742B electric fuel pump

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I have posted a few times over the years about fuel problems with my machine. I removed and cleaned the gas tank and fuel pick-up, which helped greatly, but it still won't run at operating rpm unless the choke is partly closed. I rebuilt the carb twice, and had a shop do it last winter, but no improvement. I replaced all ignition parts except the distributor itself and the vacuum advance, and that didn't help. A review of posts in the archives reveals a number of recommendations for an electric fuel pump due to hardening of the diaphragm and/or wearing of the cam lobe. These recommendations usually pertain to the Ford engine, but that is the only component left to address. I bought a Carter 4070, and now ask for recommendations on how/ where to install it. The only space not occupied by engine components is to the left of the engine. I can be pretty creative fabricating mounting brackets anchored to the starter bolts and valve cover, but has anyone done it in a way that they would recommend? Thanks in advance

 

[craigb93]

My machine is a 742 w/ the Ford. I used the bracket that comes w/ the Carter pump and mounted it to the engine stand on the lower left. For the ford. that is where the OE pump is so new fuel lines pretty much replace what came on the machine. Run 12v from the hot side of the starting solenoid in my case, add a 15 amp fuse and connect it to a solid state relay and from there to the pump. Use a second wire from the + side of the ignition coil to the trigger lead on the relay. Ground the pump and the other side of the relay trigger and you are in business, If you can mount it below the carburetor it will always be self purging of any air bubbles that may occur. i highly recommend ethanol-free fuel. A successful carburetor rebuild includes checking the main jet and the holes in the emulsion tube with the appropriate size twist drill. They will all be Number drill sizes. Corrosion from ethanol bearing fuel reduces the jet/hole sizes enough to cause a lean fuel mixture. -Dick

 

[[email protected]]

My machine is a 742 w/ the Ford. I used the bracket that comes w/ the Carter pump and mounted it to the engine stand on the lower left. For the ford. that is where the OE pump is so new fuel lines pretty much replace what came on the machine. Run 12v from the hot side of the starting solenoid in my case, add a 15 amp fuse and connect it to a solid state relay and from there to the pump. Use a second wire from the + side of the ignition coil to the trigger lead on the relay. Ground the pump and the other side of the relay trigger and you are in business, If you can mount it below the carburetor it will always be self purging of any air bubbles that may occur. i highly recommend ethanol-free fuel. A successful carburetor rebuild includes checking the main jet and the holes in the emulsion tube with the appropriate size twist drill. They will all be Number drill sizes. Corrosion from ethanol bearing fuel reduces the jet/hole sizes enough to cause a lean fuel mixture. -Dick

The fuel pump on the Mitsubishi engine is on the top right, snug between the distributor and carb. I appreciate the wiring instructions. I can fabricate brackets to mount the pump on the left, just a few inches above the starter. Also, thanks for the pointers re: main jet and drill sizes. I have not done that, and the shop rebuilder never mentioned it either. Good winter project. Ethanol-free fuel is pretty hard to find around here, and is expensive. I add ethanol treatment to all gas I use in chainsaws and other small engines. Just as effective in Bobcat gas ??

 

[[email protected]]

The fuel pump on the Mitsubishi engine is on the top right, snug between the distributor and carb. I appreciate the wiring instructions. I can fabricate brackets to mount the pump on the left, just a few inches above the starter. Also, thanks for the pointers re: main jet and drill sizes. I have not done that, and the shop rebuilder never mentioned it either. Good winter project. Ethanol-free fuel is pretty hard to find around here, and is expensive. I add ethanol treatment to all gas I use in chainsaws and other small engines. Just as effective in Bobcat gas ??

Back again. I read the fuel pump instructions, and spent the day gaining access to the right side of the engine block. (Must remove governor linkage to remove battery to create work space) There are two cast bosses just above the oil pan which are tapped to 7/16" fine thread, and they are perfect for the fuel pump location. The fuel pump instructions clearly require using 3/8" fuel hose, and the in / out fittings are 1/4" mpt x 3/8 hose, HOWEVER the entire fuel line from the tank to the carb is 1/4". I can't imagine how or why, but is there any danger in using 1/4" hose barbs instead of 3/8"??

 

[foton]

Back again. I read the fuel pump instructions, and spent the day gaining access to the right side of the engine block. (Must remove governor linkage to remove battery to create work space) There are two cast bosses just above the oil pan which are tapped to 7/16" fine thread, and they are perfect for the fuel pump location. The fuel pump instructions clearly require using 3/8" fuel hose, and the in / out fittings are 1/4" mpt x 3/8 hose, HOWEVER the entire fuel line from the tank to the carb is 1/4". I can't imagine how or why, but is there any danger in using 1/4" hose barbs instead of 3/8"??

1/4 inch will be fine sometimes you can use 5/16 hose on the fittings and just crank them a little down harder , I see this all the time, a stock 4 cylinder should not use what a 1/4 inch fuel line can provide with even a low pressure fuel pump.

 

[craigb93]

1/4 inch will be fine sometimes you can use 5/16 hose on the fittings and just crank them a little down harder , I see this all the time, a stock 4 cylinder should not use what a 1/4 inch fuel line can provide with even a low pressure fuel pump.

Sounds like progress. The relay I mentioned can come from most any auto parts store >$10. Look around again for the ethanol free fuel, especially if you have 2-cycle equipment in addition to the tractor. $5.00/gal is dirt cheap compared to the time and hassle trouble shooting and repairing the damage the ethanol causes. It is particularly bad in equipment that sits more than it operates. Some chain saw fuel lines will turn to pure slime for the part that is submerged. i changed my Stihl chainsaw line twice as a result. It is also why I added the electric pump to my Bobcat. Most marinas will dispense fuel in cans if you are willing to take the walk. -Dick