Vacuum issue

Hey guys. Just joined the forum. I have a 99’ single cab 2.7l with 228k on the clock. Purchased about a year ago, not knowing much about these trucks. It had no gas cap and runs good without one, but throws a P0401 code. When I put a cap on, it dumps fuel out of the front of the truck. There seem to be a lot vacuum line block offs in the bay, I don’t even know where to start. Any thoughts?

 

Sounds like something was deleted. Any pics of the bay?

 

Here’s a pic

 

Those vacuum ports that have the hose with bolts in them… the vacuum caps rotted and fell off, those are OK.

IIRC, the code you gave is for EGR

 

Could it be related to no gas cap? The gas cap I put on was also a cheap one from autozone, maybe it’s not venting correctly causing the fuel dumping.

 

https://www.tacomaworld.com/threads/code-p0401.471601/

https://parts.olathetoyota.com/p040...yota gives you,issue is insufficient EGR flow.

 

No, can you take a picture of where the fuel is coming out of?

 

Replaced the vsv and put a new Toyota fuel cap on, still dumping fuel and sending the P0401

 

What does the fuel line look like where it's leaking? If it's dumping fuel like that there has to be damage to the line.

Only thing I can think of related to the gas cap would be the evap canister, on a 99 its the big black box near the firewall on the driver side.

 

Fuel looks fairly clean. I’m guessing it’s related to the canister somehow, if I run it with no gas cap, like I have for a year, it doesn’t dump at all and runs great. I noticed there was a ton of pressure when I removed the gas cap as well.

 

The capped off lines in your image go to the idle up for the power steering pump. The part circled is not stock.

 

What does your evap canister look like. It is just out of view to the right of the image you posted.

 

Here's a possible reason why your power steering air control valve was removed: https://www.yotatech.com/forums/f2/beware-power-steering-air-control-valve-246778/

 

Ah that’s a great read! I have a brand new power steering rack so it would make sense if they blocked it off. Any major downsides to running it blocked off? And I will get a pic of that canister

 

So.. Where's the fuel leaking from?
Just from the fuel line on the other side of that frame rail?
Is it cracked or have a loose connection?
I could very well be missing something but I would start trying to fix the leak at the leak, not in the engine bay

 

It’s coming from the frame. Looks like a like from the canister drops into the frame, possibly for ventilation? Idk. I’m sure it’s not the fuel lines because I don’t have any leaks with the gas cap off.

 

Is this the canister you believe its leaking from, do you see anything on the other side of it or under it?
I think you need to lay under it while its running and figure out exactly where the fuel is coming from.

It might be a more complicated issue, but I would knock a simple problem like a cracked fuel line or loose connection off the list of possibilities now before you spend too much time diagnosing a more complicated issue.
I'm no expert on fuel systems AT ALL, but, is it possible its got a weak connection that only fails at full operating pressure, and with the gas cap removed the system never reaches that pressure?

 

I hear you. From everything I can tell though, it’s definitely coming from the line in the frame. Not sure is another line may be clogged or not, but it seems to stem from the canister

 

He could also have a blocked fuel tank vent. As fuel comes out, air needs to go in. With the gas cap off it has a way to do that, with it on the vent should work, but it's obviously not.