Installing Aftermarket Tach
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Installing Aftermarket Tach
Installing Aftermarket Tach
I haave read through most of the threads in the archive dealing with installing an after market tachometer. I have an ’86 F150 with the 300 ci engine. It looks like I have two wires that plug into the coil via plastic connectors. The one closest to the front of the truck is green. The one closest to the cab is brownish. Most post say that the negative side of the coils is the front wire but some say the wire I need to tap into is tan.
Anyone out there with an ‘81-‘86 truck have an opinion? I would like to be sure before I splice.
<O
Also, what is the difference between an alternator triggered and a coil triggered tachometer. Will the alternator triggered tachs work on our engines?</O>
<O</O
</OThanks.
I haave read through most of the threads in the archive dealing with installing an after market tachometer. I have an ’86 F150 with the 300 ci engine. It looks like I have two wires that plug into the coil via plastic connectors. The one closest to the front of the truck is green. The one closest to the cab is brownish. Most post say that the negative side of the coils is the front wire but some say the wire I need to tap into is tan.
Anyone out there with an ‘81-‘86 truck have an opinion? I would like to be sure before I splice.
<O
Also, what is the difference between an alternator triggered and a coil triggered tachometer. Will the alternator triggered tachs work on our engines?</O><O
</O </O
Thanks.
Posting Guru
Joined: Apr 2003
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From: Venezuela
Using alternator signal to trigger tach is not so accurate as coil trigger, since there is a pulley ratio that has to be calibrated, moreover; in older trucks using old "V" shape belts, the tach lose calibration as the belt is geting some wear.
If you want accurated readings all time, use coil trigger.
If you want accurated readings all time, use coil trigger.
Post Fiend
Joined: Jul 2004
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From: Northern California
Here's my opinion. 
If your truck has guages, why not get a factory tachometer? All the wires are right there inside the cab at the instrument cluster connector. Just get a instrument cluster with a tach in it and swap them out, and plug it in. Very simple.
If you still want an aftermarket tach, all the wires to run the tach are still inside the cab behind the instrument cluster. In the cluster connector, if you have guages.
If you have idiot lights you will need to run a wire from the coil to the inside of the truck. There might be an open pigtail for the tach on the drivers side fender skirt. The wire is green/yellow stripe, but the yellow might have come off like on my 1981.
hope this helps
If your truck has guages, why not get a factory tachometer? All the wires are right there inside the cab at the instrument cluster connector. Just get a instrument cluster with a tach in it and swap them out, and plug it in. Very simple.
If you still want an aftermarket tach, all the wires to run the tach are still inside the cab behind the instrument cluster. In the cluster connector, if you have guages.
If you have idiot lights you will need to run a wire from the coil to the inside of the truck. There might be an open pigtail for the tach on the drivers side fender skirt. The wire is green/yellow stripe, but the yellow might have come off like on my 1981.
hope this helps
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There are usually 4 wires on a tach. 2 are pos. and neg. for power. Theres one for your dimmer. And theres one for the tach signal. Assuming that you have a Can type coil it must be hooked to the negative side of the coil. There 2 posts on either side of the coil, one is positive one neg. It should be marked. Just use a ring terminal and undo the nut and slip it on. If its a TFI (square shaped) coil it is the dark green wire to the front of the truck that you need to splice into. You have to splice into it because the engine controller needs a tach signal to start it. Im pretty sure you have the TFI (square) type coil though.
Last edited by racedude48; Apr 20, 2006 at 06:34 PM.
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Hi, I have a 1986 Ford F150 with the 300 4.9L engine. I would have to ask if your running the EEC-III or the EEC-IV emissions system. I have on my truck's dash the "EL-Cheep-O" idiot light setup so I had to use the Haynes repair manual. I found out I can splice a wire onto the 6pin connector that plugs into the distributor mounted ICM to get a negitive tach out put. Make sure you have the plug located and know what order the wires go from top to bottom. I will call the pins 1 thru 6 with 1 being topmost wire. The functions are as follows
#1 PIP OUT
#2 SPOUT
#3 START
#4 TFI PWR
#5 TACH
#6 IGN GND
I must state that if you splice wrong major damage may occure. I couldn't find the wire from the tach signal in the cab so I ran my own wire. I hope that this helps.
#1 PIP OUT
#2 SPOUT
#3 START
#4 TFI PWR
#5 TACH
#6 IGN GND
I must state that if you splice wrong major damage may occure. I couldn't find the wire from the tach signal in the cab so I ran my own wire. I hope that this helps.
Posting Guru
Joined: Apr 2003
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From: Venezuela
Well... going so deep I can teach all you some electronic basic...
If your truck have any EEC computer, you already have a tach signal inside the cab. All TFI modules provide the EEC with PIP signal which basically gives timing information. This sigal can be used to drive a tach.
There is also a SPOUT signal going back to TFI module, this is basically the same PIP plus some timing correction and can be used also for any electronic tachmeter.
There are some tachmeter that are built to use only medium voltage coil imput, it means; needs to be connected to the proper coil wire, don't work with digital signals like PIP or SPOUT.
If your truck have any EEC computer, you already have a tach signal inside the cab. All TFI modules provide the EEC with PIP signal which basically gives timing information. This sigal can be used to drive a tach.
There is also a SPOUT signal going back to TFI module, this is basically the same PIP plus some timing correction and can be used also for any electronic tachmeter.
There are some tachmeter that are built to use only medium voltage coil imput, it means; needs to be connected to the proper coil wire, don't work with digital signals like PIP or SPOUT.
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Tach Installed - RPM Question
Thanks for all of the tips on installing the tachometer. I finally got around to putting it in yesterday. I used an inexpensive aftermarket tach from Advanced Auto that cost me about $35-$40. I found this to be a 2-hour job.
On the '86 300ci the negative side of the terminal IS the one closest to the front of the truck. I ended up running the hot wire (red) to the radio, the tach light wire (white) to the driver's side front head hot wire (red), and the tach input signal (green) to the negative wire on the terminal. The ground wire (black) was grounded to the metal dash frame. It seems to work fine and the engine idles at about 800-900 RPM.
I do have a question on the RPM's that I am registering… The engine seems to like revs up to about 4000 RPM's. This seems to be where I shift and is at the end of the engines natural power band. Sixty (60) MPH seems to be at about 3500 RPM and feels like the 'sweet spot' for this engine while cruising. Sixty-five (65) MPH is about 4000 RPH and seems to be about max comfortable cruising speed for this engine.
Does this match with what some of you have experienced?
<O</O
Thanks.
the_mahout
Central KY
On the '86 300ci the negative side of the terminal IS the one closest to the front of the truck. I ended up running the hot wire (red) to the radio, the tach light wire (white) to the driver's side front head hot wire (red), and the tach input signal (green) to the negative wire on the terminal. The ground wire (black) was grounded to the metal dash frame. It seems to work fine and the engine idles at about 800-900 RPM.
I do have a question on the RPM's that I am registering… The engine seems to like revs up to about 4000 RPM's. This seems to be where I shift and is at the end of the engines natural power band. Sixty (60) MPH seems to be at about 3500 RPM and feels like the 'sweet spot' for this engine while cruising. Sixty-five (65) MPH is about 4000 RPH and seems to be about max comfortable cruising speed for this engine.
Does this match with what some of you have experienced?
<O
</OThanks.
the_mahout
Central KY
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Posting Guru
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From: Venezuela
Are you sure the tach is right calibrated??? those readings are commond just for a few trucks using 4.10 ratio at rear axel and/or 4 speed manul tranny's
A stock 300 engine usually can not breath over 3000 RPM and loose its power... Cruising at 4000 will use a lot of fuel.
A stock 300 engine usually can not breath over 3000 RPM and loose its power... Cruising at 4000 will use a lot of fuel.
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I forgot to mention... the truck has the 4-speed manual transmission with the bulldog 1st gear. Not a great highway cruising transmission. I try to keep it at about 55 on the highway, 60 max... I don't make a lot of friends on the highway as this is about 15-20 mph slower than traffic.
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Had it set wrong
You all were correct. I originally bought the tach to put in the 4-cylinder VW and forgot to switch it over to the 6-cylinder setting - makes a huge difference when set correctly!
Enigine runs at about 2200 rpm at 55 mph and 2450 at 65 rpm. Seems about right now for this engine / transmission set-up.
Thanks for all the advice.
Enigine runs at about 2200 rpm at 55 mph and 2450 at 65 rpm. Seems about right now for this engine / transmission set-up.
Thanks for all the advice.
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Hey I have a question on the numbers my tach is showing. The engine seems to idle at 1700-2100 RPM fast idle then it drops to about 1000-1200RPM on slow idle. When I put my transmissin in gear it drops to about 400-900RPM while the whole time it feels like it's gonna stall. I top out at 50MPH uphill and 85 downhill but if on level ground it'll top out at 70MPH. I don't know the rpm at those spped as I'm not paying attension on the tach but I noticed that in a parking lot while in park my engine will only get up to 3500RPM before it seems to start stalling and when it gets down to 1500RPM it starts reving again. Should I be concerned, or is this normal for a 4.9L 3.08 rear axle and C6 transmission.
