Hey guys new to this forum need some help I have a 93 ranger xlt v6 4.0,auto, extended cab..Turns over but wont start these are some the symptoms turn the key on ,no check engine lite ,fuel pump does not come on,no spark.. was told probably the PCM .I have replace key switch and ignition switch checked fuses and relays and grounds,fuel pump will run if i run power to it but I only have power to one side of junction box under hood was told the other side gets power when key is on my question is what part makes this happen? Thanks Lee.

 

Welcome to FTE.

Check the computer power relay in the under hood power distribution box, or swap it out for a known good like relay, not needed to run the engine, say the A/C power relay & see how it goes.

 

I have tried that I still have no CEL when I turn the key to the on position and fuel pump does not come on to prime .odd thing is the radio is doing strange things to channel wont change bad reception use to work fine before truck broke down don't know if this has anything to do with computer I am probably going to just buy a new pcm to see if that is the fix thanks for the help.Lee

 

Hold On, you haven't completed a proper trouble shoot yet. With the dash warning lights not lighting up at KOEO for their self check, it suggests the computer/ecm isn't getting battery voltage, so maybe consider beginning with checking all of your battery connections & make sure its charge is up to snuff & then perform a load test by turning on all of the lights & the heater blower on High speed & maybe push the cigar lighter in, then measure for battery voltage across the battery posts, then across the battery cable clamps, then from the battery B+ post to the engine & body, to see if you have good cable clamp to battery post & ground connections to the engine & body. If you have a bad ground connection, voltage drop across the connection, from a loose connection, corrosion, rust, broken wire strands, ect, it can cause all kinds of mischief.

Once you know the All grounds are ok, check the B+ voltage under load at the under hood power distribution box lug, then B+ voltage going to the computer, to make sure its getting B+ without voltage drop. There is a Multimeter voltage drop testing link in the last post in the Battery Tutorial thread atop this forums thread listing page.
If all that checks out ok, perform a wiggle & thump test on the battery cables, under hood power distribution box, computer power relay & the ecm/computer firewall electrical connector & if no joy, pull the glove box & thump the ecm/computer to see if it'll wake up.

If you confirm that the ecm/computer is getting B+ at its firewall connector but isn't waking up at KOEO to light up the dash warning lights for their self test, Then suspect the computer. If you have a friend with a like vehicle, maybe you could try swapping the ecm & see if things will go right. Let us know what you find.