Ignition problems
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Ignition problems
I just swapped a 351w for the 300 in my '86 f150. Now I'm wondering if I can just get a new distributer for the same year truck and just plug it in, or if I have to bypass the computer and get some sort of ignition modual, or what.
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if it was my truck, i would go with the duraspark 2 distributor and control module. this has vacuum advance.
search this site for duraspark 2 conversions.
if your 300 distrib did not have a vacuum hose going to a vacuum advance can you will have to do the conversion, from what i have read it is not hard to do
gt
search this site for duraspark 2 conversions.
if your 300 distrib did not have a vacuum hose going to a vacuum advance can you will have to do the conversion, from what i have read it is not hard to do
gt
Cargo Master
Joined: Mar 2008
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From: Washington
I have an 86 F150 with the 300 and it has the needed plug on the left inner fender well to plug in the duraspark module. You will also need to use a round coil with the vac advance distributor. The system currently will combine 3 hot wires to feed the coil and other items. You will need to drop back to just the one wire (the fat one firewall side) in the 4 wire plug on the left inner fender. This is a resistor wire to drop the voltage to the coil.
There are 3 plugs on the inner fender, the one with 2 wires will power the DS2 module; the one with 4 wires will power the coil positive, oil press, water temp with one extra hot wire; the third plug will have 1 or 2 green wires and is the feed to the tach in the instrument cluster.
I have complete removed my computer and all the wiring harness that went with it and I would recommend you do the same as you don’t need it after you switch to the DS2 ignition. Also the 86 F150 with the inline 6 did originally have the TFI-IV system with the module attached to the distributor and no vac advance. The computer controlled the timing.
The switch to DS2 is very easy as the harness just plugs into the different components. Look on ebay for the harness and module. I would buy a new or overhauled Dissy with vac advance and not mess with a used one.
Jim
There are 3 plugs on the inner fender, the one with 2 wires will power the DS2 module; the one with 4 wires will power the coil positive, oil press, water temp with one extra hot wire; the third plug will have 1 or 2 green wires and is the feed to the tach in the instrument cluster.
I have complete removed my computer and all the wiring harness that went with it and I would recommend you do the same as you don’t need it after you switch to the DS2 ignition. Also the 86 F150 with the inline 6 did originally have the TFI-IV system with the module attached to the distributor and no vac advance. The computer controlled the timing.
The switch to DS2 is very easy as the harness just plugs into the different components. Look on ebay for the harness and module. I would buy a new or overhauled Dissy with vac advance and not mess with a used one.
Jim
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From: Virginia
The modules go by the color grommet where the wires come out. If it's a blue grommet module, then it's the one you want. I looked up this car on Online Auto Parts and Auto Accessories Store at PartsAmerica.com and they had several different engine configurations for a mustang 5.0 that year, so be careful what you are buying. A module at the junkyard shouldn't cost too much.
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I got the module and harness and everything, and plugged it all in.
Now I'm getting spark, but if the power to the motor is on and the motor is not running, the tach jumps all around and the distributor crackles. also, the coil gets hot. I can't figure out what is going on.
Now I'm getting spark, but if the power to the motor is on and the motor is not running, the tach jumps all around and the distributor crackles. also, the coil gets hot. I can't figure out what is going on.
Cargo Master
Joined: Mar 2008
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From: Washington
Are you using a round coil or a square one? When the truck is running what is the voltage at the battery and the coil positive terminal? The coil voltage on the + terminal should be lower then battery voltage when it is running if the resistor wire is dropping the voltage like it is suppose to. If the round coil is getting battery voltage it will get hot as it needs less voltage.
With the key on and the engine not running there should be the same voltage (battery voltage) on the coil neg. and pos. terminal as there is no current flow though the coil.
Where did you get the module? Is it new? It sounds like something is causing the coil negative to ground which would make it spark.
Connect a test light or voltmeter to the negative side of the coil and turn the key to the “on position” but don’t start the truck. The light should stay on steady. If it flashes disconnect the 4 wire plug on the DS2 module to see if it stops flashing. Or then try disconnecting the 3 wire plug on the dissy after reconnecting the module plug to see it that is the trouble.
It is either the dissy or the DS2 module that could be causing the coil to spark and get hot. Have you disconnected the computer which is located above the gas peddle? Are there 2 systems trying to control the spark at the same time?
Sorry, but more questions than answers.
With the key on and the engine not running there should be the same voltage (battery voltage) on the coil neg. and pos. terminal as there is no current flow though the coil.
Where did you get the module? Is it new? It sounds like something is causing the coil negative to ground which would make it spark.
Connect a test light or voltmeter to the negative side of the coil and turn the key to the “on position” but don’t start the truck. The light should stay on steady. If it flashes disconnect the 4 wire plug on the DS2 module to see if it stops flashing. Or then try disconnecting the 3 wire plug on the dissy after reconnecting the module plug to see it that is the trouble.
It is either the dissy or the DS2 module that could be causing the coil to spark and get hot. Have you disconnected the computer which is located above the gas peddle? Are there 2 systems trying to control the spark at the same time?
Sorry, but more questions than answers.
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I'm using a round coil. I ended up getting a new module and distributor from o'reillys. I'll run the tests you suggested in the morning, but in the mean time, what is the purpose of the little cylinder that is wired to most coils? I don't have one. Could that be causing my problems? Also, when you said to "drop back" to just the resistor wire in the four wire plug, you did mean to cut the others, right?
Cargo Master
Joined: Mar 2008
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From: Washington
The little round cylinder connected to the coil positive is a capacitor. I don’t have one on my truck and it would not cause the problems you are having.
Drop back, means just one source to power the coil, or cut/remove the extra wires. Removing the extra wires will give a lower voltage at the coil with the engine running as only the resistor wire will be powering the coil.
good luck
Drop back, means just one source to power the coil, or cut/remove the extra wires. Removing the extra wires will give a lower voltage at the coil with the engine running as only the resistor wire will be powering the coil.
good luck
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Wait, wait wait...... my 86 has the ignition module on its distributor and a square coil, exactly like the 87-93 mustangs. Now, I'm assuming yours had the same thing so why not get a mid 90's f150 351 dist that has the module on it, and not the fender, then plug your original harness to it and go? That's what I'm going to do with my swap nextmonth. The computer on your 86 does NOTHING to control spark from the ignition module. I know this because I removed the computer, emissions, and unplugged all the sensors, IAC, etc from the carbed 300 and it runs great. This will eliminate the need for a vacuum advance dist altogether.
