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91 f150 code 542


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m2934
New User

Apr 22, 2011, 8:02 PM

Post #1 of 4 (6197 views)
91 f150 code 542 Sign In

got this code and truck wont start. 542 is fuel pump circuit failure PCM to GRD. cant figue it out. fuel pump is good and fuel pump relay passed 2 tests with voltmeter. directly grounding the fuel pump to the frame didnt work.

wondering if the computer(PCM) is bad. but it was replaced a few years ago. not getting any power to the pump.

any help would be appreciated. Ive been without a vehicle for sometime now


autojoe
User

Apr 24, 2011, 10:27 AM

Post #2 of 4 (6167 views)
Re: 91 f150 code 542 Sign In

what size engine and 8th vin?when you turn key to on position do you hear fuel pump run for 2 seconds...take gas cap off to hear?check voltage at pcm connector terminal 8 dark green/yellow wire while cranking.....should be battery voltage....also should be battery voltage at terminal 87 at fuel pump relay dark green/yellow wire.check for power to pump and good ground....do voltage drop testing.possible bad inertia fuel cut off switch.


m2934
New User

Apr 26, 2011, 12:57 PM

Post #3 of 4 (6150 views)
Re: 91 f150 code 542 Sign In

its the 302

I keep testing things and I get a open in harness code according to the book. what about directly connecting the fuel pump to the battery or switch etc and completly skipping the harness, that way the pump can be manually turned on or connected to ignition


autojoe
User

Apr 28, 2011, 7:26 AM

Post #4 of 4 (6136 views)
Re: 91 f150 code 542 Sign In

if you dont answer questions I can not help.there are no shortcuts.have to see if you got battery voltage back at gas tank then move backwards.how do you know pump is good?do you hear pump run?koeo fuel pressure?could disconnect fuel pump relay and connect jumper between terminals 30 and 87 which will send power to pump circuit.that will only tell you something if pump runs which it probably wont unless relay is bad or computer control of relay is bad.do you have dual tanks?let me know answers to these and other questions I asked in previous post and maybe I can help you.






 
 
 






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