Do I Have A Lazy Alternator

[tricstar]

So I'm having fuel pump problems ( no enough fuel ) and I'm thinking its not enough power to the pump so i've been doing some testing, these are my results..

voltage direct from alternator obviously while running (all testing idling at 2000rpm ) 13.5v

voltage at battery ( GTR, so in boot ) 13.2v

voltage at pump ( external, hard wired ) 12.8-13.1v

I need more power to the pump.... shouldn't I be seeing around 13.5v at the pump and 14v+ at the alternator???

I would really like 14v+ at the pump?

or is all that ok?

[abr33]

You should be up around 14.5-14.8 volts

[kitto]

You should be up around 14.5-14.8 volts

Not really.

13.8 Volts is the nominal voltage of a battery. 6 cells, 2.2V per Cell = 13.8V

With the engine running @ 2,000RPM and a healthy alternator, at the alternators output, you should see around the 14.0 - 14.2V mark.

At the fuel pump, Anything less than 12.5V isn't ideal at all. You want to have it around the 13.8V mark if you can. Cable size plays a big part in this. If you have factory wiring to the pump, change it out for something with a substantial cross sectional area to support the current and minimize voltage drop.

You dont want a car's electrical system too much above 14V, a lot of the electrics won't like it.

[abr33]

I should have added when the cars running. I think it'd be up there tbh, mine runs 14.2 i think and its getting lazy too. Your right on the money with the battery alone voltage

[tricstar]

so lazy alternator ? yeah

pumps are direct wired to battery terminal with good thick cable, and best I've seem is 13.1v. @ 2k rpm

also just data logged on motec the voltage and no matter the revs it never got higher than 14.1v, during a 40 minute drive .

as I'm only seeing 13.5v at the alternator @ 2000rpm,....time to replace??

0.5v-1v could make all the difference in flow from pump..

[Dose Pipe Sutututu]

no need to replace, seems fine.. sometimes it's actually the rectifier that's stuffed not the alternator... I believe on RBs, the rectifier is actually built into the alternator