1989 Corvette cranks but doesnt start.

[1hotroc]

Hello, I am new to the forum and Im helping a friend get his 89 Vette started after sitting for a long time. I verified vehicle has proper fuel pressure, spark present at the plugs. What concerns me is when monitoring crank rpm with my scanner 0 rpm shown. Also injector pw 0. So I am convinced that the ecu is not cycling the injectors because of no rpm signal. What also bothers me is this vehicle has the vats system. The security light is flashing when cranking and I beleive there were some displays out in the digital instrument cluster. I read somewhere that there is a ccu module which could also cause this? Im not sure if thats what its called? Can anybody point me in the right direction here? Thanks so much. Is the security light supposed to be flashing when trying to start a car with the vats? Im going nuts with this!

[c4c5specialist]

HI there,

You would not be able to turn over the vehicle if the VATS was there. Also, your FUEL ENABLE data display would show that the fuel was shut off.

Ohm out your injectors, you should have 16.5 ohms for each.

Post here what you have.

Allthebest, c4c5

[1hotroc]

Ok, I will ohm out the injectors. So your saying the vats when enabled will not turn the fuel pump on? Also I wouldnt be able to crank? What about the security light it still flashes when cranking, this is normal? But like I said even if one of the injectors is bad there still not getting the signal from the ecu to open and close (actuate), I verified this with a noid light. One more question can I plug in my ecm from my 87 Iroc L98 to eliminate a possible ecu issue? Thanks.

[c4c5specialist]

HI there,

If your injectors are bad enough, it will SHUT DOWN the ECM from overload and the injector WOULD NOT be fired anyway.

So a noid light test could be invalid.

I am not sure on the L98 ECM from Camaro, because its a different system.

It may or may not work, depending on production dates.

Allthebest, c4c5

[1hotroc]

Hello again, well I went back to trying to start this vette again. I did check resistance on all injectors, were within 16.5-16.7 ohms so that wasnt it. Like I said before, I never saw rpm signal on the scanner, so I went ahead and replaced the ignition module. That fixed my rpm issue. I am now able to see rpm on the scanner, and the digital display of mph and rpm is now present. Still no start! Can anyone tell me if the security light is supposed to be staying on when Im cranking the car because it is. From what I read in the service manual it is possible to have a vats issue and the car will still crank. I am concerned that I have a vats issue or ecm problem, I dont feel comfortable seeing that security light on when cranking, I dont think this is normal. Can anyone help with this diagnosis?

[c4c5specialist]

Hi there

Yes, you may see the light on.

What is your fuel pressure??? You should have 41-47 psi when you crank your engine.

You can also check to see if your cars control computer is working by simply checking to see if your injectors are clicking.

But, the other post you stated it was flashing, but now its solid ??

Allthebest, c4c5

[1hotroc]

Yes your right, it does not flash, it just stays on steady when cranking. I dont think this is a vats issue because I verified 2.4 volts on b5 pin at ecu (vats signal) also I have distr. reference 1.4v on b4 after replacing ignition module. I did swap my ecu from my 87 l98 Iroc did not work. The next thing Im going to do is start with the basics and ground the aldl connector, to see if it flashes a code 12. This should also activate the cooling fan right? Now that I think about it my auto-xray scanner should kick on the fans when plugged in to the aldl, it doesnt. Also when I was monitoring my scanner I checked spark timing and that was pegged on 0 along with inj pw. I would just hate to buy an ecu and find out thats not the problem. Any other ideas? Thanks very much. Oh yes I almost forgot the fuel pressure is fine 38-42 psi.

[1hotroc]

I guess I'll throw an ecm at it then. Do you know the inputs to the ecm for spark timing and injector pulse width so I can check this?