454 mag mpi Horizon engine harness pin hole confusion

[Saltwater life]

Hello again
with the help from this forum and others i have got the engine running on stand.
i bought a few guages to help with the monitoring of water temp, oil pressure and RPM
when looking at the engine harness plans i sorted most things hence the running of motor.
But i still cant get the water temp or oil pressure to work.
Gauges are set up correctly.
The plans say Lt blue wire for oil pressure sender and i think it was pin hole 8 but guage doesnt move
water temp is tan wire and pin 3 but cant get it to respond, dial moves to 140 on guage on starting while cold and stays there the whole time.
RPM is grey wire and pin 2 and this works fine.
More confusing is that i have a sender where the oil pad is on the block with the lt blue wire attached.
i also have a small sender/switch just in front of the bell housing on top on the block i have no wire that goes here?

im now on second engine getting ready to start.
Any help would be great
thanks in advance
Aaron....

 

[Scott Danforth]

regarding the sensor or switch in the oil port at the back of the motor, post a pic. many times that is where the oil pressure gauge sender is, however I believe that the gauge sender gets moved to the side of the block and the alarm switch is moved to the back of the block

oil pressure sender will be a bell-looking device with a single stud coming out of it.

oil pressure switch will have 2 or 3 terminals

the fact that your temperature moves to 140 and stays there indicates that it is wired incorrectly to a switch and not a gauge sender

wire colors are standard

Black	Ground	Negative / Neutral Main Return
Blue-Stripe	Tilt up and or trim out	Tilt and or trim circuits
Brown	Alternator Charge Light	Generator Terminal or Alternator Auxiliary Terminal to Regulator
Generator Armature	Generator Armature to Regulator
Pumps	Circuit Breaker or Switch to Pumps
Brown w/Yellow	Bilge Blowers	Circuit Breaker or Switch to Blower
Dark Blue	Cabin & Instrument	Circuit Breaker or Switch to Lights
Green or Green w/Yellow Stripe	Bonding System	Grounding Wires (if insulated)
Green Stripe	Tilt down and/or trim in	Tilt and or trim circuits
Grey	Navigation Lights	Circuit Breaker or Switch to Lights
Tachometer	Tachometer Sender to Gauge
Lt. Blue	Oil Pressure	Oil Pressure Sender to Gauge
Orange	Accessory Feed	Ammeter to Alternator or Generator
Common Feed	Distribution Panel to Accessory Switch
Feed	Accessory Circuit Breakers or Switches
Pink	Fuel Gauge	Fuel Gauge Sender to Gauge
Purple	Ignition	Ignition Switch to Coil & Electrical Instrument
Instrument Feed	Distribution Panel Electrical Instruments
Red	Instrument Feed	Distribution Panel to Electrical Instruments
Power Feeds	Positive Main Power (particularly un-fused)
Tan	Water temperature	Water temperature sender to gauge
Yellow	Generator Field	Generator to Regulator Field Terminal
Ground	Negative / Neutral Main Return
Yellow w/Red	Starting Circuit	Starting Switch to Solenoid

COLOR ITEM USE

 

[alldodge]

It sounds to me that your missing a ground from the block to the gauges.
If you have manual 23 (date March 1999), the listing for the oil sender and switch should be swapped, Pg 4E-8 and 9

The oil pressure sender is the light blue wire above the pan.
The oil pressure switch is the one on the bell housing below the distributer

 

[Saltwater life]

Thanks guys
The gauges are definitely ground directly to the Battery on the big fat ground that goes to block. Tacho working fine from same ground.
i appreciate the mention of the sender and the switch as my switch (just below dizzy) on block has only a single pin (same as sender). In the same vicinity is a black wire the comes from solenoid/breaker with a small eye hole that fits the switch, but i think this is another ground for something.??????
There is a blue / tan wire here as well with no eye or fitting.
The light blue wire is going to the sender, bottom of block.
i think this works ok as my motor stopped a couple of times, i checked oil and added oil and no more stop.
I was under the impression that the switch was to stop motor with low oil not the sender.!!!!! Switch was not connected at all, just screwed into block.
i would like to know what the black wire is for?????
as well as the blue/tan wire????
Water temp not working either, when connected, if i take pin plug from the sender on thermostat housing (cylinder 2 side) the Guage drops to 0 then straight back to 140 plugged in while engine cold.
to be clear the motor is on stand with no g/box attached. (Might be obvious but thought I should mention)
cheers guys

 

[alldodge]

All black wires are ground. There are some black wires which are additional grounds for different things including the ECM, slave solenoid, and others.

The blue/tan one I don't know, if it was tan/blue I would know.

Water temp not working either, when connected, if i take pin plug from the sender on thermostat housing (cylinder 2 side) the Guage drops to 0 then straight back to 140 plugged in while engine cold.

If you ground the sender and the gauge goes to zero, you either have a European gauge or the pos/neg connections are swap at the gauges. Guess it could the gauge could be wired incorrectly in another way. USA standard is 22 ohm (hot, like when grounded) and 240 ohms cold. Same way with all gauges