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Viper 5706 Tach mode crank time


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simitch01 
Member - Posts: 8
Member spacespace
Joined: February 18, 2016
Location: Wisconsin, United States
Posted: April 12, 2016 at 12:39 PM / IP Logged Link to Post Post Reply Quote simitch01
Hi everyone,
I'm having an issue setting up my Viper 5706v (installed in a 1995 chevy 1500) to use tachometer mode for engine checking. I hooked up the violet/white wire to the white tach wire from the ECM, behind the glove box, which showed fluctuating AC voltage with engine rev and performed the tach learning procedure after install. The truck starts perfect when it has been ran within the last 10 or 12 hours. However, if I leave it sit overnight and use remote start, it only cranks about 1.5 seconds and disengages the starter before the engine fires up... it cranks again and fires up fine (the truck has always needed a little extra cranking after sitting). At this point, I changed the cranking time to 4 seconds but it still only cranks for about 1.5 seconds on the first attempt. To test that the tachometer feature was working, I unplugged the main wire feeding the distributor (so the engine wouldn't fire) and tried remote starting. The starter still only cranks for 1.5 seconds and repeats for 3 attempts before giving a "failed to start" error code. I've also tried revving the truck up to about 1200 rpm and learning the tach signal but I still get the same behavior. Can anyone tell me what I may be doing wrong or steps I may have missed? I have a full install manual for a 5701 model and it has a "Tach threshold on/off" jumper but it sounds like that is only for the voltage or virtual tach settings of engine checking.??? I also know that my "old" truck has a STRONG 12v ignition system output.
To get the vehicle to start on the first attempt after sitting, I programmed it for virtual tach and left the crank time at 4 seconds which works flawlessly but I'm still baffled as to why I can't get tach mode to work right..... Thanks in advance for advice!Viper 5706 Tach mode crank time -- posted image.
simitch01 
Member - Posts: 8
Member spacespace
Joined: February 18, 2016
Location: Wisconsin, United States
Posted: April 12, 2016 at 12:42 PM / IP Logged Link to Post Post Reply Quote simitch01
I forgot to mention that I've made sure that engine checking is set to "tachometer" multiple times.
smokeman1 
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Joined: September 14, 2009
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Posted: April 12, 2016 at 4:10 PM / IP Logged Link to Post Post Reply Quote smokeman1
I wouldn't worry about it. I had a 1992 K1500 that i put in a Viper 5301 in. It never started on the first attempt. I believe it might be because that truck had a TBI (throttle body injection),and not a fuel injection system.
My '92 had the same remote start symptoms as your '95. Never bothered me as it always started on the second attempt.
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davep. 
Gold - Posts: 624
Gold spacespace
Joined: May 27, 2011
Location: California, United States
Posted: April 12, 2016 at 7:42 PM / IP Logged Link to Post Post Reply Quote davep.
I have a 791xv in a 99 Powerstroke, and it sometimes does just what yours does if its been sitting a few days. Cranks 1.5 seconds, doesn't fire, then cranks as long as it takes to fire the second attempt. Then the rest of the day or even trip, it starts on the first try. Powerstrokes have a long crank time, especially when cold. I find it odd that it will crank for as long as it takes the second attempt, but not the first. :dunno:
I have a thread on here about it. I don't think there were any replies that helped.
Mark Mizenko 
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Joined: October 13, 2004
Location: Pennsylvania, United States
Posted: April 12, 2016 at 8:54 PM / IP Logged Link to Post Post Reply Quote Mark Mizenko
How about grabbing an injector pulse instead of tach.
simitch01 
Member - Posts: 8
Member spacespace
Joined: February 18, 2016
Location: Wisconsin, United States
Posted: April 13, 2016 at 5:46 AM / IP Logged Link to Post Post Reply Quote simitch01
Thanks for the replies everyone. There are two reasons that this behavior bothers me: 1) Extra wear on the starter and flywheel teeth. 2) My personal irritation that I can't get something to work the way it's supposed to. GRRRR!!
One thought that crossed my mind (most likely impossible) is that maybe the starter is cranking the engine over fast enough to generate high enough AC voltage to meet the threshold and disengage the starter. I dunno...
Mark Mizenko, I really don't know what the difference of AC voltage output would be between the tach wire at the ECM versus the injector wire.... Could you explain why it would be better? I'll take a shot in the dark here but is it because the injector won't actually fire unless the computer sees enough fuel pressure??? If that's the case, I could see how that would make a difference.
brownsfan1 
Copper - Posts: 65
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Joined: January 28, 2016
Location: Ohio, United States
Posted: April 13, 2016 at 1:56 PM / IP Logged Link to Post Post Reply Quote brownsfan1
It's a safety thing I believe. So it doesn't crank indefinitely. I don't think injector wire is possible on that truck. It has a throttle body instead of individual injectors. You can't extend crank time in tach mode. Only in voltage sense or engine checking off mode. I wouldn't worry about it. Especially since it starts on the second time. It's normal operation.
davep. 
Gold - Posts: 624
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Posted: April 13, 2016 at 4:54 PM / IP Logged Link to Post Post Reply Quote davep.
V8 and V6TBI units have 2 "injectors". 4 cyl have 1. The pulse widths are longer than an individual cyl injector would be, but it still has pulses. No real difference between port and throttle body injection as far as the electrics are concerned. Both systems work on the same principals.
GM EFI begins to send injector pulses as soon as it sees distributor reference pulses. And as an FYI, the fuel pump runs for a couple seconds after key=on then shuts off if there are no reference pulses. On the first pulse, the fuel pump is trigger back on.

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