PDA

View Full Version : Replaced about everything


mositso
07-30-2003, 09:17 PM
I have a 1979 F250 with a 460. I am running a Billet Distributor part number 8580 and a MSD 6AL and a MSD 2 Blaster Coil. I started having problems a month ago and have not figured the problem out. I have replaced the MSD unit, cap, rotor, coil, wires, plugs(copper as i was told by MSD). I have also replaced the solinoid, and ignition switch. The problem I am having is I lose spark when driving or idling, 5 minutes or 30 minutes. It generally happens quickly on a hot day and rarely happens on a cold day. The box is on the fender well and the coil is mounted ( to the best of abiltiy) upright and at least four inches from block behind the fan. All the wires have been rerouted. The engine at first use to just die like I turned off the key. But after changing just about everything it now sputters alittle then dies.
Test I have performed after changing everything.
1) checked for voltage to the unit - good 12v
2) shorted the magnetic pickup - no spark when problem occurs
3) check the carburetor for gas - gas spurts
4) checked the distributer for resisitence - it is good 646 ohms(checked when cool)
5) checked the wires for resistence - bought helicore wires

This last episode I drove the vehicle to work 8miles at 65mph in 69 degree weather with no problems. Then in the afternoon drove 1 mile in 89 degree weather and cutout. Then took out the timing gun to test for spark, which there was none. Then thirty minutes later I tried and with timing gun on, and the spark was weak and there was very little. The engine sounded like a four cylinder, nothing like the 460 it should be. Stopped the engine and waited another ten then started. The engine sounded better. So I continued till I got 100 feet from home and it quit again. I am a witts end. Help please.
Would testing the distributer at failure provide any answers?

:( :( :( I want my 460 to live again.

msdtech2
07-31-2003, 08:31 AM
The problem that you are experiencing is a magnetic pick up in the distributor, when the pick up gets hot, it will create an open and will shut down the engine, just like shutting the key off. Then the pick up cools off, it will start back up like if nothing was wrong. The best way to diagnosis is to test the pick up with the ohmmeter as soon as the engines shuts down, if you have an open circuit, this will indicate a bad pick up.
The only thing that kind of bothers me is that when you mentioned that you did the spark test, that it did not spark, make sure that you are shorting the violet and green going into the MSD Unit and not the mag pick up on the distributor, and also that the key is in the "ON" position and 12 volts to both the heavy and small red.
Let me know.
Thanks,
msdtech2

mositso
07-31-2003, 01:48 PM
Thanks MSDTECH2 I will test it the next time it happens. If the magnetic pickup gets hot does this mean the distributer is bad or do I just need to change the pickup. Does MSD supply a new pickup or is there another manufacture that is compatible and readily available. OR is there a way to shield the distributer from the heat?

msdtech2
07-31-2003, 04:57 PM
If the pick up is bad, it doesn't mean that the distributor is bad, the pick up itself can be replaced it is a PN 84661 and can be replaced separately. It is also the same pick up as a Ford Duraspark distributor, the only thing is that the Ford pick up has an extra wire which is a ground and does not have to be used. It will still have a violet and orange which is the same as the MSD pick up. Although I would recommend replacing with a MSD pick up, because there is a magnet that goes with the pick up and if it is not placed properly it could run erratic. The MSD pick up will come with the instructions on how to install the magnet and pick up.
Thanks,
msdtech2

mositso
08-01-2003, 09:01 AM
Well the truck died on me again. It died on me in 60 degree weather. I tested the heavy red gauge and it read 11.8 and the small gauge red wire was 11.7. The distributer was 728 ohms. The battery read 11.8 so I think my gauge is alittle off. The dash mounted volt meter read 12+. I did the magnetic pickup test, shorting the green and purple, but there was no spark from the coil. I tested the leads to the coil, with the ignition switch on, and there was zero voltage between the positve and negative leads. Even when cranking the engine there was no voltage.

msdtech2
08-01-2003, 09:38 AM
Cool, now we are finding out where the problem could be, the one thing is that you are not going to see voltage at the coil positive. The voltage that is supplied is 450 volts, but it is a pulsating voltage, so a standard voltmeter will not be able to pick it up. The best test is what you were doing with the violet and green. If there was no spark when shorting these 2 together, then use a different coil, just any good known coil and redo the test, if you get a spark then the problem will be the coil, if you still do not have spark then the problem is the MSD Unit.
Let me know.
Thanks,
msdtech2

mositso
08-01-2003, 03:28 PM
other than placing another coil, because the only coil I can get a hold of is one off an 82 thunderbird, in place of the MSD blaster 2. Can I test the resistance in the coil, and can you give me the specifications on it. I just bought a Coil a month of go can it really go bad this fast. Can a splice in the wiring for the coil be a cause for the problem if it is lying on the block. If it is the Unit How should I proceed in testing it. To verify the problem. The unit is less than a month old.

msdtech2
08-04-2003, 09:07 AM
The resistance checks on the coil are .7 ohms on primary, the secondary is 4,700 ohms. The splice in the wiring can only be a problem is it is loose or if it is arcing to ground, which could be possible since the orange wire carries 460 volts to the coil. The testing of the unit is by shorting the violet and green together, just like it explains in the troubleshooting section of the instructions. Or you can go to our website and print out the test that explains testing for spark. This is the only way to verify where the problem is. Keep in mind that this test has to be done with the engine does not want to start.
msdtech2

mositso
08-14-2003, 06:55 PM
I tried the old ford coil and it did not spark. So I checked and replace the second half to the coil wiring(orange and black). The truck started briefly and died. So i checked the wiring to the ignition switch and to the battery. I extended the battery wiring to the battery, no longer to a 12 volt source and the frame. I also decided to change the splice to the ignition switch. After working on the wiring the truck has not died out Again. I believe it may have been the 12 volt source. After fiddling with the wire to this lead the truck started, which propted me to change it. The 460 runs again. :) :) :) Thanks you msdtech2

msdtech1
08-15-2003, 06:18 PM
Your welcome.