Hello everyone, sorry in advance for the long post, but I just wanted to give enough detail in hopes to diagnose my problem.. Lately it's been quite hot outside so I started running my AC. A few days ago when it was around 86 - 92 deg I made 4 short (5 miles or less) trips around town with the AC on (**** on regular AC with fan on 2nd notch), with each stop being around 20 mins or less. After my 4th stop on my way home I started noticing a loss of power and hesitation when I stepped on the gas. I turned off the AC and continued to drive (45 mph or less). 5 minutes later, the truck seemed to have no power at all when I stepped on the gas, so I pulled over to a nearby parking lot

With the truck on Park, I slowly stepped on the gas, it seems like it is "choking". When I place it in gear, and slowly step on the gas, it goes goes forward for a second or two, then the motor dies. The temparature gauge is about 2 notches above the 1/4 mark, so it does not seem to have over heated. Attempts for the next 5 minutes to start the truck fail, the motor just cranks but fails to start. I opened the hood and let it cool down. After about 15 minutes, when the needle on the temp gauge is a notch below the 1/4 mark, I try again and the truck starts. I rev the motor and it seems to be fine. I placed it in gear and drove around the parking lot. 2 minutes later, it lost power again and would not start. I still had some starting fluid from when my truck's fuel pump start dying on me, I figured might as well try that. I sprayed a bit of starting fluid on the TB and started the truck. She ran for about 2 seconds and died again. Attempts to start the truck, fail again. Being really frustrated, I decided to lock it up and leave the truck before I did more damage to it. I came back the next day, tried to start it and you guess it... she started right up and I was able to drive her home!! (AC off.. for fears of her acting up). I've been driving the truck around for 2 days (AC off) on short 15 minute commutes to work and back without any problems. Today was around 92 deg, and she ran alright.

The same thing happend about 2 weeks ago when my brother was driving my truck. I thought it was the Cat Converter being plugged up, so I replaced that. Obviously it wasn't the problem.
When I hooked up a fuel pressure gauge on the shreader valve, the pressue would go up to about 62 PSI when the I turned the key (and the fuel pump kicked in), then it would go down to about 58 PSI. When the truck is running, it fluctuates between 55 - 62 PSI. When I turn off the truck, the fuel pressure drops to 30 PSI after about 2 hours and almost below 10 PSI overnight.

Could it be the fuel pressure regulator causing the issue? The truck idles and runs a little bit rough but the SES light is not on and there are no codes.

A little more background on my truck; Truck has about 123K miles and within the past year I have replaced:

Catalytic Converter
Fuel Pump/Sending Unit
Front and Rear Fuel presure Solenoid
Fuel Filter
Intake Manifold Gasket
Distributor Cap and Rotor
Spark plugs and wires
Water Pump
Thermostat
Alternator
Idler Pulley
Tensioner
Serpentine Belt
Battery, Connectors and Wires
Gas Cap
Air Filter
Passenger and Driver upper and lower ball joints
Torsion bar Bushings
Idler arm
Ball Joints
......

I know there's more but probably not related to the current issue at hand.

Thank you very much in advance for your input and help!

 

Did you have the codes scanned? There may be stored codes that haven't triggered a CEL and may point you in the right direction. It sounds like a sensor or electrical problem to me...

 

Thanks for the quick reply Kyle. I had the codes scanned and the last code was from when my gas cap was loose and the other was from my evap purge solenoid. Both previous codes triggered the SES light and I thought I addressed the issue that triggered them.

I had to run some errands last night after work and the truck acted up on me again. It started loosing power on my way to the store but did not stall so I thought maybe it was heat related (it was about 82 deg outside but I did not have the AC on). On my way home, I rolled all my windows down, turned the temp to full heat and blasted the fan all the way. The needle on the temp gauge dropped 2 notches to around the 1/4 mark. Less than a mile away from home, the truck started loosing power again and stalled in an intersection during a turn, luckily I had enough momentum to make the turn and pull over. 2 minutes later I started the truck and it did not have power when I stepped on the gas, but fortunately I was able to get it to limp home going around 20 mph.

I hooked up my fuel pressure meter to the sheader valve and was surprised to only find 40 PSI of pressure when I turned the key. I had my girlfriend turn the key to the on position again and this caused the fuel pump to make a louder than usual wired noise (more like a Trrrrrrrrrrrrrggggggg noise instead of the usual buzzing when it is priming correctly), almost like its trying to pressurize the system but can't and the fuel pressure does not go up even a tick on the gauge. We repeated turing the key to the on position several times and 7 out of 10 times the fuel pump would make the weird noise (but the fuel pressure will not go up) the rest of the time it won't make a noise at all.

I let the truck sit for about 10 minutes and tried this procedure again. The fuel pump made the normal buzzing noise this time and the pressure went up to 62 PSI. Started the truck and it fired up. Reved engine a few times and it seems normal, turned the AC on to MAX and the fan to max, gave it some gas a few times and it started loosing power again. The fuel pressure starts dropping to 50 psi, rev it more and it drops down to around 40 psi and the engine dies.

The tank is more than 3/4 full of gas and since I replaced the fuel pump a few months ago I have not let the gas go lower than 1/4 full before refueling. Could it be that my fuel pump is going bad again? What other components are in the fuel system between the fuel pump and the shreader valve; it is basically just the [Fuel pump] ----[Inline Fuel Filter] ----- [Shreader Valve] correct?

I was able drive the truck to work this morning without any issues.

Thanks for your input and help!

 

Sounds Like youhave a Bad Ignition wiring Harness on your 1996 Blazer?
It's A Very Very Common Problem with the 1997 Blazers...

 

Perhaps I have my terminology mixed up. When I mean the truck looses power, I do not mean it in an electrical sense. I mean when I step on the gas, the engine just boggs down (I guess I'm thinking Power = Work/Time)

If my ignition wiring harness was bad, wouldn't that also exhibit other sysmtoms like my dash lights not turning on in the truck? Also, wouldn't that stop DC power going to my fuel pump entirely and causing it not to even try to prime the fuel system?

 

The ignition wiring harness would just cut off the fuel pump, not trickle it power to maintain 40psi. Sounds like you may have either a ground issue to the pump or some other wiring issue. If it isn't the wiring or ground, then its possible the pump is failing... Although I haven't really heard of too many cases such as this... Typically, they're just dead.

 

UPDATE:

I got home late last night and when I pulled into my driveway I left the truck running and decided to go under the truck and listen to my fuel pump. The pump definately does not sound like it is running correctly. Instead of the constant buzzing sound that a "normal" operating pump emmits, it is making a wierd sound every other second. Almost like the bearings in the pump motor are going bad or the shaft is unbalanced.

I spoke a guy at NAPA where I bought the pump a few months ago and he said that its not very common for the new pumps to go bad but it is something that has happen on rare occations.
I changed the the connectors on the fuel pump and flushed the tank when I put in the new pump so I'm pretty confident that the pump failure was not caused by improper installation.

They are giving me a new fuel pump under warranty. Hopefully my truck will stay running until this weekend to give me a chance to use all the gas in the tank so I can change the fuel pump.

I'll keep you all posted next week to let you know if this solved my problem.

 

Does this fuel pump have a pulsator valve???? If so it sounds like it is failing .... I have read threads where this was the case and all they had to do was to replace that part with a length of fuel hose to replace the part and problem solved....

 

20Blazer00, I am not sure if it has a pulsator valve. I would probably have to drop the tank and take out the pump to check. However, since the current pump is still under warranty and NAPA said that they would give me a new one, I would much rather just put in a new pump that will have a warranty, than try to fix the old one.

If my pump was no longer under warranty, I would definately try to repair it though.

 

UPDATE:

Went back to NAPA and got a new replacement fuel pump (for free under warranty) and installed it last Friday. Truck seems to be running fine and the new fuel pump now sounds "normal" . Hopefully that was what was causing my problem.

Thanks to everyone for your input.