Fuel or evap issue?

[Scott88]

Hello all. I'm completely stumped on this one (again).

After putting a 2018 Gen3 Coyote in a 2005, I'm having issues that I think are related to the fuel and evap system. The car runs great at first. Then after 5-8 minutes, the gas gauge starts showing "fuller" readings until it gets up to 100% and stays that way for the rest of the drive. That's confusing but tolerable. The intolerable part is that after 20 minutes (sometimes) it gets choppy between 1K and ~1.8K RPM in every gear in acceleration and deceleration. By "choppy" I mean it seems like the governor kicks in and fights itself. Additionally, when I hold the clutch in and rev, the governor won't let it rev past ~4.5K.

Something very similar happened the first day I was test driving it after the swap. It wasn't very powerful at all and wouldn't go past 4.5k RPM. For that, the line that went from the Evap system to the passenger side of the tank was kinked (because it was too long). Once I shortened/straightened it, the problem went away and it ran great for about 5-6 months.

I think it has something to do with temperature too because it resets after sitting for a bit or putting fresh/cold gas in it.

Other details:
I installed a Make-it-Modular fuel filter return system.
The gas tank and sending unit is 2005.
The fuel pump is a DW400
The evap system is from the 2018 donor Vic.
Nothing is kinked.
The engine is controlled with a FPP PCU and harness.
The gauge cluster read the fuel tank through and AEM CD-7 screen in lieu of the stock gauge cluster (with an extra CAN installed to read the fuel levels).

My next idea was to replace the 2018 evap system with a new 2005 evap system. Any ideas would be helpful.

 

[Kev555]

Only part of that I can relate to is It possible the tank would be over pressurising causing the fuel gauge to rise?

 

[Scott88]

I almost didn't include that part, because it may be completely unrelated. However, the more I think about it, the more I think they are related for the reason you mention above. I'm wondering if the solenoid on the evap system responsible for opening and closing the tube that exits directly into the atmosphere is stuck shut. I read on the internet that the purpose of that solenoid is to open when there may be a negative "vacuum" in evac system because the engine is "sucking" the gas/fumes forward so fast. That would explain why it won't rev over the 4.5K RPM. It's just a theory. I don't know how to test a solenoid, and I wonder if the solenoid works fine, but the Ford Performance PCM isn't controlling it right because it's expecting a 2005 solenoid back there instead of the 2018 solenoid (the solenoid is inside the 2018 evap system I installed from the donor vic).

 

[Scott88]

So I was able to jack the car up and inspect the Evap system. It's not plugged in at all. I have a 2006 female end with a 2018 male end. Both have only two wires and neither fit each other. The male end from the 2018 has one green wire and one green wire with a blue stripe. The 2006 body harness side has one red wire with a yellow stripe and one blue wire with a white stripe. I'm going to splice them together, and don't want to do it wrong. Even though I have a 50% chance of being right, I'd rather not blow a fuse or complicate the ECMs job with make the solenoid be open when it should be closed, or closed when it should be open.

Or does anyone know what would happen if I reverse them - how the car might behave? Because I can identify the wires from the diagrams I pasted below, but I wonder if the Ford engineered reversed something between 2006 and 2018 and maybe hot opens now where before it closed - or vice versa.

 

[Juice]

There is no way I can see the evap causing those issues. You can disconnect and plug the evap line under the hood as a test. Your issues will remain IMO.

 

[Scott88]

2006
2018

 

[Scott88]

Follow-up. After doing some more research, I found that if the Solenoid for the EVAP Purge is stuck closed, once the pressure builds up in the EVAP system, it is supposed to open and recycle those fumes into the intake. If it cannot, the ECU puts the car into a limp-mode or conservative-mode. I think is exactly what is happening. I need to find a way to delete the EVAP system and trick the computer into thinking it's okay. Somehow, even when I unplugged the single electrical connector going into the EVAP system, the ECU still knew when there was a buildup of pressure. Perhaps that is measured/sensed from the sensor up in the Solenoid EVAP Purge valve near the intake of the engine.

I'll start a different thread since that is something different than what this question started as.

 

[Juice]

There is no way the evap fault can cause limp mode, none.

 

[Scott88]

I'm not experienced enough to argue if I was right, but here is one of the sources I used (https://answers.autocado.com/5165524/What-happens-if-EVAP-purge-valve-is-stuck-closed).

Others forums seemed to say the same thing. I got the impression that since the PCU was smart enough to know how much pressure to expect from the over-pressurized canister, it would adjust the air-fuel ratio elsewhere. But then when it didn't receive the fumes from the canister (because the solenoid wouldn't open), the PCU would sense that the ratio was wrong and put the engine in limp mode.

Again, I'm not defending my previous conclusion, but don't know how to test the hypothesis. What else might throw the car into limp-mode after it heats up for 10-15 mins???

 

[Scott88]

Is it possible that the solenoid not opening might alter the air fuel ratios???

 

[Juice]

Short term adaptive takes care of air/fuel ratio during purge. I've had the "purge valve stuck shut" fault, check engine light ON, car ran fine. Only the light came on.