Mercruiser 4.3 injection without any ignition

[navigateur29]

Hello,

sorry for my english mistake, I'm French and I don't like translators... ;-)

I bought a boat having a Mercruiser 4.3 2003 with 6 cylinders
price was low because there is no ignition and I was aware of that
I don't know exactly what did the previous owner supposed
to be a "nautic professionnal"...

I can't find the correct electrical scheme in any Mercury manuals
That's always for carburator engines and coil has wired connected
to screws but mine has a connector with 3 wires + of course the high voltage one

I made a test with a spark I put directly to the engine and there is nothing
I made another test with a direct power applied to the the coil
In the connector, the purple wire has the +12v from battery (that's fine)
I didn't find any voltage on the 2 other wires
I supposed that the wire in the connector at the oposite side of the purple one
was the ground driven by the calculator (to cut of primary of the coil)
I made a direct test and I know that it works because I received the high voltage in my fingers ;-)
so my conclusion is that there is no ground signal coming from this calcultator wire...

question1:
what is the purpose of the third wire in the middle of that connector?

question2;
what can inhibit the ignition on the calculator?
what should I check in such case?

question3:
does someone could provide the capture of the ignition wiring for this engine model?
the one showing the 3 wires connector of coil

any suggestion that may help me to go further are welcome

many thanks

 

[alldodge]

Welcome
Look for the serial number on the motor. We need that to determine what ignition system you have.

If serial number is not available, post a pic of the distributor and carb

 

[Bondo]

Ayuh,..... Welcome Aboard,..... Of the 3 wires,.... Purple is power to the coil,.....
One is the signal wire to the distributor, it tells the coil when to fire,....
The 3rd is to the tach on the dash,.... to read rpms

 

[navigateur29]

Hello

Alldodge:
that's my son's boat and I don't have access before few days
you will find attached the picture of the ignition coil 392-863704
for this engine model if it can help you to identify the exact type
in all Mercruiser manuals I never see such ignition coil in diagrams
only 2 wires connected with screws or 4 wires with a connector
never the 3 wires one
In service manual #32 that's the right reference of ignition coil
but they there is no ignition electrical diagram :-(



Bondo:
I thought that coil primary gnd was driven by the calculator
for that model and not by a mechanical ruptor in the distributor
sorry, but are you sure for that model of ignition coil with 3 wires
that the coil gnd is friven from the distributor?

thanks for you help ;-)

 

[Fun Times]

Because your engine is fuel injected, you'll need Mercruiser service manual number 36 "ECM Diagnostics" to help with your wiring questions... While I personally don't have any copies to share with you, below are some snap shots of some example pages you may need to see plus others to go with them.

With your fuel injected system, when everything is in the correct working order 12 volt power and ground wise, etc., the spark signal basically starts at the crankshaft position sensor item number 9, https://www.mercruiserparts.com/bam/subassembly/31499/7801/100
Quick note: Being a 2003 year model, though it is mounted there 'your engine shouldn't be using the CAM-shaft sensor mounted to/in the distributor assembly...No wire connector plugged in to the sensor item number 6, https://www.mercruiserparts.com/bam/subassembly/31499/7801/40

Genuine Mercury Marine parts, large inventory, fast shipping. 4.3L MPI ALPHA/BRAVO - 0M300000 THRU 0M614999 Genuine Mercury Marine, Mercruiser and Mercury Racing engines, parts, propellers. Authorized dealer with large inventory, great prices, fast shipping! www.mercruiserparts.com

8M0160555

SERVICE MANUAL, ECM 555 Diagnostics

 

[alldodge]

MPI, motor needs to be scanned for codes

When key is turned ON does the fuel pump run for a couple seconds and is there 2 beeps?

Check for 5V on the Crankshaft position sensor (CPS) or any of the other sensors in the pic. Need to see exactly 5V with key ON motor OFF. If there is less then 5V then one of the sensors is pulling to much power



When cranking is there any movement on the Tachometer?

 

[navigateur29]

Fun Times:
thanks for your help!
When I was looking for the right manual
I checked manuals titles after #18 and I found only #32 for 4.3 engine
When I saw ECM 555 in the title of #36 I didn't care about it :-(
I got it now and I will read it carefully because the extracts you attached
are really interresting and will help a lot ;-)

allDodge:
thanks for the 5v on sensors I will check that ;-)
When we tried last WE with my son I remember the fuel pump was running
he disconnected it to avoid to use it for nothing at this step of our investigations
I turned the contact several times during the tests we did
but I don't remember to heard any beep when doing that
I didn't check the instruments when turning the key and trying to start the engine
I will ask to my son if he noticed that and we will check that next time
We will check that in next tests ;-)

He is a truck driver and won't be back at home before end of next week...
so I threw a bottle into the sea but I didn't expect to receive so useful answers so quickly

many thanks for these valuable information
when engine was running just before that easier to find (not easy but easier)
but when you don't have an electrical diagram and when a bad mechanic reassembled the engine badly
that's a nightmare :-(

 

[alldodge]

Reposting the same question(s) is not allowed. The only question which has not been answered "fully" is the complete wiring diagram. You said that you have manual 32 and if so the wiring is on page 4D-7

 

[navigateur29]

sorry AllDodge, but what do you mean with: "Reposting the same question(s) is not allowed."
I don't understand

I saw it but didn't care about it because I tought it was the New York subway map
honnestly that's unreadeable and that's the first time I can see such kind of scheme :-(
I will try to interpret it
thanks ;-)

 

[navigateur29]

ok for the complete wiring diagram
that's fine now I didn't read it carefully because I tought it was only for ECM debuging but I found all components relative to ignition
that perfect and it should help us to check from point to point
many thanks for your help
don't worry if I don't give more news before end of next week
but I will then come back after positive or negative tests ;-)

 

[alldodge]

sorry AllDodge, but what do you mean with: "Reposting the same question(s) is not allowed."
I don't understand

Your original question listed in post one above, was posted again, word for word. It was reported to admins and Iboats admin removed it. I requested this thread be moved to the Mercruiser section so it would get more people looking at it which it was moved

I saw it but didn't care about it because I tought it was the New York subway map
honnestly that's unreadeable and that's the first time I can see such kind of scheme :-(
I will try to interpret it
thanks ;-)

Agree, its hard to read.
I have it in PDF and I'll zoom in so it can be traced to locations. Manual 36 is better to see where connections are made

 

[QBhoy]

Hi. Is the lanyard kill switch activated ? You’ll get cranking, but no ignition if it is.

 

[navigateur29]

sorry AllDodge for the duplicate, I probably made a bad action when I post my previous answer :-(

QBhoy:
it can be also a root cause because the "professionnal" has done some
modification everywhere including this security as well :-(
thanks to the full electrical wiring diagram 4D-7 and other extracts provided in this thread
we should be able now to follow the different connections of ignition

many thanks to all from french "Bretagne" ;-)

 

[Fun Times]

sorry AllDodge for the duplicate, I probably made a bad action when I post my previous answer :-(

QBhoy:
it can be also a root cause because the "professionnal" has done some
modification everywhere including this security as well :-(
thanks to the full electrical wiring diagram 4D-7 and other extracts provided in this thread
we should be able now to follow the different connections of ignition

many thanks to all from french "Bretagne" ;-)

In a non-bashing way, Let us know everything the professional has done to which you might feel is the reasonings the engine may not be starting? Did the engine stop running (or not start up) when you received the boat back to you from them? What is the back history?

 

[QBhoy]

sorry AllDodge for the duplicate, I probably made a bad action when I post my previous answer :-(

QBhoy:
it can be also a root cause because the "professionnal" has done some
modification everywhere including this security as well :-(
thanks to the full electrical wiring diagram 4D-7 and other extracts provided in this thread
we should be able now to follow the different connections of ignition

many thanks to all from french "Bretagne" ;-)

Ok. Let us know how you get on. I just know that these engines will do just that with the switch pulled. I pull it for spring start up to crank over a few times to get some oil about her, before she starts up and fires.

 

[navigateur29]

Hello,

To go ahead I made few tests and took few pictures
my son will be back next week so I was alone to test
and was unable to check all...

the starter engine don't start
It was running last week end :-(
When I turn the key I only hear one "clac" on the slave solenoid
if I disconnect the yellow/red wire coming from contact
there is no more "clac" on the slave sol
meaning signal arrives from contact to slave sol
but there is no crank at all
--> a second issue after ignition :-(

concerning ignition issue:
I checked voltages & continuities of wires
details are written in the pictures I took today
All signals/connections seems ok to me according
to the electrical schemes
I supposed that if the starter engine is not running
then there is no ignition because this is driven by the
position of the pistons and then calculator can't iniate the cycle
if CPS don't send signal when the position is ok...
so now starter engine is the priority issue :-(

any idea are welcome ;-)
thanks

pictures taken today:

 

[navigateur29]

My son told me he had to make a direct connection between contact of the slave solenoid and then start engine was running
because I can hear the "clac" of the slave solenoid it means that signal comes from the key so then slave solenoid to be changed for that point?

then everything on ignition is correct (voltage & continuity) and I don't see what else could be wrong that may blocks the ignition :-(

 

[alldodge]

The slave relay may be clicking but it's most likely not making good contact inside, so it's not passing enough current to energize the starter. Turn key ON and then use something to go across the top contacts, this will energize the starter. If starter does not energize when contacts are crossed, then its probably the starter

The contacts on the slave look a bit corroded and may need to be cleaned

 

[QBhoy]

There is two solenoids on top of the engine nearer the port side. Give them a dunt and see what happens. Mine does this every now and then on spring start up when damp

 

[navigateur29]

Hello,

For QBhoy:
sorry seems I didn't received an email about your post
then I saw it only when posting my last tests conclusion :-(
what do you mean by: "Give them a dunt"
to give a light hammer blow on them?

"There is two solenoids on top of the engine nearer the port side"
in the port side there is the slave solenoid and mine seems to have an issue
I will measure the voltage when turning the key next week-end with my son
alone I can't
I hear the "clac" but no crank at all
If I connect manually both wires of this solenoid contacts then engine cranks well
but no ignition anyway...
Where is the other solenoid and what if its function?




For all:
I made new tests today
I was thinking about the signal of the CPS sensor
it is a 5v square signal that depends of the detection of the
magnet
I don't have any oscilloscope then I thought it should be possible
to check the signal at a low frequency with a manual rotation of the engine
with a ratchet using a simple LED
I done a basic LED tester and it works fine



I checked it with an Arduino



I'm now surprised a what I checked this morning...

CPS sensor:
I'm supposed to measure +5v between grey wire (+5v)
and black/Pink wire (ground) but I have only 0,8v
between black/tan wire (signal) and black/pink (ground)
I have +5v
To have +0,8v instead of +5v is not ok
but to have +5v on the signal pin connected to PIN 10 of ECM
looks strange as well no?
I check it with the led and the led is on between signal/ground
and of between +5v/ground
It confirms what I measured with multimeter...
there is nothing between signal/+5v of CPS connector which is normal

continuity between CPS wire black/tan and ECM pin 10 --> ok
continuity between pin 23 ECM and coil controler wire White/dark green --> ok
continuity between coil controler wire White/light green and both wires of coil --> ok

I connected the ground wire of the test led directly to the battery
and the + wire of the test led to the coil wire white/light green
the led stayed always ON !!!



I turned manually the engine one and a half round --> the led stayed ON
(no more because its hard and I was afraid to damage the nut...)
I tried to crank the engine with the direct connection on the slave starter
the LED stayed always ON

any comments about this tests?

Thanks