tach not working on black scorpion

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nailem

Petty Officer 2nd Class
Joined
Dec 17, 2007
Messages
185
i have a 2005 5.7L black scorpion serial number 0M398298. i got the manuals off this site but am having trouble finding what i need.

the tach is not working, wires behind tach are good. as far as i can follow the manual the tach is on gray/wht off the ECM on pin A10 (on page 3a-3) the only other thing i see is on page 3a-7 it says G= tach signal out H= tach connector. the big round plug has #2 gry/wht going to A19 the chart on page 3A-3 says A19 is fuel pump relay control and should be dk-grn. am i missing something?

were should i start?
thank you
 
Bt Doctur

Bt Doctur

Supreme Mariner
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Aug 29, 2004
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19,111
Re: tach not working on black scorpion

The way I read it, #10 pin ( grey/white ) has a test port (splice 113) then to pin #2 of the engine harness plug. Manual 36 ECM 555 page 3A-8
 
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nailem

Petty Officer 2nd Class
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Dec 17, 2007
Messages
185
Re: tach not working on black scorpion

i looked at it again, and i see what you mean. so the problem can be checked at pin A10pin. what type of signal should i see on my multimeter?
 
Bt Doctur

Bt Doctur

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Re: tach not working on black scorpion

says to install an analog tach at the pigtail by the ecm, start engine. If no reading consult appropriate manual.If there was a tach reading, then I`d say retest at the grey/white in the main harness (helm side, not engine side)just after the engine plug.
 
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nailem

Petty Officer 2nd Class
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Dec 17, 2007
Messages
185
Re: tach not working on black scorpion

i do not have an analog tach. is there a way i can do it with a multimeter? and by pig tail do you think that is splice 113?
 
Bt Doctur

Bt Doctur

Supreme Mariner
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Messages
19,111
Re: tach not working on black scorpion

That I can`t answer ,ecm`s can be tricky and expensive.
splice 113 is the pig tail.most systems leave a test port available instead of piercing a wire with a probe.
That leads to corrosion and corroded opens in the harness.
 
N

nailem

Petty Officer 2nd Class
Joined
Dec 17, 2007
Messages
185
Re: tach not working on black scorpion

thank you for your help tonight, i will give it a go tomorrow
 
N

nailem

Petty Officer 2nd Class
Joined
Dec 17, 2007
Messages
185
Re: tach not working on black scorpion

i checked the big round 10 pin connector and it was corroded so i cleaned it up and still nothing. i found the test port but then got to thinking. the boat has perfect pass cruise control and it works off of speed or rpm. i looked at the back of the tach and the wire for the perfect pass (PP) comes off of the same stud as the factory signal so i switched the PP to RPM mode and the display on the PP shows the RPMs so it must be a good signal from the motor. does this sound right? if so the factory tach is probably bad. can they be rebuilt or just replace?
 
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dubs283

Vice Admiral
Joined
Jul 27, 2005
Messages
5,115
Re: tach not working on black scorpion

if the perfecrt pass module gets its RPM input signal from the same stud/wire that the tach gets its signal from, then yes - makes sense that the tach is bad

you are betterr off just replacing the tach - new with full warranty beats rebuilt with ? warranty
 
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