I'm having some issues getting fuel to the engine.. I think.

This is the second 97 5.9 I've had this issue with. The last one was worse, had to open the gas tank/ maybe unplug some lines to get it to start on a hot day.

On that truck I replaced the fuel pump, I replaced the carbon canister, evap sensor thing under the hood, all the lines, the purge valve 'cap' on top of the fuel pump. Didn't help.

Now this truck is doing the same thing. The issue is- the truck will start to die if you let it idle too long. Towing a trailer up a hill it's like I run out of gas for half a second and the truck jerks a bit from the loss of power. My mpg seems worse and at 1/4 a gallon my fuel guage needle will dance from empty to 1/4 depending on acceleration.

Could just be my transmission on the way out, but I get "stuck' at 1500 rpm's sometimes. Have to let go of the gas and try and again to get the engine to allow me to push it over 1500 rpm. Doesn't feel like its slipping, feels governed or something

I blew out the lines, pulled the new evap sensor/ carbon cans off the old truck and put it on this one. No help. I ordered new spark plugs, trying the 3923 copper.

Any thoughts on what the issue is or how I could better diagnose it?

I could be wrong but it doesn't seem like a leak it feels like a clog. Like the engine is being starved by the evap system. Could just unplug it all but it seems like the fuel economy is noticeable worse (12 on the highway with no faat acceleration).

Sorry for the wall of text. It's something I've been scratching my head over for too long. About to break down and take it to a mechanic and make another enemy lol.

Thank you! All help is appreciated

 

When I say 'lines' I'm referring to the vacuum lines from the fuel tank to the canister to the sensor to the air intake.and by blew them out I mean sprayed air in after disconnecting to clean out.. Didn't fiddle with the line going to the frame on the passenger side. My understanding is that line has something to do with engaging the front drive shaft.


My 4wd works fine, maybe worth noting- pretty sure the front shaft just spins in 2wd - pretty sure thats a separate issue for another day

 

Need to let it idle until it dies. Go to take off the gas cap and listen if you hear air escaping. Driveshaft will spin in 2wd

 

Might leave the cap off and see if it dies. Do you have an fault codes?

 

I will do this. to purge air from the tank? Or to check for leaks.

This truck doesnt 'suck' too bad when I take the gas cap off. Not even audible. The other truck, it about pulled you in the tank it sucked in air so hard.

 

getting the code for the evap sensor. It comes on when I take a line off/ stays on a couple days. If I have everythinh connected long enough the check light turns off

 

Re read this.

Front drive shaft should not be spinning in 2wd, right? Just the rear

 

It may spin. The drivers side axle is a direct connection to the the spider gears in the front diff. Normally, that will simply turn the spider gears, and the intermediate axle on the passenger side. It may also turn the entire carrier, with will spin the driveshaft.

 

I see..

Any idea on the vacuum line problem? I tried letting it die but it never actually does. Leak?

 

If the tank vent system isn't working properly, you will develop a vacuum in the tank, and the pump won't be able to do its job. The more gas that is in your tank, the more pronounced the problem will be. Drive it till it starts acting up, loosen the gas cap, run any better?