1990 F-250 tachometer question
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From: New Baltimore MI
1990 F-250 tachometer question
Ok...as you can see from the title I have a 90 F250. My problem is this. The guy that i bought the truck off of changed the engine out from the original 351 EFI to a carbed 460. now my problem is the tach does not work anymore. I would like to know if the factory gauges ran threw the computer, or if the tach is just connected to the coil?
Also if the tach is in fact ran with the computer, can i make it work by wiring it up to just the coil?
one more thing, I'll be changing the oil in the truck really soon and was wondering what people use for a "engine cleaner"...trans fluid, kerosene, motor flush stuff you can buy from the store? also what is everyone using for oil...I have an older cutlass ( RWD) with a 350 olds and i've had really good success with using 15-40w Rotella T diesel oil. Thanks
Justin
New Baltimore, MI
Also if the tach is in fact ran with the computer, can i make it work by wiring it up to just the coil?
one more thing, I'll be changing the oil in the truck really soon and was wondering what people use for a "engine cleaner"...trans fluid, kerosene, motor flush stuff you can buy from the store? also what is everyone using for oil...I have an older cutlass ( RWD) with a 350 olds and i've had really good success with using 15-40w Rotella T diesel oil. Thanks
Justin
New Baltimore, MI
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From: Easton,Ks
How ever they did run through a Ignition Suppression Resistor Resistor, E9DB-14A601-FA.
See diagrams below and look at the red boxes.
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From: New Baltimore MI
Thank you for the reply.
But would you mind helping me out one what the Ignition Suppression Resistor really is or does? does this mean I can or can not still hook up my tach ?
Thanks
Justin
New Baltimore, MI
But would you mind helping me out one what the Ignition Suppression Resistor really is or does? does this mean I can or can not still hook up my tach ?
Thanks
Justin
New Baltimore, MI
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From: Easton,Ks
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From: New Baltimore MI
Thanks...I'll have to check to see if its still there. If im not mistaken...this resistor would be under the hood on the firewall correct? I believe I remember seeing one there.
Thanks again..
I'll keep this posted.
justin New Baltimore, MI
Thanks again..
I'll keep this posted.
justin New Baltimore, MI
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From: Easton,Ks
That would mean that it was in the engine harness. If the engine was changed like you say the engine harness is more than likely gone along with the resisters.
Sounds like you need to find the end of the tach wire under the hood, put a resister in with it and run to wire to the coil tach side.
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From: New Baltimore MI
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From: New Baltimore MI
Does anyone happen to know what color wire(s) are for the tach under the hood? I think i read somewhere it was a two connector with a green wire and a black wire. Is this correct? thanks
Justin
New Baltimore, MI
Justin
New Baltimore, MI
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From: Easton,Ks
I gave you all of the colors of the wires in the two diagrams above. The wires changes more than once. You also have the wire for the number of cylinders that you have.
You have :
R/Y = Red wire with a Yellow stripe.
BK/Y = Black wire with a Yellow stripe.
DG/Y = Dark Green wire with a Yellow stripe.
R/LB = Red wire with a Light Blue stripe.
You have :
R/Y = Red wire with a Yellow stripe.
BK/Y = Black wire with a Yellow stripe.
DG/Y = Dark Green wire with a Yellow stripe.
R/LB = Red wire with a Light Blue stripe.
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From: Saukville WI
Im going to bring up this again i have the same problem efi converted to carb 1990 my tach in the truck does not work, i have a parts efi wiring harness but am clueless on what wires go to where on the drivers side fender??? the diagrams above dont work anymore??? I really dont want to have a huge tach mounted on my steering coulum and on in the dash 
thanks guys sorry to bring up the old topic....
Donnie
thanks guys sorry to bring up the old topic.... Donnie
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From: Saukville WI
Thanks for posting pictures again, very very clear and understading i found everthing i needed the coil to resister, resister to fender connection to dash console... fail.. even pulled a dash from the junk yard today no go 
(((( has this been done successfully????? Anyone???
(((( has this been done successfully????? Anyone???
Tuned
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From: Redmond, WA USA
Do you have a 12V test light and/or a multimeter?
With the engine running at idle, probe the coil-side of the resistors with the test light, it should be flashing (light may not go all the way out, but should pulsate).
On the tach-side of the resistors, if you have a multimeter that will read AC voltage, put it on a low scale and you should be able to read a voltage there. You should get this same reading at the tach pin on the cluster as well (with the other lead of the multimeter connected to a good ground).
I'm wondering if you may have a bad ground to the cluster or maybe an open-circuit between the resistors and the cluster. Something is not right and you've got to do some basic electrical troubleshooting to figure it out.
With the engine running at idle, probe the coil-side of the resistors with the test light, it should be flashing (light may not go all the way out, but should pulsate).
On the tach-side of the resistors, if you have a multimeter that will read AC voltage, put it on a low scale and you should be able to read a voltage there. You should get this same reading at the tach pin on the cluster as well (with the other lead of the multimeter connected to a good ground).
I'm wondering if you may have a bad ground to the cluster or maybe an open-circuit between the resistors and the cluster. Something is not right and you've got to do some basic electrical troubleshooting to figure it out.
