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jrloar, ASE Master Cert
Category: Car
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Experience:  ASE Master Certification
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Ford F-150 5.8L 125K miles: After sitting idle for approx

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After sitting idle for approx 3 weeks, about 3 weeks ago a 1995 Ford 5.8L V8 with approx. 125000 miles failed to start. Preliminary analysis indicated an ignition problem. This was a new experience for this truck. It always started easily in the past. Since the ignition parts were all original equipment, is was decided to replace the distributor with a new (rebuilt) unit, install a new coil and a new modulator (on this vehicle the modulator is mounted on the driver's side front fender). The repair was successful and the engine started. Last week, after sitting idle since the last repair, the truck again failed to start. Again, it was an ignition problem. The parts house checked the modulator and found it was faulty. Also, they weren't sure about the coil. So, we installed a new modulator and coil. When the starter engaged, the engine wanted to (almost did) start but, then nothing. The ignition was dead. When not in use, the battery is maintained with a trickle charger and when this most recent incident occurred was checked and found to be producing 13.02 Volts with 728 CCA at 68 Deg. F. So, what did we miss? Have a good day.
Can I ask why you say it is the ignition and not a fuel problem? Have you tried spraying fuel in the intake while trying to start? I just have to ask simple questions to eliminate them...
Customer: replied 4 years ago.

Yes, tried "Quick Start" and nothing. Not even a peep. Also, when the ignition switch is on, we have power to the primary circuit of the coil, both in and out to ground. Lastly, there is a small spark when we reconnect the battery ground cable. Have a good day.

Have you actually checked your voltages at the coil? Can you run a hot wire directly to the coil from the battery and see if that makes a difference? It sounds to me like you have got some faulty replacement parts. This is one year before they were truly computer controller. You basically have a system that is supplied a power it should work on its own. The only possibility I can think of if it is a vehicle problem is that the rectifier is bad and you have AC voltage on the system and it is burning up you electronics... I have seen new parts be bad. An example. I had a coil pack go bad on my VW and went to the parts store to get a replacement, replaced it in the parking lot and before I made it home it went bad. I went back and got another and have not had a problem since and that was 3 months ago.
Customer: replied 4 years ago.

Yes, we can hot wire the coil by removing the coil connector and running a positive lead from the battery with the negative side connected to ground. Is this what you mean? The coil was supposedly checked by the supply house (as was the modulator) to make sure they were in spec. When we turned the ignition switch on, both ends of the coil's primary circuit powered the test light brightly which implied no issue.


When we last installed the newest coil, newest modulator and tried to start the engine, it almost started and then nothing. Our impression was that the modulatory had been cooked. Do you have any simple way(s) of checking &/or bypassing the modulator to see if that helps?

Are you referring to the rectifier in the alternator? If that part was faulty wouldn't it have a negative effect on the battery, or the lighting or something else? How can we check the rectifier?


Your comments seem to imply that there is no other control, electronic or electrical device which could have any effect on the ignition system; meaning, if the distributor, coil and modulator are within spec. the system should work. No further discussion needed. Correct?

the positive wire to coil is correct. It is almost imposable to "cook" ignition components like you are referring to. Yes the alternator. You would check that with an AC voltmeter just like checking DC voltage. The ignition system only has the coil, electronic controls, and distributer. Then cap wires and plugs. Simple system...
Customer: replied 4 years ago.

Per your instructions, we hot wired the coil. After removing the connector, we attached the positive to positive & negative to ground. Nothing occurred other than the engine turning over. What do you think?


When should we expect a response?

Customer: replied 4 years ago.

Per your instructions, we hot wired the coil but, nothing. What do you think?

You only hook a positive. The ground is controlled by the distributer. This is how it sparks. So the only wire you can hook up it a direct positive. Try doing it that way...
Customer: replied 4 years ago.

Thanks for your interest. I tried the "Hot Wire" procedure you suggested and still nothing.


When we started this conversation, I noted having previously replaced the truck's modulator, coil and distributor (including a new cap, rotor and secondary wire) at which time the truck started as normal. Approx. 3 weeks later after sitting idle for that time, the engine again wouldn't start.


After trying your most recent "Hot Wire" coil suggestion, I installed another rebuilt distributor (with the same new cap, rotor and secondary wire). The engine started immediately as if nothing had ever happened. It will be interesting to see if history repeats itself.


Just between you and me, why would a distributor fail from inactivity? During the time the truck was idle, the only external input was a 15 volt trickle charger installed to keep the battery from being consumed by all of the electrical loads generally found in modern vehicles. What am I missing?


Have a good day.

There is no reason other than the fact that a new item can be bad. I gave you my coil pack issue so it happens. I just hope that was the problem. I don't see what else it could have been...
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