Cummins Where to Have Alternator Bench Tested for Diode

10-14-2018, 12:08 PM	#1
Veteran Member City: hyannis Vessel Name: BAG END Vessel Model: Marine Trader 38 Sundeck Join Date: Mar 2018 Posts: 27	Cummins 6bt shut off issue I wanted to get input for the following issue with my starboard engine. I recentl had the alternator rebuilt. I have an on/off key with a push start button at the helm. With the engine not running and when I turn the key on the power goes to the screw in type fuel solenoid and retracts the internal plunger.I get a good reading of 12v. With the engine not running and when I turn the key off the fuel solenoid shuts off and I get no 12v reading. Here is the kerfufffle. When I start the engine and have it running, then shut the key off the engine does not stop or shut off. I have a reading of 12v at the fuel solenoid with the key in the off position. If I unplug the fuel solenoid the engine shut off. Hence the fuel solenoid is not sticking. I have looked for a plug in diode but do not see one in the wiring harness These are 1988 cummins 6bt. Help!!!

10-14-2018, 12:16 PM	#2
Guru City: SWFL Vessel Name: Irish Lady Vessel Model: Monk 36 Join Date: Dec 2007 Posts: 4,285	Just to be clear, before the alternator rebuilt worked fine, next startup after rebuilt, not fine? Are the alternator connectors hooked up the same? Who did the alternator remove and install? Anything else worked on at the same time? __________________ Archie Irish Lady 1984 Monk 36 Hull #46 Currently in Ft Myers, FL

10-14-2018, 12:22 PM	#3
Veteran Member City: hyannis Vessel Name: BAG END Vessel Model: Marine Trader 38 Sundeck Join Date: Mar 2018 Posts: 27	Yes before the alternator rebuild the engine shut off fine with the key. Thank you for your reply. John

10-14-2018, 01:07 PM	#4
Guru City: Guelph Vessel Name: Escapade Vessel Model: 50` US Navy Utility trawler conversion Join Date: Nov 2015 Posts: 1,235	Sounds like a bad diode or incorrect hookup on the alternator. Without the diode the alternator will power the fuel solenoid.

10-14-2018, 01:08 PM	#5
Technical Guru City: Wilmington, NC Vessel Name: Louisa Vessel Model: Custom Built 38 Join Date: Jan 2014 Posts: 6,194	A resistor or diode is missing from the alternator. Probably a rebuild error. Exciter power is backfeeding the ignition lead somehow.

10-14-2018, 01:45 PM	#6
Guru City: Fort Myers, FL... Summers in the Great Lakes Vessel Name: Slow Hand Vessel Model: Cherubini Independence 45 Join Date: Dec 2010 Posts: 10,342	You should have a large wire going to the alternator and either 1 or 2 small wires. The small wires may either plug in or attach on a stud. Remove the 1 or 2 small wires, tape them off so they don't short out to anything Start the engine while looking at the gauge and pay close attention to the gauge panel. If it stops with the key and voltage is below 12 volts, its a problem in the alternator. If it stops and the voltage is above 12 volts (charging) it's the wrong alternator (single wire self exciting). Ted __________________ Blog: mvslowhand.com I'm tired of fast moves, I've got a slow groove, on my mind..... I want to spend some time, Not come and go in a heated rush..... "Slow Hand" by The Pointer Sisters

10-29-2018, 03:16 AM	#7
Veteran Member City: hyannis Vessel Name: BAG END Vessel Model: Marine Trader 38 Sundeck Join Date: Mar 2018 Posts: 27	Update, I removed the alternator and brought it back to the repair shop. At first the owner was questioning my findings. He said it was highly unlikely that it was the alternator. I told him the engine shut off with the key before his rebuild of my alternator. I told him I had a 12v reading from the fuel solenoid when the engine was running and the key was switched to off. Furthermore when I unplugged the field wire with the engine running, the engine was able to be shut off with the key. I asked him to do his bench test while I was there. He did it and sure enough the field terminal was producing charge. He offered his apology and is replacing the diodes in the alternator. Problem fixed. Thank you all for the input.

Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Trackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

All times are GMT -5. The time now is 01:25 AM.

Cummins Where to Have Alternator Bench Tested for Diode

Source: https://www.trawlerforum.com/forums/s10/cummins-6bt-shut-off-issue-40960.html

Share this post