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Engine fails to start (No beep)

R

Richomagic

New member
Hi,

Any tips welcome in fault finding why suddenly my 5L Mercruiser with Bravo 3 stern drive will not start.
No starter motor energising or turning when key is turned
Kill swith toggled and in run position
Throttle in neutral
Batteries >12.5v
Power to other consumables, winch, stero etc still operates.

I believe the throttle assembly is a Mercruiser 4000 genII - Does anyone know how to dissassemble this so I can check the kill swith with a multimeter?

A few questions there but thanks in advance for any help
 
I'm not an expert/tech, but your post reminded me of when i had to replace my 5L starter fuse (PN 88-79023A91). I also keep (store) two fuses. Others I'm sure will comment. good luck
 
When you turn the key to "on"" do the gauges come alive?
battery switch "on"
switch in control box is there to prevent starting in gear, not a kill switch
 
sab said:
I'm not an expert/tech, but your post reminded me of when i had to replace my 5L starter fuse (PN 88-79023A91). I also keep (store) two fuses. Others I'm sure will comment. good luck
Click to expand...
Exactly.. If the gauges do not move when you turn the key too the on position.... First thing you do is wiggle the Main engine harness Barrel plug on the back of the engine with the key in the on position. You can Identify it by the hose clamp on it..... If that changes nothing, put a test light on the Large terminal on the back of the alternator, Large Orange or Red wire... If there is battery voltage (12+ volts) there the fuse on the starter is good. No voltage change the cube fuse on the starter.
 
sab said:
I'm not an expert/tech, but your post reminded me of when i had to replace my 5L starter fuse (PN 88-79023A91). I also keep (store) two fuses. Others I'm sure will comment. good luck
Click to expand...
Thanks for the tip, I had no idea about that fuse. I have put a mutlimeter on both sides of the fuse and had >12v to eath on both sides so I think the fuse is ok.
 
Thanks for the tips. Really appreciate the help.
- When the ignition is turned to the first position no changes to the dash dials.
- I disconnected & reconnected the large mutli pin connector from harness to the engine although it made no difference
- I wiggled the harness boot with a hose clamp around itCapture.jpg
- >12v tested on the back of the alternator
 
I did look at the ignition and found what I believe is an anomily?
Capture11.jpgCapture12.JPG
With the key not in
- 12v at the Red wire (all the rest at 0v)

With the key in the first position
- 0v at all the terminals? does this mean there is a short down the line from the ignition?

Thanks for all the help, this is a great forum with great people!
 
Docksidemarineservices said:
Exactly.. If the gauges do not move when you turn the key too the on position.... First thing you do is wiggle the Main engine harness Barrel plug on the back of the engine with the key in the on position. You can Identify it by the hose clamp on it..... If that changes nothing, put a test light on the Large terminal on the back of the alternator, Large Orange or Red wire... If there is battery voltage (12+ volts) there the fuse on the starter is good. No voltage change the cube fuse on the starter.
Click to expand...
Thanks for the tips. Really appreciate the help.
- When the ignition is turned to the first position no changes to the dash dials.
- I disconnected & reconnected the large mutli pin connector from harness to the engine although it made no difference
- I wiggled the harness boot with a hose clamp around itView attachment 22843
- >12v tested on the back of the alternator
 
What you should see when changing key switch positions.

1. Wire color designation

Red= Battery + input to switch

Purple = Run-Ignition on

Yellow with red stripe = Cranking engine over to start (neutral Safety switch in shift control will not allow the 12 volts to starter if not in neutral or switch is bad)

Second smaller red = accessory +12V when key is acc position.


2. Pull coil wire from either coil or distributor cap so engine wont start.


3. Check voltages again at key switch

When you turn the key to the CRANK position there should be 12 volts to the Yellow with red stripe.(neutral Safety switch in shift control will not allow the 12 volts to starter if not in neutral or switch is bad)

When you turn key to the RUN position, 12 volts gets transferred to the Purple wire. You should see 12 volts on this wire. This also is what activates the gauges.


4. If you do not see any voltage at either wire on the back of the switch, Make a jumper wire about 8-10 inches long. (like Boat DR suggested earlier)

Touch the jumper to red +12 going to key switch and then touch the purple wire and take note of gauges. They should move and show something. This should show results as you are applying + 12 to the gauges.

Touch the jumper to red + 12 going to key switch and then touch Yellow with red stripe. Engine starter should start to crank.

If none of this happens then you do not actually have 12 volts to key switch. A volt meter may show voltage but does not show current.
If you were to use a 12 test light you could see how good a 12 volt signal by how bright the test light is. (connect directly to battery to see what a good 12 supply makes the light brightness)


Do these tests and report back


11.jpg
 
2. Pull coil wire from either coil or distributor cap so engine wont start.
Click to expand...

Removing the high tension lead from either the coil or the distributor cap (with the intent of cranking the engine over), gives the coil no means of discharging the high voltage energy, and may cause damage.

If you remove the + lead from the coil, you will not only prevent an un-wanted start-up, you will avoid any potential damage.




.
 
Last edited:
RicardoMarine said:
Removing the high tension lead from either the coil or the distributor cap (with the intent of cranking the engine over), gives the coil no means of discharging the high voltage energy, and may cause damage.

If you remove the + lead from the coil, you will not only prevent an un-wanted start-up, you will avoid any potential damage.




.
Click to expand...

PCR,

If he disconnects +12 from coil the same can happen........He could short to ground.........

He will not be attempting to start, only to check for function..............

F'n Mr wizard....................UGH
 
...............
kghost said:
If he disconnects +12 from coil the same can happen........He could short to ground.........
Are you making the assumption that he would do that?
I'll give him more credit than that!

He will not be attempting to start, only to check for function..............
Jack said:
Pull coil wire from either coil or distributor cap so engine wont start.
Click to expand...
Then perhaps you can explain what you meant by that statement!
Click to expand...
 
Richomagic said:
I did look at the ignition and found what I believe is an anomily?
View attachment 22844View attachment 22845
With the key not in
- 12v at the Red wire (all the rest at 0v)

With the key in the first position
- 0v at all the terminals? does this mean there is a short down the line from the ignition?

Thanks for all the help, this is a great forum with great people!
Click to expand...

Power to the red wire should remain no matter what position the key is in.... You have found a starting point.... Check for a fuse in the circuit that feeds power to the ignition switch.... Work your way back from the switch to the engine.... You will find the bad connection/fuse with some patience.



FYI.....A DVOM does not load the circuit and will show voltage. Use an incandescent Test Light (Not an LED) and see if you still have power at the red wire with the switch in the off position...
 
To build on what Chris said, looks like the screw fastening the RED wire to the lug isn't tight - the pic suggests the lockwasher wasn't fully compressed.

What you are seeing is a voltage drop caused by a bad (resistive) connection.

FWIW, the crimp terminals used were not the best choice and the workmanship wasn't the best either....
 
kghost said:
What you should see when changing key switch positions.

1. Wire color designation

Red= Battery + input to switch

Purple = Run-Ignition on

Yellow with red stripe = Cranking engine over to start (neutral Safety switch in shift control will not allow the 12 volts to starter if not in neutral or switch is bad)

Second smaller red = accessory +12V when key is acc position.


2. Pull coil wire from either coil or distributor cap so engine wont start.


3. Check voltages again at key switch

When you turn the key to the CRANK position there should be 12 volts to the Yellow with red stripe.(neutral Safety switch in shift control will not allow the 12 volts to starter if not in neutral or switch is bad)

When you turn key to the RUN position, 12 volts gets transferred to the Purple wire. You should see 12 volts on this wire. This also is what activates the gauges.


4. If you do not see any voltage at either wire on the back of the switch, Make a jumper wire about 8-10 inches long. (like Boat DR suggested earlier)

Touch the jumper to red +12 going to key switch and then touch the purple wire and take note of gauges. They should move and show something. This should show results as you are applying + 12 to the gauges.

Touch the jumper to red + 12 going to key switch and then touch Yellow with red stripe. Engine starter should start to crank.

If none of this happens then you do not actually have 12 volts to key switch. A volt meter may show voltage but does not show current.
If you were to use a 12 test light you could see how good a 12 volt signal by how bright the test light is. (connect directly to battery to see what a good 12 supply makes the light brightness)


Do these tests and report back


View attachment 22849
Click to expand...

Thanks for all the details. I've had a couple of days of bad weather so unable to do the faultfinding until now and in a strange twist of fate the issue has fixed itself!!
Great news to know I don't have to pull the engine to work on the starter motor but the electrical issue is still concerning!

The generic image I found on the internet shows the testing results for when I had the fault and when it was ok.

All I can think of is the slave solenoid. If it has a short to 0v when I had the issue then that could explain the 0v at the key switch?

Capture.JPG

As always, really appreciate your help.
 
makomark said:
To build on what Chris said, looks like the screw fastening the RED wire to the lug isn't tight - the pic suggests the lockwasher wasn't fully compressed.

What you are seeing is a voltage drop caused by a bad (resistive) connection.

FWIW, the crimp terminals used were not the best choice and the workmanship wasn't the best either....
Click to expand...

Thanks for that, I did check the connections and they were tight.... I think the shadow from the flash gives a gap illusion but loving the detailed look you gave!
 
Docksidemarineservices said:
Power to the red wire should remain no matter what position the key is in.... You have found a starting point.... Check for a fuse in the circuit that feeds power to the ignition switch.... Work your way back from the switch to the engine.... You will find the bad connection/fuse with some patience.



FYI.....A DVOM does not load the circuit and will show voltage. Use an incandescent Test Light (Not an LED) and see if you still have power at the red wire with the switch in the off position...
Click to expand...

Hi Chris,
Thanks for the tip, I did buy a test light. The problem self fixed itself which is good but I'm not confident to take it out on the water with this itermittant issue.
I checked the circuit breaker wired in series before the ignition which seems ok.
I posted an image of the testing I did (See reply to kghost)

From this and the lack or presence of the buzzer, I think the neutral switch and kill switch are both ok and am leaning towards an issue with the slave solenoid shorting to 0v? What do you think?
 
Richomagic said:
Hi Chris,
Thanks for the tip, I did buy a test light. The problem self fixed itself which is good but I'm not confident to take it out on the water with this itermittant issue.
I checked the circuit breaker wired in series before the ignition which seems ok.
I posted an image of the testing I did (See reply to kghost)

From this and the lack or presence of the buzzer, I think the neutral switch and kill switch are both ok and am leaning towards an issue with the slave solenoid shorting to 0v? What do you think?
Click to expand...

Again, It is STRONGLY recommended to stop using a volt meter and go to a 12 volt test light.

If you suspect the slave solenoid then replace as a precautionary measure.

If this issue re-occurs, to do a quick test would be to momentarily jump across the two large terminals on the top of slave solenoid and if the starter cranks but not with key switch then slave is bad.

Based on your original post and your description, it appeared you were not getting any output to any wires on the Key switch. (again volt meter vs test light)

If your description was accurate then the Key switch would be suspect. Wouldn't be the first Key switch to malfunction
 
Hi all, Just want to give a huge thank you to all that have helped with the fault finding. In the course of my learing I did find mutliple problems which I've slowly worked through.

1.) Black 0v terminal strip found with 80% very loose connections (1 full turn on the screws in some cases)BE3.JPG
2.) Battery isolator plastics cracked & came apart when I was trying to separate the lugs a bit more. This was replaced with a new isolatorbe2.JPG
3.) During the prior new stereo instalation (discovered this after I found the issue) it came to light there was an electrical short causing a hot wire that melted through the insulation on mutliple wires. The installer of the stereo also cut through all the wires which he had soldered up nicely with heat shrink and finished the job with all the joints wrapped up with a big ball of electrical tape!BC5.JPGBE1.JPG
4.) Red 12v terminal strip found to be unsecured behind dash, only insulated with electrical tape.

After a few days of repairs the old girl seems to be much happier.

Thanks again for all your help and support

Cheers and happy sailing

Rich.
 
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