72 Primary wiring problems
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Elder User
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From: Anderson Northern Ca
72 Primary wiring problems
Last few weeks truck has been getting harder to start each morning,today it almost did not start but did before battery was used up.Picked up new plugs,rotor,cap and has petronix ignition.Previously swapped to big cap and Mallory coil.When I swapped to the Mallory coil it would not start until I installed their reccomended ballast resistor and mounted the coil in the upright position,still don't know why this had to be done for it to start.So now tonight I put in the new parts and it fired for about 30 seconds then died for good,no spark at plugs.Have about 6.8 volts at the + coil with ignition at run,should be more when the alternator is running.Can any one tell me where to look next,bad coil mabey? Thanks for any imput.
"bowties in the rearview mirror"
"bowties in the rearview mirror"
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From: Virginia
The first thing I would check is the negative side of the coil. Put a testlight or meter on the negative of the coil, and the other side of the meter or testlight on the engine block. When you crank the motor, the meter or the testlight should flicker on and off. If it doesn't, I would suspect your pertronix may have gone south. You can put a set of points and condensor back in if you suspect this is the problem to see if it will run.
If you get it running, your cold weather problem is most likely your wiring to the coil +. You installed the resistor, but I bet you did not hook up the resistor bypass. The factory had this in the harness, but if you can't find it, all you need to do is run a wire from the "i" terminal of the starter relay over to the coil +. What this will do is give a full 12 volts to the coil during starting only. This will make the truck fire better in cold weather.
If you get it running, your cold weather problem is most likely your wiring to the coil +. You installed the resistor, but I bet you did not hook up the resistor bypass. The factory had this in the harness, but if you can't find it, all you need to do is run a wire from the "i" terminal of the starter relay over to the coil +. What this will do is give a full 12 volts to the coil during starting only. This will make the truck fire better in cold weather.
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Elder User
Joined: Nov 1999
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From: Anderson Northern Ca
72 primary wiring problem
Dave,thanks for some very good info.I did not know Ford had the bypass 12 volt start up in the harness.There are a couple of plug ins in the harness near the firewall but they have never been used.I will test light them to see if I can use them as the startup circuit.I will run the test you suggest on Friday to see what went wrong and let you all know what I find,thanks again.
"bowties in the rearview mirror"
"bowties in the rearview mirror"
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Elder User
Joined: Nov 1999
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From: Anderson Northern Ca
Dave,you were right on with with your diagnostics.The Petronics was dead as a door nail,I put the points back in that I saved just for an emergency and it fired right up.I will pick up a new Petronics and install it on Sunday,Merry Christmas One And All.
"bowties in the rearview mirror"
"bowties in the rearview mirror"
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From: Anderson Northern Ca
Well it's Sunday and the new Petronics was installed and guess what-no go-no nuthin.Put points back in and it fires right up.So I get on the internet and find a few articles on the Pertronics Ignition that imply the Petronics does not like the MSD Red coil and that it will unceremoniously burn up a Pertronix ignition.Now I added that MSD Red coil about a year ago when I did a big cap conversion on my 390 and everything ran fine until last week when my truck refused to start.I put that Pertronix module in 1995 and have had no trouble until it quit last week.Why would it kill the new module without even firing off once?I am at my wits end with this electronic nightmare,has anyone else had any similar problems?I have done all the electronic checks and the 12 volts is where it should be when it is suppose to be,anyone else have problems with the MSD and Pertronics?
"bowties in the rearview mirror"
"bowties in the rearview mirror"
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From: Virginia
I don't know what it is, but there are lots of people who hate the pertronix ignition. It seems to be more the chevy guys than the ford guys. I thought maybe it was because the ford dist was up front where it got more cooling air then the chevy. I don't know, but there is one guy that claims he has a 55 gallon drum full of pertronix modules that have burnt up. What does pertronix officially say about this? Are they going to warrenty it? A high output coil will usually draw more amperage. You may find you have reduced points life with that coil too.
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From: Anderson Northern Ca
Barking up the wrong tree
Well I finally figured out what was causing the hard starts in the mornings,the fuel pump and fuel hose are toast.Every time I turned off the engine all the fuel was leaking out of the carb,line and pump and on to the ground as the hose was cracked real good from age.There was always some left in the accelerator pump so when I jacked the throttle it looked like it was getting fuel so I never thought more about it.So as the leak got worse so did the time it took to start in the morning due to the fuel pump sucking more and more air instead of fuel.So now I have an extra petronix for a spare and will reinstall as soon as the points wear out.Hope this adventure in failed electronic diagnosis will help others on to the right trail.On a bright side I did find the cause of a coolant leak in the process of electronic elimination,a loose hose clamp on the back bypass hose at the top of the water pump.
"bowties in the rearview mirror"
"bowties in the rearview mirror"
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