engine bogs at speed.

[WD21colorado]

so im having an issues currently im thinking that my fuel pump is starting to fail the truck is at 223k currently anyway last week drove out of state for a trip vehicle did fine. until the last couple days there. when driving up a hill at 45 mph the truck randomly lost power wouldn't pull in any gear it was in. shut the engine off and restarted aafter a couple of minutes. the problem went away and afew days later the problem cam back this time it happened after driving threw i70 on the mountain passes maintaining around 65 mph with the fuel tank around 3/4th full. the vehicle started to bog down serverly and did it wheather it was going up hill or downhill. then the other problem ive noticed is that just recently the fuel tank pressure has changed it used to average negative pressure. but currently it seems to be running at a positive tank pressure and noticed it was pumping WARM fuel vapors threw the fuel filler pipe. it stopped immediately after the engine was shut down. so these two things are confusing me. i do think the fuel pump could be on its last legs but the other problem is more technical for me to understand. any ideas on what could be screwed up?

[WD21colorado]

just did fuel pressure test. idle (36 psi) aggressive rpm spike ( 42 psi) and 4000 rpm run for one minute ( 37 psi) this is for the mpfi system, and doesnt seem to be getting high enough pressure. and also tested the evap canister and has appeared the purge valve has failed so that would explain the positive pressure in the fuel tank.

[Precise1]

Have you checked the ECU for stored fault codes (highly recommended)?

When is the last time the inline fuel filter has been changed?

 

The fuel pressure should stay at aprox 43psi, all the time. The fuel pressure regulator should be checked next, and there is a resistance reading for the fuel pump as well.

Since you seem pretty handy, go to the Garage section and download the Factory Service Manual from the pinned thread. IDX file is the index and EF & EC is the one with most of this information. This is your new bible...

 

Obviously, keep asking questions, but that same section has a good trouble shooting section that does by symptoms and what to check, and in what order.

 

B

[ahardb0dy]

Make sure the vacuum line that goes to the fuel pressure regulator is still attached and that it does not have any cracks in it on the ends.

[WD21colorado]

the pressure test was done after the fuel filter. the filter it self was replaced back in February.

[WD21colorado]

just drove the vehicle for a few miles seems to be acting normal currently. charcoal canister was replaced yesterday so fuel tank pressure apears to be normal again. but have noticed lagging when you go W.O.T. for a couple minutes. also a new fuel pump was ordered yesterday since the problem only seems to show up during high fuel consumption periods. also tested the fuel regulator which is still working with in spec.

[WD21colorado]

found the problem a couple years ago. being dirt found its way into the 4 junction connecter by the passenger side bank. cleaned it out. problem hasn't shown up in two years.