Engine Light Troubleshooting, Sensor Testing
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Engine Light Troubleshooting, Sensor Testing
OK, first post here after lurking and getting most of my questions answered.
1988 F250 7.3 IDI
I cleaned my engine yesterday with simple green and a hose. Started fine and it runs great, but now the red engine light is on and the temperature gauge is pegged.
The guage sensor is shot for sure, because when I pull the connector it returns to normal. Pulling the overtemp sensor on the driver's side doesn't do anything, with or without the other sensor plugged in. How do I test it?
Next suspect is the oil pressure sender behind the air cleaner. The gauge seems to work. How do I test it?
Ditto for the temperature sensor with two wires that controls the engine (behind the alternator). Is there a way to test this?
One more question: I have a sensor by the oil filler at the front of the vehicle. I thought that was oil pressure, but posts I've read indicate its in back.
New truck to me, and its my first diesel. Going through and cleaning it up now....
1988 F250 7.3 IDI
I cleaned my engine yesterday with simple green and a hose. Started fine and it runs great, but now the red engine light is on and the temperature gauge is pegged.
The guage sensor is shot for sure, because when I pull the connector it returns to normal. Pulling the overtemp sensor on the driver's side doesn't do anything, with or without the other sensor plugged in. How do I test it?
Next suspect is the oil pressure sender behind the air cleaner. The gauge seems to work. How do I test it?
Ditto for the temperature sensor with two wires that controls the engine (behind the alternator). Is there a way to test this?
One more question: I have a sensor by the oil filler at the front of the vehicle. I thought that was oil pressure, but posts I've read indicate its in back.
New truck to me, and its my first diesel. Going through and cleaning it up now....
Tuned
Joined: Jan 2011
Posts: 271
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From: Bluffton, IN
the sensor by your oil fill would be your tach sensor. the gauges in these trucks suck. i would advise you put some aftermarket gauges in to better monitor you engines functions. ex. the oil pressure sender on these trucks are just an idiot light. they do not show actual oil pressure just if it has enough to close the switch. so you could have four pounds of pressure but the gauge shows it ok because of the way the sender is.
Elder User
Joined: Feb 2008
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From: North Bend
Firstly, welcome to the Forum!! 
Did you have a hot engine, or cold? Be careful with cold hose-water around a hot IP! That can lead to damage that costs around $450 plus labor... 
Yeah as Forddiesel17 said, certain gauges in these trucks are just on/off switches. I found personally that my temp gauge reads great when it's unplugged, lol!
As for testing it... I suppose if it registers normal it's working?... again, they suck. The coolant one moves around a bit, but doesn't actually read temperature. I have a real gauge now and the stock one doesn't even correlate a LITTLE BIT to the real one.
Also just an on/off switch. If it reads, it's "working". But I've read that it switches ON with only 6psi, which is too low for these trucks, even at hot idle.
Ok, this is where you lost me. These engines are 99.99% mechanical. The only electrical bit that "controls" it is a simple fuel-shut-off solenoid, and that's on the driver's side of the IP.
Hope this helps,
Joshua
I cleaned my engine yesterday with simple green and a hose. Started fine and it runs great, but now the red engine light is on and the temperature gauge is pegged.
The guage sensor is shot for sure, because when I pull the connector it returns to normal. Pulling the overtemp sensor on the driver's side doesn't do anything, with or without the other sensor plugged in. How do I test it?
As for testing it... I suppose if it registers normal it's working?... again, they suck. The coolant one moves around a bit, but doesn't actually read temperature. I have a real gauge now and the stock one doesn't even correlate a LITTLE BIT to the real one.
Next suspect is the oil pressure sender behind the air cleaner. The gauge seems to work. How do I test it?
Ditto for the temperature sensor with two wires that controls the engine (behind the alternator). Is there a way to test this?
Hope this helps,
Joshua
i ain't rite
Joined: Mar 2005
Posts: 65,573
Likes: 5,609
From: Marlboro Mental Hospital.
give it about a week for the temp sensor to dry out and it will start working again.
there are only two things hat will pop the check engine light, low oil pressure and high water temp. since you know it is not running hot, just let it dry out.
there are only two things hat will pop the check engine light, low oil pressure and high water temp. since you know it is not running hot, just let it dry out.
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Real gauges are a low priority now. 1st, I need a clutch.
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Could be wrong.
Was wondering if it would affect fuel economy.
Mine seems to work, sine I get fast idle at start at 950 rpm. Comes down to 77 ish once she's warm
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OK, the oil and two coolant sensors on the driver's side didn't dry out and Im gonna replace 'em.
question on the two-prong sensor for the solenoid: Is this just a simple switch I can check for continuity, or does it provide a rheostat like function as temperature goes up?
Figured I'd replace them all, but this one's dealer only it seems while the others were under $20 each.
Cheap insurance, since I gotta drive this beast 1500 miles this weekend.
question on the two-prong sensor for the solenoid: Is this just a simple switch I can check for continuity, or does it provide a rheostat like function as temperature goes up?
Figured I'd replace them all, but this one's dealer only it seems while the others were under $20 each.
Cheap insurance, since I gotta drive this beast 1500 miles this weekend.
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i ain't rite
Joined: Mar 2005
Posts: 65,573
Likes: 5,609
From: Marlboro Mental Hospital.
the one under the alternator is a temp switch. once the engine reaches 110 degrees(i think it is) it will turn the high idle and timing advance off.
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