Hi, I need help!!! I have a 1998 chevy blazer ls with 120k miles. The truck recently threw some codes and I replaced the sensors and recharged my ac. After driving it for a while the truck began to stall. It first happened on me five min into driving I thought maybe low on gas so filled the tank seemed to help. Now the truck is stalling when it gets to operating temp even if I hold the accelerator n brake pedal( initially stalling when at stop sign or red light.) I have replaced the iac, icm, tps, ignition coil, fuel filter, Maf, cleaned throttle body ever valve PVC valve and map sensors I've put about 600 and it still stalls. Now it's lunging forward like if it wasn't getting air n when u step on the gas it feels like the choke is on and Boggs. If someone can help me !!

 

Check your fuel pressure. Your fuel pump may be failing.

 

Fuel pressure and spark gas been checked... The fuel pump does him really loudly

 

What was your fuel preasure? key on engine off should be 60psi, and no less then 55psi after ten mins.
Spark must be a clean blue/white spark, yellow/orange will not do.
Any trouble code?
What engine? W or Z?
You said pump is very loud so it is most likely on its way out the door, especially at 120k miles

good luck report back

 

The pressure was around 55 with engine off then when car stalled it would drop to 40 ima check the pressure again tonight if I get out early I will repost the pressure and yea the pump sounds loud even when car is on and it sometimes back fires when u step on the gas along with really bad hesitation engine is w

 

*Moved to the correct section, '2nd Gen Tech'*

 

Do a proper leak down test,
~Attach you FP gauge
~Turn the key to the "ON" position (do NOT start the engine)
~Check and record you FP at that moment
~Dont touch anything for ten minutes
~After ten minutes look at the FP gauge and record the pressure.
Post your Results

Remember, during this entire process there is no engine starting


Also, as a referance point for you, at idle, my FP is about 55psi, seems to me like 40ps at idle is too low. But I could be wrong, maybe someone with a little more insight can confirm that for us.

 

sorry it took so long but i checked the fuel pressure earlier today here are results:
first time checked engine hot;
key on engine off- 60 psi
key on engine off after ten min -15 psi
engine on-53 psi
when the engine stalled it was at 40 psi and coolant temp was 190 degrees
and then after i let it cool down the fuel pressure would fluctuate sometimes dropping to like 30psi and sometimes only droping 5 psi(this is when key is on and engine off)
I dont know if this affects it but when i turn the car off the pump pressurizes

 

Because of the way you typed this I'm not sure if you mean the pressure dropped by fifteen psi after ten minutes or that it was down to fifteen psi after ten minutes. Either way, it's out of spec and indicates that there's a leak somewhere, either in the plenum or at the fuel pump. To find the leak, test the fuel pressure coming directly off the pump at the fuel filter. If the pressure holds after ten minutes then the leak is in the plenum.

It's normal for the pump to pressurize the system when you turn off the key. I'm not sure why it does that. Given that the fuel pressure was very low for operation when the truck stalled I would be suspicious that the pump is beginning to fail. I'll leave it to others to give more troubleshooting guidance at this point. However, if you do replace the pump get an AC Delco or Delphi. All other pumps fail relatively soon after replacement.

 

thank you Toby for your help. The 15 psi is where the pressure was when i let it sit for ten min. today I'm going to remove the upper intake and replace the fuel pressure regulator n also be able to look at the spider. i will also check the fuel pump today n possible order an acdelco or delphin pump thank you once again ill post the outcome