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fuel pump PSI
Posted: Sun Jul 25, 2004 8:54 pm
by lukeash
GDAY all. so tech ?s so please help me out. just finished puttung in 350chev into my GQ. the budget was tight so i went for a cheap fuel pump(5-7psi) and ive just started to have flow probs especialy off road. some ppl have said i need alot bigger pump is this true? those guys with the v8's what pump do you use? whats a good psi for a 350 with a quadrajet rochy? please help im going INSANE
Posted: Sun Jul 25, 2004 9:16 pm
by MKPatrolGuy
I just have one of the cheap Repco pumps on mine. Never had a prob. (Except when the fuse blows or the plug gets pulled appart
)
Posted: Sun Jul 25, 2004 9:22 pm
by J Top
You are talking about 2 differnent things here,flow and pressure.
Lack of flow has more to do with restrictions,pipe sizes,size of pump,was it a diesel and are you running the petrol thru the diesel filter?
You can probably get 5-7 psi from a syringe.How is your float level?
J Top
psi
Posted: Mon Jul 26, 2004 4:42 pm
by lukeash
no it was not a diesel and its not running through the old filter. the pump is realy loud all the time sounds like its empty but the tank is full. i dont no whats doing i will just have to investigate it more
Posted: Mon Jul 26, 2004 9:27 pm
by dow50r
Pumps like to pump and not suck. If u mounted in the bay, try moving it down to tank level.
Andrew
Posted: Tue Jul 27, 2004 9:24 am
by 80UTE
If the pumps real noisy it could be cavitating which indicates a restricted suction line. Elec fuel pump should be as close to the tank as possible with a suction hose atleast the size of the pump "in" port.
Wally
Posted: Tue Jul 27, 2004 12:50 pm
by mkpatrol
5-7 psi is spot on. If you have any more then the fule will push past the needle & seat & flood the engine.
How hot is the engine?
when was the quadrajet recoed last?
What sise are the fuel lines?
What condition are the rubber hoses?
psi
Posted: Tue Jul 27, 2004 3:51 pm
by lukeash
not sure what exactly you mean by how hot but if it is wat i think you mean its pretty stanfard. the carby has been rebuilt in the last 4months the hoses ar in good nick. not sure of the exact hose size but we did leave the standard GQ lines that run along the chassis
Posted: Tue Jul 27, 2004 4:03 pm
by mkpatrol
Hosed should be ok as standard holden items were 5/16 (almost 8mm).
What is actually happening when you go off raod?
Does it cut out going up steep hills or flood going down hills?
psi
Posted: Tue Jul 27, 2004 6:30 pm
by lukeash
it dies going up steep hills mbut also on the road normal driving i put my foot down and it just doesnt do what it is meant to do being a V8. feels like the pump is not keeping up with the engine
Posted: Wed Jul 28, 2004 8:22 am
by mkpatrol
Sounds like you float level is too low. If the fuel pump is pumping at the correct psi the flow will be generally correct. The float bowl is actually the fule supply to the engine, the pump supplies the float bowl. If the float level is too low then the float bowl cannot keep up with the demand. Ther is no pressure in the bowl, the fuel is supplied through jets using atmospheric pressure and vaccum.
The other thing to remember is all the Aussie Quadrajets were designed for passenger cars and might not be able to cope with 4wheeling.
I would start with the float level if it is starving for fuel.
How is the tune?
Is the dissy advancing ok?
if there is no advance then that will make it feel flat.
Generally with the float what will happen is the engine will cut out intil the fuel is returned to the float bowl.
Keep at it, you will find ther will be a simple cure to this.