Oil & Fuel Electric fuel pump/fuel presure regulator...

[DJ54]

Please excuse me for posting this in the MF section, but have gotten a lot of good info from you guys... And being most of you have lots of other "stuff', and maybe have had, or seen a similar situation..., and could shed some light on the subject. I will try and make it short and sweet, and to the point... This has to do with my 450 Bobcat...

I bought it used, from a rental company. The original mech. fuel pump apparently bit the dust. They replaced with a small electric pump. Approx. 35 gph, 4 - 5 psi. It lasted approx. 8 months, then bit the dust.

I replaced it with a Mr. Gasket model 12S 35 gph, 4 - 5 psi pump. Worked great for a while. As time went on, and the temps got hotter, it would run maybe 20 minutes doing medium load work. Then it would like vaporlock. But the pump had a different sound, or pitch to it. Running, but not pumping fuel. Cool for 20 minutes, it would run another 15 - 20. It lasted about a year. Replaced it, and worked good for a while... Would run several hours with no problems. Now having the same issues, after 20 minutes of use. I've pretty much ruled out the fuel supply line collapsing, because of the extra running time with the new pump...

I went to the Mr. Gasket online site. Checked out the tech info on the pump. On there in the first paragraph it states, that if used with a carb., there should be a fuel pressure regulator installed... Probably on the paperwork I got with it... But who reads that...!! No problem, they make one, and under $30.00...

I had a brainstorm about using the supply line as the return line also... Just Tee into it, between the pump and tank. Much like a municipal water system, where one line fills the water supply (ie: water tower), but yet supplies the demand on the system. My concerns were aeration of the gasoline, and will there be any friction, or static buildup.

I wrote their tech dept. for an answer. No real answer/explanation to the concerns above... Just " No, you'll have to run a seperate return line..." Liability concerns I'm sure... Still seems like it would work to me... Just concerned about causing extra vapor returning in the same line... Will it cause air bubbles, cavitation..?? Just plain won't work..?? If not..., how come..??

Not that big of a deal to run a return line, since the tank is plastic. Will just need another..., uh..., can't think of the word I'm looking for... Maybe "thimble" for the line to go through the top of the tank, and a piece of 5/16" brake line to put on the end of that... Although it would be a lot easier to just put a Tee in the supply line...

Any ideas/comments/suggestions..??
DJ

 

[ArTrvlr]

This almost sounds like a "why haven't I thought of that???". I say try it, what have you got to loose?
The only negative I can think of, is the fuel circulating in the loop could get hotter (from any heat generated by the pump), and heat is already your problem... but trial and error is the only way to find out.
jp

 

[banjodunn]

Gday have you got a return line out of the carb already? If not where do you plan on picking the return up from? As far as a press reg goes you only need one if the press from the pump is overiding the needle and causing it to flood it doesn't sound like this is happening. Have you got the pump right back at the tank or is it up near the eng as they work really well pushing fuel but don't like to suck all thet well. Just a bit of food for thought



Jon

 

[DJ54]

No, no return from the carb. Would be great if it did. There is no auto pressure relief in the pump. It's sitting there trying to pump 35 gph, and just gets hot.

The pressure regulator has 3 ports... One is a return for excess fuel. They are adjustable, with adjustments from 1 to 5 lbs. of pressure.

I may have to play with it, but I'm thinking minimum pressure will be sufficient, as many of the small engines were gravity fed anyway, Although these had fuel pumps. I'm guessing because of the height of the carb in reference to the fuel tank is within a couple inches. So a slight incline, and or rough terrain and low level gas in the tank, wouldn't provide an ample supply of fuel...

Keeping the fuel circulating in a loop at a low pressure should keep the pump cooler. Not like deadheading against the floatvalve.

 

[DEWFPO]

If this is a carbureted, gasoline engine you only need ~6 psi. A regulator is not necessary at these pressures and with a carb. A mechanical pump is typically very reliable at these pressures.

If your running the 35 gpm pump to combat the vapor lock, then a separate return line will help keep things cool.

DEWFPO