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12v Mod Question


terribleturner
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Does the 12v mod as described on MKIV.com make the pumps run after the ignition is turned off?? Im pretty sure mine is wired up the same way but my pumps run just with the first click of the key.

Anyone direct me to any other ways of doing it if there are any??

 

mine did this mate, i was trying the mod to try to sought out some slight det on the 4k change over point when i was BPU, i was alarmed to find the pump running i think it is linked to the ecu, it didn't solve my det (soughted when i went single) the other major thing with this would be in a crash situation :bang:

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does anyone know exactly how the fuel pump ecu works? what signal does it get to change from 10v to 12v? Why do you not need it with an aem? I asked a similar question on my single install thread but never got to the bottom of it. Many questions I know but I dont want to run my walbro on any less than 12v but also don't want to blow up if I crash (touch wood)

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From my understanding the 12v mod send a perm 12v signal to the fuel pump when the ignition is on, not good if you crash and are upside down or something, I think bypassing the fuel pump ECU.

 

The fuel pump ECU sends a lower voltage to the pump below approx 3500rpm, this is from a signal wire from the ECU.

 

With the AEM and no wiring mods, from memory the pump runs 12v all the time through the fuel pump ECU as the AEM does not switch the signal.

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mine did this mate, i was trying the mod to try to sought out some slight det on the 4k change over point when i was BPU, i was alarmed to find the pump running i think it is linked to the ecu, it didn't solve my det (soughted when i went single) the other major thing with this would be in a crash situation :bang:

 

Taking a couple of degrees of timing out at BPU boost pressure over the changeover point sorts this. I think the air gets heated too much by turbo #1 before turbo #2 can help it, and the stock ECU hasn't yet dramatically upped the fuelling. Of course, you can also push in more fuel at that point as well, which would be a good idea :)

 

Just as a note, I appreciate you have this fixed now. Don't shout at me again ;)

 

-Ian

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I just thought with it being inline to the ecu it possibly could have some sort of control over it. What do you think it is then Ian that is keeping it running??

 

The stock ECU controls the fuel pump but that line isn't intercepted by the E-Manage. The 12v mod keeps it running because it powers the pump off the 12v feed to the fuel pump ECU. The fuel pump ECU decides whether to feed the pump itself either 9v (off boost), 12v (on-boost) or 0v (engine not running). However the 12v feed to the pump ECU is 12v from position II on the ignition key, hence when the ecu is bypassed the pump runs all the time.

 

It's dangerous and unneccessary and should be reverted to stock. Plus it's plain annoying as it flattens the battery if the engine isn't running.

 

-Ian

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Taking a couple of degrees of timing out at BPU boost pressure over the changeover point sorts this. I think the air gets heated too much by turbo #1 before turbo #2 can help it, and the stock ECU hasn't yet dramatically upped the fuelling. Of course, you can also push in more fuel at that point as well, which would be a good idea :)

 

Just as a note, I appreciate you have this fixed now. Don't shout at me again ;)

 

-Ian

 

thanks Ian, i am sure it will help someone as this does seem a quite a common j-spec problem and it is a bit extreme to go single to cure it but it was a good excuse to use on the wife:D

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