No injector pulse on 89 Formula 350 .. HELP!!
10-04-2016, 02:49 PM
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No injector pulse on 89 Formula 350 .. HELP!!
New to the forums after buying a 89 Formula 350 as a project car for my son and I to work on. He's 12 so we have time, but we're both very anxious to finally hear it run after tinkering with it for 6 months.
It had numerous electrical issues but I have sorted out most of them, including no power to ECM (solved, ran new fused circuit after not being able to find any blown fuses), not reading resistor pellet in tumbler (bypassed with correct resistance), various broken wires, etc.
After fixing the resistor/pellet issue, I found that the VATS was enabling the starter relay so it cranks over fine and properly controlling the Security light but was not outputting the pulse to the ECM to enable the injectors. I have tried both a piece of electrical test equipment (pulse generator, 0-5V, tried both 30 and 50 Hz) and a VATS bypass pulse generator (with both 30 and 50 Hz options, tried both), properly wired into the ECM. Still no injector pulse.
When I run codes on the OBD2, I get the three code "12" pulses and that's it. No other codes come up at all.
When I turn the key, the check engine light comes on, blinks quickly, and comes back on solid, showing the ECM is running.
All other electrical functions on the car work fine at this point.
Can somebody tell me what all inputs are needed at the ECM in order for the ECM to enable the injectors? I have the ECM down and have multimeters and scopes and can measure any signals just fine. I have years of electronics experience but just not with ECMs/TPI/etc. It was micro-electronics, not automotive electronics, but I know my way around test equipment, haha.
Thank you in advance for all your help and inputs!!!
It had numerous electrical issues but I have sorted out most of them, including no power to ECM (solved, ran new fused circuit after not being able to find any blown fuses), not reading resistor pellet in tumbler (bypassed with correct resistance), various broken wires, etc.
After fixing the resistor/pellet issue, I found that the VATS was enabling the starter relay so it cranks over fine and properly controlling the Security light but was not outputting the pulse to the ECM to enable the injectors. I have tried both a piece of electrical test equipment (pulse generator, 0-5V, tried both 30 and 50 Hz) and a VATS bypass pulse generator (with both 30 and 50 Hz options, tried both), properly wired into the ECM. Still no injector pulse.
When I run codes on the OBD2, I get the three code "12" pulses and that's it. No other codes come up at all.
When I turn the key, the check engine light comes on, blinks quickly, and comes back on solid, showing the ECM is running.
All other electrical functions on the car work fine at this point.
Can somebody tell me what all inputs are needed at the ECM in order for the ECM to enable the injectors? I have the ECM down and have multimeters and scopes and can measure any signals just fine. I have years of electronics experience but just not with ECMs/TPI/etc. It was micro-electronics, not automotive electronics, but I know my way around test equipment, haha.
Thank you in advance for all your help and inputs!!!
10-04-2016, 07:42 PM
#2
Re: No injector pulse on 89 Formula 350 .. HELP!!
The VATS system on these cars has always been a major pain in the rear. There are 15 different resistor values that GM used in the keys.I am not familiar with how to trick the system.
I eliminated it on my last car by basically removing 90% of the cars wiring.
My current car has a custom EPROM in it that has the VATS shut off. You may want to look at that option as a last resort if you cant figure it out.
I eliminated it on my last car by basically removing 90% of the cars wiring.
My current car has a custom EPROM in it that has the VATS shut off. You may want to look at that option as a last resort if you cant figure it out.
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