I have a 99 Blazer 4.3 auto, I drive it very little but it has been running fine until now. It will crank and run a few seconds and go dead, let it set a few mins and the same happens. I checked the fuel pressure at the fuel filter and it pegged out past the 100 psi mark, I then checked it under the hood and it was 53 and fell pretty quick to the 40s, look for leaks from the filter back to the engine, none was found. So, what is under the intake that it may be. Seems the only place to look now. Thanks in advance for your help

 

When you checked the fuel pressure at the fuel filter, what was the pressure after the 10 min leakdown test? If it failed the 55 psi limit then its fuel lines or the fuel pump. If it passed given that you failed leakdown at the service port then its the regulator, injectors or fuel lines.


George

 

You can be leaking into the cylinders from the injectors, leaking inline at the regulator or leaking into the intake plenum from the regulator or the injector lines. When you take off the intake plenum cover you will see clean metal if there is a leak into the plenum as is seen at 1:40 in this video. You might also see that under the regulator.



George

 

. Thanks George, the pressure at the filter dropped very little. I will take take the intake plenum off and check it out, I did put the updated spiders yrs back. It was a great improvement, I will get back on what I find, thanks again.

 

I finally got the fuel pressure regulator on. Before I put the intake on I hook the electrical and look for leaks, none, after putting the intake back on I fired it up, ran for a few seconds and went dead, just as before. I then checked the pressure at the fuel filter and it was 105, after 10 min it was 89. Next, I check the port, it was 51, fell to 39 after 10 minutes. Whatcha think it is, fuel pump?

 

Its not the fuel pump because pressure holds at the fuel filter. There is still a problem after the fuel filter. When you start it and it dies what is the fuel pressure doing during that few seconds at the test port shrader?

Were there any shiny/clean areas inside the intake plenum?

Are you having any security light issues? This can cause the truck to start and then the fuel injectors get turned off after a few seconds.


George

 

After the last no start, I again removed the intake before I read your last post, so I got no pressure reading while starting the engine. There is a clean spot under the injector at the no one cy. not bight and shiny but possibly a leak in the past? I pressurized the lines and saw no leaks, You mention injectors could be leaking in the cylinder, so I am going to pull the injectors out and pressurize the system and see if one is stuck open. Hope this is the way to go. Thanks for helping

 

You definitely need to find why you cant hold pressure after the pump energizes. Its either in the line from the fuel filter to the engine, the lines in the plenum, the regulator or the injectors . Since you seem to have ruled out everything else then yes it makes sense to look at the injectors themselves.

After you can hold 55 psi of fuel pressure for 10 min then hopefully it will run well. If not then we need to find out what malfunctions when it dies:

Spark
Fuel pressure
Injectors
Timing
Sensors

The best method is to catch the offending item at the moment that the truck dies.


George

 

finally got the injectors out between rain showers, ran a wire from the batt to the fuel pump prime in the fuse box, the pressure went to 57, checked for leaks, and found none, nothing around the regulator, injectors of any of the lines. Found no leaks from the filter to the port. I turned the ign on and pressure went to 57, fell to 46 in 10 minutes, So I decided to turn the engine and see what happen, ign on. The pressure went to 57, turn ign to start and the pressure fell to 47 until the pump kicked in and went back to 57. I put a new regulator on a few weeks back, looks like just one way to put it on, don't know if it could be the trouble Also the disat, cap was off, will that make any difference?

 

Since you can hold 89 psi at the fuel filter after 10 min, everything from pump to filter is good. This is with a 2 second pump on cycle followed by 10 min of the pump off, correct?

The fact that you only develop 57 psi at the test port at key on says that you either have a leak or a bad regulator. That value should be 60-66 psi. Then you fall below the 55 psi min after 10 min which says the same thing. Did you watch for leaks at the regulator and injectors for the entire 10 min after key on? The fuel pressure test sticky has a picture of the regulator and the hook up ports.

Is the behavior the same before and after the new regulator or did the new regulator change any of this behavior?


George