Scout 800 Fuel Problem

[duffelpud]

This weekend I installed my refurbished left side gas tank, fuel lines, fuel switch and rebuilt carb. I then attempted to start my Scout. Here are the results. I welcome suggestions. Note that the fuel pump was removed and cosmetically cleaned and the unit tested by hand - it seemed to be pumping both air and fuel adequately. At any rate, I cranked and cranked (after putting about three gallons of fuel in the tank) to no avail. I tried pouring a little gas in the carb and only got an occasional sputter. I then disconnected the fuel feed from the pump and rigged a gravity feed directly from a jug sitting on the radiator. After a a little bit the old engine fired up and ran like a champ, although it idled high. Everything looked and sounded good with only a little clicking coming from the valves. I located a giant sucking sound coming from a rat-chewed hose that bent down from a fitting on the side of the manifold to the vacuum pump on the top of the fuel pump. When I plugged this hole the idle dropped to what seemed like normal. I then reconnected the carb to the pump and tank, started the Scout back up and set myself to correcting and connecting the vacuum hoses from the wiper and the manifold, hoping that having fuel in the carb and line would magically fix the fuel flow problem. After about a minute or two it died and wouldn't start again. Here are a few other troubleshooting tidbits:

- When I disconnect the fitting at the carb and crank, no gas comes out of the fuel line from the pump.

- All of the lines were tested and cleaned prior to assembly.

- The fuel tank switch was rebuilt and is in working condition.

- The vacuum pump on top of the fuel pump is blowing and sucking air vigorously.


I plan to test the fuel pump next by rigging hoses directly to it and a coffee can of gas to check flow. I also plan to check the fuel lines again by blowing air backwards through the system and listening for air in the fuel tank. Any other suggestions?

[Doc Stewart]

Sounds like your 'refurbished' fuel tank is not letting the fuel out. Pull the line off the tank and run a wire up through whatever sealant they used. When gas is running all over, you fixed it!

[duffelpud]

Originally Posted by Doc Stewart

Sounds like your 'refurbished' fule tank is not letting the fuel out. Pull the line off the tank and run a wire up through whatever sealant they used. When gas is running all over, you fixed it!

I didn't have to place any sealer in the tank - just cleaned the gunk out - and I also cleaned out the pickup tube that bolts on and enters from the top of the tank. I will check it all again, though.

[Gary Billings]

Do you have the fuel selector valve turned to the right position? Yeah, it's a stupid thing to look for but it's happened to the best of us.

-Gary

[nickl]

see if you can blow air through the fuel line back into the tank. If you can't there is a blockage somewhere.


Nick

[76 xlc]

Could it be the fuel tank is not venting properly?

[duffelpud]

At lunch I crawled under the Scout and unscrewed the fuel line where it attaches to the fuel selector mechanism on its way to the pump (yes, it was pointing to the correct tank) and applied compressed air to the line back towards the tank. After a fraction of a second I heard a noise that sounded like a pellet gun firing into a stock tank followed by a the sound of a scuba diver's tank being penetrated by a pellet. Apparently a dobbler thought that nice, clean pickup tube would make a dandy place to deposit a wad of mud between the time I cleaned it out and installed it. Ten minutes later the little 4-banger was running like a sewing machine.

Next question - The vacuum pump has two lines coming our of its top - one on the engine side and one on the fender side. What connects to which one? I've attached a photo of the way things are configured now. It looks like this:

[Thomas]

---The pop you heard was most likely the sock/filter at the end of the fuel sending unit. If I would have caught this in time, I would have added to the suggestion of "blow air", the key advice of "not compressed air".

---If this is what popped off, not only will you be picking up trash that floats around as well as sediment, but at any given time, if the fuel doesn't completely cover the pickup tube, you won't be able to pick it up. The "sock" function uses saturation of the mesh to aid suction. FWIW, any time can even be when you'd climbing or descending while you only have 1/4 tank.

---In addition, never blow through the fuel line to a connected carb, or into the inlet of the carb itself. Damage to needle, seat, float, or all could be the end result and gasoline is unforgiving to bearings when the engine floods severely.

---BinderBlues has a wide collection of wiring diagrams and maybe even vacuum diagrams for the Scout 80/800s. Check there if you don't get any response or if you need a full diagram. If you can't find anything. Give me a yell in PM and I will look to see if I can find one for your application in my* collection of diagrams.

[duffelpud]

When I took the tanks out of the vehicle and disassembled them, the pickup tubes didn't have any socks on them - in fact, that's the first I've ever heard of such a device. I removed the tubes and soaked them in carb cleaner and also gave the tank interiors the same treatment prior to pressure washing and plugging a few small holes with putty epoxy. The pickup tubes were open and clear, but sat on my bench for a few days before I installed the tank. That's why I assumed it was a dauber glob.

I'll look around for vacuum diagrams. Thanks for the info!

[gregor]

When I replaced my 800 tanks, the pickup tubes didn't have socks either. Based on the condition of the whole truck, I would be extremely surprised if they had been removed, it didn't look like anyone had touched the tanks (or really, anything) since they were first installed.