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FPCU/Revolution Sensor~Help with Diagnosis


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In my hands-on efforts, and research done thus far @USMB (thank you! great content, but nothing that I can interpret as a sure thing with my limited knowledge) I have a  guess as to a likely cause for my 86 Brat not starting.

Here's what I can tell you so far:

New battery, cables, ignition coil, fusible links. (had a no-spark issue for a while, but that's been fixed)

When I chased down the no spark problem I had, I replaced the ignition coil. Once that was done the IGN fuse would blow at every attempted start. My neighbor found a short (photo with the red wire nut, next to the carb) Now with this wire disconnected the fuse does not blow and for a while the car started and ran fine for a few weeks. But eventually it would not start (turns over, but would not run)

 

So now I've determined that the car is not getting fuel at the carburetor, and there is no sound of the fuel pump initial kicking on when I turned on the ignition, (which I could always hear before). In checking the voltage at the fuel pump when turning the key, there is nothing. Also, checking fuses, none are blown. Direct wiring of the fuel pump to the battery and it kicks right on.

The two big questions: In my install of the new ignition coil (and the disconnect of the wire by the carb) if I have any wiring incorrect, could that be a cause of voltage not getting to the Fuel pump? And, is there a way to take a meter to the FPCU off of the car and determine whether it's bad? The photo gallery section has the photos as well, with brief descriptions of what is there and what I'm trying to determine.

My apologies for the long-windedness. I'm hoping that there are some good explanations to this, as my lack of car knowledge has most likely caused some of my problems. Thanks in advance! 

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That is the float bowl vent solenoid. It should open with the ignition on. If it blows the fuse when connected, it's shorted internally. It has nothing to do with the FPCU. You do need to replace or bypass it or you'll have power issues when cruising under a load.

 

The FPCU only turns the pump on when it gets a signal from the distributor that the engine is indeed running. If it doesn't get that signal, no pumpy. You'll need the schematics to see exactly what does what and test it. I don't have access to mine right now. If memory serves, the negative side of the coil goes to the tach, the FPCU and the ignitor. There are two fused power circuits coming into the FPCU powered buy fuses 14 and 15 IIRC. One circuit out to the fuel pump and one to the choke. Couldn't tell you the colors or pins right now though.

Edited by skishop69
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