Go Back  Offshoreonly.com > Technical > General Q & A
Sending unit questions >

Sending unit questions

Notices

Sending unit questions

Old 03-29-2023, 11:46 AM
  #1  
Banned
Thread Starter
 
Join Date: Jan 2022
Location: West Michigan
Posts: 552
Received 152 Likes on 88 Posts
Default Sending unit questions

I'm setting up my new engines and can't figure out what these sending units do. I thought I did but met with a guy at shop where I was going to buy new sending units (to operate the alarms at the dashboard) and he didn't know what I needed. I have attached a few pics. FYI, these were on my stock 7.4's and as far as I know all factory installed.
There were 2 units in the thermostat housing. I pulled them out and they are different. 2nd pic. Does one of these operate the alarm at the dashboard? I ask this because there was also another unit (the largest one pic #3) installed in the block by the starter. It's actually in the "block drain location" I thought this was maybe an overheating sending unit but maybe it's for water pressure? That sending unit also is the only one that had a GM clip for the wire instead of the sending unit having a stud and the wire held in place with a washer and nut. The last fitting was mounted in the block above the oil filter location. I think this is for low or no oil pressure? Thanks for your help.




PQ290Enticer is offline  
Old 03-29-2023, 11:50 AM
  #2  
Registered
 
Join Date: Aug 2007
Location: Merritt Island, FL
Posts: 1,302
Received 971 Likes on 441 Posts
Default

The knock sensor is the one in the block drain.

The 2 in the thermo housing, one is for the gauge, the other is probably the alarm buzzer.

One above the oil filter adapter is for pressure but I am unsure if what you have there is for gauge or buzzer.


Last edited by DrFeelgood; 03-29-2023 at 11:53 AM.
DrFeelgood is offline  
The following users liked this post:
PQ290Enticer (03-29-2023)
Old 03-29-2023, 11:54 AM
  #3  
Banned
Thread Starter
 
Join Date: Jan 2022
Location: West Michigan
Posts: 552
Received 152 Likes on 88 Posts
Default

Did they install knock sensors in 1995 on a 7.4 that is carbureted?
PQ290Enticer is offline  
Old 03-29-2023, 12:15 PM
  #4  
Were doomed!
Charter Member
iTrader: (1)
 
Wally's Avatar
 
Join Date: Oct 2000
Location: Chicago, IL
Posts: 6,668
Received 913 Likes on 459 Posts
Default

Originally Posted by PQ290Enticer
Did they install knock sensors in 1995 on a 7.4 that is carbureted?
If its got the Tbolt V ign module then yes it can have a knock sensor...
__________________
-Wally

Money can't buy happiness, but it can buy horsepower. And I've never seen a sad person hauling a$$!
Wally is offline  
Old 03-29-2023, 12:17 PM
  #5  
Were doomed!
Charter Member
iTrader: (1)
 
Wally's Avatar
 
Join Date: Oct 2000
Location: Chicago, IL
Posts: 6,668
Received 913 Likes on 459 Posts
Default

or maybe you have a motor that was in that gray zone when they were transitioning over to EFI and were still using old stuff to get rid of things
__________________
-Wally

Money can't buy happiness, but it can buy horsepower. And I've never seen a sad person hauling a$$!
Wally is offline  
The following users liked this post:
PQ290Enticer (03-29-2023)
Old 03-29-2023, 12:35 PM
  #6  
Banned
Thread Starter
 
Join Date: Jan 2022
Location: West Michigan
Posts: 552
Received 152 Likes on 88 Posts
Default

Well I ditched whatever was there for the MSD ready to run stuff. Just out of curiosity this is what was there. Did this use the knock sensor? Mercury is a big outfit and it could be that it's cheaper not to "think" about each engine separately and just wire them all the same. Shotgun affect. Can't go wrong with that.

PQ290Enticer is offline  
Old 03-29-2023, 12:39 PM
  #7  
Banned
Thread Starter
 
Join Date: Jan 2022
Location: West Michigan
Posts: 552
Received 152 Likes on 88 Posts
Default

Originally Posted by DrFeelgood
The knock sensor is the one in the block drain.

The 2 in the thermo housing, one is for the gauge, the other is probably the alarm buzzer.

One above the oil filter adapter is for pressure but I am unsure if what you have there is for gauge or buzzer.
I'm going with alarm. The one for operating my gauge is up on top kinda behind the distributor.
PQ290Enticer is offline  
Old 03-29-2023, 12:43 PM
  #8  
Platinum Member
Platinum Member
iTrader: (6)
 
F-2 Speedy's Avatar
 
Join Date: May 2012
Location: Midwest & T-Rock
Posts: 10,388
Received 3,029 Likes on 1,347 Posts
Default

yes thats a knock module mounted to the distributor
F-2 Speedy is offline  
The following users liked this post:
PQ290Enticer (03-29-2023)
Old 03-29-2023, 12:45 PM
  #9  
Platinum Member
Platinum Member
iTrader: (6)
 
F-2 Speedy's Avatar
 
Join Date: May 2012
Location: Midwest & T-Rock
Posts: 10,388
Received 3,029 Likes on 1,347 Posts
Default

Originally Posted by PQ290Enticer
I'm going with alarm. The one for operating my gauge is up on top kinda behind the distributor.
if its in the block by the bell housing that an oil pressure gauge,
F-2 Speedy is offline  
The following users liked this post:
PQ290Enticer (03-29-2023)
Old 03-29-2023, 12:50 PM
  #10  
Registered
 
Join Date: Aug 2007
Location: Merritt Island, FL
Posts: 1,302
Received 971 Likes on 441 Posts
Default

Oil pressure switch vs gauge sender can both work correctly in either location (top of bellhousing, or above filter adapter). It's oil temp senders that don't work well in low-flow or blind-ended passage locations. Good pressure readings available in either place.
DrFeelgood is offline  
The following users liked this post:
PQ290Enticer (03-29-2023)

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.