Factory installed natural gas system on f150

electrical-wiring

#1

Need some direction here. I just bought a 1995 F150 with. 300ci straight 6 with automatic trans. It was formerly a fleet truck with the Texas Highway Department. It is a bi-fuel vehicle and can be switched over to run on either gasoline or cng.Not sure about the status of the cng system. I have only ran it on gasoline. The cng system was factory installed, not aftermarket. I was told it had been disabled and could only run on gasoline. The truck runs and drives great BUT when it gets up to operating temp and you turn the air conditioner OFF, the truck stops running. Two of the relays in the fuse box that is under the hood on the driver side wheel well get really hot and the second one in toward the center of the truck clicks on and off repeatedly. You can switch a couple of them out and get back going after it cools off for a minute. I have had a couple of people tell me that there is a short and the ECM is trying to switch the fuel source back and forth from gasoline to cng. I have taken it to one mechanic and he said he could not track it down. From what I understand, OBD codes do not apply to natural gas equipped trucks. How effective and how difficult would it be to change out the ECM and totally bypass the cng system?
Any feedback would be appreciated.
Expo Guy


#2

“The truck runs and drives great BUT when it gets up to operating temp and you turn the air conditioner OFF, the truck stops running.”

This implies that if you leave the AC on it will keep running, correct? If you leave the AC on will the relays still heat up?