Hi everyone,

Just wondering what I should check first? 2015 Express 3500. Went to fill up today and fuel was extremely hard to get in, pump kept stopping every 5-10 seconds like something is blocking the fill tube. Check engine light came on with codes P0171 and P0174, system too lean bank 1 and 2, van also seems to have some loss in power.

I put a fuel pump in it a few thousand miles ago and it had no issues for quite a while, so I don’t think that’s related, but possibly could be? Also seems like I can’t get the fuel gauge to read completely full, seems to stop about 7/8 on the gauge. Not sure if that’s a separate issue or maybe the top of the tank is full of air and not letting the last bit of fuel in or something? (If that’s even possible)

Just wanted to try and get some opinions on what to check first? Thank you all for your feedback

 

If you have trouble filling the tank, odds are there is an issue with the EVAP system. There is a vent from the tank to the EVAP canister under the vehicle, near the fuel tank, and if you ever overfill the tank up into the neck, gas can spill into that vent tube, getting gas into the charcoal canister and clogging it all up. When that vent tube is clogged up, it becomes hard to fill the tank very fast.

All that said, I would expect some EVAP codes to be set.

 

Did you need to drop the tank to change the pump? Maybe something got pinched??

 

Thank you! So would I need to replace the charcoal canister or the vent tube then? Or is this just something I could clean out somehow?

 

Yes I did, but that was a few months and a few thousand miles ago and it worked fine up until pretty much last week. I didn't personally do the fuel pump, so I suppose it could have been caused by someone not putting everything back correctly, but it seems like I'm going to have to dig into it to find the culprit

 

Thank you! So would I need to replace the charcoal canister or the vent tube then? Or is this just something I could clean out somehow?

 

I wouldn't do anything until I used a code reader to see if any evaporative emissions codes are set. I had 3 set for my 2006 Silverado, and the fix involved replacing the canister vent solenoid assembly (under the car, hanging on side of fuel tank near spare tire), the purge valve solenoid (under the hood), and finally the tank pressure sensor (on top of fuel tank, but I could reach it without dropping tank). I don't think my charcoal canister was ruined in other words.

The charcoal canister is bolted to the frame under the vehicle, near the gas tank, and has several rubber hoses - one going to the purge valve on the engine, one going to the vent tube to the gas tank, and one going to the canister vent assembly. I've read reports of folks pulling it off and blowing it out with compressed air, but if you diagnose it as failed (you can't blow air through in a certain direction on the 3 connectors), you can replace it for maybe $100.

I would also lis@Rednucleus and check the fill vent tube under there first.

This very short video a guy shows where it is located on a 2007 Express 3500:


Now, this video discusses your exact issue with a 2013 Express, with an interesting finding - the "anti-siphon" device had gotten pushed in and turned sideways in the fill tube, causing issues with filling the tank! Ignore the video past where he shows what he found, as he goes off rambling about his air compressor and other stuff in his shop...


Anyway, there are a million Youtube videos you can find yourself. I would pull codes first, and then inspect the fill tube yourself as much as you can. There are very cheap little cameras that can be inserted into a hole to inspect things like that as well.

 

Great find, thank you! The anti-siphon little plug thing was turned sideways in the fill tube. I'm also going to replace the canister since it was kind of a bitch to get off and not that expensive. I wasn't pulling any other codes except lean bank 1 and 2, which I found the nipple on my intake hose had popped off, so I think the codes were due to that. Hopefully this solves it when I put it back together...appreciate the help!

 

Wow! I am so glad my random Youtube video find was able to help solve the puzzle!