automotive/blowing electronic modules

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howard coleman

Joined Oct 1, 2011
Hello All:)

i just discovered your forum and it appears to be a wonderful resource.

i am in need of some serious help and the problem is just a tad past my current elec understanding.

i have a highly modified turbo (rotary) RX7. while a dual purpose car, it employs alot of electronic subsystems. i will try to keep this brief.

the car ran flawlessly from 2004 to late 2009. from late 09 forward it started blowing electronic modules.

i do log much (not all) of the ontime. i have not seen any voltage readings other than from 13.4 to 13.7.

all failed modules were fused and no non OE fuses blew.

here is the sequence of mishaps:

april 09 installed "high output" alternator
may 09 good dyno session. 507 rwhp at 20 psi boost
sep 09 good brief dyno session
winter 09/10 converted to a different turbo system and transmission... (should have no effect)
summer 10 ran a few hundred break-in miles
nov 10 while on dyno my Datalogit failed. (DL is an interface module between car ECU and laptop. allows for changing ECU/ Apexi Power FC/ settings and logging) had worked fine since 04. derives power from the ECU/Power FC.
we replaced it and continued on with the session.
a few more power pulls and we blew an OE Fuel Pump fuse (20 A) this is the only fuse ever to blow.
i have a Kenne Bell Boost A Pump (BAP) in my fuel system. after sensing boost (positive manifold pressure from the turbo) the module raises Voltage to the fuel pump. it is set at +20%. the BAP had run fine since 04. it employs a 20 A fuse that did not blow.
inserting a test instrument into the OE fuse holder we could see amps rising to unacceptable levels (24 Amps and rising). we wired around the BAP.
all was fine w the fuel system at that point.
a month passed and we were back to dyno but the engine would not start. after much analysis it was determined that the Apexi Power FC (ECU) was not outputting an injector signal to the front primary injector. the Power FC had been fine since 2000. (OE 30 amp fuse did not blow)
i elected to replace the entire OE Mazda wiring harness w new.
we returned to the dyno this August w a new Power FC and generally cleaned up wiring.
after a few runs it was determined that the motor was not getting it's supplemental 2000 CC/Min of methanol. the MILSPEC FJO controller was dead. that ended the session. (fused w 15 A which did not blow)
i designed and implemented a new methanol system. after approximately a month of work i started the motor to find the front primary injector was not getting a asignal to fire.
this is the same malfuction as last november when we lost the other Power FC. (BTW, the Apexi Power FC has an excellent reputation)

i did insert an OE computer in the car and the motor ran on all the injectors...

clearly something is amiss and i have reached a point where the problem needs to be diagnosed and fixed.

i did mention that i changed alternators before much of this happened.
i also acquired a Schumacher SpeedStart battery charger and have always had it hooked into the car during my dyno runs. it is set on 10 A and AGM. my battery is an Odyssey PC925 and has worked well.

it has been suggested my modules have been taken out by voltage spikes. someone felt my battery charger could be the culprit. another suggestion was Voltage Dump. (i have seen nothing on my battery voltage logs)

something has changed as my car ran fine w most of the components for a number of years. my fuel pump has checked out and i do log fuel pressure at all levels of boost and it is fine.

it has been suggested that i install

"a V24ZA50P MOV between 12v and Gnd at the input of the units."

apparently there are a number of elec components that would surpress V spikes.

of course ideally it would be really good to know the cause of my recent problems.

i realise i have probably given only a part of the info needed but hopefully it is a start on the road to recovery.

i would be greatly indebted to any who might be of help.

also, i now have two Apexi Power FC computers w blown (i think) front primary injector drivers. my current option is to send them to Apexi Ca who will forward them to Japan for repair... 2 months. i would so like to have someone in the good old USA fix them. (that would be a good side business for someone out there as there are alot of the units outstanding)

unfortunately i doubt if wiring diagrams are available...

thanks for reading this lengthy plea for help!



Joined Jul 17, 2007
Hello Howard,

Sorry, but "automotive modifications" are on the restricted list of our Terms of Service (link available on the bottom of every Forum page) paragraph 6, which reads:

6. Restricted topics. The following topics are regularly raised however are considered "off-topic" at all times and will result in Your thread being closed without question:
  • Any kind of over-unity devices and systems
  • Automotive modifications
  • Devices designed to electrocute or shock another person
  • LEDs to mains
  • Phone jammers
  • Rail guns and high-energy projectile devices
  • Transformer-less power supplies
In this topic:
there are a few websites listed where such discussions might be welcome.
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Joined Nov 25, 2009
SgtWookie makes my job a breeze

@howard coleman

For all the reasons Sgt explained, this forum will be closed.

Please understand the reasons behind this action and bear no grudge.
Feel free to tread on the rest of the forums.
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