Cooling problem fixed... Now 5v to pumps, won't idle!!

redfr03svtsnake

Import Killer since 03'
Established Member
Joined
Aug 1, 2006
Messages
1,211
Location
Louisiana
Ok let me try to give all the facts, I am only getting 5v to the fuel pumps at idle, doesn't matter which way I try it, with or without Bap etc.... Made a good hit and noticed it was lean (14 afr to be exact).... It was running ok while testing the new mishimoto rad, staying cool finally, keeping a decent amount of voltage too, ~13v, but it all of a sudden(after running and idling fine for 30 mins )didn't want to idle and ran lean during a test pull.... Got it home, it only gets 4.5-5v (constant, no huge spikes, tried revving to 3k n holding, same story)out of wires running directly to pumps. Car will run but I've got to give it some gas. Duty cycle is at like 32% and pressure is still stable at the rail, 38.5-40 psi.... Anyone care to help me figure this out? I've got dual fpdms, dual gt40s, had a single Bap that I figured was causing this so I removed, same result. Changed relay for dual fpdm, same result, fuses good..... What else could it be? I don't figure a bad frps could cause this as I'm getting a good rail pressure reading..... Any insight?
 

AMB

Active Member
Established Member
Joined
Mar 4, 2003
Messages
976
Location
SAN DIEGO,CA.
5v?

You need to check where you get the +12v FROM!!! Make shore you HAVE +12v there!!! Then CHECK/TRACE the wire going to the FPDM ?- RELAY ? - PUMPS ?, to see where you are LOOSING the +12v and seeing +5v !!! :??:
 

Black306

Active Member
Established Member
Joined
Sep 4, 2002
Messages
1,687
Location
State Capital, Ca
5v and 32% duty cycle sounds about right. The only time you are going to get close to battery voltage at the pumps is with 100% duty cycle. Simply reving an engine isn't going to demand much more fuel; the engine needs to be under load.

Do you have any logs to share?
 

redfr03svtsnake

Import Killer since 03'
Established Member
Joined
Aug 1, 2006
Messages
1,211
Location
Louisiana
Nah I haven't done that, that's strange though, I guess I need to be looking elsewhere. So you are saying fuel pump voltage is commanded and that the rail pressure and duty cycle are correct? I might have popped off a vacuum hose or something because it will not idle at all. I'm going to check the plugs in the passengers side head and see what that gives me, then go from there.
 

Users who are viewing this thread



Top