Alternator pin 61 - engine carries on running after it's connected.

[loco]

Hi all,
Pin 61 on the alternator wasn't connected after a new engine was installed, so initial excitement wasn't happening and the alternator wasn't charging.

My ignition switch is a simple 0-1-crank system, and I'd installed a new line recently from the 1 position to the fuel pump (old engine had a manual fuel pump).
With no alternator warning light on the dash, I tried a quick and dirty fix by wiring the line from position 1 on the ignition switch to pin 61 on the alternator.

The engine cranked and started as it should and my electrical system was running at a healthy 14.0v. Happy days. Then I turned the ignition switch to the off position, but the engine carried on running - oops!
My thought here was the alternator was then producing current from pin 61 which was then running the fuel pump and electrical system, thereby bypassing the ignition switch.

Having clearly failed miserably using my intuition, I reverted to the manual for the engine and checked where pin 61 should be connected (it's a repower GM 4.3L V6 petrol with holley carb), I saw that it connected to the same circuit as the positive on the electronic choke. I tried connecting here, but again the engine carried on running after power had been turned off.

I know it only really needs a momentary voltage applying to it, so how can I solve this?

Many thanks in advance!

the manual for my engine with circuit diagram (mine's the v6 carbed): http://marinepowerusa.com/pdfs/MarinePowerUSA_Engine_Owners_Manual_Pre-2011.pdf

 

[Don S]

Re: Alternator pin 61 - engine carries on running after it's connected.

You DO NOT hook up your fuel pump directly to the ignitions switch or the alternator.

You need to hook your fuel pump up to an oil pressure switch and the starter. Then the pump will only run when you are cranking the engine and when the engine has over 3 to 5 PSI of oil pressure.

Here is how it's wired on a Mercruiser, but it will work on any engine with an electric fuel pump.

 

[loco]

Re: Alternator pin 61 - engine carries on running after it's connected.

I might be confused here, but according to that diagram it looks like the purple/yellow cable comes from the starter and constantly powers the pump. The pin 61 on the alternator then gets a voltage until the engine is started and the pressure switch then opens, preventing it from getting a constant voltage?

You DO NOT hook up your fuel pump directly to the ignitions switch or the alternator.

You need to hook your fuel pump up to an oil pressure switch and the starter. Then the pump will only run when you are cranking the engine and when the engine has over 3 to 5 PSI of oil pressure.

Here is how it's wired on a Mercruiser, but it will work on any engine with an electric fuel pump.

View attachment 195823

 

[Don S]

Re: Alternator pin 61 - engine carries on running after it's connected.

It comes from the outboard small terminal. D in this drawing.

 

[loco]

Re: Alternator pin 61 - engine carries on running after it's connected.

Ok - and is that pin D switched in any way or is it constant? The fuel pump surely needs to run constantly and needs to fuel the carb before you start cranking (assuming a dry engine), and pin D being switched or constant, I don't see how the pressure switch would affect the pump according to that diagram.

On the first diagram, the pressure switch goes to a purple wire which goes to alternator pin 61. The purple then goes up to what I presume is the engine warning light and then a ground.

So, the engine warning light represents both oil pressure and voltage problems:

- Before the engine runs, the light is on, powered by pin d from the starter solenoid going through the pressure switch.
- Engine is started, alternator gets trigger voltage until pressure builds.
- Engine reaches minimum pressure, voltage is shut off via switch and warning light on dash goes out
- If engine pressure drops the light is lit, and I understand if the alternator stops charging pin 61 goes to +12v, so the light would come on again too.

That sound about right? I'll have to see if I have an oil pressure switch & install one if that's the case as that could be a good solution.

cheers

 

[Don S]

Re: Alternator pin 61 - engine carries on running after it's connected.

The D terminal on the solenoid only powers the pump while the engine is cranking.
Once the engine starts, the oil pressure switch is closed and power comed from the purple ignition wire on one side of the switch and the fuel pump positive wire on the other side.
It's set up that way so the pump does run when the engine isn't running. If the engine blew up and caught fire and the fuel line was broken, you don't need an electric fuel pump running and blowing gas on a fire.

Forget about using the alternator for the job.

http://www.iboats.com/Oil-Pressure-...72511911--session_id.517324152--view_id.74365

 

[loco]

Re: Alternator pin 61 - engine carries on running after it's connected.

OK, that makes sense now - thank you! So - the purple wire is switched power from the ignition, then?
Is the thread on the switch going to be a 1/4" NPT thread? I'll need to put in a T-junction on my oil pressure sender and put the switch on there.

The D terminal on the solenoid only powers the pump while the engine is cranking.
Once the engine starts, the oil pressure switch is closed and power comed from the purple ignition wire on one side of the switch and the fuel pump positive wire on the other side.
It's set up that way so the pump does run when the engine isn't running. If the engine blew up and caught fire and the fuel line was broken, you don't need an electric fuel pump running and blowing gas on a fire.

Forget about using the alternator for the job.

Oil Pressure Switch, 1/4 Spade - MarineWorks OP72533 - iboats