Electrical Issues Help
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5th Wheeling
Joined: Apr 2009
Posts: 45
Likes: 0
From: Charlotte NC
Electrical Issues Help
Hi,
I recently got a 86 f150 with 5.0 and FI. I've been going through and checking the electrical to try and get it started. It had no spark, Then it had a weak spark. I replaced the coil and now it has intermittent spark. What is confusing me is this: I put a spark test light to see when it was getting spark. When I have the switch on, not running and not cranking, the light on the tester flickers. Also, when cranking the engine, the tester flashes dim and then 1 very bright on which I assume is that cylinder firing. Then as I started to crank again it lost all spark, then it came back after cranking again. I went through some tests and it showed the ignition module was working, the ground showed ok and the pip signal was there. I hope this isn't too confusing and thank for any help!
I recently got a 86 f150 with 5.0 and FI. I've been going through and checking the electrical to try and get it started. It had no spark, Then it had a weak spark. I replaced the coil and now it has intermittent spark. What is confusing me is this: I put a spark test light to see when it was getting spark. When I have the switch on, not running and not cranking, the light on the tester flickers. Also, when cranking the engine, the tester flashes dim and then 1 very bright on which I assume is that cylinder firing. Then as I started to crank again it lost all spark, then it came back after cranking again. I went through some tests and it showed the ignition module was working, the ground showed ok and the pip signal was there. I hope this isn't too confusing and thank for any help!
Moderator
Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
Go over to the battery. Look at the large negative wire. You should have a smaller black wire attached to the large black wire, and then will go to a single disconnect connector, and then it will disappear into the harness. Check these connections, pull the single connector apart and see if it's corroded. This is a main ground for the computer system and it's prone to corrosion.
Cargo Master
Joined: Mar 2008
Posts: 2,573
Likes: 207
From: Washington
Do you have a voltmeter?
Are you getting 12 volts, or a bright test light, on the coil positive with the key ON, engine not cranking? And also while cranking?
Is the test light just a normal 12 volt bulb? Test the brightness across the battery posts.
If you don't have good supply voltage, run an wire from the battery positive to the coil positive for testing.
I would disconnect the spout connector while testing.
Jim
Are you getting 12 volts, or a bright test light, on the coil positive with the key ON, engine not cranking? And also while cranking?
Is the test light just a normal 12 volt bulb? Test the brightness across the battery posts.
If you don't have good supply voltage, run an wire from the battery positive to the coil positive for testing.
I would disconnect the spout connector while testing.
Jim
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