Ignition problems
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New User
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Ignition problems
I am having some problems getting my truck to fire . I have a 76 F-150 and it has a 390 in it I originally thought it could be the cap and rotor were bad so I changed those, I also changed the ignition coil because when I had unplugged my coil wire and grounded it to my valve cover bolt I had no spark.I came ot this conclusion by seeing if I was getting spark to the plugs, which I had just a tiny one and that was it , I checked and my distributor rotor works like it should. I then thought maybe my ignition module is bad , well I took it in and had them check it at the parts store and it checked fine two different times that i took it in. I have exausted my knowledge of how it should fire . I also checked I am getting plenty of fuel to carburator. the timing chain is not broke either
Cargo Master
Joined: Dec 2006
Posts: 2,511
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From: hinckley ohio
could try to hot wire it to see if it will run then go from there. run a wire from positive side of coil to the positive on battery then try to star with the key if it starts probably got a bad wire somewhere.If it doesn't them its something mechanical.Also if it starts you it will stay runing till you deconnect wire from batt. to coil
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Let me clear some things up for people:
This will not work. The coil fires by the ignition module constantly grounding and ungrounding the coil. If you connect the coil to the valve cover bolt, it will be constantly grounded, and never fire.
Do not do this, as the coil is only rated for 9 volts.
Try this test: Connect a test light from the TACH side of the coil (negative side) and ground it on the engine block. Use the key to crank the engine, and the light should blink. Post back with results.
Try this test: Connect a test light from the TACH side of the coil (negative side) and ground it on the engine block. Use the key to crank the engine, and the light should blink. Post back with results.
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OK, so I connected the test light to the engine block and had my buddy turn the key . I had power when this happened that is why I am confused I have power to the coil which in turn should give me spark, i am just curious if the ignition module tests good but is not working correctly, I just did not want to start replacing parts that I did not need to. I appreciate your insight on this do you happen to have any more suggestions
New User
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you should also check to make shure your engine is grounded good with a ground strap or the negative battery cable my be hooked to engine
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MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
OK, so I connected the test light to the engine block and had my buddy turn the key . I had power when this happened that is why I am confused I have power to the coil which in turn should give me spark, i am just curious if the ignition module tests good but is not working correctly, I just did not want to start replacing parts that I did not need to. I appreciate your insight on this do you happen to have any more suggestions
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I had tested the negative from my coil and my test light does not even come on, I gronded it to the block. the light to the positive side stays contant, but nothing from the negative when turning the engine over.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Do you have a multimeter? Next you need to check the resistance of the pickup in the distributor. Unplug the distributor and measure the resistance between the orange and purple wires - use the side of the plug that is coming off the distributor, not the side that comes from the harness.
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so I went to test the orange and purple wires and decided to follow the wires all the way to the pickup, well after removing the distributor cap i looked at the orange wire, it was not even attatched to the magnetic pickup, so next question? I see that there is a small metal clip and a grounding screw inside the distributor , but I did not figure out how to remove the magnetic pickup so that I can replace it.I guess I am afraid of breaking something inside there and having to replace the whole distributor, Any pointers??
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
You don't need a whole new distributor; that's a waste of money. You probably didn't even need a new coil; this is why it pays to test first, spend money later.
Okay, so it looks like we're very close to solving the problem. The veined aramature has to come off of the distributor shaft before the pickup can be removed. The pickup comes as one unit comprising of the baseplate and a pivoting breakerplate (a term leftover from points style ignition) with the actual Hall Effect sensor mounted on the pivoting breaker plate. The assembly looks like the following:
Okay, so it looks like we're very close to solving the problem. The veined aramature has to come off of the distributor shaft before the pickup can be removed. The pickup comes as one unit comprising of the baseplate and a pivoting breakerplate (a term leftover from points style ignition) with the actual Hall Effect sensor mounted on the pivoting breaker plate. The assembly looks like the following:
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Just so I am understanding you, I will need to remove my distributor to accomplish this task? If this is what I need to do I am fine with doing it ,but I have read in my chiltons manual to make sure not to remove the oil pump driveshaft with it is there a way of preventing this?