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Blowing Ignition/Fuel Pump Fuses


William Hurt
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I have a 2004 USDM STI newly built 2.5L with non-avcs cams and DBC TB using Link G3 EM. The new motor has approximately 250 miles but shortly after getting the car back from the engine builder, I began blowing 15A Ignition/Fuel Pump fuses and the AFRs showed lean. The fuel pump was replaced (Walbro 255lph). The car is now doing the same thing (except for going lean - but I think its just a matter of time). As I understand it, the builder/tuner by-passed the OEM fuel pump controller and is using the EM system to control the fuel pump. At the recommendation of the builder/tuner, I stepped up to a 20A fuse, but those are not holding. Fuses typically blow during highway cruising. Sorry for the lengthy post, just looking for some ideas how to identify the possible causes.

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If you send through your pcl file I can have a better understanding of what is controlling what

I suspect that you are runing to much dwell time for the coils   if it is the individual coils with ignitors built in then the dwell from 12volts on should be 1.9ms

also if the ignition and fuel pumps are running of the same relay then they will need to a reasonable sized fuse as the fuel pump can easily get up to 14amps current draw and each coil can be drawing 6amps at any one time

hope this helps

David

info@dtechmotorsport.com

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Thanks for the reply. I'll have to get the pcl file from the tuner. As for the coil packs (coil-on-plugs), I'm unclear how this would affect the fuel pump. Are you saying that if the coils are firing say 2.5ms, the difference is enough that the fuel pump is having to work to hard (i.e. drawing too much current) and therefore causing it to fail prematurely?

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from reading your first message it sounded like your fuel pump and ignition was feed off the same power supply/fuse

if this is the case then a coil on plug coil will be drawing approx 6amps and the fuel pump can easily be 14amps which equals 20amps current draw which will blow a 15amp fuse any day 

this is calculating one coil and the pump if the dwell is higher then the charge time at rpm could be happening at a point when another coil is charging and then the current draw will be even higher   4 coils  6amps each and a fuel pump at 14 equals  38amps        with individual coils you do not normally get more than one been turned on at any time so it is not a problem  but shows how important specing the wiring and fuses is

if the coils are not feed from the same fuse then i would say if it is poping 20amp fuses then you have a faulty fuel pump or a dodgy wire connection some where

info@dtechmotorsport.com

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