Still no tach!!!!
Still no tach!!!! Have a speedhut tach, E38 ECM w/T56. I added a pinout to pin 48 of connector J1. I verified continuity from the connector to ecm to my tach. I added a 680 ohm resister (see pic; purple wire is to my tach, red wire is 12V ign keyed). I've tried in multiple settings for pulse (1/2, 2, 4) although it should work w/2 pulses per rev from what I've read. My tuner said he followed the instructions here:
http://www.hptuners.com/forum/showthread.php?t=36611
setting tach output on crank, and HIbRES 14 and LO RES 15. but I have no joy. When the engine starts I get a temporary uptick to 500 rpm and then it goes directly back down.
Any thoughts what I could have wrong, or better yet, how to isolate what my problem is?
Thx!
http://www.hptuners.com/forum/showthread.php?t=36611
setting tach output on crank, and HIbRES 14 and LO RES 15. but I have no joy. When the engine starts I get a temporary uptick to 500 rpm and then it goes directly back down.
Any thoughts what I could have wrong, or better yet, how to isolate what my problem is?
Thx!
Last edited by Goldhawg; Sep 7, 2012 at 06:17 PM. Reason: fixed error
On The Tree
Joined: Jul 2011
Posts: 186
Likes: 3
Resistor looks like it's in the right place.
What tach? I tried two older Sun "Super Tach II"'s that just would not work. Then used a newer Autometer tach and it worked fine.
If you have access to a scope hang it on the tach line and see if you're getting pulses.
What tach? I tried two older Sun "Super Tach II"'s that just would not work. Then used a newer Autometer tach and it worked fine.
If you have access to a scope hang it on the tach line and see if you're getting pulses.
I don't have a scope or particularly know how to use it, but I have some electronic technicians that probably can. Is there anyway that HPTuners can tell anything; i.e., does it see output from each pin?
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I drove the car yesterday to work for the first time. A couple of times during the drive I saw the tach spike up but it came back to zero immediately. Still haven't had a chance to verify any signal coming over wire w/a scope.
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Verdad Gallardo I finally got my swap running and was able verify the mod works on the factory '92 vette tach when using the pull up resistor. I initially tried a 1K ohm pull up resistor but the tach is reading a little low. I need to experiment with some other values before soldering it all together.
Did you use a 680 ohm or 680,000(K) ohm pull up? 680k wouldn't do much and may be your problem.
Did you use a 680 ohm or 680,000(K) ohm pull up? 680k wouldn't do much and may be your problem.
I finally got my swap running and was able verify the mod works on the factory '92 vette tach when using the pull up resistor. I initially tried a 1K ohm pull up resistor but the tach is reading a little low. I need to experiment with some other values before soldering it all together.
Did you use a 680 ohm or 680,000(K) ohm pull up? 680k wouldn't do much and may be your problem.
Did you use a 680 ohm or 680,000(K) ohm pull up? 680k wouldn't do much and may be your problem.
TECH Regular
Joined: Dec 2011
Posts: 420
Likes: 115
I would 2nd the notion to try a different tach, if you can borrow one. Or get an oscilloscope on the line. Some nicer handheld multimeters can read out frequency, which you can also use. Get a reading at idle, then rev up, and see if the frequency reading increases proportionally.
