1967 GTX Oil Pressure wiring 426 Hemi

[gtxfanatic]

Evening All

Nearing completion of my 67 gtx restoration and have run into a problem with the oil pressure warning light.
I have put an original 426 Hemi 4 speed into my gtx, an original 440 car. Purchased all new m&h hemi underdash, front engine/light harnesses and positive battery cables.
The gray wire included on the battery cable wiring seems redundant as my engine compartment harness already has that wire and it is connected to the oil pressure sending unit. There is no other provision for the redundant gray wire on the engine side wiring bulkhead and my oil pressure light does not work..meaning it is not red with key on or initial start up.
Sending unit, bulbs are new etc. Am I missing something or has anyone come across this? Help or input greatly appreciated, thank you.

 

[RemCharger]

Sounds like the tach wire

 

[AR67GTX]

Yes, I ran into that. I will have to go out and dig up my notes if someone doesn’t answer shortly.

 

[HALIFAXHOPS]

One way to check fast with the key on not running touch the wire to a ground it should light up then. The sender is 0 Ohms with no pressure hence its a ground then at usually 5-6 psi it opens and turns off the light.

 

[gtxfanatic]

Yes, I ran into that. I will have to go out and dig up my notes if someone doesn’t answer shortly.

Morning, thanks I’d appreciate that

 

[AR67GTX]

There are some differences with my 66 Hemi harness but I think the gray oil pressure sender wire connections are consistent in 66/67.

With a 4-speed you should have a backup light switch from the transmission feeding a 3- contact plug with a gray lead to the oil pressure sender. Hooking this plug into the 3-way plug on the forward lighting harness will send the sender signal reading to slot “T” in the bulkhead ( lower plug). And I believe the other gray wire in the battery harness gets taped off. If you have an automatic, then you don’t have the 3-way plug from the gray wire in the battery harness would connect to the oil pressure sender. The auto reverse light switch has only 2 leads.

I’m not great on electrical stuff but I think that is how it goes.

 

[gtxfanatic]

One way to check fast with the key on not running touch the wire to a ground it should light up then. The sender is 0 Ohms with no pressure hence its a ground then at usually 5-6 psi it opens and turns off the light.

Thank you I will try that

 

[Dave6T4]

Evening All

Nearing completion of my 67 gtx restoration and have run into a problem with the oil pressure warning light.
I have put an original 426 Hemi 4 speed into my gtx, an original 440 car. Purchased all new m&h hemi underdash, front engine/light harnesses and positive battery cables.
The gray wire included on the battery cable wiring seems redundant as my engine compartment harness already has that wire and it is connected to the oil pressure sending unit. There is no other provision for the redundant gray wire on the engine side wiring bulkhead and my oil pressure light does not work..meaning it is not red with key on or initial start up.
Sending unit, bulbs are new etc. Am I missing something or has anyone come across this? Help or input greatly appreciated, thank you.

Do you have the right sender on your engine? Oil light in the dash uses the short sender. An actual gauge in the dash uses the tall sender. Your GTX should have the short one.

 

[AR67GTX]

My car is up on a lift but I’ll back the car out from under out in a bit and verify the other gray lead is just taped off.

Scratch the above. My manual reverse light switch harness is taped into the battery cable harness, the gray lead from the oil switch hooks to it. It jumps out of the battery harness into a 3-terminal plug with the forward light harness and back to the bulkhead and T slot. I don’t have a gray wire in my 66 Hemi engine harness, only a Gray/BS wire to the coil leads back to near the bulkhead plug and then pops out to connect to a green wire feeding my console tach. So there must be too many differences between 66 and 67 for me to help.

Good luck.

 

[gtxfanatic]

There are some differences with my 66 Hemi harness but I think the gray oil pressure sender wire connections are consistent in 66/67.

With a 4-speed you should have a backup light switch from the transmission feeding a 3- contact plug with a gray lead to the oil pressure sender. Hooking this plug into the 3-way plug on the forward lighting harness will send the sender signal reading to slot “T” in the bulkhead ( lower plug). And I believe the other gray wire in the battery harness gets taped off. If you have an automatic, then you don’t have the 3-way plug from the gray wire in the battery harness would connect to the oil pressure sender. The auto reverse light switch has only 2 leads.

I’m not great on electrical stuff but I think that is how it goes.

Thank you, Got the back up circuit figured that was the easy part (FSM)
so the gray wire in the battery harness is redundant then...but I do not understand why they (Mh) would Put that wire there if one was already in the engine side harness, and what purpose would the oil pressure wire have in the starting circuit battery side of the harness?

 

[gtxfanatic]

Do you have the right sender on your engine? Oil light in the dash uses the short sender. An actual gauge in the dash uses the tall sender. Your GTX should have the short one.

Thanks yes it’s the non gauge one new. One thing I’m learning on this restoration that new means nothing these days....

 

[gtxfanatic]

My car is up on a lift but I’ll back the car out from under out in a bit and verify the other gray lead is just taped off.

Thank you

 

[R413]

On your engine wiring harness, did you order a hemi or a 440 harness? They are different. I’ll wait until you answer before I type any more.

 

[gtxfanatic]

On your engine wiring harness, did you order a hemi or a 440 harness? They are different. I’ll wait until you answer before I type any more.

Morning, yes Hemi specific wiring for all three including Hemi 4 speed for the positive cable

 

[Dragon Slayer]

the oil sender is gray to T junction. Is that were it goes? On non hemi Gray with TRACER goes to Tach via J terminal. On HEMI the tach wire does not go through wiring harness bulk head terminal. At least for the 67 Dodge cars.

So not sure if this helps or not, but I would check your gray to terminal T for continuity. Then through bulkhead, then from bulk head to gauge.

If harness wiring is correct you have a break/high resistance somewhere.

 

[R413]

Let’s not interchange or confuse 1966 and 1967 wiring, they are different.

1967 hemi auto has short gray wire coming out of headlamp harness outboard of the master cylinder with a connector that plugs into the battery cable gray wire. it is the wire that is on the far right in the photo.

The hemi engine wiring diagram does not specify auto or 4 speed. And they don’t show or tell you the NSS and oil pressure wiring are both made into the positive battery cable.

 

[R413]

1966 tach is different than 1967 also. Remember the 1966 tach has only 3 wires and a tach sender.

1967 tach wiring, they have:
orange
violet
black
dark green

The 1967 has a different 4 speed and auto console diagram for the differences in backup lamp switch and gear indicator lamp. The tach part is the same. There is no hemi or non hemi console wiring diagram.

 

[gtxfanatic]

Let’s not interchange or confuse 1966 and 1967 wiring, they are different.

1967 hemi auto has short gray wire coming out of headlamp harness outboard of the master cylinder with a connector that plugs into the battery cable gray wire. it is the wire that is on the far right in the photo.

The hemi engine wiring diagram does not specify auto or 4 speed. And they don’t show or tell you the NSS and oil pressure wiring are both made into the positive battery cable.

View attachment 1544198

View attachment 1544207

Thanks to all for your input and replies
After some time with an meter figured out that the gray wire needs a new female plastic clip (Came bare spade) plug and it joins into the mystery gray wire And ureaka the oil pressure light works like a charm
I will make a separate post for those like me that were puzzled by these wires and hopefully save some time
Cheers