Buick Fuel injecton 101 question

[montecarlofast]

So Ive been trouble shooting a injection issue on my 85 T type that I converted to all 86-87 injection exhaust and wiring (factory harness and all)
Heres my question. my injectors fire all at the same time. I do not have a grounded harness and all of the wires to the ecm from the injectors test correct for continutiy and resistance. Right when I turn the car over to start it, With my Fluke Ociliscope (dual channel) I can watch both channels show a fire at exactly the same micoseconds. go arround and test the other injectors and the same thing. all six injecors fire at the same time. from the harness at the ecm, I can fire them one at a time with a negative trigger with the key on. My question is, first i don't think this is right, and second what drives the injectors. My cam sensor is set properly (checked 3 times) TDC is correct, TPS sensor is right on for voltage and slope of voltage, Crank sensor is correct, Tested the yellow wire (cam hi) and it shows up and down voltage on my scope like it should, and the crank sensor shows the same as well. What other than the crank sensor, and the cam signal from the CCCI module dictates the ecm firing injectors? All of my grounds are low resistance and also grounded at the kick pannel to be sure, Voltage at the ECM is good, what am I missing? Thanks

 

[notacarlo]

I don't know if this helps or you already know this.

The cam sensor sends the signal to trigger the injector timing and if working properly is SFI. If the cam sensor fails it goes into limp home which is batch fire, but will not restart once then ignition is shut off.

 

[RmvBfrFlght]

It's been a while since I've looked at the GN ECM code. But, IIRC, during cranking the injectors do fire in batch mode. Then once the engine is running the ECM switches to SFI mode.

Note that the '148 ECM can also remain in batch mode when the engine is running. There is a flag in the calibration that is used for this. So if there is an aftermarket chip in the ECM, this may have been changed.

RemoveBeforeFlight

 

[montecarlofast]

So if it batch fires at first cranks how does it know to go into sfi mode?

 

[montecarlofast]

So if I have a caspers cap on it with the LED, which blinks so I know the hall effect is working, it shows a correct DC wave form on my O scope at the ECM is the timming on it off?

 

[WSLN 6]

Hopefully the wave is correct, I have had a Caspers cap blink and it was off 40 degrees according my XFI. Put the stock cap back on, and it worked fine.

 

[bmackinnon]

It cranks in batch, and switches to sfi when the ecm sees 400 rpm.. based on the crank sensor.... This will help explain the cam/crank sensor, timing/fueling relationship.... specifically faq #24....

FAQ-Buick Turbo Regal Chips - Thrasher Engineered Performance

The whole article should be required reading for TR owners.... fwiw... Originally put together by Tom Chou, AC Delco efi systems engineer and Buick guru...

 

[montecarlofast]

Awesome info! thanks

 

[jay dcpt]

x2 Thanks for posting that good stuff. i cant read enough about these cars.

 

[DailyDrifter]

might want to check the EST module

 

[ROYAL_6]

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