car(88 auto) has been sittin idle for a few months because of damn Vats,had it towed home ,did a search& jumped out the green wire which goes to start relay behind the radio(also a new relay) it cranked ran rough for a few seconds each time ,tried the bypass & checked& changed keys before,also its a new relay,looks like the injectors arent gettin juice because I got 42lbs. on the fuel rail,looks like the Vats brain might be bad ,any input,please NO PREACHING about how the car can be stolen because I dont care ,Im so pissed I could take a mallet to it.

 

did it crank but not run?

 

after I did the search& found out about grouning the wire it cranked but ran for 2 seconds

 

VATS, if it reads the correct ign key pellet resistance, closes the start enable relay so the starter solenoid will operate the starter, AND it tells the ECM to exercise the injectors so that you cannot push start the car. Most likely you have worn contacts in the ign tumbler that make connection to the pellet. First try your spare key as its pellet contacts aren't worn like your everyday key. Next, remove the hush panel above the drivers feet and find the 2 wires that come out by the steering column and go to a 2 pin connector. Unplug the connector, insert ign key and measure the resistance across the wires from the steering column. It should measure the same as the pellet. If over 13k ohms, you need a new ign tumbler which will have new contacts that connect to the pellet. You can temporarily bypass VATS by clipping a resistor the same value as your pellet across the socket on the wires from the wiring harness (goes to the VATS module). You can use a 1/4 watt 5% resistor from Radio Shack. In spite of your statement, I recommend that you schedule the replacement of your ign tumbler because 99% of thefts are done by bashing the column and jumping the ignition and if you have VATS bypassed you are a target for a theft.
I replaced my tumbler about 8 years ago and haven't had a problem yet and I drive my 87 every day.

 

I did all that(checked out ok)& put a resistor from mid-america& still nothing at all ,till today when I grounded the green wire ,I got it to crank& run for 3 seconds,as I said that eliminates the igntion swich & key & also the relay which got replaced,whats left???in a nutshell,ignition switch& key are good ,battery& starter& relays are good.

 

Did you measure your key? and did you measure the mid-america kit?

 

Hello fellow BSS member. If in fact your problem is VATS, you're half way to a complete bybass. As you've seen, the relay ground is only half the story. The other thing the VATS Module does is signal the ECM that all is well in the Anti-Theft department and go ahead and do your ECM thing (i.e. pluse injectors). You have one of two methods to fuel enable the ECM. 1. Have a replacement chip burned that subtracts 10H from address $0014. The checksum will also need to be disabled or 10H subtracted from the checksum address $0006-$0007. In my opinion this is the most elegant solution. 2. Get a VATS Signal Generator. This simulates a valid Fuel Enable to the ECM in place of the VATS Module. I believe it is a 50Hz Squarewave, but don't quote me, it's been a while. Available from Gordon Killebrew for $75. They are available elsewhere so you may want to shop around. If you're so inclined, you could even build one yourself for a few bucks. I'll have to verify the signal though if you want to go this way. If I can't find it in my notes, I can always scope my VATS Module for you to get the signal details.

This is all assuming you really have isolated the problem to the VATS.

Good Luck.

 

just finished design /build of 30 hz sink ....got it hooked up on bench test with a -165 (86-89 vette) ecm right now, 40 hrs into 100 hr proof test...uses a 555 ic chip, etc, total cost of parts from raddyshack should be $10 at most, about a dozen connections to solder to build it, three wires hook to ecm wiring....as above, this tells the ecm to fire the injectors but you also need to jumper the starter enable relay

i just discovered that once the ecm has been told ok, you can turn off the sink and the ecm will continue to pulse the injectors ubtil the key is turned off, then will not restart until a new ok signal is received--so a toggle switch that shuts off the signal generator also makes your car theftproof again (if you remember to use the switch-duh)

asuming the 100 hr test ok, i'll make copies of my schematic/parts list (with raddyshack p/n) available to forum members free, SASE reqd.

somewhere in later years gm went to 50 hz, rumor is mid 93...that will need two resistors changed in my schematic--thats a few weeks away to build/test, calculations will take abt 3 min

 

The OP jumpered the Start Enable Relay in his first post. 30 hz eh. I'll buy that, as I said it had been a while. What are the three wires that hook to the ECM? I only remember a Purple wire that carries the square wave signal to enable fuel.

 

12v hot in start/run, ground (earth),to power the simulator, and signal to the ecm....tying all 3 in at the ecm to make it easy, short leads...could get 12v and ground lots of other places, but current draw is so small that this should be ok piggybacked at ecm--if you see a problem please shout

 

first off this type of electronics is not my forte,is there any other easier solution,this is what I got so far,on 20k setting on ohmmeter, key resistance 8.96, mid-america chip 0.89,still just cranks & run for 2 seconds,seems as the injectors are shutdown,got 50 psi fuel pressure,anything else,seems if the vats brain is a problem,where is it& can it be replaced,Im open for suggestions???

 

You need to recheck your info. You have got one of your values messed up. Look at my write up, http://forums.corvetteforum.com/show....php?t=1389952

This will show you my chart on VATS. The reason I say you have something messed up is 9.52 is a VATS #14, New key 8.96 is not an acceptable value, and lastly .89 is VATS #4.

One other thing, if your old key worked, and your resistance is 9.52, then the key is not your problem. Your key is good. Your problem is probably in you ignition switch. I say, put a bypass resistor in, and get rid of the VATS....

Recheck you readings, and repost your results.... By the way, what VATS value did you ordered from Mid-America?

Just my 2 cents....

 

there sure is. I bought a bypass unit from www.bakerelectronix.com for $29.99. Three wires to hook up - power, ground, then the signal wire you hook into the wire that goes from the VATS controller to the ECU. Thats it. You can put a switch in on the ground side if you want to enable vats. I went round and round with the VATS crap and this was the best $30 I've ever spent.

BTW your car being a '88 needs a 30mhz bypass module.

 

Why would you spend $30 for a VATS bypass kit when you can clip a $.10 resistor across the 2 pin connector in the wiring harness behind the steering column? Also, why subject your car to an easy theft? Keep your car in good repair! If you have worn ign tumbler contacts with the pellet, replace the tumbler that has new contacts. I did about 8 years ago in mu 87 and I haven't had any problems since and I drive it every day! You bypass VATS only until you can schedule a repair.

 

OK ,got more time to mess with this, car has been sitting for awhile,info I got, key resistance is, old key 8.96( I use all the time) newer (spare)key resistance is 9.52,both worked previously,measured ignition resistance with(both) key(s) in at end of 2 white wires& got no reading,so I have mid america resistor that measures0.89 ,Im using the 20k setting to do all measurements& writing down exactly ,the resistor # I got was off the old key,maybe its worn because new key resist,. is different & Im using the resistor,this is an aggravating problem,try to fix it if not will do the $30 fix.

 

count me in on the schematic...

 

looks like possibly could be that the old key wore out & I ordered a #4 bypass instead of a #14 bypass as the spare key reads higher,this 20k scale is throwin me off with the decimals& zero's,or the vats brain is bad.

 

It isn't only the VATS brain that is in question.

 

yeh,just moved ,had a lot of things goin on,priorities, figured the problem out,see other post

 

If your car cranks, it's not the VATS. Or perhaps you've successfully bypassed the VATS to get the crank. That was probably #1 of 2 troubles.
The other trouble was that the engine ran for 2 seconds or so then died. That indicates that the oil pressure didn't meet muster, the oil pressure switch didn't sense the oil pressure, or the 'brain' didn't get the message. Most likely, the oil pressure switch went south. There are two oil pressure sensors. One feeds the gauge, the other feeds the 'brain' and both are located at the back of the intake where they are really difficult to see. I don't recall which is which but your Helms manual will indicate the read-out vs the kill switch.
They aren't expensive.
Hope this helps.
(Posted in other thread too)