F-150 4.9L Engine will not start No Spark
05-13-2009, 10:44 PM
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F-150 4.9L Engine will not start No Spark
Followed all the testing in the Haynes manual. Tested the PIP circuit by reading the Volts AC Pip signal. With the PCM connected I have no volts, but with the PCM disconnected I get between 3.5 and 8 VAC per manual. Replaced PCM, ICM and checked all wiring in harness. Still do not get PIP voltage with the PCM connected. Fault code reader does not detect any faults. I have cleaned and checked all grounds. Any ideas what else to check?
05-14-2009, 09:00 AM
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Additional items completed to troubleshoot this problem
Here is some additional items completed to help troubleshoot. Originally replaced the timing belt to help correct, also replaced distribute and insured timing was accurate. Was able to start it once right after replacing the timing belt, but when I hit the gas pedal the engine died. Checked all starting and ignition circuits per tests in the manual until I got to testing the PIP circuit. When I found there was no voltage at the connector, I commenced to isolate by disconnecting the PCM, where the voltage returned. Assuming it was a bad PCM, I replaced it. Still no voltage when it is connected, but it returns when it is disconnected. Is it possible that maybe I am missing a ground circuit coming of the PCM so it isn't going to ground properly?
05-14-2009, 12:59 PM
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More troubleshooting
Today I went ahead and disconnected the PCM and ICM while reading resistance from the PIP signal wire at the distributer to ground. With everything connected I read .01 Ohms. When I disconnect the PCM and ICM I still read .01 Ohms to ground. When I disconnect the connection to the distributer I get open to ground. Reconnect the PCM and ICM modules I read 17 K ohm to ground. Is it possible the PIP signal is grounded out in the distributer, or am I suppose to be reading to ground when the distributer is connected?
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05-14-2009, 09:06 PM
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Looks like I found the problem
Looks like the problem was in the connector that connects to the ICM. After playing with that for a little while I was able to get the truck to start 12 consecutive times. I then played with it again and no start. Played one more time and got it running again. Will see if i can check the pins in the connector.