Help with tach?

[inline6]

I did a 1j swap a while back and used the tach from the clip but it seems to be off. On the dyno the car hit 7000 and the tach read about 4800 so I think it only reads 2/3 of the actual RPM. Anyone know why this is? I swapped it into a 87 n/a chassis but thought it was supposed to work. Could it just be a faulty tach? I'm also curious, if on the gte's on the connector that goes into the gauge cluster behind the tach if there is a wire in the third slot. My n/a body harness has no wires in the 3rd and 4th slots and I know the third one goes to one of the 5 screw connections from the tach on that green super thin circuit board thing for the cluster. Help Please!
P.S.
sorry if this is confusing.

T.I.A.
Derek

 

[slidingsidewayz]

at least your tach work man. i been trying to figure out how to fix mine. i tried tapping the #1 pin from the small ignitor plug and tried to tap the black wire from the ig1 body plug connector and still wouldn't work. is there any other tach pin beside the black wire from the ig1 connector?

 

[msdg137]

Hmm I swapped the tach from the clip into my N/A and it works fine. :dunno: Stupid question but did you remove the needle?

 

[inline6]

Yea i removed the needle and used my old one because they are different. I wonder how you got yours to work right. mine works but is just off.
And sidewayz, check out 1jz-gte.com for the diagrams. The black one from the ma70 body harness needs to connect to the black wire from the 1jz body connector and there is also a tach ground wire. not sure if there are others for the tach but check out the website.

 

[Clint]

try putting a turbo tach in it should do the trick, same thing happend to me, I have a 91 n/a tach in my supra and its off about 4500 rpm so im swapping it out with a 92 turbo tach it should do the trick .

 

[suprastanger507mgte]

try putting a turbo tach in it should do the trick, same thing happend to me, I have a 91 n/a tach in my supra and its off about 4500 rpm so im swapping it out with a 92 turbo tach it should do the trick .

So a turbo tsch works fine...or is close enough???

 

[Clint]

It should work fine, from what I have gathered is that turbo and n/a tachs have different kinds of current for reading RPM so bye swapping over to a turbo tach should straighten any conflicts in reading rpm.

 

[slidingsidewayz]

i swapped my tach from the clip and it doesn't work at all man. i got all of my diagrams from rick(1jz-gte.com) website and i did connect the black wire from the 1jz harness to the 7m wire harness. i really do not know whats going on with it.
inline6, do you know how to hot wire the negative ignition for the tach if that is the issue?
if anyone can help me out with this i'll appreciate it, thanks

fred

 

[cormschr]

same problem here.....i swapped over the tach and it moves a little when you turn the key to on but doesn't move at all when you rev it up. i'm starting to get real frustrated with it. starting to run out of ideas...

 

[Clint]

Okay my question is are you guys using a turbo gauge cluster or a none turbo gauge cluster?

 

[cormschr]

i'm using a nonturbo gauge cluster...but i have the tach from the clip installed. i have 12v to ign+ and continuity between the battery and earth, and continuity between the igniter and ign-. i was thinking that there was something wrong with the tach itself.

 

[Clint]

See that’s your problem; try swapping in a turbo gauge cluster I can guarantee that it will work. I have the same deal none turbo gauge cluster with a 1jz tach and my RPM is off like crazy; bye swapping to a turbo gauge cluster should solve your RPM issue.

The gauge clusters between none turbo and turbo are different even if you have the 1jz tach the signal coming out of the cluster is different which is why your RPM is having a hard time reading.

 

[slidingsidewayz]

is that really the problem? because i've heard before i did the swap that all you need is the 1jz tach from the clip and its should work fine. i guess that i was wrong.
and cormschr, i'm in the exact same situation you're in. i got so frustrated that i wanted to just hard wire that crap into an aftermarket tach, but don't even know where to tap the ign + line because of the individual coil w/ no ignition wire to tap

 

[cormschr]

the signal for the tach comes from the wire on the igniter. what kind of voltage variation should there be in the signal from the igniter. at idle it is like .3-.4 volts i think.... when i give it gas it goes over one volt(i wasn't going crazy with the gas). is this the normal valtage range? are you sure swapping the cluster would work. if all the signals are there at the tach, i wouldn't think it would matter what cluster it's in. unless it has something to do with where the ign+ goes after it leaves the tach. by the way, the car is an 86.5. anyone else with an 86.5 have this prob?

this ign+ is the yellow wire on the blue connector that goes into the back of the cluster....i believe....

 

[Clint]

I'm pretty sure that for you both to switch over to a turbo gauge cluster should solve this mystery at hand. I have a turbo tach waiting to go in but my supra is down at the moment so I am unable to test this theory out.

But I am sure that bye switching clusters should solve the problem and if it doesn’t then it goes beyond the tach and cluster and is probably a wiring issue. If there is anybody else that can back this theory up or has any insight on the differences between the two gauge clusters please feel free to chime in!

 

[inline6]

Im not sure about the n/a cluster and turbo clusters. I know on the back of the tach there are 5 contact points that you screw down to the green flexible circuit board thing. On the n/a cluster the circuit board thing has 2 of the contact points covered. I thought this was my problem initially but using a razor I scraped away the green film and still no luck with more accuracy. I havent got to look at a turbo cluster yet. Also I find it really wierd that some guys have no trouble at all, I am only reading like 2/3 of actual RPM, and others dont get it to work at all. If you post in here try to add what year, t or n/a, if it works or what your problem is. This way maybe we can conclude what type of car the 1j tach works with and what kind it doesnt or maybe that we just suck at wiring.
Also, I noticed that some of the contacts on the circuit board run up to the connector where there are no wires going into the connector. I'm thinking that maybe some wires for the tach were omitted in the n/a body harnesses.
-Derek

 

[slidingsidewayz]

what about hardwiring the ign+ straight to the ignitor pin #1 on the small plug. i tried it out with the 1jz tach and on an aftermarket autometer tach and still no response from both of the tach. this is really frustrating me. i'm seriously all out of ideas. oh i've got an 89 n/a

 

[suprastanger507mgte]

See that’s your problem; try swapping in a turbo gauge cluster I can guarantee that it will work. I have the same deal none turbo gauge cluster with a 1jz tach and my RPM is off like crazy; bye swapping to a turbo gauge cluster should solve your RPM issue.

The gauge clusters between none turbo and turbo are different even if you have the 1jz tach the signal coming out of the cluster is different which is why your RPM is having a hard time reading.

I think he is right due to tha fact the tach circuitry may be different.
Different size resistors on the circuit board on the cluster itself...

Makes sense.

 

[suprastanger507mgte]

is that really the problem? because i've heard before i did the swap that all you need is the 1jz tach from the clip and its should work fine. i guess that i was wrong.
and cormschr, i'm in the exact same situation you're in. i got so frustrated that i wanted to just hard wire that crap into an aftermarket tach, but don't even know where to tap the ign + line because of the individual coil w/ no ignition wire to tap

If you look at the actual igniter, near the plug , there is a small cover.
Open the small cobver, and there is a green wire kinda looped.
THAT is your tach signal.

Correct me if I am wrong guys.

 

[slidingsidewayz]

If you look at the actual igniter, near the plug , there is a small cover.
Open the small cobver, and there is a green wire kinda looped.
THAT is your tach signal.

Correct me if I am wrong guys.

oh yea, i heard about how when people get their timing guns hooked up they usually tap that wire to the gun since we don't have spark plug wires.
good looking out suprastanger. do you think i can run that wire to that black tach wire on the body plug or run it directly to the ign+ behind the gauge cluster. what do you think?

fred