New in-tank fuel pump

[bsorcs]

I pulled my in-tank pump and tested it on the bench...sticking and stopping, does not run for more than a second or two. Tried the tap-tap approach with a wee hammer...no joy. Sometime back I installed an in-line pump atop the tank, but for some reason it would not lift. There are replacement in-tank pumps out there, new and re-built, that are available with and without a housing. They are pricey but seem the simplest solution...out with the old, in with the new, a bit of copper tubing and back in business. My questions are: how readily do the new pumps mount onto the old harness, and how certain can one be that the electrical plug and wiring from the pump up to the flange will be correct? I'll call a supplier tomorrow to get their word, but thought it made sense to query here as well.

 

[rustystud]

You might have to "jury rigg" it a bit, but they usually fit pretty well. I installed two of them in my truck (dual fuel tanks) and have had no problems.

 

[bsorcs]

A thousand thanks. Ordering today.

 

[swbradley1]

I probably would have just gone with an Airtex E8131 24v inline fuel pump.

 

[HDN]

Can the multifuel injection pump prime and draw from the tank on its own with enough cranking? The M35A3 did away with the electric fuel pump and just relies on the injection pump. It just takes 5-10 minutes of on/off cranking to get the motor primed. I'm a fan of electric pumps myself. One of my dad's Jeeps had a hand primer on it.

 

[banditt1979]

Can the multifuel injection pump prime and draw from the tank on its own with enough cranking? The M35A3 did away with the electric fuel pump and just relies on the injection pump. It just takes 5-10 minutes of on/off cranking to get the motor primed. I'm a fan of electric pumps myself. One of my dad's Jeeps had a hand primer on it.

Mine did. Truck sat for 8 years and pump wouldn't turn but the ip pulled fuel to start it and drive about a mile from delivery point to my house.

 

[KN6KXR]

Can the multifuel injection pump prime and draw from the tank on its own with enough cranking? The M35A3 did away with the electric fuel pump and just relies on the injection pump. It just takes 5-10 minutes of on/off cranking to get the motor primed. I'm a fan of electric pumps myself. One of my dad's Jeeps had a hand primer on it.

Yes it runs fine with a dead pump. Pulls straight through the stock pump. Mine's been dead for a minute..... Problem is filter changes.

There are adaptable in tank pumps out there. For the price though I would go to a marine rated Walbro. They are about the same cost and the "gold standard" in this area. This is the same pump folks like Boyce will sell you as a replacement. Retail is about $200 but keep your eyes out for deals they do come up on eBay and the like.

 

[HDN]

If the existing IP can draw fuel, I'd consider bypassing or removing the stock electric fuel pump. If the fuel system is tight enough one shouldn't have to worry about using the electric pump to prime it all the time, in my opinion. While I like electric fuel pumps, I also like less failure points

 

[gimpyrobb]

If the existing IP can draw fuel, I'd consider bypassing or removing the stock electric fuel pump. If the fuel system is tight enough one shouldn't have to worry about using the electric pump to prime it all the time, in my opinion. While I like electric fuel pumps, I also like less failure points

They can not pull fuel from the tank if air is in the system.

If the pump was working and then stopped, the truck will pull fuel through. But if there is any air in the system you need the in tank pump to get the truck running.

 

[HDN]

They can not pull fuel from the tank if air is in the system.

If the pump was working and then stopped, the truck will pull fuel through. But if there is any air in the system you need the in tank pump to get the truck running.

Agreed, but will lots of cranking not prime the motor? I know that takes awhile without a priming pump.

Also if there's air getting into the fuel system, I think there are other problems that need attention, like potential fuel leaks.

 

[KN6KXR]

Agreed, but will lots of cranking not prime the motor? I know that takes awhile without a priming pump.

Also if there's air getting into the fuel system, I think there are other problems that need attention, like potential fuel leaks.

Probably not. Maybe after a lot of cranking but you will likely run out of battery first. Also not good for the starter you would really work it hard. Also how are you periodically draining the bowl on the primary fuel filter without it?

The high pressure pump in the governor/pump/injector pump assembly is a simple close fit gear pump. Much like the injector pump it relies on the fuel making the seal. If it's full of air the air will slip around the gear and pump in a circle.

I mean.... theoretically.... maybe if you crack the line to the high pressure fuel filters.... eventually....

My lift pump is busted and has been for some time. Been driving the truck no issues. So it's nice that when it fails it pulls through. When I go change the filters a Walbro will get mounted that will solve the issue. Gotta get the radiator back from the repair shop and my new injectors in first then I can work on that... Always something seems like.

 

[HDN]

Probably not. Maybe after a lot of cranking but you will likely run out of battery first. Also not good for the starter you would really work it hard. Also how are you periodically draining the bowl on the primary fuel filter without it?

A couple things that may not be a thing on the A2 trucks, and I don't know that for sure since I've never worked on the multifuel:

1) For priming the motor after a fuel filter replacement, the M35A3 TM says to crank the motor for a certain amount of time (which I can't remember off-hand), let the motor rest, and repeat until the engine starts. If I remember correctly, when I last replaced the fuel filter I cranked the motor for about 15 seconds at a time instead of what the TM specified - I'm pretty sure the TM specified a longer cranking time. I really don't want to replace a starter motor - of course it's easy if you're the Army

2) After I drain the fuel-water separator, the next time I start the truck it takes only a couple more seconds than usual to fire up. My truck mostly starts up instantaneously if I don't drain the separator.

 

[glcaines]

The same with my M35A3. I basically only flip the starter lever and it fires right up. My A3 is the easiest starting diesel I've ever had.

 

[Charlie175]

Both of my trucks the in tank pump did not work. Removed them and cleaned them up good and now both work. Both had a lot of buildup of goo on them.

 

[banditt1979]

Both of my trucks the in tank pump did not work. Removed them and cleaned them up good and now both work. Both had a lot of buildup of goo on them.

Same here, wasn't gunked up but there was a sliver or two of metal that I think was binding mine up. Still working fine.

 

[KN6KXR]

Mine was dead. Pulled it out it would spin if it was upside down. Since it's hard to keep fuel in the tank driving that way I figured a replacement was in order.

Walbro 6067 sideways so I can get to the screen easy. If I didn't have a dump bed I would probably put it by the primary filter. Used a premium 1/2" parker fuel line. Thing will pull 4 feet of lift at 43 gph I foresee no issues.

 

[Floridianson]

1) For priming the motor after a fuel filter replacement, the M35A3 TM says to crank the motor for a certain amount of time (which I can't remember off-hand), let the motor rest, and repeat until the engine starts.

Find it funny on the 35A3 no primer ball /filter but they added one on the 3116 cat on the FMTV's. Wonder if one could be added to the A3 system? That would make filter changes much faster / easer.

 

[gimpyrobb]

Probably not. Maybe after a lot of cranking but you will likely run out of battery first. Also not good for the starter you would really work it hard. Also how are you periodically draining the bowl on the primary fuel filter without it?

The high pressure pump in the governor/pump/injector pump assembly is a simple close fit gear pump. Much like the injector pump it relies on the fuel making the seal. If it's full of air the air will slip around the gear and pump in a circle.

I mean.... theoretically.... maybe if you crack the line to the high pressure fuel filters.... eventually....

My lift pump is busted and has been for some time. Been driving the truck no issues. So it's nice that when it fails it pulls through. When I go change the filters a Walbro will get mounted that will solve the issue. Gotta get the radiator back from the repair shop and my new injectors in first then I can work on that... Always something seems like.

No, I have never seen a multifuel start after a filter change without the in-tank pump working. there is a bleeder screw on the top, in between the secondary filters on the side of the motor. I turn power on, open the bleeder, and wait for fuel. Close the bleeder and start her up.

 

[Computerdoc08]

Would it be possible to leave an Airtex in line pump in place without power and have the OEM lift pump running fuel to the primary filter? The Airtex would be left in line as a back up and only energized if needed.

What fittings are on your fuel pump mount and the OEM primary filter?