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Discussion Starter #1
So I did a little cleaning on the engine bay today. This included taking off oil pressure gauge line to oil pressure sending unit and cleaning it. Put it back on and now gauge does not read correctly. Car has new sending unit. Any ideas? I made sure fitting is snug against sending unit. I do believe this is the original engine to gauge harness.

And while we are on the subject, I noticed that my steering column is starting to get hot...is this possibly a wire grounding out to the column? Made sure it was not the radio since the constant is wired to the ignition by removing the fuse and driving the car...column still gets hot.
 

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a) Did you use teflon tape on the sender extension? You shouldn't need sealant on NPT threads but if you must, use a paste.

b) Check your engine to firewall ground strap. I have seen instances where the ground strap is gone, broken, bad, etc., and the steering column wants to be the new ground.
 

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for a stock system just ground the engine side of the terminal and put car key in run
gauge should peg out. this will tell you no problems up stream

sounds like you got a bad sender or you broke the terminal when you pulled it off
 

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Discussion Starter #4
a) Did you use teflon tape on the sender extension? You shouldn't need sealant on NPT threads but if you must, use a paste.

b) Check your engine to firewall ground strap. I have seen instances where the ground strap is gone, broken, bad, etc., and the steering column wants to be the new ground.
I know my mechanic used teflon tape on the sender extension when he installed it.

Oh wow...that is a big thing if it is the engine to firewall ground strap...will check.
 

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Discussion Starter #5
for a stock system just ground the engine side of the terminal and put car key in run
gauge should peg out. this will tell you no problems up stream

sounds like you got a bad sender or you broke the terminal when you pulled it off
Would not be surprised if I broke the terminal. wiring is 50 years old. Thankfully the replacement wiring is cheap and easy to do :)
 

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Well I may have solved one electrical gremlin...repositioned oil pressure sender terminal and now the gauge seems to be working fine (maybe reads a little lower than normal, so for piece of mind I will replace this harness.

The other electrical gremlin I will have to ask my mechanic about.
 

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Discussion Starter #7 (Edited)
b) Check your engine to firewall ground strap. I have seen instances where the ground strap is gone, broken, bad, etc., and the steering column wants to be the new ground.
I believe you were right about the ground strap...except that on the 70s and later, the engine ground is run through the negative battery cable. I had no idea that is what the metal tab with the hole on the negative battery cable was for. Found an extra bolt that fit and grounded it to the fender below the voltage regulator. Will test drive it tomorrow morning to see if the issue is now gone. If not...off to the mechanic to diagnose.
 

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I still think there needs to be something tying the engine into the firewall. If your mechanic is putting Teflon tape on an electrical sending unit, you might want to start searching for a new mechanic.

Better yet, get the official ford shop manuals and start posting questions here. I personally would not start putting new harnesses in until you know if there is a problem and what it is. There is a good chance you might solve one problem, while creating 2 new ones. If you did happen to break the terminal, pretty easy to splice a new one in.

Just my $.02.
 

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I believe you were right about the ground strap...except that on the 70s and later, the engine ground is run through the negative battery cable.
A solid no. EVERYTHING from the late '60's on has an additional firewall to cylinder head small ground strap. Everything. In fact some of the late model cars can get fuel injection fits should just that particular ground be broken or left off. Even the front wheel drive stuff has them. You have to dig to spot them these days but they are there. And still important.
 

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Discussion Starter #11
A solid no. EVERYTHING from the late '60's on has an additional firewall to cylinder head small ground strap. Everything. In fact some of the late model cars can get fuel injection fits should just that particular ground be broken or left off. Even the front wheel drive stuff has them. You have to dig to spot them these days but they are there. And still important.
See this thread...https://www.vintage-mustang.com/threads/ground-strap-for-1970-mustang.648877/

and this one from a 70 boss 302 (read entire thread)

They did not do a ground strap to firewall for 1970 apparently.

I still think there needs to be something tying the engine into the firewall. If your mechanic is putting Teflon tape on an electrical sending unit, you might want to start searching for a new mechanic.

Better yet, get the official ford shop manuals and start posting questions here. I personally would not start putting new harnesses in until you know if there is a problem and what it is. There is a good chance you might solve one problem, while creating 2 new ones. If you did happen to break the terminal, pretty easy to splice a new one in.

Just my $.02.
This is the oil pressure sending unit...teflon tape on sender to extension tube. May not be right per say...but it does not leak. I'll keep my mechanic for now thanks.

The reason for the new harness is that it is not that easy to splice in a new terminal...it is one of those right-angle ones and I cannot find a new one without a pigtail...besides the harness is 50 years old. I already have a new one on the way from NPD, but I drove the car this morning and it seems to be working ok...so maybe I will give it a couple of days.

One last thing for everyone...I will do mechanical stuff but when it comes to electrical problems, I will let the pros handle it.
 

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This is the oil pressure sending unit...teflon tape on sender to extension tube. May not be right per say...but it does not leak. I'll keep my mechanic for now thanks.
[/QUOTE]
Leaking isn't the point- tape will electrically insulate the body of the sender from the engine so no current can flow and the gauge will be inoperative. That is a very dumb mistake for a mechanic. The threads are NPT so it gets tighter the more it is screwed in- that's what stops the leak. This is very basic stuff. Get another mechanic.
 

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Discussion Starter #13
This is the oil pressure sending unit...teflon tape on sender to extension tube. May not be right per say...but it does not leak. I'll keep my mechanic for now thanks.
Leaking isn't the point- tape will electrically insulate the body of the sender from the engine so no current can flow and the gauge will be inoperative. That is a very dumb mistake for a mechanic. The threads are NPT so it gets tighter the more it is screwed in- that's what stops the leak. This is very basic stuff. Get another mechanic.
[/QUOTE]

Went out and looked at the sending unit...no tape...all is good there...so I am pretty sure that I may have hurt the gauge feed...the gauge works (took for drive this morning and it registered the pressure)...just not at what it normally does...that is why I figure I hurt the wiring harness. Will keep everyone updated.

Sad to say that even though I have now grounded the engine, steering column still gets warm...so there is either a short somewhere or something else.
 

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I think you miss the point. The fact that in production Ford didn't put a firewall ground strap on a certain year and specific model of car has no effect on the fact that such a ground is beneficial and present on almost everything else. If you like searching up old posts, perhaps you can find the one where someone complained about their temperature gauge not reading correctly and adding a firewall ground strap fixed the issue. (Whether Concours correct or not.)
 

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Well the fact of the matter is there was indeed a ground between the engine and firewall (indirectly through the apron/shock tower). It was just inline with the negative battery cable. If you are going this route, just make sure you are using the proper cables and that the grounds are good.
 

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Discussion Starter #16
OK everyone...thank you for the replies. I fixed the grounding problem last night (bolted inline grounding assembly to top bolt of voltage regulator per several other forum post suggestions). Even after doing that, steering wheel column still gets hot...thinking maybe ground wire in column has gone bad...will have mechanic diagnose.
 

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Discussion Starter #17
Update...replaced the engine gauge feed wiring harness...gauge seems to be working ok now (plus engine bay looks cleaner). One thing I have not checked was how the gauge has been calibrated. Since it is the original gauge from 50 years ago, I imagine it could do with a rebuild/re-calibration (same with my other gauges). Still have to take car to mechanic to figure out why steering column is getting hot...but this will have to wait...need to make some repairs on my daily driver (2015 mustang).
 

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How quickly does the steering column heat up? I would think it would take a lot of current to actually heat up a steering column. If the source of the heat was electrical, wouldn't you think some fuse should blow?
 

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Discussion Starter #19
How quickly does the steering column heat up? I would think it would take a lot of current to actually heat up a steering column. If the source of the heat was electrical, wouldn't you think some fuse should blow?
It takes a while...around 15 to 20 minutes i would say. Now that you mention it...I think a fuse would blow if it were an electrical problem and that is something I should check. If it is not a fuse, what could it be?
 
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