

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Discussion Starter #5
and C) removed the fuel-level sending unit from the tank and removed the strainer.
Yes, I removed the strainer before the exact symptoms presented themselves the second time.

The idea of clear nylon lines is interesting to me. Anyone have input on what kind of nylon (or other plastic compound) line would be diesel compatible, etc? One problem I see with that idea is that it is the later, higher pressure lines after the lift pump that are probably the most important ones to see into, and I doubt that plastic is a good idea in those places.

Scott - are you out there? I think I need a piston pump.

Air somehow getting into the fuel lines sounds like a highly likely explanation for the intermittent symptoms of smoky exhaust / rough idle, but I still can't wrap my head around the persistent low power since the lift pump installation.

Christian
 

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I was at Scotts' shop a couple of weeks ago picking some parts and he was telling me some things to be careful of. He told me to be sure that the fuel return line is not routed close to the pick up line in the tank. The return line aerates the fuel. Could this be your issue. I did buy a lift pump while I was there too.
 

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Did you change the fuel filter? Water in fuel this time of year is common. If a new filter does not help then:
Check the injection pump's timing mark for being within tolerance.
Check the fuel shut off solenoid for constant power by running a jumper lead directly to the battery. If nothing changes -
Run a temporary set of fuel lines to a gallon jug with fuel in it. See how it acts. If the problem subsides suspect the tank and related plumbing.
If the problem continues remove the shut off solenoid and inspect the plunger tip for damage. There is a very slim ultra rare chance that a bit of the tip is lodged in the pump head. Normally it will just pass through the pump and into the return line to the fuel tank. If no damage the next thing would be to have the injectors tested. If they test within specifications the the only remaining thing to do is suspect the injection pump is failing.
 

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Discussion Starter #9
OK, thanks Bob.

I appreciate the step-by-step trouble-shooting approach.

Already changed the filter (twice). However I couldn't help noticing that the filter I am using (NAPA 3358) does NOT have a water separator like the filters I've used in the past on first-gen Dodge 6BTs. Should I be using a 6BT water-separator filter?

Although you didn't mention this, I am intending to upgrade to a piston lift pump, and install a pre-pump filter as well as some clear tubing before (and maybe after) the lift pump to diagnose air problems.

I will go through the rest of the trouble-shooting procedures you suggest and update this thread with the results.

Christian
 

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Remove your fuel filter and dump the contents into a clear glass jar and let it set inside for about an hour. See if there is any water in the bottom of the jar. Water has a tendency to cause some fuel filter elements to swell partially shut.
 

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Discussion Starter #11
The intermittent symptoms, the smoky exhaust and rough idle, went away by themselves..... overnight.

The more constant symptom, the low power and poor acceleration, persists. It seems particularly gutless in fourth and fifth gears.

--------------------------------
Checked a few things....

- Definitely no water in the fuel.

- Pump timing mark is right on the money, looks like it's never moved.

- Used an infrared thermometer to measure temps of injectors at various engine temps. They are always within a few degrees of each other, hottest always in the rear, coolest always in the front.

- Jumper wire directly from shutoff solenoid to battery makes no difference.

However.... there's one symptom from yesterday that I forgot to mention, and it might be important.... On two occasions, during the rough idle/white exhaust episode, when I turned to key to OFF the engine did not shut off immediately, but ran for 3 or 4 seconds, then died. I think this is referred to as "dieseling" - I searched that term here in the site to no avail. But it makes me think I need to look at the shutoff solenoid.

Any opinions?

I've never messed around with the shutoff solenoid on any of the three VE pumps I've had, so I guess it's time to start reading.

CR
 

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An injection pump running on aerated fuel is usually a bad thing. I am not a guru, but I know failure can happen quickly after and it sure sounds strange. I am also not familure with the ve pump like the p7100, but I know improper operation of the fuel shutoff can cause wierd problems. The late shut off sure points to the ip, whether shutof solenoid or pump, in my opinion.
 

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Discussion Starter #14
whats the fuel pressure when the truck acts up
Dunno. I've got three gauges arriving in the mail tomorrow, but unfortunately none of them are fuel pressure. (I'm getting tach, EGT, and boost)

Piston pump arrives in the mail Friday or Monday. I will try to get a fuel pressure gauge so that I can install it while I am in there monkeying around with the piston pump.

Right now I am thinking that if the plunger tip is torn on my fuel shutoff solenoid, I will probably just gut it and install a pull cable for shut down. I've been reading a lot about the shutoff solenoid here and also on dieseltruckregister.com, and the rubber tip on the plunger seems like a repeat offender.

Now if a piece of that plunger is in the pump..... well I guess I'll cross that bridge if I ever get to it.

CR
 

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Discussion Starter #15
I don't like to leave threads like this unfinished... so....

I am pretty sure that what was going on with this situation was just air in the fuel line and in the injector lines which was very hard to get out.

I ended up replacing the fuel line from tank to lift pump (this was actually four different pieces of hose with something like 10 hose clamps along the way to join them) with one single 5/16" ID piece of clear tubing. This helped a lot.

Then a lot of bleeding and it seems like it came back to normal.

I am having some other more pressing problems right now, which I will write about in another thread momentarily....

Thanks again, as always, for the help.
C
 
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