2003 4.3 mpi not firing

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Sep 20, 2014
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i cannot get the coil to fire. i am getting ground to the icm and coil, and 12 v to icm and coil. i am using a led to check switching signal and ignition control signal.the light comes on as soon as the key is turned on and goes off during cranking instead of flashing while checking switching signal to either.the ignition control signal barely dims light as engine is cranked over.the tach jumps almost to 7000 rpm.all 3 wires on cps have approx. 5.6 volts with key on.engine is not original to boat .
 

achris

More fish than mountain goat
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....the tach jumps almost to 7000 rpm...

That sounds like a low battery problem, but you should put a scan tool or a laptop with the software on to read the trouble codes in the ECU... It will also read out the system voltage...
 
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i am getting approx. 5.6 volts on all 3 of the cps wires and i cannot figure out why? where can i get the software for the computer?
 

achris

More fish than mountain goat
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The only place selling it is Rinda Technologies. And it's not cheap. They sell cheaper options, Techmate and code readers, but the software is nice. :)

5.6 volts on each wire is not right. You should have 5v on the grey, the black/pink wire is the 5v transducer ground (and is NOT connected to the engine ground), and the tan/black is the signal (which will just be a on/off pulse as the engine turns)...

Because the transducer ground is not connected to the engine block, you can't use the engine block as you ground reference when trying to measure the other wires, you have to use it as the reference for the other wires., so measure between the black/pink and the grey, you should see 5volts.

Chris.....
 
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thanks guys for the the info . i may not respond for a day or two so please dont take it personal.i snagged a big hook in my wrist this evening and didnt want to go to the e room and i was a bit worried about pushing it through the viens but after further examination i thought i could do it as good as they could and save myself 5-8 hours at the e room.so tomorrow i get to go get a tetnis shot.by the way it was the rustiest hook of all of them , but a razor blade kept me from having to push it through. i will try to get back to my problem within a day or two please dont abandon my problem
 

Fun Times

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Ouch! Get yourself better, we'll be here to try and assist the best we can when you're ready.;)
 
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i checked between black w pink stripe and grey .53 volts ,grey has 5.6 ,black w pink stripe 5.05 ,brown with black stripe 4.88 using battery ground.checked between battery positive and black w pink stripe 7.1 volts red multimeter lead to pos. black lead to wire i also checked to see if the injectors are pulsing and they are not which i guess makes sense with no cps signal.
 

achris

More fish than mountain goat
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As this is the '5v transducer' circuit, you can't use the engine block or the battery negative as a '0 reference'. All readings must be reference to the black/pink, not the engine block or battery negative. Any readings with a mutimeter lead on the battery negative or the engine block are invalid. If you have 5 volte between the grey and the black/pink, then the system providing voltage is working fine. The next thing to check is the CPS itself.

Now, if you buy it from Merc it's nasty expensive (like about $160), but you will find a number on it. Search that number in google and you should come up with a few thousand sites, some of whom are selling them. And it shouldn't be more than about $10.... (BTW, when you pull the CPS out can you post the number on it here. I'd like to add it to my list of 'alternate parts supplies')....

The other thing you could do is check the output pulse of the CPS, but you would need an oscilloscope for that. If you are that interested, you can get laptop based oscilloscopes for around $200... I've got a 'Hantek' unit, 40MHz, fantastic for what I need it for...

Chris......
 
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i only had .53 volts not 5.3 , and i was using a led for testing signal as recommended by easyautodiagnostics.com in place of an oscilloscope.
 

achris

More fish than mountain goat
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Then something is wrong. Do you have diagrams for that circuit? Here's the drawings from the manual. What might be interesting is to check those same wires on the TPS... Splice 100 is '5v transducer ground' and splice 101 is '5v transducer power'...

MPICPScircuit_zps1f493642.jpg


Chris......

EDIT: Just found this article. Looks very good...

http://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-crank-sensor-1
 
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Sep 20, 2014
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the tps the mapt and cps are only getting approx. 6 v and that was the web sight i was using. i even made the led tester for checking signal
 

achris

More fish than mountain goat
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Is that 0.6v or 6v? If it's only 0.6v, then I would check directly on the ECU pins (B1 & B21). If you have the 5v there, then measure from the ECU pin B1 to the grey wire on any of the sensor connectors (that's checking splice 100), and if that's good measure from ECU pin B21 to the black/pink on any sensor connector (checking splice 101)...

Just realised another possibility. If one of the sensors is dead short, it will drag down the 5v, and even measuring at the ECU will show low. You need to unplug all the sensors on that circuit and recheck the voltage. If it's good, one of the sensors is bad. Leave the meter connected and replug the sensors one at a time. When the voltage drops off again, the sensor you just plugged is the culprit.

This is the list of sensors that use that 5v supply, so it could be any one of these.
Sea water pump pressure sensor (this one is a known problem BTW)
Digital oil pressure
Shift interrupt switch
TMAP (Manifold air temperature and pressure)
CPS (Crank position sensor)
TPS (Throttle position sensor)

Chris.......
 

Fun Times

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I only had .53 volts not 5.3 , and i was using a led for testing signal as recommended by easyautodiagnostics.com in place of an oscilloscope.

Sounds like you may have an internal ECM problem not producing 5 volts or you have a sensor shorted and drawing down the 5 volt signal somehow.

Could try unplugging all the sensor while watching the 5 volt power and ground coming right out the ECM to see if the 5 volts goes back up as you unplug them.

Where do you live? If you'd like to have your ECM tested, Whipple superchargers in CA will test it for $100.00 and if they are able to repair it then it's $500.00 vs $1500.00 + for a new one. You'll have to call them for more info though. https://whipplesuperchargers.com/ind...product_id=291

What is your engine serial number? For the heck of it, try doing the test on page 3/3 while on the trailer to see if the engine will start/spark, http://www.marinemechanic.com/merc/d...fi-nostart.PDF
 
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