EJ Swap: Tach doesn't work after wiring it up

[hellosubaru]

After getting my EJ22t swap running, everything works great, except for the tach. Currently I have the tach wire from the ECU (B56.16) hooked up to the yellow wire that came from the old coil to the tach.

 

I've read through the EA2EJ writeup, the harness info.pdf, and searched on here as well, but have not found an answer.

 

Any ideas why it won't work?

 

Thanks,

-Jason

[nipper]

Allow me to be uninformed, but i am assuming this uses the usual waste spark system. if so I would think that there is an RPM outpup from the ECU. the waste spark fires 2 plugs at one time.

 

I would think the source either comes off the ignitor, but more likely the ECU reading the crank position sensor since that is used for timing spark.

 

Just a guess as I am not familiar with the engine.

 

What is this transplanted into?

[hellosubaru]

The EJ was swapped into an '86 GL. Like I said, the tach is hooked up to the ECU pin labeled tach in all of the EJ wiring diagrams.

 

-Jason

[nipper]

The 86 tach is not compatable with the newer ECU driven tach. The newer output is just a signal pulse, where the older one is a true voltage pulse

[hellosubaru]

Hmm, disappointing. What do people do to get the stock tach working, or what do they do for a tach? From all the posts I read, I just assumed everyone was hooking the tach straight up to the ECU.

[nipper]

Hmm, disappointing. What do people do to get the stock tach working, or what do they do for a tach? From all the posts I read, I just assumed everyone was hooking the tach straight up to the ECU.

 

Thats just an educated guess. They may be using aftermarket tachs. Have you tried picking the pulse up at the ignitor?

[Numbchux]

The 86 tach is not compatable with the newer ECU driven tach. The newer output is just a signal pulse, where the older one is a true voltage pulse

 

Nope. works fine. the signal output from the EJ ECU is close enough to the signal coming off the coil. one pulse per spark.

 

both the EJ swaps I did myself had the tach working 100% like stock. '96 EJ22e in an '86 EA82 GL and '92 EJ22e into '92 Loyale. Now, the '86 had problems with the gauge cluster before the swap, so it was replaced with a newer EA82 cluster, so I can't say FOR SURE that the '85-'86 cluster will work, but considering the '87+ cluster is plug and play into an '85-'86, I assume it wouldn't make any difference.

 

 

 

 

Something is not functioning correctly. I've always grabbed the signal right at the plugs on the back of the gauge cluster (I think pulling the cluster is the easiest way to tap in all the signal wires for it), so I'm not sure if this could be an effect of where you tapped it in.

 

I'm assuming all your other gauges work? the power/ground sources for the tach are shared with most of the other gauges too, so it's unlikely that only the one would fail.

Edited December 14, 2010 by Numbchux

[nipper]

i love learning new things

[hellosubaru]

Nope. works fine. the signal output from the EJ ECU is close enough to the signal coming off the coil. one pulse per spark.

 

both the EJ swaps I did myself had the tach working 100% like stock. '96 EJ22e in an '86 EA82 GL and '92 EJ22e into '92 Loyale. Now, the '86 had problems with the gauge cluster before the swap, so it was replaced with a newer EA82 cluster, so I can't say FOR SURE that the '85-'86 cluster will work, but considering the '87+ cluster is plug and play into an '85-'86, I assume it wouldn't make any difference.

 

Something is not functioning correctly. I've always grabbed the signal right at the plugs on the back of the gauge cluster (I think pulling the cluster is the easiest way to tap in all the signal wires for it), so I'm not sure if this could be an effect of where you tapped it in.

 

I'm assuming all your other gauges work? the power/ground sources for the tach are shared with most of the other gauges too, so it's unlikely that only the one would fail.

 

Yes, all of the other gauges work (well, fuel and volt, oil and water are aftermarket gauges). Tach worked before the swap. I traced the yellow wire from the old coil back under the dash, and tapped in there. Maybe I need to source a new cluster.

 

Thank you,

-Jason

[hellosubaru]

Any other ideas on this one?

[Numbchux]

Just spent a few minutes double-checking diagrams and such. Sounds like you've got it right. And if your fuel and volt meters work, you should have good power and ground to the cluster. And since the tach worked before, I'll assume the problem is not within the cluster itself.

 

 

that leaves one wire, the signal wire. double check that it's the correct wire (if you mirrored the plug, and actually have B56, 9, that'd be the A/c switch....). Make sure that it's the Black w/ Blue stripe wire on pin 16, and not the Blue w/ Red wire on pin 9.

 

If you've got the correct wire, pull the cluster, and check for continuity between that wire at the gauge cluster and the signal wire on the ECU.