98 Ford F150 4.2 Liter Engine will not crank keeps blowing fuse #21 (15amp) as soon as I turn the ignition key. Was running fine just stopped to gas up and it wouldn't crank. Jumped the posts on the solenoid and engine started but still will not start with the key. Checked starter@ autozone (ok) replaced solenoid on firewall and ignition switch. Still same results. Any ideas?

Ignition Switch / Starter Fuse keeps blowing. - CarGurus

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CarGurusAug 14, 2010 - Ignition Switch / Starter Fuse keeps blowing. - I own a 2002 Ford Focus, 2.0l SPI engine. 5-speed manual trans. Recently bought from a friend's ...

Well u will need an amp meter that will check out the current thru fuse with nothing on " multi function" besides the motor running and see if it solves your problem and tell us your current reading .

you have a short in that circuit chck your harness for wiring that might be exposed to ground or pinched

Bad earth on starter motor or alternator

i had this problem with my 1999 jeep grand cherokee laredo with the brake lights it kept popping fuses right after the ignition was turned on try putting a higher amp fuse in place of the old one that keeps blowing then check for shorts to the starter and check grounds and wires and also the transmission issue check the fluid and then if the fluid is fine change the transmission filter the filter may have not gotten replaced when the transmission was rebuilt and may be clogged or dirty

No spark or no gas. Are you sure the gas gauge acurrate? When you turn the ignition key from Off to Run, but not all the way to start, listen carefully for the sound of the fuel pump. If you don't hear anything, check the fuse. If the fuse is good the pump may be bad.

Remove a spark plug wire and hold the metal end close to [but not touching!] a metal ground [use a pair of insulated pliers to keep from possibly getting shocked. Have a helper crank the engine. If you see a spark, the ignition is probably ok, although that's not 100% certain, as the timing or dwell angle could still be off.

Good luck!

Hi, if you're talking about fuse "R", it powers most everything on the engine. What you can do is disconnect everything, put a fresh fuse in, and reconnect things one at a time. After reconnecting something, turn the key on to see if the fuse burns. When the fuse burns, the last thing connected has a short. Here are the things that run on fuse R:
EGR solenoid
IAC valve
intake runner solenoid (this one is on the back of the upper manifold)
runner position sensors (only on 3.8 liter engine)
evap purge valve
all 4 oxygen sensors
MAF sensor
all fuel injectors
cam position sensor

Is this fuse 11--10 amp under hood fuse block?
If so, I'd unplug your ignition module. With dis ignition, the coil pack sits on ignition module. The end of ignition module that has two electrical connectors, one is a two wire connector, wire colors pink and black, disconnect it, see if fuse still blows? If it still blows and we're talking about the same fuse, at least you know what isn't causing it to blow. I'm trying to make sure we're on the same page about the fuse, according to my wiring diagram?

This could be caused by either a faulty Crank Shaft Position Sensor or the anti-theft system. Try put key in, turn to ON position for EXACTLY 10 minutes, As SOON as anti-theft light shuts off or stops flashing, then IMMEDIATELY start the engine.

Could be the ignition switch. When you crank the engine, the ignition coil gets a voltage source that is different than when the car runs.This would give you the symptom you describe.