Diesel tach swap - strange donor

[mat in tn]

If I recall correctly, the tach for the old IDI Bullnose relied on a simple pickup on the crank or flywheel

Correct concept

the tach for the later F600/F800 diesel trucks was electronic and worked off a completely different signal.

I think this is what I am looking at. Wish I knew beforehand.

The 3500 RPM tach I have does not look like the one from the technical section. It must be newer.

yet the question stays unanswered. is it a difference in the tach or signal? is it the same signal replicated another way? I'm very curious also.

[85lebaront2]

yet the question stays unanswered. is it a difference in the tach or signal? is it the same signal replicated another way? I'm very curious also.

The idi Diesel tachometer used a pickup on the injection pump driven gear, which if I remember correctly is 105 teeth, it is driven by a mating 105 tooth gear on the camshaft. This means that 105 pulses = two crank revolutions.

The only reason I know this, was helping a friend in Dover DE, set up a Diesel TCM to control an E4OD on a carbureted engine. He had to come up with something to make 8 pulses into 105 pulses.

[PossumTruck]

The idi Diesel tachometer used a pickup on the injection pump driven gear, which if I remember correctly is 105 teeth, it is driven by a mating 105 tooth gear on the camshaft. This means that 105 pulses = two crank revolutions.

The only reason I know this, was helping a friend in Dover DE, set up a Diesel TCM to control an E4OD on a carbureted engine. He had to come up with something to make 8 pulses into 105 pulses.

Well, I've done more research than I care to and it looks like the cluster was mis-labeled on ebay. Sold as an 80-86 F series.

Its from a 97'-ish 600 to 800 with a diesel. Anybody want a gauge cluster? The needles are in good shape/color...

Probably just going to re-list it on ebay.

[mat in tn]

Well, I've done more research than I care to and it looks like the cluster was mis-labeled on ebay. Sold as an 80-86 F series.

Its from a 97'-ish 600 to 800 with a diesel. Anybody want a gauge cluster? The needles are in good shape/color...

Probably just going to re-list it on ebay.

smart call. spending a few dollars for education is not really a bad deal. move on and dont look back

[PossumTruck]

yet the question stays unanswered. is it a difference in the tach or signal? is it the same signal replicated another way? I'm very curious also.

I've got more info on that now, too. The cluster/tach was likely associated with a 5.9 cummins. Unlike in a dodge, the F-trucks used a sensor to count teeth on the flywheel (180 teeth). Similar in concept to counting teeth on the IP gear.

I would need to figure a way to turn 180 pulses into 106. Maybe that is what the dial-looking deal is on the back of the tach.

Edit to add: One obscure post from another forum:

"I set one up in my F700 using an F-series tachometer and the bell housing sending unit. 3 prongs on the tach, ground, signal, +. There was an adjustment on the back of the tach for the RPMs. The two wires off the bell housing are ground and signal I believe."

So, perhaps, you can just hook it up to a signal and adjust.

[mat in tn]

yet the question stays unanswered. is it a difference in the tach or signal? is it the same signal replicated another way? I'm very curious also.

I've got more info on that now, too. The cluster/tach was likely associated with a 5.9 cummins. Unlike in a dodge, the F-trucks used a sensor to count teeth on the flywheel (180 teeth). Similar in concept to counting teeth on the IP gear.

I would need to figure a way to turn 180 pulses into 106. Maybe that is what the dial-looking deal is on the back of the tach.

Edit to add: One obscure post from another forum:

"I set one up in my F700 using an F-series tachometer and the bell housing sending unit. 3 prongs on the tach, ground, signal, +. There was an adjustment on the back of the tach for the RPMs. The two wires off the bell housing are ground and signal I believe."

So, perhaps, you can just hook it up to a signal and adjust.

keep in mind that most of these tach's are not "lab quality". they are more general in design but close enough. although 200rpm is a bigger percentage on an idi than a ho5.0

[85lebaront2]

yet the question stays unanswered. is it a difference in the tach or signal? is it the same signal replicated another way? I'm very curious also.

I've got more info on that now, too. The cluster/tach was likely associated with a 5.9 cummins. Unlike in a dodge, the F-trucks used a sensor to count teeth on the flywheel (180 teeth). Similar in concept to counting teeth on the IP gear.

I would need to figure a way to turn 180 pulses into 106. Maybe that is what the dial-looking deal is on the back of the tach.

Edit to add: One obscure post from another forum:

"I set one up in my F700 using an F-series tachometer and the bell housing sending unit. 3 prongs on the tach, ground, signal, +. There was an adjustment on the back of the tach for the RPMs. The two wires off the bell housing are ground and signal I believe."

So, perhaps, you can just hook it up to a signal and adjust.

Two questions, how many teeth are on your flywheel or flex plate and could you mount a rear wheel anti-lock brake sensor where it would "count" teeth?

If that would work the setup might be simple. One more item. the 105 tooth count or 106 is for cam and injection pump revolutions. To match the Cummins flywheel count, it will be either 210 or 212 pulses. Error would be .17 or .18 so your tach would read 85 to 86% of actual engine rpm and the adjustment might get you real close.