battery voltage and EMS
08-18-2009, 03:07 PM
#1
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battery voltage and EMS
After going nuts troubleshooting a no fuel pump activation condition and finding nothing wrong in the fuel pump circuit (grounds, relays, etc) I realize that EMS may need a fully charged or almost fully charged battery to just activate the fuel pump
What I mean is, in the past I thought (as my car's been garaged for a while) that even with a battery voltage of 12.15 - .20 that I thought I would still be able to hear the fuel pump kick on upon turning the ignition on.
So after troublehsooting I decided to give my Braille battery a full charge, and the fuel pump activated and car started.
So my question is does EMS require a fully charged or near fully charged battery to just activate the fuel pump? Car cranks NOT so low to notice a discharged battery either. Obviously, the norm is to have a good working fully charged battery, understood. I'm just questioning the fact of the fuel pump not activating with 12.15 - 12.18 volts and yes I understand also that means battery is 25% charged only.
I'd like to rule out a bad fuel pump circuit or whatever circuit it is that controls the fuel pump inside the EMS.
On that note my 1.5 year old Braille battery seems to have sulfated from sitting
What I mean is, in the past I thought (as my car's been garaged for a while) that even with a battery voltage of 12.15 - .20 that I thought I would still be able to hear the fuel pump kick on upon turning the ignition on.
So after troublehsooting I decided to give my Braille battery a full charge, and the fuel pump activated and car started.
So my question is does EMS require a fully charged or near fully charged battery to just activate the fuel pump? Car cranks NOT so low to notice a discharged battery either. Obviously, the norm is to have a good working fully charged battery, understood. I'm just questioning the fact of the fuel pump not activating with 12.15 - 12.18 volts and yes I understand also that means battery is 25% charged only.
I'd like to rule out a bad fuel pump circuit or whatever circuit it is that controls the fuel pump inside the EMS.
On that note my 1.5 year old Braille battery seems to have sulfated from sitting
08-18-2009, 03:56 PM
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with out the car running and the alt. working your not going to get more than 12.X volts.
i had a car with individual throttlebodys kick my ass that had one of those little batteries in it. read 12v..... car started sometimes, not always. fought and fought with the idle etc. put a real battery in the car and it started perfect, idled perfect, and all of the weird problems went away.
i had a car with individual throttlebodys kick my ass that had one of those little batteries in it. read 12v..... car started sometimes, not always. fought and fought with the idle etc. put a real battery in the car and it started perfect, idled perfect, and all of the weird problems went away.
08-18-2009, 04:40 PM
#3
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Originally Posted by Joe @ Tempest,Aug 18 2009, 06:56 PM
with out the car running and the alt. working your not going to get more than 12.X volts.
not sure what you mean by that and how it relates to my EMS question
Well, i'll tell you that once the car is running the alternator is working-battery reads 14.2 -.3 at idle. I know the battery is shot now after sitting for a while.
08-18-2009, 05:10 PM
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you said that your battery was only reading 12v.
"I understand also that means battery is 25% charged only."
unless i missread what you said....was kind of letting you know that the voltage you are seeing is what you would see with a brand new battery. 12v with out the car running, 14v with the car running and alt working.
just curious, did you try unhooking the ground off of the battery previously, and reconnecting it? i have seen some really odd, unexplainable thing with ems boxes. sometimes simply removing all power to everything and reconnecting will make it work again. also seen unplugging the ecu and plugging it back in fix issues like you are seeing as well.
to answer your question, if the battery is showing 12v that would be enough to activate the fuel pump. if it has enough power for it to crank over, it has more than enough power to turn on the fuel pump.
again if the battery is weak it could cause odd things, but if its enough to crank the car it sounds like you might have something else going on
"I understand also that means battery is 25% charged only."
unless i missread what you said....was kind of letting you know that the voltage you are seeing is what you would see with a brand new battery. 12v with out the car running, 14v with the car running and alt working.
just curious, did you try unhooking the ground off of the battery previously, and reconnecting it? i have seen some really odd, unexplainable thing with ems boxes. sometimes simply removing all power to everything and reconnecting will make it work again. also seen unplugging the ecu and plugging it back in fix issues like you are seeing as well.
to answer your question, if the battery is showing 12v that would be enough to activate the fuel pump. if it has enough power for it to crank over, it has more than enough power to turn on the fuel pump.
again if the battery is weak it could cause odd things, but if its enough to crank the car it sounds like you might have something else going on
08-18-2009, 05:39 PM
#5
Thread Starter
Originally Posted by Joe @ Tempest,Aug 18 2009, 08:10 PM
you said that your battery was only reading 12v.
"I understand also that means battery is 25% charged only."
unless i missread what you said....was kind of letting you know that the voltage you are seeing is what you would see with a brand new battery. 12v with out the car running, 14v with the car running and alt working.
just curious, did you try unhooking the ground off of the battery previously, and reconnecting it? i have seen some really odd, unexplainable thing with ems boxes. sometimes simply removing all power to everything and reconnecting will make it work again. also seen unplugging the ecu and plugging it back in fix issues like you are seeing as well.
to answer your question, if the battery is showing 12v that would be enough to activate the fuel pump. if it has enough power for it to crank over, it has more than enough power to turn on the fuel pump.
again if the battery is weak it could cause odd things, but if its enough to crank the car it sounds like you might have something else going on
"I understand also that means battery is 25% charged only."
unless i missread what you said....was kind of letting you know that the voltage you are seeing is what you would see with a brand new battery. 12v with out the car running, 14v with the car running and alt working.
just curious, did you try unhooking the ground off of the battery previously, and reconnecting it? i have seen some really odd, unexplainable thing with ems boxes. sometimes simply removing all power to everything and reconnecting will make it work again. also seen unplugging the ecu and plugging it back in fix issues like you are seeing as well.
to answer your question, if the battery is showing 12v that would be enough to activate the fuel pump. if it has enough power for it to crank over, it has more than enough power to turn on the fuel pump.
again if the battery is weak it could cause odd things, but if its enough to crank the car it sounds like you might have something else going on
I'll have to try the unplugging/pluggins thing on the ECU
On the battery I have a quick disconnect knob but I guess I'll have to unplug/plug there too and see.
Yeah that's where me questioning the ECU fuel pump circuit came in. It defenitely takes more power to turn a damn starter than a stupid fuel pump so something is going on
08-18-2009, 06:20 PM
#7
Thread Starter
Originally Posted by Joe @ Tempest,Aug 18 2009, 08:42 PM
did you do anything else to the car before this issue came up?
I'm gonna swap out the battery tomorrow with the battery from my maxima. It's a big huge foker and see what happens. At this point I have a feeling since the battery doesnt hold a full charge anymore, it may be doing something weird as you stated.
Regardless, i'm still at a loss because starter > fuel pump
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