CEL help

[Raduque]

My truck is throwing some codes. I've got a p0455 (EVAP large leak) and P0457 (gas cap loose/off). I can also way overfill my tank - the gas pumps will not shut off. I put 23 gallons in my 26 gallon tank with 1/4 tank left... smelled gas for days. D: But, I went over 430 miles on a tank :awe:

Anyway, I need to get this fixed. I'm trying to find the exact cause for this so I know what needs to be replaced. I'm thinking the evap canister purge flow solenoid is malfunctioning and causing the valve to be stuck open. That would explain the gas pump not shutting off, right?

Other ideas?

 

[LTC8K6]

Might be covered under the longer emissions warranty?

 

[phucheneh]

The evap system is not really related to the fuel pump shut-off. That's controlled by the nozzle of the pump. The evap system is designed in a way that at the level where auto shut-off is triggered, there is still an air pocket at the top of the tank.

The charcoal canister is attached to this high point and is used to store vapors. Purge valve allows them to get sucked into the engine when the PCM deems it appropriate. Canister vent valve simply allows atmospheric pressure in so that this can happen- engine vacuum has to be a lower absolute pressure than that of the evap system for vapors to flow into the engine, obviously.

Anyhow, basic point: your fueling issue is not due to any of the evap parts.

I would venture to guess that the gas pump was defective and allowed you to overfill and flood the charcoal canister. Hard to say exactly how this would affect the system...I mean, it would surely cause the evap monitor to fail; but I'm not sure if a 'large leak' code would be the most likely to set.

 

[Raduque]

The code happened before the overfilling issue, and it's the same pump I always use at the same station.

In fact, I've had the code for over a month (I think it first hit around the 10-12th of July).

The evap canister on the F150 is mounted to the frame rails between the spare and the rear diff - I guess if there was vacuum in it, it could've sucked some fuel into the canister, but am I correct in reasoning that the PCM is throwing a p0455 because it can't pull vacuum in the canister?

 

[Zenmervolt]

Anyhow, basic point: your fueling issue is not due to any of the evap parts.

The pump's auto-shut-off depends on pressure in the fuel tank. For example, '05 and '06 Ford Mustangs were infamous for the pump shutting off far too early (sometimes between 1/2 and 3/4 tank) because the gas tanks on those cars did not vent properly (part of the evap system was essentially designed with too much obstruction).

Conversely, if the tank vents too much, the pump won't shut off until fuel reaches the tip of the nozzle and obstructs the sensing tube itself.

If you had a massive evap leak to atmosphere (which is exactly what the two codes he's getting indicate) you very well could have the fuel pump shut off much later than normal.

ZV

 

[phucheneh]

Perhaps I'm misunderstanding how the valve in the pump works. I thought clogged vents caused the pump to shut off because the filler tube was 'burping' the air out and causing fuel to back up and cover the end of the nozzle.

I've seen plenty of cars with unrepaired evap leaks, or simply a disabled evap system (old cars with a hose to the canister, but the rest of the stuff ripped out, usually)...never heard of them over-filling.

 

[Zenmervolt]

Perhaps I'm misunderstanding how the valve in the pump works. I thought clogged vents caused the pump to shut off because the filler tube was 'burping' the air out and causing fuel to back up and cover the end of the nozzle.

I've seen plenty of cars with unrepaired evap leaks, or simply a disabled evap system (old cars with a hose to the canister, but the rest of the stuff ripped out, usually)...never heard of them over-filling.

The system depends upon there being a vacuum at the end of the sensor pipe. Typically the flow of fuel out of the nozzle is sufficient to create this but it's possible for over-pressure in the tank to cause shut-off even without the filler neck "burping."

Similarly, a large enough evap leak could even stop the filler neck from ever "burping," leaving the pump to keep running until the filler tube was full up to the end of the nozzle's spout. This would depend on the specific design of the filler neck though. It still shouldn't allow "over-filling" where the pump was running and gasoline was spilling out of the fuel filler, but it doesn't sound like that's what happened here since the OP didn't mention gasoline actually spilling onto the ground.

If I were the OP, I'd be looking at the breather connections on the top of the tank and in the filler tube itself, as well as all the rubber lines in the evap system. He probably has one or more either dry-rotted or completely disconnected leaving the tank to vent to atmosphere.

ZV

 

[Raduque]

I did not think about checking the vacuum lines - though I'd rather not drop the tank if I could avoid it.

As for the fuel, no I didn't let it over flow. I wasn't watching the numbers, and ended up putting in about 3-4 more gallons than I should've.

Might be covered under the longer emissions warranty?

Interesting point - but my truck is 9 years old and has 129k miles.

 

[Zenmervolt]

I did not think about checking the vacuum lines - though I'd rather not drop the tank if I could avoid it.

Unfortunately, that's likely where the issue lies if you're throwing a code for a massive evap leak. You can try the purge valve, but in my experience those usually fail closed/obstructed and not open.

As for the fuel, no I didn't let it over flow. I wasn't watching the numbers, and ended up putting in about 3-4 more gallons than I should've.

Those two claims are contradictory. No tank holds an extra 3-4 gallons over its rated capacity; there's just never that much expansion room.

It's more likely that the tank was shutting off a gallon or two early before (quite possible, many fuel gauges read "full" for the first couple of gallons) and this was the first time you actually filled it to capacity. The combination of a tank filled to the brim plus leaks in the filler neck or filler neck vents would also go a long way to explaining why the smell of gasoline was most prevalent then.

ZV

 

[Raduque]

Unfortunately, that's likely where the issue lies if you're throwing a code for a massive evap leak. You can try the purge valve, but in my experience those usually fail closed/obstructed and not open.

Unfortunatly, you're probably quite right. I was getting a few "small leak" codes that would come and go for a few days before the "gross leak" code.

Those two claims are contradictory. No tank holds an extra 3-4 gallons over its rated capacity; there's just never that much expansion room.

It's more likely that the tank was shutting off a gallon or two early before (quite possible, many fuel gauges read "full" for the first couple of gallons) and this was the first time you actually filled it to capacity. The combination of a tank filled to the brim plus leaks in the filler neck or filler neck vents would also go a long way to explaining why the smell of gasoline was most prevalent then.

ZV

I meant over flow, as in run out the filler tube. I have run the truck down to E (but not run it dry) and filled up with 23 gallons - the general consensus on F150 boards is a 3 gallon reserve, which jives with almost every previous fillup from E.

Unless the damn thing's just actin' a fool to mess with me, cause I've been researching the '13 F150s.