Vovlvo penta Alternator, starter and fuel pump questions

[Jay reno]

Hello. First time posting here. After quite an extensive search for alternator issues, (there is alot of info here wow ) i still have a few issues in need of guidance.
New alternator installed before 1st trip.
1) Used to have a motorola alternator, now with mondo. From what i have found on this forum, the green diode wire for fuel pump relay goes to L2 terminal and purp/white for choke goes to P. My supplier advised to install BOTH on the P terminal and to not use the L2 as this only puts out like 1.5v ish or goes out when alternator is running. Also said i didnt need the sense wire but from the info found here, i jumpered to battery out dirrectly from alt. The issue is that the relay at fuel pump shuts off while cruising or throttling down, and sometimes while trolling. (Diode has been replaced and in proper working order). Pump relay good and i carry a handfull of them anytime i go out. I metered the coil trigger and was able to whitness the trigger goes out moments before the boat starves for fuel. When i got stuck, i removed the relay and bypassed using a jumper between 12v supply and +12 pump at the relay base and enjoyed the whole day. Just had to be quick when shutting the boat off
2) purple wire, ign 12v+, when ign switch is on, i have 12v at coil pack, alt, and starter i terminal, but not battery voltage, it is lower. When engine running, i have 12.5v but alternator and batt is at 14.1v. When ign is off, that circuit and all the point right up to the key are toning to ground (continuity check on good ground, from any point on the purp wire). Is this normal or could there be an issue at starter solenoid? When ign on and wire has 12v however, i no longer has continuity to ground.

 

[Jay reno]

FYI, 1996 four winns bowrider, with volvo penta 4.3 GL, and i believe osx cobra drive

 

[Bondo]

Ayuh,..... Welcome Aboard,...... One thread per problem,.... if ya want it at the top of the forum,....
Post in it,......
I deleted yer other one,......

Btw,.... As nasty as that wirin' is,..... I'm surprised anything works,....

 

[alldodge]

Start with disconnecting Bat and then remove every wire on the starter. Clean all the connections to shinny metal and reinstall

The image below is for a V8 but wiring is the similar

The L2 connection should have same 12V as P terminal (purple ignition) but connecting them both to same terminal will not be an issue. Not having full voltage when not running as well as running may be a bad connection. After cleaning the connection on the starter this may fix that issue

Also said i didnt need the sense wire but from the info found here, i jumpered to battery out dirrectly from alt

The Mando ALT must have both Sense and Excite leads.

Sense is the Red/Purple wire at the starter or the Orange wire on the ALT (note the jumper between output and Sense terminal). The Sense tells the ALT regulator how much voltage is being produced. This can also be connected to the Bat but better in your case at the ALT

Excite lead (purple wire) is what turns the ALT ON when motor is running

 

[Scott Danforth]

Holy corrosion batman

As indicated above, clean all the connections with 150 grit sandpaper until each mating connection surface is clean and shiny enough for your mother in law to eat off them

If you have any green between the terminal and the cable conductor, you need new cables

 

[Jay reno]

I figured you guys would loke that lol. So this is the first time i noticed the issue (3rd year as the owner, and had never even been on a boat) and discovered this yesterday while inspecting, tracing, cleaning up issues. So as i understand, the purple wire should NEVER have a path to ground, meaning this corrosion is likely creating said path?

Should the purple wire have BATT voltage when running or be lower as it also goes to coil? What i mean is that when engine is running, batt is at 14.1v from a properly charging alternator but this wire is at 12.5v. On the old alt, it had a jumper (red/purple) between the excite and sense, purp being excite, jumper being sense and causing alternator to ramp up to 15.3v . When i replaced with new alternator, i got the same ramp up, so i removed the jumper from sense, and installed a new one between the output and sense, like in the diagram which corrected the voltage. It would seem the corrosion is causing that drop...

Thanks for the help, i will start with that project once i return from work on the week end.

Fyi, for those who are interested. I have built a bypass using the fuel pump relay and an extra one to latch the pump relay on once the engine is running. This would take the green diode wire of the alt and used to latch the relay only once the engine crank is performed. The only draw back is that if the engine stahls or quits without you returning the key, the pump will keep working. It will not trigger on the initial key turn until crank is preformed, and releases when key is off. (I was worried i couldnt find any answers until i found you guys)

 

[alldodge]

Red/purple and purple should not be connected together

Reading 12.5v on the purple is most likely from bad connections, it should read full V of the ALT

If your motor is wired like the drawing above (less keep Green and purple together) it should run as designed

Mando ALT wiring J is purple on Merc

 

[Jay reno]

Ok thanks. I have a picture of the old alt before taking things appart. The new one is wired like the other diagrame earlier in the post

 

[alldodge]

Not Motorola its prestolite
Yes, red/Pur and Pur are connected together

Clean the terminals up and see what the readings are

 

[Jay reno]

Yes, prestolite. I got hung up on motorola from my supplier. He said they were the same or one is by the other or something like that. Thanks for all your help guys. I will start with that.

 

[Jay reno]

Yeah, well update... started to clean up the corrosion, and found that the fault to ground is not caused at the engine components. It's somewhere ahead of the main harness connecting the front to the engine. When It's disconnected, all faults are gone. About to disconnect the wires from the front to see if it's the fuse panel or damaged wires along the 13 feet of loom and tape Fun evening maybe?