02 Blazer stalling on stop when at or below 1/4 tank
 

Hey guys,
I have a 2002 Chevy Blazer LS 2WD 4DR 225,000+ miles that I have an issue with it stalling at coming to a stop or sometimes a hard brake. It only does it when it is around 1/4 tank of fuel or less. It will immediately crank back up and other wise runs fine. Doesn't do it at all above 1/4 tank of fuel. I have recently replace the MAF sensor, radiator cap, thermostat, fuel pump, vacuum hoses and put on a new alternator. Also had new rear axles and both rear brake calipers replaced. Here is a list of codes I just cleared after the replacement parts:
C0265 Electronic brake control module motor relay circut
P0101 Mass or volume air flow circuit range/performance
P0128 thermostat
P0131 o2 sensor low voltage bank 1 sensor 1
P0137 o2 sensor low voltage bank 1 sensor 2
P0151 o2 sensor low voltage bank 2 sensor 1
P0171 system too lean bank 1
P0174 system too lean bank 2

Also the ABS light and brake light would come on at times probably related to the C0265 but not sure if the deteriorated vacuum hoses I replaced could have been the culprit. I am thinking the MAP sensor may be causing the stall, but also wonder if the fuel tank pressure sensor could be the culprit as when I replaced the fuel pump the new pump didn't come with one so I reused the old one. Any tech experts here that can give me some direction to correct the stall issue? I also should note that my 4.6L engine is a non EGR valve engine from the factory. Cleared all the codes yesterday, so far only the ABS light and brake light came on once briefly on the way home.

Thanks,
John

Obviously something is uncovering the fuel pickup in the tank when it gets down below 1/4 tank and you slosh the gas forward in the tank by braking. Forget all about lights and codes for now. It's like you can't see the tree because the forest is in the way. You can verify my theory by hooking up a fuel pressure gauge and watching the pressure while driving. Be careful no leaks.

I thought about that but physics defies that in my mind as the fuel pump is at the very front of the tank with the pick on the bottom of the pump so on stopping all the fuel would go forward towards the pump pickup and would go towards the rear of the tank on a hard acceleration from stop which doesn't trigger a stall. I thoroughly cleaned the tank out when I changed the pump, even let it dry out a day then used a shop vac to removed even the smallest of particles in the tank before reinstalling. I will see if I can put a gauge on it that I can see from the drivers seat, The one I have has a short hose.

In the interim, try this: use some Techron or Berryman B12 for a few tanks until you decide what to do. My theory is the wiper on the sending arm is corroded and this gasoline cleaner may remove some of that corrosion. When you replaced the fuel pump, did you also replace sending unit ? When you hit the brakes , the gasoline in the tank sloshes forward and that makes the sending arm move violently.

Hi John, did you ever find what was causing this problem? I have the same issue with my 2000 Blazer, but it didn't occur until I replaced the fuel pump. I removed the new fuel pump to check to see if any crud was lying at the bottom of the tank which there was not, so I separated the pump assembly from the reservoir to find there is another strainer which runs vertical to the pump that I had found to be longer than the strainer in the original pump that may be causing the problem. I question that theory because the pump inlet is actually at the bottom but the strainer would extend above the fuel level when it reached 1/4tank. This is an aftermarket fuel pump that I'm referring to and may not have been assembled correctly at the factory.

Here's a simple thing to do to prevent the stalling at a stop or hard braking. Not so good for explaining the 1/4 tank level symptom, though. If the throttle plate is dirty, it will stick and cause stalling. The throttle plate is in play at slow and idle speeds. Once underway, it is no longer touching the sides of the throttle bore so the problem goes away.
It is a easy fix, just clean the area with a 3M intake throttle body cleaner in a spray can. Don't use harsh carb cleaner or brake cleaner. I am not sure if John aka Jam71 is still following this thread.

I just got around to replacing the fuel pump a couple of weeks ago that I put in when I started this post. It was most definitely a faulty fuel pump assembly as the problem immediately went away as soon as I put in the new pump. The new pump I just ordered was close to the same price as the first one I ordered in 2019 but by a different company. I got this one off of amazon, the first one I got off of one of the discount auto parts stores online - I think it was either APW or PartsGeek but I can't remember. It now runs fine all the way to the E without hard starts and without stalling when braking. I am thinking there may have been a crack in the fuel pickup tube or a faulty assembly or component that allowed air in when the fuel level got to a certain point.

Glad you had a happy ending to your problem. Thanks for posting the outcome.