high voltage with only 12.1 in

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briansexsmith
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high voltage with only 12.1 in

Post by briansexsmith »

Attached is my MSQ and datalog of a quick bench test of the wiring harness and MS3x that has been sitting for a few years.

I dont understand why I am seeing about 22 volts in tunnerstudio and in the datlog. I tried reburning the voltage voltage calibration but no still reads high.

ideas at what is wrong?
kjones6039
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Re: high voltage with only 12.1 in

Post by kjones6039 »

I know nothing about MS3, but I'm wondering about your grounds...............

Ken
1979 Corvette - 383 CID SBC w/ Holley Pro-Jection 900 CFM TBI, 4-85 lb lo-z injectors & Walbro 255 pump
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briansexsmith
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Re: high voltage with only 12.1 in

Post by briansexsmith »

well right now the harness is not in the car so no ground per say. I using a battery and putting 12 volts into the ms where the power relay would normally do so and ground to the power ground normally at the engine.

my multi meter reads 12.1 volts at the between pin 28 and pin 19
jsmcortina
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Re: high voltage with only 12.1 in

Post by jsmcortina »

Check the voltage on TPSVREF. If there's a short over overload and that is reading low, it will show the Battery voltage as artificially high.

James
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grom_e30
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Re: high voltage with only 12.1 in

Post by grom_e30 »

check for dry solder joints on r3 & r6 thats the voltage divider circuit for the battery voltage reading, also measure the voltage on the 5v inside the ecu if the 5v is low the 12v will read higher
1990 bmw 320i daily driver with m20b25 ms3 sequential fuel, 380cc injectors, d585 coil near plug, home made cam sync, launch control, fan control, vss, homebrew egt logging what's next????
briansexsmith
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Re: high voltage with only 12.1 in

Post by briansexsmith »

James,

I removed the harness and powered pin 28 and grounded pin 19. measuring between ground and pin 26 I am getting 4.7 volts and I am still reading 22 volts on tunerstudio.

I think grom e30 is on the right idea, the soldered joints a bit of brown stuff around them from sitting I guess. I heated R3 and r6 joints with no change.

items to check to narrow down a bad soldiered joint?

Thanks
briansexsmith
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Re: high voltage with only 12.1 in

Post by briansexsmith »

mesuring 4.13 volts between pin 1 and pin 2 on the 40 pin connector to the ms3 board
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Re: high voltage with only 12.1 in

Post by jsmcortina »

briansexsmith wrote:mesuring 4.13 volts between pin 1 and pin 2 on the 40 pin connector to the ms3 board
Something is partially shorted.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
briansexsmith
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Re: high voltage with only 12.1 in

Post by briansexsmith »

11.5 volts on the Vin of U5 and 4.98 volts on the output

0.2 volt drop across the F1 polyfuse
briansexsmith
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Re: high voltage with only 12.1 in

Post by briansexsmith »

Problem solved! I put the PM2 from the knock board to a ground pin.

Thanks for the help guys! I guess I foolishly installed the knock module and never tested or ran a car in it in years.
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