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Just installed a new pump. problems.

Bass Junky

By Bass Junky,
in Engines & Forced Induction

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Sydneykid Grand Master

Sydneykid

Posted
Posted
yep,

Two voltages

That shouldn't change the fuel rail pressure, it only affects the flow from the pump. I thinks it is more of a noise reduction effort than anything else, so you can't hear the pump when sitting idling. :idea:

Sydneykid Grand Master

Sydneykid

Posted
Posted
Question.

Should the pressure rise when the pump changes voltages?

BASS OUT

No not usually, even on low voltage they have enough to pump 36-38 psi, after all the engine isn't using very much at idle. :burnout:

GTRgeoff Grand Master

GTRgeoff

Posted
Posted

This was something I found odd when I installed my GTR pump. The car was rich as buggery and I was running almost full static advance to make any power (Really).

I changed the filter to no avail, but it was full of crap anyway so this was a good move.

I then installed the Malpassi and drove to get the PFC installed and tuned and all was better. Strange but true. I have no explanation.

Sydneykid Grand Master

Sydneykid

Posted
Posted
This was something I found odd when I installed my GTR pump. The car was rich as buggery and I was running almost full static advance to make any power (Really).

 

I changed the filter to no avail, but it was full of crap anyway so this was a good move.

 

I then installed the Malpassi and drove to get the PFC installed and tuned and all was better. Strange but true. I have no explanation.

See it all the time, the standard pump was stuffed and the filter blocked. So when it was tuned, the tuner compensated for the low fuel pressure. Then when you put the big pump in and a new filter, the correct amount of pressure was being applied at the rail and the engine runs rich. This is where the BS stories start about retuning being needed after larger fuel pumps are installed.

Bottom line, if it had 38 psi rail pressure (above boost) when it was tuned then it will run the same as long as it has 38 psi (above boost) rail pressure. You could put 50 pumps on it, as long as the rail pressure was 38 psi it would still run the same A/F ratios.

Hope that clarifies :D

YOYO Contributor

YOYO

Posted
Posted
yep,

Two voltages

Yeah, I've heard of this before in 180s as well. It appears that the engine management only applies the full voltage at higher revs by limiting the ground at lower revs. You can get a constant full voltage applied if you wire the pump directly to the chassis for a "complete" earth (i.e 0V at all revs, as opposed to 1-2V at low revs, and 0V only in the upper rev range).

PHATR32 Grand Master

PHATR32

Posted
Posted

you sure about the ground thing? in the mazda's the fuel pump voltage gets cut instead. so when hit boost you get 12v so you get full pressure, and then it drops to 10v for idling and cruising.

a trick was to bypass the whole thing and run a fat cable directly from the battery through a relay which would give the pump 14.4v, which would increase the pressure a bit more over stock.

i have seen stock fuel ppumps die running at 14.4v constantly (happened to my stock laser pump), dont know about aftermarket fuel pumps.

steve

GTRgeoff Grand Master

GTRgeoff

Posted
Posted
See it all the time, the standard pump was stuffed and the filter blocked. So when it was tuned, the tuner compensated for the low fuel pressure. Then when you put the big pump in and a new filter, the correct amount of pressure was being applied at the rail and the engine runs rich. This is where the BS stories start about retuning being needed after larger fuel pumps are installed.

Bottom line, if it had 38 psi rail pressure (above boost) when it was tuned then it will run the same as long as it has 38 psi (above boost) rail pressure. You could put 50 pumps on it, as long as the rail pressure was 38 psi it would still run the same A/F ratios.

Hope that clarifies :)

I'd agree whole heartedly if it had ever been tuned, but on the stock computer....

The only thing you have prompted me to think of is that the stock pump was buggered, so why did it then run so rich that I had to crank in so much advance? I'm still puzzled by this one. (Queue X files music)

B-Man Grand Master

B-Man

Posted
Posted

Put the standard pump & old filter back in and measure the fuel rail pressure. SK is on to something here.

I have an upgraded Bosche pump, standard fuel rail, standard fuel pressure regulator, 550cc injectors and 330rwkw - PLUS 300+ kms per tank.

GTRgeoff Grand Master

GTRgeoff

Posted
Posted

I'm certain there would ba a logical explanation, but I changed the filter, no difference, then installed the malpassi and pfc and had the tune. Anyways it runs fine now.

So do you measure your duty cycle on the injectors? I was set to upgrade mine before the next step up.

ylwgtr2 Grand Master

ylwgtr2

Posted
Posted
you sure about the ground thing?  in the mazda's the fuel pump voltage gets cut instead. so when hit boost you get 12v so you get full pressure, and then it drops to 10v for idling and cruising.

a trick was to bypass the whole thing and run a fat cable directly from the battery through a relay which would give the pump 14.4v, which would increase the pressure a bit more over stock.

i have seen stock fuel ppumps die running at 14.4v constantly (happened to my stock laser pump), dont know about aftermarket fuel pumps.

steve

The pressure regulator controls the pressure...not the pump...the only way it will alter is if the reg is totally overcome by the supply and cant let off enough volume

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