PO450 Low Evap Flow

[Cheese]

I am ready to sell the truck.

For the second time in a month, the CEL has come on with PO450. Apparently it is a low evaporative flow. Last time I checked all the related cell connections, cleared the code by pulling the EFI fuse and crapped a fuel pump about 10 days later. Awesome.

It came on this morning in the cold on the way home from hunting ducks. The drive there was no worries. Since then I have driven less than 10 miles and will be working on course work so I don't need to drive much more except to get parts to fix this.

The truck is a Frankenstein. It has a cell, a 3.4 engine swap and miscellaneous other crap.

All the hoses and wiring appear visually to be in tact. The truck was driving fine since July with the new in tank Toyota pump. I have experienced no decrease in performance, new sounds or other changes.

What am I missing?

Thanks.

[AxleIke]

The cell.

With everything you have cut out back there, have you considered a simple stock tank conversion...Its not hard once you have all the shit back there out (spare tire BS, frame brackets). It takes a weekend.

Sorry for your troubles.

[MTL_4runner]

Cheese, not sure what OEM EVAP stuff you have left on your truck but from my FSM it shows P0450 as an EVAP pressure sensor malfunction.....which should be pretty easy to test. It says if the pressure sensor remains above 4.5V or below 0.5V then the ECU throws the P0450 code on 2 trip detection logic.

Then it gives the possible causes:
*Open or short in the pressure sensor
*Malfunctioning pressure sensor
*ECU

[Cheese]

I went to get groceries and it went off.

Where would the pressure sensor be?

Should I assume it is on the vapor return line? There are only 4 things that come to the cell, HP out, LP return, sending unit wiring and vapor line to the charcoal canister.

Is it reasonable to assume that this code, rather than starving the pump when low on fuel and taking sharp corners, killed the last pump? If so, how?

Thanks. I am used to a truck that just runs, none of this sort of thing.

[MTL_4runner]

I went to get groceries and it went off.

Where would the pressure sensor be?

Should I assume it is on the vapor return line? There are only 4 things that come to the cell, HP out, LP return, sending unit wiring and vapor line to the charcoal canister.

Is it reasonable to assume that this code, rather than starving the pump when low on fuel and taking sharp corners, killed the last pump? If so, how?

Thanks. I am used to a truck that just runs, none of this sort of thing.


I attached a pic of the sensor in question.

Double check that your fuel regulator isn't malfunctioning and causing your pump to run continuously.
Do you hear the pump running when the key is on but with the engine off?

[SAR_Squid79]

Whoa, Whoa, Whoa, guys!!!!

...Dont' get crazy just yet. Your gas cap can also be the source for this CEL code. Make sure your gas cap is all the way tight, and if it is and you're still getting the code try replacing the gas cap, and then proceed from there.

Let's not go replacing gas tanks, ECU's, or pressure sensors just yet. Start with the simple stuff.

K.I.S.S.

[MTL_4runner]

Whoa, Whoa, Whoa, guys!!!!

...Dont' get crazy just yet. Your gas cap can also be the source for this CEL code. Make sure your gas cap is all the way tight, and if it is and you're still getting the code try replacing the gas cap, and then proceed from there.

Let's not go replacing gas tanks, ECU's, or pressure sensors just yet. Start with the simple stuff.

K.I.S.S.


Jamie, with all due respect, just because the OBD code says EVAP doesn't mean it's related to a bad-sealing gas cap. That stuff up above is right out of the FSM diagnostic, so if it was a gas cap I'm sure they would mention it as a possible source. There are other EVAP codes where the gas cap can be a culprit, but not this one. I'll read the title right out of the FSM "P0450 Evaporative Emission Control System Pressure Sensor Malfunction (Only for 4WD models)" and the only diagnostics listed are voltage checks. If the EVAP code was P0440 then you might be on to something.

[Cheese]

Ike was in part joking. I have a fuel cell that has been a pain on and off since I put it in.

Looking at the picture, I apparently still have 3.0 Evap stuff as my charcoal canister looks nothing like the picture.

The light has gone off and I did nothing other than look around the truck and gripe about it.

I checked the cap, but that has never caused problems before.

Should I be worried about pending doom or if the light cleared it self should I just let it be?

[20005spd]

the gas cap has nothing to do with this code, dont throw parts at stuff ever. if the code was a gross evap leak, then its most likely a bad cap or a disconnected hose.

this code or any related evap codes would not kill a fuel pump. the only purpose of the evap system is to contain fuel vapors from the tank and release them into the intake at certain times to prevent emmisions.

its tough to diagnose this stuff without proper scan tools. 1st thing id do is check all your hoses for cracks or anything of the sort. actually get in there and check every hose there isnt many for evap. after that the correct way to do it would be monitor the pressure sensor voltage with a scan tool. most likely the sensor is junk.

if the code went off id forget about it till/if it comes back on. like i said its not going to cause damage.

[AxleIke]

Well, mostly joking...

I do believe your cell is the root of your pump issues. Unless I'm nuts, you said it does not have baffles...I think you are starving the pump, and it wears out prematurely.

Perhaps you need to swap in 3.4 evap gear, see if that helps, and keep some spare pumps around.

[20005spd]

with a 3.4 engine swap in a 3.0 truck you can use the 3.0 cannister but must use the 3.4 sensors and solenoids :thumbup:

[MTL_4runner]

Ike was in part joking. I have a fuel cell that has been a pain on and off since I put it in.

Looking at the picture, I apparently still have 3.0 Evap stuff as my charcoal canister looks nothing like the picture.

The light has gone off and I did nothing other than look around the truck and gripe about it.

I checked the cap, but that has never caused problems before.

Should I be worried about pending doom or if the light cleared it self should I just let it be?


Adrian, this frankenstein setup is making it hard to diagnose codes at all. What parts do you have from the 3.4L vs what's left from the 3.0L motor (ie do you even have a pressure sensor hooked up?). A pic of everything might be helpful too if you can get it. I don't think this code would ever do any damage but the problem is that it will set off the CEL and you may end up getting used to ignoring the CEL enough it may mask a more damaging code later. So the bottom line is you can ignore it, but I would suggest fixing the problem regardless.

I attached a pic of the old 3.0L and newer 3.4L EVAP to help us see what we're looking at:

[mt_goat]

Adrian, check with Mike, he had an updated diagram for using the 3.0 can with the 5VZFE. It runs the tubing different and I think he did this after you left ORS.

[Cheese]

Interesting that this was bumped.

The truck just through this code again about a week ago. 441, low evap flow.

I haven't talked to Mike in a good long time, just busy with school.

The truck was on the road for almost 35k miles before I did the axle work and there were no problems at all.

I have the 3.0 canister up at the firewall, the rest is stock 3.4 on the engine and a fuel cell, now with Toyota pump.