gas cap loose but no check engine light????

btw What I *DID* notice was that when the gas cap was loose the ignition would respond like I had a dead battery for the first 3-4 attempts to start the truck. Then it would start. Seems a loose gas cap shuts down the electrical system--even my truck radio clock reset it self to "12:00".---I never did get a "check engine light", though.

df

Sounds like it has to work harder to start with no cap and draws down the battery enough to reset things. New battery or cable maintenance needed is my guess.

Thanks-not sure now that the cap and shutdown are related-...still testing. ...its not that the engine cranks and draws the battery down, it more like there is a relay or something stopping most of the conection with the battery -i.e. there are no headlights or accesories the first minute the key switch it turned, but give it a minute--wait for it--- and then you hear the fuel pump and see the dash lights and gauges come alive. At this point the starter is alive and the truck is "crankable"...

Jeez.... let's get real guys..... equating the gas cap to starter draw is like saying my neighboiurs garage door opener doesn't work when my fridge door is open....

Without a fuel tank pressure sensor, the PCM has no idea if you even have a gas cap....

Instead of chasing things with no understanding of the system, why not spend a few bucks and have a capable shop smoke test the EVAP system?

FWIW, all too often I see DIYers throw hundreds of dollars at a $50 problem... worse yet, along the way they jerry rig God knows how many suppoesed "fixes" that can cost serious money to undo...