Fuel Pump relay / PCM issue

[RonD]

There are two fuses for the shift control, a 15a for the dash board panel and a 40a for the motor that does the shifting.
I would check both, because of the EEC fuse being blown.

This is a good resource page
http://www.therangerstation.com/tech_library/EDiagrams/index.htm

Look at the two Shift Control diagrams

 

[pw2buz]

My rough idle problem is related to the problem described above, I believe.

My 3.0 liter V6 Ranger (1993) has had an intermittent rough idle since early 2012. I
have read numerous forum posts on the problem, replaced many parts (IAC
valve, mass airflow sensor, coolant temperature sensor, air charge
temperature sensor, and both oxygen sensors). Some parts were replaced
to help my Ranger pass a smog test.

Some of these replacements seemed to help somewhat. I thought I could
live with the sometimes rough idle, which was unpredictable except for
one instance: driving through the pickup lane of a local McDonalds,
which I visit several times a week on my way to work.

Then I took the truck to a shop, one I trust (Auto Repair Master,
Oakland, CA), for a seemingly unrelated problem: diagnose and fix an
intermittent cranks, no start problem. Before I took the truck in, I
replaced the fuel pump relay (which made no difference), and checked
fuel pump pressure, which was good (KOEO 31 PSI. Started engine:
KOER 36 PSI). The shop kept the truck over a long weekend and reported
an intermittent problem with the PCM relay, and replaced the relay.
Result: the idle is smoother, as is the engine throughout its rev range
(and more power). My Ranger has been running very sweetly since the repair,
9 days ago. Best $124 I have ever paid for a repair!

I learned that the PCM relay signals the fuel pump relay to activate the
fuel pump. I kept the old relay and intend to check it with a volt-ohm
meter, and compare it with the new one.

 

[FF1077]

Thanks bmxr123, your writeup saved me and my 94 Ranger. Followed your instructions and turned out my EEC relay had gone bad.