euphoria18_79

Hi to everyone on the forum. I am hoping someone can help me with a problem that i am having. My grandfathers truck worked fine when he parked it in the garage a couple days ago. When he tried to start it, it would not fire. I thought it was the battery since it was cold, but tried again today, and t will turn over, but will not fire. It is a 1993 Ford F150 with a 5.8l ( i think ) V8 in it.
When you turn the ignition, you can hear the hum from underneath, which i believe is the fuel pumps. Sorry, i am deffinately not a mechanic.
So, hoping someone can point me in a direction, where i can look at for a start at least.
Thanks

'89Lariat

Is that the only thing you hear? Does it make a click noise, or crank slowly?

euphoria18_79

it cranks fine, sounds like it wants to start, but just wont. Going to change out all the spark plugs, no idea if that will affect anything, but i am unsure if my granpa has done anything for maintenance.

'89Lariat

It won't be the spark plugs. It could be that you have no spark, and it wouldn't hurt to change them out, however spark plugs don't just all decide to quit working at once. They gradually get gunked up over time.

There are two basic causes for a crank-no-start. You could have no fuel, or you could have no spark. Technically you could have no air and that would have the same effect, but that doesn't really happen under normal conditions.

I think the most likely culprit is your secondary ignition system. Single points of failure are the distributor rotor/cap, and the coil. Check for spark at the end of your plug wires, if you have spark then your problem is elsewhere. If you don't have spark, replace the rotor and cap because they are cheap and probably need replacing anyway. If you still don't have spark, test for primary voltage at the coil (+12v). Assuming you have primary voltage but no spark, replace the coil. If you still have no spark there's probably a relay in your primary that's bad.

Reason I'm not focussing on fuel is that you said you heard the fuel pumps come on. You may want to use a stethoscope or a long screwdriver to listen to the individual tank pumps, and the rail pump. You actually have three pumps (assuming you have dual tanks), one in each tank, and a step-up pump on the frame rail somewhere. Try switching to the other tank, sometimes one pump will fail and the others still work. You can borrow a fuel pressure gauge from Auto Zone or another parts store, then measure the pressure at your fuel rail. I'm guessing it should be around 40-50 PSI but that's actually guessing from other vehicles I've worked on.

If you have normal pressure and spark then you have a weird problem that will require further diagnostics.

ridge903

that said it all!!!!!