Sending unit questions
#1
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Thread Starter
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.
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.
#2
Registered
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.
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.
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PQ290Enticer (03-29-2023)
#3
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Thread Starter
Did they install knock sensors in 1995 on a 7.4 that is carbureted?
#5
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
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-Wally
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-Wally
Money can't buy happiness, but it can buy horsepower. And I've never seen a sad person hauling a$$!
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PQ290Enticer (03-29-2023)
#6
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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.
#7
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I'm going with alarm. The one for operating my gauge is up on top kinda behind the distributor.
#8
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yes thats a knock module mounted to the distributor
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PQ290Enticer (03-29-2023)
#9
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PQ290Enticer (03-29-2023)
#10
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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.
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PQ290Enticer (03-29-2023)