virtual tach no start avital 4103

Just installed a avital 4103 on my 98 chevy malibu. The system has a virtual tach on it but it doesn't always start the car (pass lock 2 permanently bypassed a few years ago... not the issue). It just doesn't crank long enough some times. I can program th RS to have a longer crank time but i'm not sure this will correct my issue since the car seems to have irregular crank when trying to start with the key. I've worked as a GM Technician for 5 years specializing in electrical and electronics but installing remote starts is new for me. will installing a tach wire compensate for the irregular crank times?


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Nate

yes running a tach should solve you issue virtual tach isnt reliable at all

The TACH wire is WHITE on the 4-cylinder engine at the IGNITION COIL and on the 6-cylinder engine it is a PURPLE / WHITE at the COIL PACK, located at the top rear of engine.

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If i Can't Install it    I Don't need it   Joe

yup run a tach.

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A DMM is a beautiful thing.

MECP Advanced Installer Certified.

Turn off the virtual tach...Set crank time to.8 or 1.0...Or as others has suggested you can run tach(this is always a good idea)...We install alot of these units and after a few installations have decided this is the best method...We use the bitwriter and set crank time usually at .8 or 1.0 and turn virtual tach OFF...This is not necessary in all situations but seems to work well...I f you can find a bitwriter at a good price i would get one...! This makes changing the features very,VERY easy and you can also increase the run time in 1 minute increments(up to 60 max,maybe higher just never went that high)...There is also an adjustment for the virtual tach fine tuning...Good Luck...If you are planning on doing the installs yourself from now on...Defitnely get a bitwriter...You will see  why once you get one...!

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M.E.C.P & First-Class
Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

Thanks for that info guys. like i said i'm new to RS installs. Do i need to change the crank time if i install a tach wire? Also this vehicle has a tach test port in the under hood fuse block. couldn't i just tap in there? Thanks for all the help!

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Nate

This whole virtual tach seems a bit barbaric to me. Shouldn't it just crank until it sees the voltage increase from the engine firing? You should't have to adjust the crank times. With all the technology we have today you would think they could figure this out?

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Nate

no changing crank time or anything if you run a specific tach. it'll keep cranking as necessary until the vehicle fires up. i've tested this on my own vehicle by putting my foot to the floor then remote starting it which as you know on some vehicles cuts off fuel. it kept on cranking until i took my foot off the gas.

just make sure you SOLDER your tach wire, and learn it properly by starting the vehicle with the key, and right once it starts hold the valet switch fora few seconds and once you let go the parking lights should flash. then you're good.

And honestly virtual tach to me seems like they invented it for lazy people. it's rare to find a car where tach won't learn right.

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A DMM is a beautiful thing.

MECP Advanced Installer Certified.

I use virtual tach on almost every car that comes in to the bay with no problems.

buddholly wrote:

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I use virtual tach on almost every car that comes in to the bay with no problems.

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ok. was there a point to this post?

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A DMM is a beautiful thing.

MECP Advanced Installer Certified.

Even after changing the crank times for the virtual tach, it still will not start every time when it is cold out. It will crank for a half second and shut off. It's like it's seeing a slight voltage increase during cranking. I'm running a tach wire when I get some free time to work on it. Not impressed with the virtual tach!

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Nate

you have to set your tach. start the car with the key and hold the programming button until the led light goes solid.

njerje23 wrote:

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This whole virtual tach seems a bit barbaric to me. Shouldn't it just crank until it sees the voltage increase from the engine firing? You should't have to adjust the crank times. With all the technology we have today you would think they could figure this out?

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This would be impossible to do.  The starter is a high current device and the voltage will ALWAYS drop when cranking.  It is impossible to use voltage monitoring to control the crank time.   To compensate for this, you program in a crank time that "should" work.  The remote start engages, fires the starter for as long as you programmed, and then a few seconds later checks the voltage of the system.  If it is above x.xx volts the remote start knows the car started, if it is below x.xx volts then it knows the attempt failed.

Hooking up a tach reference is the ONLY way to provide closed loop monitoring and control crank time.  When a motor cranks it is typically around 200-300RPM.  When it starts it is generally between 8-1200rpm.  Since the tach signal references motor speed under both conditions it is easy to electronically determine when the motor has started. 

The main problem with voltage alone is that generally over time motors take longer to crank before they fire up.  So, it may work now, but in 3 years from now the crank time may need to be extended.  The tach wire, on the other hand, will adjust and continue to work.

The virtual  tach was created as a way to combat the issues with starting over time.  As someone else already mentioned it is the lazy way to install a remote start and a tach wire should always be hooked up.

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Kevin Pierson

Yes, i agree with kevin, in short virtual tach is a waste of time.