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  View original topic: 79 Bay Window Fuel Injection Resistor pack.
Robert-OR Fri Dec 29, 2017 7:59 pm

Hi Guys, first post. I have a random issue with my FI, for the most part the bus runs but every once in a while it will run then cut out. I have been using the A.F.C. guide that I downloaded from a link from this forum. checking all the specs to make sure everything is correct so when it dies I can recheck to find the issue also have the fuel pressure gauge installed on the rail to keep any eye on pressure.
I got that part under control, my question is about the resistor pack, that should take the 14 volts to "3 - 5 " volts. My voltage drop at the injector is still 13 volts while the bus is running. does not seem to be where it should be. I am getting 6.3 ohms on all 4 resistor.

Is this ok? Do the resistors fail? Do they fail open or closed? What about getting a power converter to replace the resistor pack to give me 5v?

Wildthings Fri Dec 29, 2017 9:22 pm

Can we assume you have a federal model and not a California model?

Where are you attaching the meter leads when you are reading the voltage? It sounds to me like you probably have a problem with your methodology.

Robert-OR Fri Dec 29, 2017 9:36 pm

Sorry, Yes I have the non-California model. I checked the voltage two ways with the car running.
1. On the out put wires of the resistor pack.
2. Pulling the connector off 1 injector at a time while it was running and sticking the probe on the contact point in the connector.

Wildthings Fri Dec 29, 2017 10:09 pm

It would matter where your ground lead is as well, but what you are seeing is probably quite normal. Assuming you are reading to ground, then you will be reading the average voltage over time between the hot side of the injector and ground. When the injector is firing the voltage will be the specced 5v, but when the injector is not firing (not being grounded) you will see battery voltage. Averaged over time at idle you will see closer to battery voltage than firing voltage.

You would need an oscilloscope to accurately read the dynamic firing voltage.

I would say to clean your FI grounds one more time and to make sure none of the pins are push back out of any of the plugs in the FI harness.

bbrowncods Wed Feb 14, 2018 2:46 am

Should see approximately 7 ohms at the ecu plug on each of those injector circuits per the AFC manual you have. That would be about 2.5 ohms for the injector, 5.0 for the resistor pack (between the center pin and each of the other four), and 0 for the harness.
Do a search here on "harness" and you'll find info on how to check for a bad harness, and how to fix it.

Good luck!

Randy in Maine Wed Feb 14, 2018 5:57 am

If it comes up in Double Jepordy (where the scores can really add up quickly), the 1979 California models don't use a resister pack or an EGR set up for that matter.



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