Here we go...the good old VATS problem (I think).

1988 C4 wouldn't start the other day. Cranked strongly but wouldn't fire up. After leaving a while, emergency garage started it fine and said it had flooded. Indeed - that was what it felt like to me, but it's never happened before. So I drove home and next day the car did the same thing. Cranked good, half hearted fire for about half a second then died. Persistent cranking resulted in nothing so I left it for a few hours (full depression of accelerator had no luck btw) and lo and behold it started! And yet again this morning, no start from cold on first attempts. So I disconnected the battery, left it for a couple of minutes and then reconnected, did a code check and 46 flashed up. So VATS problem. (Incidentally, I thought that engine codes were zeroed out when battery was disconnected but the 46 came up before I tried starting.) Key is ok, but I tried another just in case and still no start. Left for an hour or so then the car started sweetly - drove around the block a few times - all good. Even restarted properly after the run.

So what's going on? Intermittent issue seems odd for electronics. FSM says VATS module not getting message through to the ECM so the fuel is not activated. If that's so, why does the car sometimes start?

And if I bypass the VATS with a suitable resistor, will that enable the ECM for fuel to get to the injectors OK?

It's summer here in New Zealand and perfect Corvette weather so it'd be great to get this issue sorted. Ideas or (solved) experiences welcome!

 

VATS won't even let the car crank. It's something else. Probably weak fuel pressure. Hook up a gauge to Schrader valve. Report back.

 

Yes, that's what I thought too. However the FSM has a 'crank but no start' alternative in its diagnostic section. The Code 46 thinks its VATS. I'm puzzled for sure. Will follow up on your suggestion.

 

I have an 87 so I can't say if yours is the same but if you have a code 46 and engine cranks its a short in my case "white wire" from ECM to Vat's module. Look in your FSM and see what wire it is and check. If ok the VATs module is failing... I just had mine deleted in a tune along with emissions and other things for $95 Here is a vid of VATs module location.

 

Thanks, that looks like a possibility. I'll look into it - being an intermittent problem it could well be a dodgy wire somewhere. How did you do the VATS delete?

 

https://tunedperformance.org/?contac...ntact-form-100 Paid this guy to tune it out along with emissions stuff. Had him turn the electric fans on sooner and bump in timing. I think it was $95.00 or so. Great guy! Just did it this month referred by forum members on here.

 

Thanks for that - some light at last. I'll check for a bypass and work from there.

 

Well...Corvette specialist had a bit of a challenge to fix this. Turns out that the VATS module had developed a fault. So, new VATS module, new ignition barrel and new keys. I guess on a 32 year old car it was time to fix at least the barrel - key was occasionally sticking anyway.
Many thanks for all the suggestions that have been posted. It was a matter of gradual elimination and wire checking to pinpoint a faulty component.

 

I have a 86 i Ohm the key built a resistor checked and rechecked it to bypass VATS. Still have code 46 and intermittent starting like its bypolar. Does anyone know shouldn't a vats bypass eliminate the code 46 and allow the injectors to pulse.