01 5.3 Hard Starting - Helps If I Prime Fuel System First

[aftershock00]

I have an 01 5.3 with about 105k miles. For the past month or so, I have noticed that the truck doesnt instantly start up with the tap of a key like it used to. It cranks for a few seconds. At first, it seemed like this would only happen after the engine was warmed up and then sat for about an hour, but now it doesnt seem to make a difference when I try to start it. Once it starts, the motor runs relatively normal and gas mileage is average.

I noticed that the truck will start right up if I turn on the ignition and wait a few seconds while the fuel system/pump primes

and then I engage the starter.

I read through many forum threads and I changed the FPR with one from advance auto. No change. I changed the fuel filter about 6 months ago so I dont think thats the problem and I changed the fuel pump about one year ago with an AC delco "updated" pump from the chevy dealer. Because it starts faster after being primed/represurized by the pump, im thinkin its a fuel pressure problem.

I dont know where to look at this point. I dont have a pressure gauge btw, but im going to take it to a mechanic in a few days if i cant figure it out.

It may be worth noting that when I put the key in and turn the key just enough to start the pump, the whine that the pump makes changes tone half way through the three second "prime". I dont recall it doing this before, but who knows at this point. The pump always made some type of "whine" since new, but it was a consistent one.

[rob_rrt]

My 2001 Silverado 5.3 did this exact same thing. The way the problem was diagnosed was to put a fuel pressure gauge on the Schraeder valve on the fuel rail. The fuel pressure should be 55-62psi with the fuel pump running. If you turn the key on without starting the engine the fuel pressure should jump up to 55-62psi. After the pump shuts off after several seconds the fuel pressure should drop back about 5-7psi and then drop no further. There is a check valve device in the fuel pump that isn`t seating and holding pressure in the fuel system when the key is off. Replacing the fuel pump is what fixed my truck. I am surprised you are having trouble with a fuel pump that is only a year old. I hope this helps.

[ColoradoSkiCountry]

I would have to go with it being the fuel pump again. You'll likely end up replacing the pump and the filter again.

 

My 99 5.3L made it to 80,000 before I started having the hard start issues, priming it helped, but it continued to get worse. THey replaced the fuel sending module, which also fixed the wacky gas gauge, and no problems after that. Never once had to touch the FPR

[2018GMC]

I would replace the fuel pump. It would be nice if you are within the warrenty period of the pump since you just replaced it. I have learned though many vehicles, just because you replaced a fuel pump recently dosent mean that new parts cant fail.

 

Another possible cause is bad / dry / cracked o-rings on your fuel injectors. I'm not sure how prone your truck is to this but I have had hard starting cars that run great but dont start well when cold. Replaced o-rings and was like new again.

 

My real life examples:

 

Audi Bosh fuel pump - replaced new - lasted 8 months

97 Chevy Carter fuel pump - replaced new - now is giving same starting problem same as you after 4 months.

 

Not sure if this is an old wise tale but...

 

I always fill with name brand gas

I never run below 1/4 of a tank and never below 1/2 tank in winter.

 

Then I have buddies that fill whereever, run on fumes and have never replaced a fuel pump.

 

Even following these supposed tips I go through fuel pumps. Some say that the ethanol additive leads to less fuel pump life in non E85 vehicles.

[NothinButBowTies]

This may sound like overkill but after replacing a fuel pump in my old chevy, I change the filter every 10,000 miles on the dot. I know on the newer trucks I know the filter is in the tank and thus 'lifetime'.

[ColoradoSkiCountry]

just gotta know how to get the bed off and then you have easy access to the fuel tank and filter

[cdmm151]

Don't forget the pressure regulator. I have a 01 GMC that was doing the same thing. I changed the regulator first because it was easier. Fixed the problem. I have also had to change the fuel pump on a 97 suburban because the check valve went bad.