Why Isn't The Check Engine Light Coming On?

I just had a customer drop off their 2001 Chevy S10 pickup with a complaint of a gas odor coming from the vehicle. They said this had been happening for about a month. Before bringing it to me they brought to another shop and they were told that the top of gas tank was rusted out.

When they arrived, I took a flashlight and thru the rear wheelwell I could see that the gas tank was made of plastic. And at the same I could see that half the fuel pump wasn’t completely seated down to the top of the gas tank and there was gas all over the top of the fuel pump and on top of the gas tank.

If the gas tank is leaking this bad, why hasn’t the Check Engine light come on with an EVAP code? This is an OBII vehicle. And if you leave the gas cap loose the Check Engine light comes on.

And I did check to see if the Check Engine light worked with the ignition in the run position. And it does.


What’s the status of the EVAP readiness monitor? Any other monitors not ready or DTCs stored? This uses FTP sensor in top of tank module, right?

Like I said, they just dropped it off. I’ve hadn’t had a chance to hook the scanner up to check the readiness monitors.

And with a leaking gas tank, I’m not pulling it into the shop to let it sit overnight.


I had a similar one once, poor seal around flange. It would leak sloshing gas but the vacuum when the purge valve opened was just enough to seal it temporarily.