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1991 ford f150 won't start


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coyoteugly543
Novice

Feb 4, 2017, 7:36 AM

Post #1 of 17 (998 views)
1991 ford f150 won't start Sign In

1991 ford f150 won't start I am getting some spark at the plug wires but weak spark


Tom Greenleaf
Ultimate Carjunky / Moderator
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Feb 4, 2017, 9:31 AM

Post #2 of 17 (985 views)
Re: 1991 ford f150 won't start Sign In

Which engine? How did you determine "weak" spark but has it?


Will it prime and run or react at all with some fuel for starting fluid. Need to rule some things in or out for a beginning,


T



coyoteugly543
Novice

Feb 4, 2017, 2:18 PM

Post #3 of 17 (978 views)
Re: 1991 ford f150 won't start Sign In

302 motor
just a small spark at pug wire when I crank the motor
no motor not fire at all


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 4, 2017, 4:40 PM

Post #4 of 17 (966 views)
Re: 1991 ford f150 won't start Sign In

Use an adjustable spark tester to get an accurate measurement of KV available. Make sure your battery is fully charged.





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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



coyoteugly543
Novice

Feb 5, 2017, 7:37 AM

Post #5 of 17 (941 views)
Re: 1991 ford f150 won't start Sign In

new coil didn't help


Tom Greenleaf
Ultimate Carjunky / Moderator
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Feb 5, 2017, 8:44 AM

Post #6 of 17 (939 views)
Re: 1991 ford f150 won't start Sign In

Why did you do that? Nobody said coil was an issue and you could have tested old one. IDK -99% are good or do nothing at all. Get a spark tester if you think spark is weak. If so it's probably NOT the coil rather a relay or in distributor. It's old and can just blow air thru those and watch junk come flying out,


T



coyoteugly543
Novice

Feb 5, 2017, 8:59 AM

Post #7 of 17 (933 views)
Re: 1991 ford f150 won't start Sign In

just trying different things


Tom Greenleaf
Ultimate Carjunky / Moderator
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Feb 5, 2017, 9:05 AM

Post #8 of 17 (929 views)
Re: 1991 ford f150 won't start Sign In

Try getting a DVOM and spark tester as the original items are tons better than the junk you'll replace stuff with!


T



coyoteugly543
Novice

Feb 19, 2017, 11:31 AM

Post #9 of 17 (870 views)
Re: 1991 ford f150 won't start Sign In

ok I got my old ford run but don't want to idle down I had the same problem before I had the problem of not starting


Tom Greenleaf
Ultimate Carjunky / Moderator
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Feb 19, 2017, 1:07 PM

Post #10 of 17 (862 views)
Re: 1991 ford f150 won't start Sign In

OK - I take that it's running just doesn't come off of a high idle - right?


Try unplugging the IAC (the thing near air intake on 5.0 (302) engines held on by two 5/16" small bolts should idle down if that is stuck or not working properly.


Don't just replace those check first as most fail to a wandering idle not just stuck on higher than it should be,


T



Hammer Time
Ultimate Carjunky / Moderator
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Feb 19, 2017, 1:25 PM

Post #11 of 17 (858 views)
Re: 1991 ford f150 won't start Sign In

It should stall if you unplug the IAC.




First eliminate all vacuum or air leaks in the system (very important)

. You may have a bad IAC ( idle air control) but try cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



coyoteugly543
Novice

Feb 19, 2017, 2:39 PM

Post #12 of 17 (843 views)
Re: 1991 ford f150 won't start Sign In

yes running just doesn't come off of a high idle
don't seem to be any vacuum or air leaks
I did clean the throttle body
it doesn't do any thing when I unplug the IAC.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 19, 2017, 2:42 PM

Post #13 of 17 (841 views)
Re: 1991 ford f150 won't start Sign In

Somebody may have adjusted the throttle plate stop thinking they could adjust the idle.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



coyoteugly543
Novice

Feb 19, 2017, 3:32 PM

Post #14 of 17 (837 views)
Re: 1991 ford f150 won't start Sign In

no the bolt is loose


Hammer Time
Ultimate Carjunky / Moderator
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Feb 19, 2017, 3:36 PM

Post #15 of 17 (835 views)
Re: 1991 ford f150 won't start Sign In

The engine is getting unmetered air from somewhere. If it's not the IAC and not the throttle plate, then you need to find out where.

Use a scan tool to make sure the TPS is coming down below 1V



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



coyoteugly543
Novice

Feb 19, 2017, 3:54 PM

Post #16 of 17 (830 views)
Re: 1991 ford f150 won't start Sign In

no code shows up
what a good way to find vacuum or air leaks
thanks


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 19, 2017, 3:57 PM

Post #17 of 17 (826 views)
Re: 1991 ford f150 won't start Sign In

Smoke machine



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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