Reversed polarity 40 hp Mercury -Coughs but it won't start

[JoeRo]

Reversed polarity 40 hp Mercury -now it won't start
All 4 fuses tested good Replaced sparkplugs and have spark at all plugs I pulled gas line gas from low pressures pump and it pumps gas

When first turning the key it coughs / start for 1 second reeves up and dies next only get short coughs if I wait and retry starting may get a 2 second run time and dies Any suggestions?

 

[jimmbo]

Welcome to iboats

Any idea what yr the engine is?
2, 3, or 4 Cylinder?

You hooked the Battery up Backwards? That pretty much fries the Recitifier, so no charging and no Tach. Switchboxes and other Ignition Components usually survive, but I guess they too could be fried.
Have you tested to see if there is a Spark that can jump a 3/8" gap, at all Cylinder. Use a Spark Tester like this

Is it Carbed? If so see below. If Fuel Injection, that's it, I'm outta here...
Is/are the Carb(s) getting Fuel?
Did you prime the Fuel System?
Are You using the Choke/Enrichment System while trying to start it?
Are you advancing the Throttle while trying to start it?

 

[Texasmark]

As stated, reverse polarity pumps unlimited (sorta) current through the reverse rectifiers in your rectifier assembly as there is no resistance (to speak of in the circuit and the diode junction melts and shorts the stator output to battery negative (ground).

Replace the rectifier (rectifier/regulator assembly). Measure the voltage at your battery terminals and record. Start the engine and re-measure the battery terminal voltage. If it is higher than when you started (assuming you didn't use up a lot of battery power getting the engine started) or starts slowly increasing 0.01 volt or something like that or more over time, you may have burned up your stator battery charging windings (under the flywheel).

 

[JoeRo]

Reversed polarity 40 hp Mercury -now it won't start
All 4 fuses tested good Replaced sparkplugs and have spark at all plugs I pulled gas line gas from low pressures pump and it pumps gas

When first turning the key it coughs / start for 1 second reeves up and dies next only get short coughs if I wait and retry starting may get a 2 second run time and dies Any suggestions?

Reversed polarity 40 hp Mercury -now it won't start
All 4 fuses tested good Replaced sparkplugs and have spark at all plugs I pulled gas line gas from low pressures pump and it pumps gas

When first turning the key it coughs / start for 1 second reeves up and dies next only get short coughs if I wait and retry starting may get a 2 second run time and dies Any suggestions?

I reversed battery polarity to a 2003 Mercury 40 hp EFI 4 stroke 3 cyl Fuel Injection - now it won't start coughs and then dies immediately. Will fire like it’s trying to start, sometimes on a couple of cylinders fire in succession on the first try then dies. Then only a single cylinder will fire unless I wait a few minutes.

I had to replace the Cable Asy-Diode Adaptor #84 883834T01 and a 20 amp fuse to get it to turn over. Now all 4 fuses tested good Replaced sparkplugs and tested each plug, have spark at all plugs I pulled gas line gas from low pressures pump outlet and it pumps gas.

When first turning the key it coughs / start for 1/2 second reeves up and dies next only get short coughs. If I wait and retry starting may get a 1/2 second run time and dies again. Any suggestions?

 

[garbageguy]

did the timing get thrown-off? all the coughing and short run time seem to suggest that (I am no expert on your kinda engine)

 

[JoeRo]

2003 Mercury 40 hp EFI 4 stroke 3 cyl Fuel Injection

I have to replace the Cable Asy-Diode Adaptor #84 883834T01 and a 20 amp fuse all 4 fuses test good.
Replaced sparkplugs and spark at all plug
I pulled gas line gas from low pressures pump outlet and it pumps gas.

Will test the Rectifier with meter and will let you know how it turns out
I have a Mercury Service Manual with step by steps instructions for testing

 

[JoeRo]

I reversed battery wires/polarity to a 2003 Mercury 40 hp EFI 4 stroke 3 cyl

Model # 1A40412AD Serial # OT783080

Restoring old fishing boat with new controller and old ignition switch.

Motor ran before removing old console switches and motor controller.

For testing, I bypassed the shifter neutral start switch and motor dash kill switch. Checked wire harness for continuity from key switch to motor tested good

Motor wires show no sign of damage from overheating

Regulator/Rectifier Tested bad told motor would run without it

Replaced Diode Adapter Cable was fried

All 4 fuses tested good after replacing bad ones

Replaced sparkplugs and tested all plugs have spark

After pumping gas line ball hard motor coughs and dies.

2 of the 20 amp fuse positions on fuse holder assembly hotside are dead

No power to Red / Pur striped wire at/to High Pressure Fuel Pump (shorted with 12 volts and pump runs) or hot side at fuse holder.



What did I fry?

Why do Regulator/Rectifier (893640T01 ) prices vary from $10.oo to $376.oo online. Which are the good ones? I think I want an OEM part for reliability.



Suggestions?

Joe

 

[JoeRo]

First you must have all ground wires at the ignition switch and kill switch connected. If not you may NOT be able to turn the motor off after starting and running.
After days of testing I found I connected the purple wire at the ignition switch WRONG, to the wrong barrel connector on the wiring harness at the key switch. There are several purple wires ends at the ignition switch.
Thery are for a plug for the tack, a plug for gauges, power going back to the motor for power .....ext.
I plunged the purple wire into the wrong connector.
Simple test.....do you have power going to each fuse on the hot side before the fuse? Next are your fuses good? If you turn the key ignition to the run position on you should hear the high pressure pump start running.
If not the purple wire may be connected in the wrong spot on the wiring harness at the key.

How stupid of me!
The motor now runs when connected properly.

Joe

 

[alldodge]

Merged threads, don't start a new on for same problem