Oops I just posted this over on the main forum, instead of this one. Anyway, here it is, where it belongs....

I have a 1990 F150 with a 302 and 5-speed manual. I replaced the engine about 4 years ago, along with all new electronic components/accessories, etc. I have driven it about 30,000 miles since then, with virtually no problems....till now.

About 3 weeks ago, the engine started dying on me while going down the road. It is happening more often now, to the point where it happens several times each time I drive anywhere.

I noticed that when it dies, the tach drops to zero, even when I am going down the road and the engine is still spinning and tranny is in gear. To me, this might mean that it's an ignition problem.

When it dies, it often comes back on its own after a few seconds. If it does not, then I reach over and shut off the ignition switch and then quickly move the switch back to "run" position and the engine comes back to life. This is with it in gear, mind you, so the engine is still spinning.

It seems to happen whether the engine is hot or cold, running fast or slow, and happens in any gear, or even when idling.

I haven't had time to hook it up to a code reader, as I have been working 60+ hours per week for several weeks. I was hoping someone here might have an idea on a common cause for this.

Thanks.

Matt

 

My guess and it is only a guess, would be a faulty ign/start switch (bolted onto steering column under the dash). It could also be loose/dirty ground wires or loose/dirty connectors at computer relay. Hope this helps.

 

had same problem on my 1990,changed fuel pump relay and eec relay never had a problem after. good luck.

 

Thanks for the responses. I'll take a closer look at the ignition switch, although kind of doubt that's it, because I've tried jiggling the switch when the engine has died, and it doesn't seem to help.

It's only if I turn the switch off then back on that it helps. Seems like something is getting re-set and works again when I do that.

I'll check the wires for dirt and corrosion at the computer relay, and other places too.

Also, regarding the fuel pump relay, if that was bad, would that cause the tach to drop to zero even though the engine is still spinning due to the truck being in gear (manual tranny)? It seems like something electrical is happening, like no spark getting to where it needs to be, including the tach.

Maybe the EEC relay would do that, though.

I'll see if I can get any codes, just haven't had time yet with work the way it is.

 

I think wha Lazy K meant was the actual ignition switch (off white box under the steering column) and not the ignition cylinder where you put your key. If some contacts are getting shot it's possible that it could act up. It's cheap to replace yourself.
The contacts on the cylinder might be getting messed up too if you have a lot of miles on it.Does your "accessory" key location still work?

 

Yes, the "accessory" position does still work. I'll go out and look at the ignition switch box that you are talking about, and if it's that cheap, maybe I'll just go ahead and replace it. Thanks for clearing that up.