Reply
 
Thread Tools Display Modes
 
Old 11-28-2015, 02:19 PM   #1
Guru
 
windmist's Avatar
 
City: Port Orchard, WA
Country: USA
Vessel Name: Violet A
Vessel Model: Nordic Tug 42
Join Date: Mar 2008
Posts: 908
Cummins Electromagnetic Relay

I have a spare part called a electromagnetic relay, Cummins part # 3916301. I am wondering what it is used for on the engine. I have a QSC 8.3 - 450HP on the boat.

If it fails what is going to happen? I did try and google this but no luck.

Thanks
__________________
Advertisement

__________________
Ron

The five stages of life: Sailboats, Motorboats, Motor Homes, Nursing Home, Funeral Home.
windmist is offline   Reply With Quote
Old 11-28-2015, 03:06 PM   #2
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 4,810
Believe it's part of the starting circuit. On my B and C engines they were located below the starter.

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
O C Diver is offline   Reply With Quote
Old 11-28-2015, 03:12 PM   #3
Senior Member
 
Retriever's Avatar
 
City: Seattle, WA
Country: USA
Vessel Name: Safe Harbour
Vessel Model: Nordic Tug 37
Join Date: Apr 2014
Posts: 191
That part looks like a relay for the grid heater on my 6BTA 5.9. Do the 8.3 engines use grid heaters for preheat and smoke reduction after starting?

If they do, and the relay fails, the preheat system won't work. Expect slower starts with more smoke. On my engine (6BTA 5.9, 330 hp), Cummins recommends a starting aid (i.e. preheat) any time the temperature is below 50 degrees.

The problem with the preheat system is it draws an enormous amount of power, something like 100 amps, and by default it cycles whenever the engine is running below 950 or 1000 rpm and the intake temperature is below a certain temperature. I can't remember the temperature off the top of my head, but it's something pretty high, like 90 degrees. So when you're in a long no wake area, the preheaters keep cycling, putting a huge load on the alternator creating a lot of heat in the relays. Eventually the relays fail, so it's a good thing you have a spare!

I have a switch at the helm so I can turn the preheat system off entirely. I typically use the preheaters when I start the engine in the morning, especially in winter, but quickly turn it off to avoid the big electrical drain.
Retriever is online now   Reply With Quote
Old 11-28-2015, 08:51 PM   #4
Guru
 
C lectric's Avatar
 
City: Somewhere
Country: , Canada
Vessel Name: Island Pride
Vessel Model: Palmer sedan 32'
Join Date: Oct 2007
Posts: 1,864
Cummins use relays for two different purposes and both posters are correct. I believe it is used for both the grid heaters to reduce cold start smoking but also as the intermediate starter control relay to save the ignition switch.

If it fails and is used in the grid heater it is simply a nuisance.
If it fails and is the one in the starter circuit it could be a serious problem depending upon circumstances. There is a work around but look into it.

Not a bad idea to have a spare especially for the starter function. They are usually mounted close by the starter.
C lectric is offline   Reply With Quote
Old 12-01-2015, 10:39 PM   #5
Guru
 
windmist's Avatar
 
City: Port Orchard, WA
Country: USA
Vessel Name: Violet A
Vessel Model: Nordic Tug 42
Join Date: Mar 2008
Posts: 908
Thanks everybody for the responses. I wanted to post a picture of the relay but something happen to my ability to download a picture from my cellphone. Anyway, on checking my QSC 8.3 Cummins, it looks like one is located by the starter and there are two more that are located below and behind the aftercooler. Maybe one or both of them have something to do with the pre-heater.

I have a maintenance manual and I couldn't find a thing about how the pre-heater is wired.

Thanks for the help.
__________________
Ron

The five stages of life: Sailboats, Motorboats, Motor Homes, Nursing Home, Funeral Home.
windmist is offline   Reply With Quote
Old 12-02-2015, 07:29 AM   #6
Guru
 
jleonard's Avatar
 
Join Date: Jun 2008
Posts: 2,736
You may have 2 for the grid heaters. I had 2 on my 6BTA.
__________________

__________________
Jay Leonard
Attitude Adjustment
40 Albin
Mystic,Ct. /New Port Richey,Fl
jleonard is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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





All times are GMT -5. The time now is 11:10 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012