Weak spark? plz help
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7th Gear
Joined: Dec 2023
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Weak spark? plz help
Hello, I have a 94 f-150 5.7 that has been sitting for over a year, deciding to fix it. i check for spark which it didnt have, replaced the ignition module, has spark, very weak still not starting, i said **** it and purchased a new coil, wires, and a distributor, only for the spark to still be "weak"??? using a spark tester i noticed light that should be bright is pretty damn dull i also noticed after starting it multiple times the ignition module gets hotter then hell... Something i found the most weird!! when i leave key on and NOT start i can put a screwdriver to the coil and it will still make that zap and you can see current going to my damn screwdriver, but when i put a test light off of ground of battery in to the yellow control wire of the ignition coil then put the screwdriver back on.... no zaps. im concluding its a short but if has anybody experienced this painful dilemma or close to and can give me any advice i would appreciate it so much thank you so much.
Last edited by thepipman; Dec 28, 2023 at 09:01 PM.
Hotshot
Joined: Jul 2020
Posts: 10,359
Likes: 2,594
From: Near Salt Lake City
The processor may be at fault, specifically the timing advance circuits in the processor
Try disconnecting the spout plug and starting / running it
The key on power to the coil is good right? And lights the test light?
The other side of the coil (negative side) test light blinks while cranking in run or start? Indicating a working stator in the distributor?
Check those and report back if needed
Leaving the key on will sure heat up the coil and module (normal) do not overdo it when testing and give it a rest to cool down
Try disconnecting the spout plug and starting / running it
The key on power to the coil is good right? And lights the test light?
The other side of the coil (negative side) test light blinks while cranking in run or start? Indicating a working stator in the distributor?
Check those and report back if needed
Leaving the key on will sure heat up the coil and module (normal) do not overdo it when testing and give it a rest to cool down
Thread Starter
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7th Gear
Joined: Dec 2023
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So grounding my test light on the coil. It does not light up. And it also doesn’t light when cranking… BUT. I can hear and see the spark literally coming from the coil can see the damn electrons moving from my coil to test light. But no light up from test light! Also if I go to the yellow wire under it. My test light lights up. And I was saying in my original post that it will be sparking with just ignition on. When I put my test light on the yellow wire, it stops sparking with ignition on. I know it’s getting control from the ignition module, because it flickers when cranking.and the red wire with green stripes also lights on the test light so that’s good.
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7th Gear
Joined: Dec 2023
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It was the spout plug thank you bro, i was swapping new stuff with old just to see if it was anything else, and the new distributor it runs alot better as well. will order a new spout read a wiring diagram and a little about it pretty cool stuff thank you so much
Cargo Master
Joined: Jan 2004
Posts: 3,118
Likes: 149
From: South Dakota
Don't count your blessings yet. Removing the spout connector takes the computer out of the equation atleast for the ignition. You may have a bad computer.
4wd Low
Joined: May 2023
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when you say spout are you referring to the plug for the tfi? Have an 89 460 with no spark. Trying to solve issue. New dizzy cap rotor tfi and coil still no spark from coil
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Cargo Master
Joined: Jan 2004
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From: South Dakota
If you do, pull the spout and check again for spark when cranking the engine.
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Hotshot
Joined: Jul 2020
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From: Near Salt Lake City
thepipman with that spout out set the timing to 10 degrees hot engine
Then see if it will stay running and restart with it plugged back in
Like 88n94 said
Removing that spout plug takes the processor out of the timing equation (so you can set base time)
When the processor flips out you can remove the spout and run it to verify your processor is malfunctioning
You do the same Slumdog, remove the spout plug and retry it. Yes, it is the plug by the TFI module
Then see if it will stay running and restart with it plugged back in
Like 88n94 said
Removing that spout plug takes the processor out of the timing equation (so you can set base time)
When the processor flips out you can remove the spout and run it to verify your processor is malfunctioning
You do the same Slumdog, remove the spout plug and retry it. Yes, it is the plug by the TFI module
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7th Gear
Joined: Dec 2023
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Hey question I did try using a jumper wire for the spout harness and died immediately like the new spout is plugged in. Would this indicate a faulty ecu or would there be anything to check for thank you!
Cargo Master
Joined: Jan 2004
Posts: 3,118
Likes: 149
From: South Dakota
Seems like a bad ecu(computer) but I hope someone else comments on other possibilities.
Cargo Master
Joined: Jan 2004
Posts: 3,118
Likes: 149
From: South Dakota
Did you put in a new distributor or just a distributor cap? Do you have power up to the coil through one of the small wires that hook onto the coil with the ignition switch turned on?
Hotshot
Joined: Jul 2020
Posts: 10,359
Likes: 2,594
From: Near Salt Lake City
I would try another processor in it or at least examine the caps in yours
My caps for instance were just barely leaking but caused a bad miss and hard trans shifting
Sure, there other hoops to jump through like intermittent or wiggle test diagnosis with a Star tester
Like the above post, power to the coil has been checked numerous times and is okay
If you've ever done any of that intermittent wiggle testing diagnosis, it is a good way to waste some time but learn a few things
If you have a new Ford module and stator in it, and the problem persists (will not start without the spout removed) replace the processor
My caps for instance were just barely leaking but caused a bad miss and hard trans shifting
Sure, there other hoops to jump through like intermittent or wiggle test diagnosis with a Star tester
Like the above post, power to the coil has been checked numerous times and is okay
If you've ever done any of that intermittent wiggle testing diagnosis, it is a good way to waste some time but learn a few things
If you have a new Ford module and stator in it, and the problem persists (will not start without the spout removed) replace the processor
Thread Starter
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7th Gear
Joined: Dec 2023
Posts: 7
Likes: 0
Hey question I did try using a jumper wire for the spout harness and died immediately like the new spout is plugged in. Would this indicate a faulty ecu or would there be anything to check for thank you!
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