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Tachometer Interchangability

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Sideflop

Tachometer Interchangability

Is it possible to make a 6k RPM tach work on a diesel? And will it read correctly?

Nathan
1984 F250 XL with International 6.9L IDI, Borg Warner T19 transmission and Borg Warner 1345 transfer case. Dana 50 limited slip front end, Dana 70 open rear end with 3.73 gears

85lebaront2

Re: Tachometer Interchangability

Administrator

Probably not, the Diesel tack is triggered from the teeth on the injection pump drive gear, 105 teeth so it is an odd number of pulses, gas engine uses the coil - terminal for it's source.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Ford F834

Re: Tachometer Interchangability

Administrator

In reply to this post by Sideflop

I read a post from a guy who swapped an IDI into a gas F150 and he hooked up the gas tach to the diesel sensor. He said it did read, but he didn’t think it was correct. He didn’t mention by how much, or if it was higher or lower than expected. Since the IDI is governed at about half of the 6K’s sweep, it’s not a very desirable tach for that engine anyway. You really need the 4,500 rpm with the yellow and red zones for the 6.9 IDI. The diesel tachs from the medium duty F600/F700 read flywheel teeth and shouldn’t read right either.

SHORT BED 4-DOOR DIESEL: 1986 F350 4x4 under construction-- 7.3 IDIT ZF5+GVOD

STRAIGHT SIX 4X4: 1981 F150 2wd to 4x4-- 300 I6 close ratio diesel T19, hydroboost brakes, Saginaw steering

BIG F: 1995 F-Superduty under construction— converting to 6.9L IDI diesel ZF5+DNE2

Ford F834

Re: Tachometer Interchangability

Administrator

In reply to this post by Sideflop

I don’t know if you are aware, but the 83 & 84 diesels did not have the tach option. The injection pump gear housing does not have the threaded port for the tachometer sensor. There is no wiring for it in the harness. I looked at the pics in your build thread and yours does not have it. You can still add a factory tach, but it isn’t plug and play like the 85/86 trucks. You need to supply the wiring and you need a late 6.9 or 7.3 injection pump gear housing with the port. You also have to know how to remove the housing without getting the engine out of time. It’s not that bad, you just need to be aware of it and it is an involved project.