Fuel Pump

[eafree]

I have a question for all you smart guys out there. My fuel pump started blowing the 20amp fuse all of a sudden. I'm running a Holley red pump with a holley fuel pressure regulator 12-804, feeding a Edelbrock 1405 600CFM carburetor. The fuel pump is wired in to the ignition side of the ignition switch. I have about one hour of run time on this fuel system setup. It now runs for about 5 minutes, and then the fuse blows and the pump gets really hot. I have inspected all the wiring and there are no pinched wires, and the ground is good. Am I missing something simple?

 

[2old2fast]

IF you're wired direct from switch to pump ,you may not be getting enough juice to the pump. Better to have a relay in the system to carry a higher load. some of you guys who have a diagram you can post, help out .

dave

 

[CrAlt]

http://www.holley.com/12-801-1.asp

Is this the pump you have?

It says it should be pullin 2 amps.
And that it has a built in by-pass.

Maybe the by-pass is clogged or stuck and its stalling the motor making it get hot and draw to much. .

I never was a big fan of those dead end fuel pressure regulators. I have a maroso by-pass regulator with a holley blue pump on another car. It dumps the extra fuel back to the tank.. so fuel is always flowing through the pump keeping it cool.

 

[Golly]

I believe the "red' pump is self regulating to about 8 PSI so the reg shouldn't be needed. Do you have a good filter before the pump, maybe it's sucking dirt from the tank and jamming it up?

 

[gfigms]

I had a RED that would get hot and shut down ... at the most unopprotune time ... like the middle of major highway during rush hour. After car sat for about 15 minutes, it would start working and off you'll go. Called Holley and they said the motor winding was proably shorting out and to replace the pump. I did and have not had any more issues.

 

[Wild Mango]

Whoah! Fire Danger! The fuse is doing it's job by melting and disconnecting a fault. Keep in mind its a 20A fuse but thats a nominal rating, there's probably more than 20A to melt the fuse in 5 minutes. The pump motor is on the fritz, its sending out distress signals by getting hot and melting fuses. Get that sick puppy out of there before it tries to send up smoke and flame signals as well.
BTW, when you replace the pump, check the wiring. First symptom of over heated wiring is usually the insulation becoming discolored and/or hard. If you strip a bit of insulation off, the conductors are discolored. Either way, replace the wiring with the pump, cheap insurance.

 

[Mike]

I've never been a fan of the Holley fuel pumps. Electric or mechanical. If you're buying one, you may as well buy two, because the first one is going to fail well before you anticipate. The electric pumps are going to have armature problems and the mechanical pumps are generally more effective at pumping out oil than they are at pumping gasoline.

I'm with CrAlt on the bypass-style regulators. Yes, it requires plumbing a return line, but it puts an end to dead-heading the fuel pump. The dead-heading is what causes heat build-up in the pump.

This is one of those areas where the K.I.S.S. principle comes into play. I'm betting the majority of you using a big, electric pump really don't need it. Why run another electrical circuit, unless it is actually necessary? Unless your frame/motor mount design is not going to physically allow you to use a mechanical fuel pump, there really is no reason to run a ginormous, electric pump. I know, all you guys running dual carbs are going to tell me how you need all that extra volume, but what you're overlooking is the fact it's easier to supply fuel to a dual-carb motor than a single-carb. You already have twice the float bowl volume as the guys with the single carbs.

We had a really popular engine combination we built for guys running IMCA-type modifieds. Nothing real fancy, but the combination would make 550 HP and 540 ft/lbs on the flattest torque curve I had ever seen. And they would do it all day long. And those numbers weren't something we pulled out of our arses, or calculated on a Web site. We used a SuperFlow 901T, with the big absorbtion unit, so we could dyno the Pro Stock stuff. Those modified motors used Carter mechanical fuel pumps. We would recommend customers run a -10 line from the tank to the pump and we would run -8 out of the pump, up to the carb. We used return-style regulators on everything. And I never saw a single one of those engines ever run out of fuel. On the unlimited late model stuff, we would run higher-end pumps, but that was stuff making 750+ HP.

On the race car, I used one channel on the RacePak to monitor fuel pressure. For a handful of races, before I took the transducer off. We used Mallory pumps and regulators and the regulator was set at 7 lbs. The fuel pressure graph was always a flatline, from one end of the track to another. Any combination of a pair of split Dominators, a single Dominator with a single split or a pair of 750 carbs on a motor that makes in excess of 2.6 HP per cubic inch and fuel pressure was steady as a rock.

And you guys are running 110 GPH electric pumps because...?

 

[2old2fast]

So, O Great Guru of technical data, isn't there a chart that says, lbs./hr. of fuel per X horsepower ?

dave

ya' know ,positive data instead of negative .

 

[Mike]

It's not a chart, but rather a couple of simple formulas. Simple that is, assuming you can provide the variable quantities.

If you are calculating consumption after all parasitic losses, that would be -

BSFC = r/P

r = fuel consumption in grams per minute and P = brake power in watts.

You'll need to calculate brake power as P=τω

τ = engine torque in newton meters and ω = engine speed in radians per second.

That will give you a number expressed in grams per kilowatt-hour.

If you are measuring consumption based on in-cylinder pressures, that would be -

ISFC=r/I

r = fuel consumption in grams per minute and I = indicated power

Once you have those calculations complete, you can use the BSFC to determine fuel requirements at wide open throttle. If your BSFC number comes out to .50 (for an example), your engine will require 1/2 pound of fuel per hour, for each horsepower it is making. 100 gallons comes out to ~660 pounds. For an engine with a BSFC number at .500 to require 660 pounds per hour would mean the engine was making 1320 HP.

Sadly, you cannot just use a single formula for every engine out there, as engine volume plays into the equations, as does engine speed and compression ratio. Heat losses to the cylinder walls will drop an engine's thermal efficiency. You can determine BSFC at a pre-determined engine RPM and then see BSFC go up with increased engine speeds, because of the increased friction losses that will result. And increased compression ratio will give an engine better thermal efficiency, so BSFC will drop.

Positive enough for ya?

 

[2old2fast]

After digestion, yes ,useful info, however ,I'm sure you could dumb it down for those w/out a degree.

dave

 

[eafree]

Well, I pulled the pump apart and found the bypass port plugged. It works perfectly now. I would have prefered to run a mechanical fuel pump, but I have a later model engine block.

 

[Mike]

After digestion, yes ,useful info, however ,I'm sure you could dumb it down for those w/out a degree.

Seeing as how I don't have a degree, I don't know enough to dumb it down any further. Multiply your BSFC by horsepower to get pounds per hour. Divide that value by ~6 pounds per gallon to get an approximate gallons per hour number. If someone can't get that, send me a copy of the dyno sheet and I'll figure it for you.

I guess I lost the plot, I thought that was what you were asking.

eafree, I would say that's a pretty good reason for using an electric pump. :winkn:

 

[Mr. Fixit]

I have a question for all you smart guys out there. My fuel pump started blowing the 20amp fuse all of a sudden. I'm running a Holley red pump with a holley fuel pressure regulator 12-804, feeding a Edelbrock 1405 600CFM carburetor. The fuel pump is wired in to the ignition side of the ignition switch. I have about one hour of run time on this fuel system setup. It now runs for about 5 minutes, and then the fuse blows and the pump gets really hot. I have inspected all the wiring and there are no pinched wires, and the ground is good. Am I missing something simple?

Hey, how are you doing. Sounds like you have it all together. I am the guy who sold you the used fuel tank that clogged up your new pump. lol Well, I hope that's not the case... A 20 amp fuse is really exessive since 16 gauge wire is only good for 20 or so amps on short distance runs. You would be putting the feed wire at risk of a meltdown before the fuse blows, if it blows at all prior to the wire melting. Since the 20 amp has already blown repediately, I suggest changing the wire feeding the pump since it has probably been heated and cooled too many times. BTW, based upon the way you have indicated that you hooked up the pump, I believe that the instructions call for a 7.5 amp fuse rating without a relay being used, or 15 amp with a relay. Just trying to help...

Good luck..