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fuel pressure question

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mrsprite

mrsprite

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My Bugeye has a Datsun A15 engne in it and I'm running an electric fuel pump that I got from NAPA. I just installed a Holley pressure regulator with guage and it shows ~2.5psi max (this is with the regulator adjusted all the way for max pressure). According to the Datsun manual, I should have between 3 & 3.8 psi, so my question is what ill effects (if any) will running the pressure too low be on my car?

I am thinking about getting a higher pressure pump (7psi) and regulating it down to around 3.5 psi. Any problem doing that?

Thanks.
 
I would think fuel starvation would be an issue and make you run lean, which could be damaging to the engine. I would definitely get a higher rated pump and dial it down.
 
Yes, agree.
 
Pressure not going to be that be of a deal if you have the volume to keep it filled. You could gravity feed it as long and you have the volume. ( gotta remember, old 4 cylinder bikes were gravity fed, made stupid horsepower per cc and used lots of fuel when wide open.)

I'm supried it calls for ~3psi. I figured 6-7. Try running it w/o the reg and see what happens. If it doesn't flood out you're o.k. Why use it if you don't need it.

My personal feelings are you'll be fine @ 2.5 as my Weber calls for 2-3 on my 1500 and it never runs dry or lean. I can't see how your motor will require more fuel than mine.
 
I have been driving it around for over 3 years without a regulator......I just installed the electric pump a year or a year & a half ago. I decided to buy the regulator in case the pump was putting out too much pressure, but was surprised when it was just the opposite. It seems to run fine, but every once in a while it likes to stall when coming to a stop sign, etc. That was pre-regulator......I literally just installed it today.

As long as I'm not hurting anything, I will just leave it alone until decide to swap out pumps. I will keep an eye in things though. I guess I'm a little paranoid since I plan on taking the Bugeye on a 5000 mile roadtrip in 2 weeks.....I don't want anything to break on that trip! :smile:
 
That could have been from too much pressure and fuel level was too high. It might have sloshed out the bowl vent and down the carb. Drag cars use fuel line for bowl vent extentions cause the car launches so hard, fuel would climb the vent and down the throat of the carb. The car would stall due to an excessive rich condition. Hitting the brakes could do the same thing if level is too high.


Sometimes I'll play w/ float level if I think pressure's a bit too high. I'd drop it down a bit in case the needle was spring loaded or needed a bit more float push to seat it. Not "correct", but it does work in some curcumstatnces. Keep that in thr back of your mind while on your trip.
 
It's important to distinguish between flow and pressure. One does not imply the other.

You need enough pressure at a reasonable flow rate to get past the obstructions and raise the fuel to the carbs. On a Spridget, this isn't more than about 1.5 PSI. In fact, you don't want a lot of pressure, or it will push fuel past the float valves. I run my bugeye at about 1.5 PSI back-off pressure (i.e., with the fuel flow stopped). I use a regulator, so it's probably close to that when flowing.

Any reasonable pump will have a decent flow. You only need a couple gallons per hour to keep the bowls full.

My feeling is that unless you have problems, which seems unlikely, just use it as is.
 
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