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91 F150 engine ignition system failure
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Danmarion
New User
Feb 15, 2016, 2:46 PM
Post #1 of 6
(1913 views)
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91 F150 engine ignition system failure
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Hi everyone, this is my first time posting to one of these forums but I really need some help this time. My 91 F150 is down for the count, and the repairs are running me in circles.
Drove it to work last Thursday and everything was fine, when I went to take off at the end of the day, it wouldn't start. No spark. After making sure all of the cables and plugs were good, I pulled the tfi and had it tested. The tfi failed so I replaced it, with no effect on the truck. Still won't start. So I puller the new tfi and had it re tested, failed as well, so I got another that tested good and installed it. I also checked the resistance on the coil and it was almost 0 so I replaced it also. The truck still wouldn't start.
My dad suggested testing the pip stator sensor, and the voltage supply was below the range indicated in the book. Since my rotor and cap were getting a bit worn anyhow, I just replaced the whole distributor, timed it, and the truck started. Ran like a champ. For about 15 miles.
It died on me in traffic the same night, same symptoms. Again, no spark. After making sure that all of the cables and wires were tight, I went straight to the pip stator sensor check, and this time it reads high of the range in the book.
On to my question. I am no mechanic, and am doing all of this out of the book and with help over the phone. Is there something else going on here to cause the system to fail again like that? Do I need to pull this *%$# distributor again? What am I missing?
The specs:
1991 Ford F150 2wd
5.8l 351 engine
Getting up to around 180k miles
(This post was edited by Danmarion on Feb 15, 2016, 2:47 PM)
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Hammer Time
Ultimate Carjunky
/ Moderator
Feb 15, 2016, 3:58 PM
Post #2 of 6
(1895 views)
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Re: 91 F150 engine ignition system failure
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) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.
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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.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 15, 2016, 4:14 PM
Post #3 of 6
(1889 views)
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Re: 91 F150 engine ignition system failure
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? No spark: Without testing a thing the most common reason is the module on side of distributor but at age also connections to it or other totally. New distributors don't always come with that module which my experience either are good or not no intermittent unless poor connections. Same with EEC relay for Fords can get wet on some and be intermittent. Testing inconclusive with intermittent items sometimes the "wiggle" test of connections can tell you which?
If old module re-used and failed again it's a guess only that it's connection is messed up right there,
T
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Discretesignals
Ultimate Carjunky
/ Moderator
Feb 15, 2016, 4:58 PM
Post #4 of 6
(1883 views)
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Re: 91 F150 engine ignition system failure
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If you remove the SPOUT plug, will it start?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 15, 2016, 10:18 PM
Post #5 of 6
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Re: 91 F150 engine ignition system failure
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Interesting? Should set timing with it removed or may be missing but run at least. No time right now but OP those look like this if it shows or Google it for images..............
Pic was there ^^^^
It defeats auto timing on Fords - all engines possible for this vehicle,
T
(This post was edited by Tom Greenleaf on Feb 15, 2016, 11:16 PM)
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Discretesignals
Ultimate Carjunky
/ Moderator
Feb 22, 2016, 7:30 PM
Post #6 of 6
(1800 views)
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Re: 91 F150 engine ignition system failure
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It will actually make the ignition control module run in base mode. Sometimes a PIP signal that has low amplitude will cause the PCM to not send a SPOUT signal to the ignition control module to fire the coil, but the PCM will fire injectors. When you remove the SPOUT plug the module goes into base mode and the module fires the ignition coil on its own, which will actually make the engine start.
I've run into this twice on TFI systems so far and it was due to a weak PIP signal from the distributor hall sensor. Also, if you have a power issue to the ignition module, that can cause a weak PIP signal from the hall sensor.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Feb 22, 2016, 7:56 PM)
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