Test Run 4.3 Mercruiser on stand

[amking75]

I recently finished rebuilding our worn out 1997 4.3 Mercruiser. Started with a rebuilt long block and swapped everything over.

I currently have the motor mounted on a pallet to test run it before putting in back in the boat. I have watched several YouTube videos but think I am missing something in the process.

Motor is fully dressed less throttle cable assembly and shift linkage assembly. I left these in the boat.
1997 Chaparral 1930SS, 4.3L Mercruiser Gen+, Thunderbolt V(?)

Setup:
Battery + to Starter
Battery - to Engine Ground
Fuel from 2-gallon container through fuel-water filter
Jumper in wiring plug 5-6 (ignition on)
Jumper in wiring plug 6-7 (start)

When I touch 6-7, slave solenoid just clicks.
If I jump across slave solenoid, engine will turn over, but not start.

What is preventing me from engaging the starter by touching 6-7?

Thanks

 

[kghost]

Make a jumper rig as my image describes. Connect as I describe directly to starter solenoid. Deal with slave solenoid after engine is reinstalled

Also you will need to jump out the oil pressure switch near oil filter. Remove both connections and jump them together. This will TEMPORARILY remove the oil pressure switch from power to fuel pump and allow pump to run when On/OFF switch is turned on. (NOTE: ON/OFF Switch must be turned off to shut fuel pump off for any reason) On/Off switch controls power to ignition. Momentary switch is used for cranking

 

[Dieter]

I recently finished rebuilding our worn out 1997 4.3 Mercruiser. Started with a rebuilt long block and swapped everything over.

I currently have the motor mounted on a pallet to test run it before putting in back in the boat. I have watched several YouTube videos but think I am missing something in the process.

Motor is fully dressed less throttle cable assembly and shift linkage assembly. I left these in the boat.
1997 Chaparral 1930SS, 4.3L Mercruiser Gen+, Thunderbolt V(?)

Setup:
Battery + to Starter
Battery - to Engine Ground
Fuel from 2-gallon container through fuel-water filter
Jumper in wiring plug 5-6 (ignition on)
Jumper in wiring plug 6-7 (start)

When I touch 6-7, slave solenoid just clicks.
If I jump across slave solenoid, engine will turn over, but not start.

What is preventing me from engaging the starter by touching 6-7?

Thanks

I'm assuming your slave solenoid is bad or the terminals on it are wired incorrectly. Most likely since it clicks the control side of it is correct closing the contacts, thinking the 12 v. Do you have 12 v on the red/purple (12v supply to load side of solenoid) and 12v going to the yellow/red ( 12 v feed to starter solenoid) when it clicks? these should be the two larger terminals on the solenoid.

 

[kghost]

I'm assuming your slave solenoid is bad or the terminals on it are wired incorrectly. Most likely since it clicks the control side of it is correct closing the contacts, thinking the 12 v. Do you have 12 v on the red/purple (12v supply to load side of solenoid) and 12v going to the yellow/red ( 12 v feed to starter solenoid) when it clicks? these should be the two larger terminals on the solenoid.

He is approaching this the wrong way by jumping connections at the harness plug.

He should do as I suggested!

 

[Dieter]

He is approaching this the wrong way by jumping connections at the harness plug.

He should do as I suggested!

Kghost, respectfully, either will work. I did exactly as he outlines jumping the cannon plug connections when I ran my repower on the ground before installing it. I did this to test the wiring harness out before I dropped it in the boat, worked perfectly.

I believe the electric fuel pump gets powered from the starter during cranking and only goes off the oil pressure switch when it is in run and purple #5 gets power in run position.

 

[amking75]

Make a jumper rig as my image describes. Connect as I describe directly to starter solenoid. Deal with slave solenoid after engine is reinstalled

Also you will need to jump out the oil pressure switch near oil filter. Remove both connections and jump them together. This will TEMPORARILY remove the oil pressure switch from power to fuel pump and allow pump to run when On/OFF switch is turned on. (NOTE: ON/OFF Switch must be turned off to shut fuel pump off for any reason) On/Off switch controls power to ignition. Momentary switch is used for cranking

View attachment 28662

In you diagram, the on/off and momentary switch are external devices, correct? I need to pick up a toggle and a push button to wiring up this rig?

Thanks

 

[amking75]

I'm assuming your slave solenoid is bad or the terminals on it are wired incorrectly. Most likely since it clicks the control side of it is correct closing the contacts, thinking the 12 v. Do you have 12 v on the red/purple (12v supply to load side of solenoid) and 12v going to the yellow/red ( 12 v feed to starter solenoid) when it clicks? these should be the two larger terminals on the solenoid.

With ignition on (5/6 jumped), I have 12V at red/purple. When 6/7 is touched (click), I don’t have voltage on yellow/red to starter.

Wiring appears correct and matches my “before tear down” picture.

Thanks

 

[Dieter]

With ignition on (5/6 jumped), I have 12V at red/purple. When 6/7 is touched (click), I don’t have voltage on yellow/red to starter.

Wiring appears correct and matches my “before tear down” picture.

Thanks

that shows a bad slave solenoid. You could measure ohms across it when 6/7 is jumped based on what you are saying it should show an open circuit and thus is defective. Good news is slave solenoid is a cheap part i think napa has marine relays like this

as for not starting when you crank by jumping slave solenoid did you try jumping some gas down carb? May not be cranking long enough jumping out slave to get gas to carb

 

[kghost]

In you diagram, the on/off and momentary switch are external devices, correct? I need to pick up a toggle and a push button to wiring up this rig?

Thanks

Yes and no,
You dont need a push button switch but if you prefer that type then that works.
I use twp toggle type, one is on/off and one is momentary.

I have been using this test rig for many many years.

As an example,
You are trying to start and run your engine out of boat for first time.
Your method may have revealed a problem.
What do you do? You now have to trouble shoot your cranking problem before proceeding.

Using my suggested rig you can bupass (easily) the slave and connect directly to the starter bypassing the entire engine wire harness and focus starting and tuning your engine. Once complete you can then trouble shoot any cranking issues.

The need for the test rig is for trouble shooting electrical wire harness starting issues but also allows simple connecting to starter or slave and coil.
It allows easy control in your hands without jumping pins in a connector..

I did not do this for no reason and it has made controling the starting at the engine of the engine simple.

Oh, use alligator clips on the wire ends if you choose to make this test rig..


Personally I have never jumped pins in the connector in over 30 years...never even considered doing so.....i took the simple solution as for me itvis another tool to be used as needed.

 

[kghost]

Typing in a small window from a SMAHT Phone I make a lot of spelling mistakes..........Oh well............

 

[bondo]

Typing in a small window from a SMAHT Phone I make a lot of spelling mistakes..........Oh well............

Ayuh,.... That's Ok, it's completely understandable,....
'n I agree, alligator clips,. directly to the components is also how I test run motors,....

 

[amking75]

Using my suggested rig you can bupass (easily) the slave and connect directly to the starter bypassing the entire engine wire harness and focus starting and tuning your engine. Once complete you can then trouble shoot any cranking issues.

The need for the test rig is for trouble shooting electrical wire harness starting issues but also allows simple connecting to starter or slave and coil.
It allows easy control in your hands without jumping pins in a connector.

I got this wired up today and was able to get a few cranks on it. Got a few puffs of smoke out the exhaust.

Do I need to do anything with the green/white for the shift cut out switch? It’s currently disconnected.

Also the purple/white and tan/blue? I believe these reconnect to the shift linkage.

Thanks for all the advice!

 

[Dieter]

I got this wired up today and was able to get a few cranks on it. Got a few puffs of smoke out the exhaust.

Do I need to do anything with the green/white for the shift cut out switch? It’s currently disconnected.

Also the purple/white and tan/blue? I believe these reconnect to the shift linkage.

Thanks for all the advice!

rotate the distributor when you crank it likely timing is off

 

[amking75]

I had a friend give me hand this weekend. Timing was off almost 180. Got that squared away and it’s firing right up.

Timing is set. Probably get another good 20 min run on it this week and the. Stick it back in the boat!

Thanks for all the help!

 

[Dieter]

I had a friend give me hand this weekend. Timing was off almost 180. Got that squared away and it’s firing right up.

Timing is set. Probably get another good 20 min run on it this week and the. Stick it back in the boat!

Thanks for all the help!

you must have timed the distributor at tdc on the exhaust stroke not compression . Done that a few times …