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Possible PCM problem


1994Ranger$$$pit

Well-Known Member
Joined
Aug 10, 2011
Messages
159
City
MA.
Vehicle Year
1994
Transmission
Automatic
I have 1994 Ranger 4.0 and have a strange issue with my truck starting. It cranks,has spark but the fuel pump was not running at key on.
Checked fuses and relay, all good. Pulled the bed and changed out the fuel pump. Truck started right away. But, on the 5th try the issue returned and cranking with no start.
Noticed that every time this happened the "CEL" would not illuminate at the first key click position.
Every time the "CEL" would light after the truck sat a while it would start right up.
Seems almost as if when the truck warms up the problem comes back.
I've ordered and received a new PCM from Rock Auto.
I'll be installing it Friday after work. Any info or experience about these types of problems would be greatly appreciated.TIA
 
the check engine light comes on when the ecu is powered up and the engine is not running.

if the check engine light does not come on with the ignition on then the ecu is not getting power

most likely cause is a faulty ecu relay which is very common, its very unlikely the ecu itself is faulty
 
The relay tested good.
I ended up changing out the PCM to a rebuilt and everything seems to be back to normal. Truck is running good and CEL is on at every first click key turn. I'll post if something happens in the next week. Truck is a 94 so old module.
Guessing maybe something in the PCM that transfers power was shot.
 

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