SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: 79charger on April 24, 2011, 01:24:17 PM

Title: Fuel Preesure while under load
Post by: 79charger on April 24, 2011, 01:24:17 PM
Have a BBF  with Holley 750 street avenger with vacuum secondaries , Holley red fuel pump , and a electric "helper pump" . have 6-8 psi at idle , drops to zero at full throttle 4200 rpm and the rpms bounce up and down from 3900 to 4200 like it is not getting enough fuel to maintain ...... BTW all new parts . Thanks guys
Title: Re: Fuel Preesure while under load
Post by: Ralph Brunt on April 24, 2011, 01:53:29 PM
what size lines?

sounds like a bad fuel pump
Title: Re: Fuel Preesure while under load
Post by: ka0tyk on April 24, 2011, 01:56:42 PM
have u tried it without the "helper pump"?
Title: Re: Fuel Preesure while under load
Post by: 79charger on April 24, 2011, 01:59:53 PM
3/8 Fuel Line , I never run the helper pump except to prime the motor after it sitting . Could the electric fuel pump be bad or slowing down the fuel flow from the mechanical one ???
Title: Re: Fuel Preesure while under load
Post by: Ralph Brunt on April 24, 2011, 02:04:40 PM
have u tried it without the "helper pump"?
thats what im thinking, try one pump at a time.... hell get a good mech pump and dont look back

remove the unused pump to try the other
Title: Re: Fuel Preesure while under load
Post by: ka0tyk on April 24, 2011, 02:14:16 PM
3/8 Fuel Line , I never run the helper pump except to prime the motor after it sitting . Could the electric fuel pump be bad or slowing down the fuel flow from the mechanical one ???

the mechanical pump is probably struggling to suck the fuel thru the impeller of the electric one when its not on. 
Title: Re: Fuel Preesure while under load
Post by: 79charger on April 24, 2011, 04:39:41 PM
Ok I will remove the electric pump then ..... Should the pressure stay 6-7 while a load is on the motor?
Title: Re: Fuel Preesure while under load
Post by: Ralph Brunt on April 24, 2011, 05:14:46 PM
Ok I will remove the electric pump then ..... Should the pressure stay 6-7 while a load is on the motor?
yes
Title: Re: Fuel Preesure while under load
Post by: 79charger on April 24, 2011, 07:44:06 PM
Thank you
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