Switch 22hp gas to 18hp diesel, will it be less powerful?

[john_bud]

Because the cap unscrews, how would you remove it if there is a fuel line attached to it?
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1/4 turn connector? Quick connect coupler? The options are endless and vary with the amount you want to spend!

jb

 

[MJPetersen]

Most often the fuel return is in the upper part of the tank above the normal fuel level. My yanmar has a fuel return in the neck jsut below the cap. You should be able to reach that as it just has to be below the threads on the filler neck. Then you could put a very small bulkhead fitting and have peace of mind.

Mike

 

[Superduper]

Mike: Great suggestion. The only thing is that I don't think a bukhead fitting on the filler tube would work because I haven't found any that would mount to a round surface, only a flat surface. I think the neck is like 4" long.

 

[MJPetersen]

Make a small "flat" spot. Since the tank is plastic it is "moldable" heat a small area and reshape it flat by using a "C" clamp to flatten out an area large enough for the fitting below the threads. I think that you could get it flat enough to work with a small fitting. Then if you clean the area well you and not allow any extra "slop" room around the fitting you should be able to seal it. Use and extra rubber gasket if necessary. It will be above the normal level of the fuel. You might have to be a little careful that you do not bang it too much with the nozzle when you fill the tank.

PLEASE do be careful. Remember that the tank once contained gasoline and I would not want to read about a plastic tank explosion. You need to drain and clean it out anyway for your interesting project.

Mike

 

[Soundguy]

Regardless of the naysayers.. I've seen it plenty of times in OEM setups for both hyds and fuel setups... it -all- depends on the application. Example.. the diesel fuel tank on a scrapper pan like we use at the co I work for is in the rear of the machine... there is a fuel tap at the tank.. it runs softline for a few feet, then converts to hardline to run about 25'.. then converts back to softline where the machine articulates, then back to hardline till you get to the fuel seperators and filters. Unit uses a low ( 4 psi ) charge pump inthe tank to get the fuel the 30-40' forward to the front of the machine... then to a water trap, and then a low mic and a hi mic filter, then to the injection lift pump and then the injector pump... return line from the injector pump drops in before the water trap and filters. the manufacturere decided to save te customer some money and not carry the return fuel back 40' to the tank... guess their engineers were wrong then.. right?

The real issue is heat.. Again.. Depending onthe fuel system plumbing, you may well have no problem with it. A sufficiently large fuel sump inline ( like a fuel setteling bowl ).. or a spin on fuel filter should handle any heat or areation problem. Lots of modern apps have multiple filters and 'sumps' in line. For instance.. on my 7610sm once you leave the tank, you hit 2 water seperators and one canister filter. the water seperators probably hold 6-8oz each, and the canister filter must hold that much as well. That's alot of ounces and places for cooling to occur.. add in about 5 foot of 3/8 fuel line.

In Matt_JR's following statement "If it goes back into the supply line before the pump it will cause cavitation of the fuel, or as Ciderman said, cause aeration, unless the only pump is on the rail. then the fuel will never be pulled out of the tank. It will just go in circles if not just pump air."

he forgets some fundamental things.. one side of the fuel supply line is open to the tank.. so there is no presure buildup inthe supply line between the pump and the tank except by fluid pressure of the fuel inthe tank.. IE.. if fuel is dumped into the supply line in excess of what the lift pump is using, it can displace the fuel inthe tank .. besides.. it's hard to return more fuel to the tank than you are actually pulling for it.. unless this is some kind of perpetual motion fuel making vehicle.. IE.. it uses 4oz of fuel fromthe tank.. but returns 6oz!! .. As for fuel not being pulled out of the tank... I guess Matt forgets that in this hypothetical scenerio there is a hardline from the tank to the pump with a fuel return line 'T' into it.. if the pump needs more fuel than is coming from the return line.. the tank sump will supply it... just like it would if the return fuel was being dumped on the ground.. or back into the top of the tank...

To the original poster.. there are lotsa ways to get a sealed fitting onto a tank.. some easier than others choose a safe one you can live with and go for it. it will make the witchhunters all feel better

Soundguy

Well, the tank is plastic. Getting a backup nut in there might not be so easy as the filler is at an angle (not straight down) and the gascap mod is not practical. Because the cap unscrews, how would you remove it if there is a fuel line attached to it? Ciderman: cutting and rewelding sounds interesting but I have zero experience with a plastic welder and a fuel cell might not be something I'd like to start experimenting on. In the past, my attempts to weld with something other than the correct tool results in nothing more than making ugly holes in plastic. Seems plastic likes to shrink. Oh, BTW, the tank is one of those fitted/molded plastic tanks that looks like it was blow molded in place, flat pancake shape. Need to remove, rear seat, fenders which wraps around and the foot rests, etc to get at it. Will take another look later. Thanks guys for all the great info. A collection of brains is always better than a single one.

 

[Soundguy]

Mike: Great suggestion. The only thing is that I don't think a bukhead fitting on the filler tube would work because I haven't found any that would mount to a round surface, only a flat surface. I think the neck is like 4" long.

Get a saddle mount fitting.. they are usully an adjustable metal band that has a rubber facing and a tap built into it... Saddle the filler tube and dump excess fuel back in there..

soundguy

 

[Matt_Jr]

Didn't mean to be a naysayer. Just putting out some things that you should think about and why engineers do what they do. It is totally possible to put in a "T" fitting. I just wouldn't recommend it. My previous posts are based on theory, not imaginary perpetual motion machines that drive 18hp diesel tractors. What I said is fuel pumps carry more fuel up to the injector pump than the engine needs. The fuel that is not used "usually" goes back to the tank. The only way for the T fitting to work that I can think of is have the lifter pump in the tank and a relief valve in there to allow the extra fuel to go back into the tank unless the lifter pump is of low enough pressure that it doesn't risk getting burned up. I have seen too many times blocked fuel filters that cause high amperage of electrical flow through the pump that causes the pump to fail. The scraper pan that Soundguy mentioned has very long lines capable of cooling the fuel. But he also said "depends on application". About the cavitation....Only something to consider. Like I said "theory". I want to see posts that tell how stong the tractor is when completed. As an automotive diagnostician I use theory I learned in physics more than I crack open the books to make my money. I fix stuff others have given up on. I'm not saying stuff won't work and all you'll have is problems, just tryin' to point out what those problems could be before they occur. Now about that perpetual fuel multiplier machine, I think I'm gonna go out to my shop and start drawing up plans and hire a patent lawyer. I think soundguy just clued me in on a way to make my prius get better mileage

 

[Soundguy]

Matt.. not alot of tractors have a lift pump IN the tank. Many of them have a simple fuel tap in the tank with a gravity feed line that then goes out to a charge or lift pump.. or to the injector pump itself.

My original message on this SPECIFICALLY stated that a fuel return 'T' setup would have to be BEFORE any pump in the system, .. IE.. between the tank and the 1st pump.. thus the returning fuel is dumped into the same low pressure line the tank is feeding, before any pumping occurs. Given the low pressures involved here ont he 'suction' side of the pump, and the temps a diesel engine might see on a sunny work day, plus the usual filter and water sumps you normally see in an ag application... I don't forsee cavitation or fuel vaporization being anything but a theoretical issue here.

Soundguy

Didn't mean to be a naysayer. Just putting out some things that you should think about and why engineers do what they do. It is totally possible to put in a "T" fitting. I just wouldn't recommend it. My previous posts are based on theory, not imaginary perpetual motion machines that drive 18hp diesel tractors. What I said is fuel pumps carry more fuel up to the injector pump than the engine needs. The fuel that is not used "usually" goes back to the tank. The only way for the T fitting to work that I can think of is have the lifter pump in the tank and a relief valve in there to allow the extra fuel to go back into the tank unless the lifter pump is of low enough pressure that it doesn't risk getting burned up. I have seen too many times blocked fuel filters that cause high amperage of electrical flow through the pump that causes the pump to fail. The scraper pan that Soundguy mentioned has very long lines capable of cooling the fuel. But he also said "depends on application". About the cavitation....Only something to consider. Like I said "theory". I want to see posts that tell how stong the tractor is when completed. As an automotive diagnostician I use theory I learned in physics more than I crack open the books to make my money. I fix stuff others have given up on. I'm not saying stuff won't work and all you'll have is problems, just tryin' to point out what those problems could be before they occur. Now about that perpetual fuel multiplier machine, I think I'm gonna go out to my shop and start drawing up plans and hire a patent lawyer. I think soundguy just clued me in on a way to make my prius get better mileage

 

[Matt_Jr]

Soundguy I agree. I missed the part where you said the T fitting would be between the 2 pumps. My bad. I stand corrected. At those low pressures and flow I don't foresee any cavitation problems either once the fuel system is properly bled. I would however make sure that the return line didn't go anywhere at all close to the exaust side of the tractor and maybe even put a cooler on it. Under hood temperatures not withstanding injector pumps absorb the heat from the engine and could warm up the fuel a little. Making a few 180 degree bends in the return line near some air flow would help radiate some of that heat if it's a problem. In a project like this space is far too valuable to add stuff that may not be needed. I would put the return line in a T fitting like you said without the cooler. The filters surface area just might radiate enough heat. Vaporization of fuel generally isn't a problem with diesels. Diesel just isn't as volatile as gasoline. The fuel being warmed up a little will help with fuel efficiency anyhow.

 

[Soundguy]

Ditto. I think fuel temp will be fine.

I've seen some designs that routs the return fule line thru an OHV cover before it hits the tank..with no issues ( unless the line leaks! ).

If this were gasolene.. different arangements would probably need to be made depending on design.

soundguy