I have a 1997 Ford F150 with a new 4.2L V6. New fuel filter & new battery. About one in every 20 attempts the truck will crank over great, but will not fire (start).
I thought fuel pump. however once it starts, it never fails. I took it too mechanic & of course they could not recreate. But they replaced fuel filter (again) & said fuel pressure again.
So, that leaves me with possibility of ignition not firing. But i live alone, & when it does not start, i cannot go out, pull wire & hold to block to see if i am getting spark.
So, is there a way to check such an intermittant issue? can i just buy some parts (Relays, coil?) that i can swap to verify? Or check?
If I am getting fuel, (or so it seems,) and starter is cranking strong, what would intermitantly prevent starting?
Without knowing what’s missing (spark, fuel, etc.) this could possibly turn into a real guessing game.
What I would do first is have the truck scanned for codes. AutoZone, Checkers, etc. will do this for you free. While no means definitive this at least opens the possibility of a code surfacing that could point to an intermittent electrical fault in the ignition or fuel pump controls.
Making a huge wild guess here, I could theorize that the electrical part of the ignition switch is failing. This kind of failure is not day to day common but it’s also not terribly rare.
I did not look up a wiring diagram for your truck but a number of Fords run their cabin blower motors directly through the ignition switch. An aged and worn blower draws more current than a new one and it’s possible over time for the lowly blower motor to take out the ignition switch.
Sometimes one can look at the plastic on the switch closely and the housing may be bubbled or distorted due to heat which was created over time by the blower motor and a number of other items that were running in conjunction with the blower.
There was this rumor that a bad temp sensor could cause that. Most people never change their plugs or ignition wires either. When I see “new fuel filter and battery” I get these warning signals that say Problem, Problem, ongoing. In cool weather, some of the Fords of that era needed block heaters. If you have only one ignition coil, it could be cheap. Don’t get it at NAPA.