Ford F-150 - 1997-2003 :: 1998 - No Fuel Pump Buzzing Sound When Turn The Key To On Position

Ok I have recently bought a 1998 Ford F-150 V6 4.2L 2WD and when the guy sold it to me the check engine light was on and he told me that randomly when you turn the key to the on position you will not hear the fuel pump buzzing sound and he knew it wouldn't start, he said you would have to turn the key from the on and off position many times until you hear this sound and then the truck will start and run fine.

First off I got the codes read and there were three of them P0171, P0174, and P1537 some things to note are that the drivers air bag looks like it had deployed, the cover is loose and when I pulled it back the air bag looks duct taped up inside there that would cause the air bag light to continuously flash while driving. I noticed the battery leads were corroded so I replaced the battery and put new battery clamps on both wires, after that the problem did not happen for a week and I though it was over but it happened again.

Next is that the truck has the PATS system and it did not come with a remote which I have also read that the PATS system can cause the fuel pump not to turn on but not sure if this would cause it to not start randomly because sometimes it starts right up. When I started to look at the simple things to fix I noticed it did not have an air filter in the housing. so I thought the MAF sensor could be dirty so I cleaned it with the special cleaner, I put sea foam into the intake via a vacuum hose and also have put a fuel system cleaner in a full tank and have driven most of the gas out. After putting in an air filter, cleaning the MAF sensor, and sea foaming the intake, it seems to run a bit better but I am still having the random fuel pump issue.

I have checked the fuses and the and the fuel pump and ECM relays both are fine. Today I put new exhaust on it because it had some bad exhaust leaks and the truck did not start again, so the guy trying to put my exhaust on, hit the fuel tank with a hammer and it didn't work then hit it again and it finally worked. Im not sure if the hitting it did it or if it just randomly turned on like always from turning the key on and off. The new exhaust has made a huge difference in driving it feels and sounds much better.

Also to note is that when I am stopped at stop lights it will idle at about 1500 and then it drops down to 500 and back up and back down again and it does this at most stop lights, and it is not an abrupt drop it just slowly idles down and back up again. Again once the truck is started it runs perfectly fine with no issues, and there are no specific times when it has the problem it seems to be randomly. I know that many people will tell me to change the fuel pump out and I am already prepared for this but if there is any easy things I haven't thought of yet...