86 R-688 Tach

[randyp]

Where does the tachometer connect to the engine on an 86 R688 ST? Engine was put in before I bought it and previous owner said it never worked after that, its a 300,,,thanks,,,Randy

[Rob]

Where does the tachometer connect to the engine on an 86 R688 ST? Engine was put in before I bought it and previous owner said it never worked after that, its a 300,,,thanks,,,Randy

Is that a mechanical, or electronic tachometer your asking about?

Rob

[e9500v8]

Where does the tachometer connect to the engine on an 86 R688 ST? Engine was put in before I bought it and previous owner said it never worked after that, its a 300,,,thanks,,,Randy

right under the injection pump !!

[randyp]

Is that a mechanical, or electronic tachometer your asking about?

Rob

I took cover off top Rob, looked at back of tach, must be mechanical, cable is completely gone from back, no trace of it even hanging or anything, I turned little brass knob where it hooks in and tach registers(I almost did 100 rpm with my fingers)I guess i need to get a new cable, only saw one hole on back of injector pump where it may screw in, no other wires or place for wires on back of tach,,,thanks,,,Randy

[Rob]

I took cover off top Rob, looked at back of tach, must be mechanical, cable is completely gone from back, no trace of it even hanging or anything, I turned little brass knob where it hooks in and tach registers(I almost did 100 rpm with my fingers)I guess i need to get a new cable, only saw one hole on back of injector pump where it may screw in, no other wires or place for wires on back of tach,,,thanks,,,Randy

Hi Randy you have a mechanical tachometer. If you cannot find the jacket with a .104 square end on the protruding cable, you are missing some parts. These can be had from most any speedometer shop and sometimes aftermarket parts suppliers. The jacket will have either a smooth outer end that is held of the rear of the speedo by a friction clip, or a knurled knob that will screw onto the threads in the rear of the speedo housing. The other end of the housing attaches to the engine under the injection pump on the rt. side of the engine. This will be a knurled knob that has a round end crimped onto the cable with a tang one the end. This tang will slide into the gear on the engine that meshes with the auxilary shaft to be driven. It is the same setup used on the B series truck. It is also very common to failure due to age.

Rob

[randyp]

Hi Randy you have a mechanical tachometer. If you cannot find the jacket with a .104 square end on the protruding cable, you are missing some parts. These can be had from most any speedometer shop and sometimes aftermarket parts suppliers. The jacket will have either a smooth outer end that is held of the rear of the speedo by a friction clip, or a knurled knob that will screw onto the threads in the rear of the speedo housing. The other end of the housing attaches to the engine under the injection pump on the rt. side of the engine. This will be a knurled knob that has a round end crimped onto the cable with a tang one the end. This tang will slide into the gear on the engine that meshes with the auxilary shaft to be driven. It is the same setup used on the B series truck. It is also very common to failure due to age.

Rob

Thanks Rob, yeah, im missing the entire cable all the way to the injector pump, on the back of the tach it has threads for the cable to screw onto. I havent checked out the end at the pump very thorouly yet, did find the hole in firewall where they removed cable though, thanks for the help, i just gotta start scrounging and find some parts. Really appreciate all the help,,,Randy

[HK Trucking]

Thanks Rob, yeah, im missing the entire cable all the way to the injector pump, on the back of the tach it has threads for the cable to screw onto. I havent checked out the end at the pump very thorouly yet, did find the hole in firewall where they removed cable though, thanks for the help, i just gotta start scrounging and find some parts. Really appreciate all the help,,,Randy

Randy:

The Tach drive is not on the inj. pump, it is under the pump, toward the front, sticking out of the block, pointing upward. It will have threads similar to what you saw on the back of the tach (but larger) where the tach cable screws on.

Hope this helps.

.

[randyp]

Randy:

The Tach drive is not on the inj. pump, it is under the pump, toward the front, sticking out of the block, pointing upward. It will have threads similar to what you saw on the back of the tach (but larger) where the tach cable screws on.

Hope this helps.

.

yeah HK and Rob, got out there this evening looking under injector pump,,lo and behold there it was sticking straight up, traced cable up to air cleaner tube climbed up on front tire, looked behind tube and there it was all wadded up and tied with tiewraps, sorta hidden in middle of engine. Wadded up like that cant be good for cable specially old cable,,anyway got it all straightened out, got all the oil in it i could, still hand clamps in 2 places on it to give it a good slow curve to firewall,,hooked it to back of tach,,,,no work,,I guess it must be broken somewhere,,I may unhook it from tach in the morning and see if it spins,,but i doubt it. I guess i need a new cable dont i Thanks for all help and input HK and Rob,,,later,,,Randy

[Rob]

yeah HK and Rob, got out there this evening looking under injector pump,,lo and behold there it was sticking straight up, traced cable up to air cleaner tube climbed up on front tire, looked behind tube and there it was all wadded up and tied with tiewraps, sorta hidden in middle of engine. Wadded up like that cant be good for cable specially old cable,,anyway got it all straightened out, got all the oil in it i could, still hand clamps in 2 places on it to give it a good slow curve to firewall,,hooked it to back of tach,,,,no work,,I guess it must be broken somewhere,,I may unhook it from tach in the morning and see if it spins,,but i doubt it. I guess i need a new cable dont i Thanks for all help and input HK and Rob,,,later,,,Randy

Although you could just replace the cable and may be fine, I would replace the jacket also, (basically complete assembly). Those parts wear from age and I've seen bouncing needles due to wear in the jackets.

Rob

[HK Trucking]

............. parts wear from age and I've seen bouncing needles due to wear in the jackets.

Rob

Sounds like you're talking about the Rolling Stones (Keith Richards especially). lol.

[randyp]

Sounds like you're talking about the Rolling Stones (Keith Richards especially). lol.

LOL,,,yeah,I will just get a complete assembly,,thanks fellows,,Randy,,,(My daughter has a guitar pick Keith Richards came off the stage and handed to her at an austin texas concert)