Tach isn't working.

[Eclipst]

Can anyone please tell me why my tach is not working? I am not throwing a check engine light and my safc is showing the rpm's. ANy one have any suggestions?

 

[sjgYFZ200]

ECU

 

[steve]

More specificly, which model year ECU is in the car?
People don't usually hook their SAFC up to the same signal that the tach uses, so that fact that it works isn't really telling you much.

The '90 tach circuit needs a '90 ECU or it doesn't work right.

Steve

 

[Eclipst]

it can't be the ecu. the tachometer was working before the motor took a crap on me. I don't see it as going bad all of a sudden. Does anyone know where the tach gets it's signal from, or where the ecu gets its signal from?

 

[steve]

The tach gets it's signal from the sender on the coil pack on a '90
The ECU is passive, it uses the signal just to check that the coils are firing. It's RPM and timing reference comes from the CAS.

When youe engine took a dump, what did you do to fix it? Did you swap in a new engine or possible replace the coil assembly?

Steve

 

[Eclipst]

The tach gets it's signal from the sender on the coil pack on a '90
The ECU is passive, it uses the signal just to check that the coils are firing. It's RPM and timing reference comes from the CAS.

When youe engine took a dump, what did you do to fix it? Did you swap in a new engine or possible replace the coil assembly?

Steve

The car itself is a 90. The motor is a 93 with everything new internals. So what your saying is that the tach gets its signal from the coil pack as well as the cas? The coil pack is working, and I don't doubt that the cas is bad. I have a spare cas as well as coil packs. If the coil packs were bad, it just wouldn't send spark to any of the plugs. But all plugs get spark.

 

[jott5555]

People people.. as we all know the 90 dsm is for some reason completly diffrent form the 91-94 the 90 has a small "noise filter" that the tach signal goes through before it hits the gauge, did you swap the 93 engine in? btw 93 is a 7bolt why would you do that? but back to the subject

on the intake manifold bracket on a stock 90 motor there is a small silver box that is about 1x.5.x.5in it has one pigtail wire comming out of it..

without this the stock tach in a 90 WILL NOT WORK!!!

so make sure its there, satan will sell you a new one for a hefty 85 bucks..

 

[Eclipst]

on the intake manifold bracket on a stock 90 motor there is a small silver box that is about 1x.5.x.5in it has one pigtail wire comming out of it..

without this the stock tach in a 90 WILL NOT WORK!!!

so make sure its there, satan will sell you a new one for a hefty 85 bucks..[/QUOTE]



Do you have a picture of exactly what you are talking about? Which side on the intake manifold???

 

[steve]

No, what I said was the tach gets it's signal from the sender on the coil on a '90.
On 91+ cars it gets it's signal from the Power Transistor Module.

The ECU doen't use that signal for RPM information, it has a more accurate reference in the CAS. It just checks that signal to make sure the coil is firing.

When you swapped engines what did you do to adapt the different plugs to the PTM and coil?
Where are you getting the signal that runs back to ECU pin 109?

Jott, The '90 has a tach sender in addition to the noise filter. The later coils have a condenser build in. to filter the RFI from the power feed. It's the sender under the bracket that may be needed. The upper is a new style coil the lower the '90.

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Noise filter.

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More information http://www.ecanfix.com/~mdhamilton/ecuconversion.html

Steve

 

[InjenTalon96]

sorry mods for bringing up a beat thread, but im having the same problem. first thing u think of when a tach dies is replacing the coil pack. well ive replaced it with my other 90 coil pack and the tach still doesnt work. apparently it stopped working when the original owner had a different motor put in it. can someone take a picture of the small silver fiter box in a motor where is hasnt been removed please..... i think thats what is making my stock tach not work.



edit: after about 20 min of looking i came to find out that there is a plug that is not plugged in, that lookes like it is the end of the plug that the noise thing goes into.

 

[90blacktsiawd]

There is a pic of it right above your post.

 

[InjenTalon96]

There is a pic of it right above your post.

ok well i cant find that anywhere on my intake mani....some ppl said its on the firewall so im gonna look for it.