I have a 2001 Crew Cab with ~138k miles. I've been noticing that after sitting for 3 days or so, when cranking to start, I could tell the battery seemed a little weak. While I was out and about near a Sears store, I decided to stop there and get a replacement - Die Hard.

They put there tester on there, and sure enough, it indicated it was bad and needed to be replaced. So I go back in and order the Die Hard. Then the customer service rep and I go out to get the mileage. I turn the key to the on position and nothing on the odometer (takes about 1-2 minutes before it shows up - being doing this for years - not a big deal to me). At this point, I decided to start the car since the old battery was still installed.

Turn the key and it would not start - it would turn over but not start. So they take out the old battery - Interstate that was installed back in 2002. I had thought the battery was ~6-7 years old. I had no idea it was already at 11 years LOL. Anyway, we get the new battery installed and it won't start. Turns over but no start. We used a little start fluid and it would not start. So I ask the tech if they have a fuel pressure gauge. They did not. WTF? You don't have a fuel pressure gauge? They had to cal an auto parts store to borrow one.

While we are waiting, we check all the fuses and all were good. Tapped on the gas tank thinking it might have been the fuel pump was stuck. Still no go. We finally get the fuel pressure gauge and connect it to the Schrader valve. I then proceed to start the truck and it starts. Fuel pressure is slowly building. After about 1 minute, we have 30 psi and holding. We turn the truck off and it's still holding at 30. Looking at the specs, we should have: Engine running 28-50 psi and key on engine off 35-45 psi.

So I drove it to a shop for a possible fuel pump replacement. They called me today to state that the fuel pressure is at specs. Running I have 41 psi, and 32 with the key turned on. WTF?

Was this some type of weird electrical glitch because the old battery, and having a load test messed up something with the fuel pump?

 

The load test puts a heavy drain on an already old low capacity battery.
What would you expect the result to be?
Some circuits monitor the battery voltage and conclude there is a possible theft action going on and can take actions to prevent starting for awhile.
The dash checks for low voltage as well.
This is the momentary gauge sweep it does.
You should have noticed the dash action as well as the slow cranking.
The PATS system reacted to prevent starting as it's supposed to do.
Your lucky it did not auto lock on you with the key in the ignition and no window down to get back in..
Why would you rush to test fuel pressure with no indication fuel is the issue after knowing the battery was just changed?
In addition, changing the battery forces the PCM into a full diagnostic mode and retests all parameters because all learned programming had been lost.
If a scanner were to be connected it would show all these actions going on.
The proper way was to plug in a voltage source to the cigar lighter to maintain 12 volts to the critical circuits before removing one battery cable.
If you had the radio memory set up with station selections you lost them as well.
Sorry to sound a little harsh but you wanted to know and got more than you thought to be the case.
It's not just a matter of replacing the battery but one that is connected to a smart system.
There was no harm done but it reacts in a way you and your shop was not prepared for. A normal reaction.
Good luck.

 

No problem sounding harsh (no butt hurt here). Thanks for the explanation. What is this "PATS system" you refer to? I have a 96 Corvette that has the VATS system to prevent theft. When activated, it can take hours before you can attempt to start the car. Is that similar to the PATS system?

Wanted to rule the possibility of the fuel pump being an issue. That is all.

We did connect a scanner to check for any coded, and no codes where thrown.

 

I assume your truck has PATS but maybe not.
If there is a dash Theft light that flashes, you have it.
A look with the scanner should have shown all PIDS were being retested unless you are using a reader, then you won't see them.
A code 1000 should show on a scanner until all the testing is complete and passes.
A reader may not show a code 1000 and there is no CEL lamp for a code 1000 unless there is a trouble present.
Good luck.