sudden voltage drop problem

alper · Post by **alper** » Sun Apr 05, 2015 7:17 pm

hi

I've been having sudden voltage drops in my own car.

when the ignition is on, there's no problem.
when the car is running, problem starts :

https://www.youtube.com/watch?v=430whKcu4aw

I changed the coils, crank sensor, ecu.
no solution.
I made new cables for coils, ecu power, and ecu ground, power ground,
no solution.
I disabled everything but the crank sensor, coils and injectors,
no solution.
I changed the fuel pump, also fed the fuel pump from another battery, no solution.

what is the problem, do you think ?

Jan32 · Post by **Jan32** » Sun Apr 05, 2015 11:24 pm

Did you test it without alternator? Maybe there is the problem.

alper · Post by **alper** » Mon Apr 06, 2015 12:24 am

I tried it already - no difference..

Jean Niemi · Post by **Jean Niemi** » Mon Apr 06, 2015 7:33 am

I used to see similar happening, but it was only with older SW/FW.
What Software/Firmware are you using?

Jan32 · Post by **Jan32** » Mon Apr 06, 2015 9:19 am

Did you measure the same with an Multimeter or better an oszilloscope?

alper · Post by **alper** » Mon Apr 06, 2015 10:03 am

I dont have an oscilloscope, but I measured it with some multimeters, the multimeters dont show any voltage drop, however, they are not as sensitive as an oscilloscope.

Urosch89 · Post by **Urosch89** » Mon Apr 06, 2015 11:22 pm

Maybe try to mount a capacitor on the line of the coils, tell me if there are news.
Bye

astra vxr · Post by **astra vxr** » Mon Apr 06, 2015 11:34 pm

could be battery ,alternator , or just a crap ground its not dropping enough to cause much problems so it will be something simple

alper · Post by **alper** » Tue Apr 07, 2015 10:34 am

I think I've found the problem.
I have another car (sierra dohc turbo) with the same setup, with the same problem.

both are wasted spark operated.

the other cars with sequential firing don't have the same stuff.

soo...

can it be because of wasted spark ?

Post by **Jadzwin** » Tue Apr 07, 2015 6:33 pm

It is rather connected to bad grounding. The coils draw lots of current and if they share ground with EMU it can make such problems.
Is the battery realocated from the hood ?

alper · Post by **alper** » Tue Apr 07, 2015 6:41 pm

they dont share the grounding with emu. but I will check all the grounds again and report

astra vxr · Post by **astra vxr** » Tue Apr 07, 2015 6:58 pm

are you useing brand new loom or useing adapter ?

alper · Post by **alper** » Tue Apr 07, 2015 7:08 pm

two different fresh looms on two different cars.

Post by **Jadzwin** » Tue Apr 07, 2015 7:27 pm

Try to draw the schematic with ALL of your car grounds.

alper · Post by **alper** » Wed Apr 08, 2015 1:53 am

ok I will..

the voltage drops are more likely like parasites - not drops like heavy load as a fan turns on.

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