hdj81 Tachometer issues and where to begin troubleshooting. (1 Viewer)

[veiloctane]

Hi guys,
I have a issue here with my 1991 HDJ81 with the Tachometer.
all was fine and normal until just a couple of days ago.

here is a description of the issues that I am having.

when the transmission is in drive the Tach reads 0rpm While driving at any speed the tach immediately jumps to 3000rpm

When in Park the Tach reads 2000-2200rpm
when in neutral Tach reads 2000-2200rpm
gears D,3,2,L read 0rpm and jumps to 3000rpm as soon as I touch the pedal.


what would cause this and how to start trouble shooting?

 

[IanB]

I would start by checking the tach pickup on the injection pump, and all your grounds. Have you done any recent work just before this happened?

 

[veiloctane]

no recent work done on the pump. the odd time i can get the tach to work by hitting a large bump or by taping on the cluster... I am assuming something could be loose like a poor ground wiring or sticky tachometer? maybe i can replace the tach? or the whole cluster?

 

[BCR4619]

the latter sounds expensive. Mine works 95% of the time... the other 5% its way off or bounces up and down +/- 200RPM... I was told that when it dies to replace the pickup on the pump....

I would check all the connections on the pump first as its prob the easiest

 

[veiloctane]

I tried sourcing a part for the pickup its unavailable from toyota I wonder if there are alternative part numbers for the pickup sensor.

 

[BCR4619]

Locally? I would not be surprised.... Either source from outside canada or talk to @yotahed who deals with these pumps.

 

[yotahed]

Sometimes the wires on the tach pickup get brittle with age and crack. Its on the engine side of the pump with 2 wires coming out of the sensor. Worth a check anyhow. More likely than a cluster issue.

Be very careful if you choose to remove the sensor. They are very soft aluminum and will surely snap off on reinstallation if you overdo it.

 

[veiloctane]

I am still on the trouble shooting phase. I checked the "Pick-up Sensor" as shown in the FSM I am getting a reading of 780 its a little bit higher then the approx. 730 value in the manual does this mean that the Pick-up sensor be replaced or are the readings close enough?

I am going to check the wiring next on the other side of the connector that goes to the cluster.

as far as I can tell the brown wire is ground and the black wire goes to the cluster for the rpm signal.

upon disassembly of the combo meter i have found a loose nut on the back of the motor of the tachometer this could of contributed to the intermittent jumping tach. I go over a bump or tap on the cluster and sometimes it would read correctly and work for a moment. fixing the loose connection behind the meter fixed my problem. I hope this helps someone with tacho problems

 

[veiloctane]

I am still on the trouble shooting phase. I checked the "Pick-up Sensor" as shown in the FSM I am getting a reading of 780 its a little bit higher then the approx. 730 value in the manual does this mean that the Pick-up sensor be replaced or are the readings close enough?

I am going to check the wiring next on the other side of the connector that goes to the cluster.

as far as I can tell the brown wire is ground and the black wire goes to the cluster for the rpm signal.

upon disassembly of the combo meter i have found a loose nut on the back of the motor of the tachometer this could of contributed to the intermittent jumping tach. I go over a bump or tap on the cluster and sometimes it would read correctly and work for a moment. fixing the loose connection behind the meter fixed my problem. I hope this helps someone with tacho problems

it happened again time for some Loctite