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Thread: No power to throttle body injectors.

  1. #1
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    No power to throttle body injectors.

    I have a 1995 motor home with a 454. I am not getting any power to the injectors. I am getting fuel to them and ignition spark. I jumped power to them and they sprayed fine and even ran while they were jumped. This leaves me to believe that it must be either the controller or a broken circuit. What controls the voltage to the injectors?

  2. #2
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    Not an expert but you should have 12v at the injectors with the key on. I think the power comes from the ign switch, probably via a fuse.

  3. #3
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    In the process of checking things out. I did have 12v at the injectors once but do not have it now. If I put 12v directly to the inj. it sprays continuously. What controls the flow? Other wise when you turned the ign. on it would spray fuel even if the engine was not running. I will check all the fuses. Maybe your right.

  4. #4
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    I checked all the fuses and found 1 that was blown. I now have 12v to the injectors with the key on, but still no fuel getting through. Are they possibly controlled by the amperage put in to them?

  5. #5
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    As I understand it there should be 12v at the injectors while the key is on but the injectors should not spray. The injectors should be grounded by the PCM (computer) in pulses timed by the ignition system. So it sounds like you have bigger problems. It would seem like that the injectors are grounded at all times. Maybe a bad tigger wire between PCM and injectors. If you could google for a pinout of the PCM you could check that the trigger wire between it and the injectors is good and not grounded. Worst case senario is that the PCM is bad but I don`t know enough about it to say for sure.

  6. #6
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    Did some research here and a common theme is to check that the ground wire that bolts to the engine at or near the thermostat housing is clean and tight. Also that a bad engine coolant temperature sensor can also be a cause.

  7. #7
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    I must have a ghost. I checked the wires for continuity and voltage to figure out which was the trigger wire. I took the hot wire out of the connector and put it on the post of the injector. I was going to check for cont. between ground and the trigger wire while I was turning it over. When I started to turn it over it tried to start and I noticed that the second inj. was firing. I took my ground wire that I had in my hand and started to pulse the 1st inj. I managed to keep it running. I turned it off, put the connector back together plugged it in. Started right up and runs great. But I still do not really know what was wrong with it. But then again it is really hard to fix it when it is not broken. I'm sure it will show up again.

  8. #8
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    Good man. Maybe do a wiggle test at the connections to the injectors in case you have a bad connection there. Also check that ground wire where it bolts to the engine.

  9. #9
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    Thanks for your help.

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