And I bet the FSM says not to check the ECM impedence with an ohm-meter. (Some ohm-meters can damage electronics.)

 

Sorry if I confused anyone. Did not mean to do that at all. There are 2 of us on here trying to find the right answers and I guess 1 of us asked the same thing twice. Once again I'm sorry if anyone has been upset by this. I really like this car and want to get it back as close as original condition as I possibly can.

 

Yes it fires everytime. Just no fuel getting through injectors. Fuel pressure on the rails and gets good hot fire to plugs. Now I am told that the security light is flashing. Could this thing have a factory anti theft that has been triggered?

 

oil pressure switch?

 

Well, I don't know about that one. Can't get it to run long enough to see any oil pressure. I've got a factory service manual coming for it. Hopefully that will help us. Can't hurt though. Thanks to all!!!

 

if the ecm doesnt see oil pressure it wont let it start

 

Even starting should give you enough oil pressure to satisfy the ECM.

 

Security light should flash , key on. Have actually checked the injectors with a noid light ? If they have been on the shelf a long time, they could be stuck.

 

Extended cranking will give greater OP than the 4 psi needed to close the switch

As noted in his OTHER POST

Makes no difference to the start sequence (OP switch is only backup to pump relay )
But once again his OTHER POST he says he has fuel pressure at the rails so pump is working.

His PROBLEM is the injectors are not pulsing;
whether it is a injector problem , wiring problem or ECM problem is yet to be determined
As he has been told already , a FSM is invaluable for fault finding in cases of butchered wiring

 

thankyou rodj, always count on you for excellent tech,

 

There was no VATS on a '85 but nothing to say someone has not installed the later system.
What is the part # on the ECM?
What you are describing is exactly what happens whens VATS ( anti theft ) is activated.
It shuts off the injectors to prevent engine starting

 

The ECM needs to see distributor reference pulses before it will turn on the injectors. It uses the pulses to determine when to fire the injectors.

There is a 4 wire cable coming out of the back of the distributor that goes to the engine wiring harness and then to the ECM. The distributor reference signal comes from the ignition module in the distributor.

There are some checks you can do to see if the injectors are getting the correct voltage. There are two fuses (INJ 1 & INJ 2) for the two banks (left and right) of injectors. You can check that the fuses are doing their job and voltage is getting to the injectors by probing an injector connector (you need to check both sides). The pink/black wire comes from the fuse. Unplug a connector, key on, and probe the pink/black side of the connector with a test light or voltmeter (DC volts). To see if pulses are getting to the injectors, probe the injector connector light green or light blue wire. You should see flashes on the test light or voltage jumps on the voltmeter. Here's a pic of the relevant page in the Factory Service Manual (you should have one):



I saw a note on the above page and remembered that there is one other possibility. If you press the accelerator pedal to the floor, the ECM will go into "clear flood" mode and cut off the injectors. Make sure your TPS sensor is reading about 0.54 volts with the throttle closed. If that signal is over about 3.5 volts the ECM will cut off the injectors. The TPS sensor should have 5 volts on the top wire, .54 volts on the middle wire and zero volts (ground) on the bottom wire.

 

Yeah, that's where I was heading with my question. VATS doesn't shut off the fuel immediately. It's supposed to also provent cranking but doesn't in my car so it will fire for a second till the injectors are disabled. But if there's no VATS...

Clearly a FSM for the model year in question is needed. I'll go back to read-only mode.

Good luck

 

Getting old ; forgot that tricky little one that catches many out
Highly possible since OP is installing a new TPI on a previously carb car

 

The ECM will not supply ground to injectors unless it's receiving reference signal from distributor's ignition module.
Might be a good place to start.

 

How is your fuel pressure?


One possibility is the fusible link that supplies power to ECM and Fuel pump. It is near the gaggle of others by the battery and there is a long black funky connector just after it (is used to clear ECM without disconnecting battery). If no power at fuel pump fuse this is next in line

Mine was weak - about 3 volts on the car side. It would run if I sprayed fuel/starter fluid down intake but not otherwise.

 

Refer to his parallel post also running on the same problem
http://forums.corvetteforum.com/1579638949-post14.html

 

This far down the track anything could have been done to your car.
Is not uncommon to bypass the starter lockout part of VATS while still retaining the fuel injector shutoff

 

Possible, but if so it was done without the PO's (i.e. Dad's) knowledge. The mechanic who worked on it for the last 7-to-9 years before I bought it replaced the fuel pump while prepping it for sale before realising it wasn't getting fuel 'cause the worn key was triggering VATS.

 

Yep. Got me too. If the ground connection is open on the bottom TPS wire you'll get 5 volts going to the ECM instead of the correct .54 volts.