ron1

My 89 corvette will turn over but won't start. I keep it in my garage and crank it 1-2 times/month and bring up to temp. Never had a problem before. Added 5 gals. gas, cranked fine but hasn't run again since I turned it off. Fuel pump is ok, new fuel filter, fuel pressure at rail ok, getting fire to the plugs and have bypassed the vats with a baker electronix module. Still won't start. I can spray gas into the throttle body and it will run until it burns what gas I sprayed in and then dies. Any help would be appreciated. I'm at " wits end"

Cliff Harris

The fact that it runs with fuel sprayed into the throttle body means that the ignition system is good.

I'd suspect lack of injector pulses. Have you put a noid light on it? One of these guys:

http://www.amazon.com/OTC-7602-Port-...662775&sr=1-14

Things that can cause no injector pulses:
Missing (or wrong frequency) 30 Hz signal from VATS module
TPS bad or somehow ECM is seeing "clear flood" signal from TPS (unplugged, for example)
Missing distributor reference pulses (used for timing injector pulses)
Blown fuses (though it's unlikely that both of them would be bad)

ron1

Thanks for the info. As far as the vats bypass, I hooked up the 30hz (didn't help), then hooked up the standard, still nothing. I'll try the noid next. I appreciate the help.

yaknow

I'd ohm the injectors at this point, replaced the injectors on the wife's '89 last year after being stranded, no starting problems since.

ron1

Thanks for the info. I haven't had a chance to work on it in several days. Out of town. I'll get back on it in a couple of wks. and post a reply as to the outcome.

ron1

I checked the injectors with a noid light and getting no power to them. I installed a vats bypass module from baker electronix and still won't run. The horn will blow constantly, not pulsating. Could the ECM be stuck in the vat mode for some reason? Is it possible to check the ECM and if so where?

joe paco

ron1, you checked harness plugs using chart a-3 in fsm, 6 e3, I assume, no blnking light on either side? page 2 says to probe each harness plug with a test light to ground, each terminal. you did that and no light?

joe

ron1

I just checked one of the injector plugs with a noid light and it wouldn't light up. Sorry I'm technically challenged but I didn't understand what you were saying. Thanks for the quick response.
Ron

joe paco

sorry. just following the diagnostic chart in my 91 FSM, section 6E-3. it says to perform the second test on each terminal of each harness plug, in case circuit 467 or 468 is shorted to a voltage source. before you replace ecm, so it says.

saludos

ron1

Thanks for getting back to me. I know what you mean now. I don't have a fsm but will get one. I'll work on it again tomorrow and let you know my progress. Again, Thanks
Ron

Cliff Harris

On the '89s all 8 injectors are connected together. If one is shorted/low resistance then none of them will fire.

The fact that the noid light doesn't light up could be caused by one of TWO things. One is no voltage. The other is shorted injector(s)/wiring, which means no voltage across the noid light to make it work. Just to be sure: you need to be cranking the engine so the injectors are being pulsed to see the noid light flash.

I suggest using a meter to measure the resistance of all the injectors. They should be around 15 to 18 ohms. Also measure the voltage at one of the connectors on each side, with the ignition on. It should be around 12 volts. There are two fuses for the injectors (INJ1 & INJ2), one for each bank.

joe paco

good info, Cliff. it is easy to get lost in the simple details: either cranking, key "on", test with all harnesses disconnected, whatever. the book says: disconnect all injectors; test one harness on each side for BLINKING light while cranking.
if there is a blinking light, then ohm the injectors. if there is no light or steady light, go to page 2 of Chart A-3.
the point is that if you were looking for a light, other than blinkng, you would make a mistake. to your point, no lght could be a harness issue -or fuse out, or key off. (it's happened.)

page 2 says to check each harness terminal, two per, with test light to ground, WITH KEY ON. there is more to do, per the chart, but the ultimate goal is to isolate harness issues from ECM.

I went thru the exercise last summer, for the fun of it, so I could do it if I ever felt the need.

saludos, joe