jeepnut24

I need to run one of these to pass emissions and Im wondering how I can setup a working solution on my 94 Jeep YJ. How have those who need them, been setting this up? My YJ has a charcoal canister from the original setup.


Along those same lines, is the Fuel Level sensor part of the EVAP system?

oange ss

iTrader: (50)

yes, PCM uses fuel level to schedule EVAP action as part of leak test

bczee

iTrader: (12)

I'd be interested in knowning what other solutions there are to adapt the sendor...

Schitzo

iTrader: (6)

I am interested in knowing this as well since I have to make it work as well.

Here is what I intend to do so far. For the fuel level, the ECU needs to see a tank at least 15% full to run the emissions check. I will use a resistor to fool the ECU into thinking the tank is 50 % full.

For the fuel tank pressure, I will integrate the actual pressure sensor somewhere onto the tank.

then run the usual 2 valves.

thats my plan so far.

pdsq98gt

Good plan. If possible, just drill a hole in the top of the fuel sender assembly and put the sensor in with a grommet.

jeepnut24

Any suggestions on the fuel level sensor? What resistor value do you plan to use? Im going to have to find that sensor as well. I found the pressure sensor part number for my app, but haven't found the level sensor?


Is there anyway to run the pressure sensor up under the hood? I have read at least one thread where they set it up this way.


Anyone else running these sensors? Pictures would be awesome.

Schitzo

iTrader: (6)

i believe the stock Fbody fuel level sensor provide 270 ohms when full, 33 ohms when empty. I intend to use a resistor between 100 and 200 ohms.

here is some more info


GENERAL - The Evaporative Emission (EVAP) Control system used on all vehicles is the charcoal canister storage method. This method transfers fuel vapor from the fuel tank to an activated carbon (charcoal) storage device (canister) to hold the vapors when the vehicle is not operating.

When the engine is operating, the fuel vapor is purged from the carbon element by intake air flow and consumed in the normal combustion process.



MORE IN DEPTH - The EVAP purge solenoid valve allows manifold vacuum to purge the canister. The Powertrain Control Module (PCM) supplies a ground to energize the EVAP purge solenoid valve (purge on). The EVAP purge solenoid control is Pulse Width Modulated (PWM) or turned on and off several times a second .

The EVAP canister purge PWM duty cycle varies according to the operating conditions determined by the mass air flow, the fuel trim, the engine coolant temperature, and the intake air temperature. For certain EVAP tests, the diagnostic will be disabled if the TP angle increases to above 75 percent . The evaporative leak detection diagnostic strategy is based on applying vacuum to the EVAP system and monitoring for vacuum decay.

The fuel level sensor input to the PCM is used to determine if the fuel level in the tank is correct to run the EVAP diagnostic tests. To ensure sufficient volume in the tank to begin the various diagnostic tests, the fuel level must be between 15 and 85 percent .

The PCM monitors the fuel tank pressure/vacuum level via the fuel tank pressure sensor input.

jeepnut24

By installing the resistor, wouldn't that cause the EVAP tests to run more often than they need too? IE when the fuel is above 80 or below 15%?

oange ss

iTrader: (50)

that's just a requirement to start the test, I cant find any data on when the actual schedule is

jeepnut24

Thanks

Any other details on the pressure sensor setup or pictures? I haven't been able to find a factory sender/sensor in a local JY yet. All of them have been taken before I get there.

flame

iTrader: (13)

The only problem I could see is if the tank is full and the EVAP test runs. It pulls the tank into a vacuum and you could end up sucking liquid fuel into the motor through the canister purge solenoid. Or if the tank is too empty it wouldn't be able to reach the required vacuum soon enough and may think you have a vapor leak.

You could mount the gauge sender to your orignial unit and have it feed into the pcm and keep the stock one there to run your gauge.

Marky522

iTrader: (8)

Are you going to add the charcoal canister also? Because I know other car lines monitor the O2 sensor to verify the increase of HC in the exhaust (mixture will go slightly rich when the extra fuel is allowed into the intake)

Mark

350SS

iTrader: (38)

Can you just install the pressure sensor into the evap line using a tee fitting rather than having to modify the tank or tank's fuel level sender? It'll still read the tank pressure just less modfication required.

Mtrhd329

I am running a LM7 in a 79 truck. I had to run a 87 blazer tank for the efi which has 4 ports on the sending unit. I used three to the motor and for the fourth on i clamped a piece of rubber hose on it and then clamped the FTPS on the other end of that. So far no issues although i am currently diagnosing an idle problem so i havent looked to far into how well it worked. Here in cali i was going to just run some dummy wires from it for inspection and tune it out but i think that i might just leave it hooked up. I know a guy who is running with it just mocked up and tuned out and he passed smog just fine.

jeepnut24

There is already one in the stock system that Im going to keep.

My stock level sensor is 1ohm empty and 88ohms full.

busta9876

iTrader: (3)

DTC P0461

This diagnostic tests for a stuck fuel level sensor signal. The PCM sets this DTC if the fuel level sensor signal appears to be stuck based on a lack of signal variation expected during normal operation.

Conditions for Running the DTC: Ignition is ON

Conditions for Setting the DTC: The PCM does not detect a change in fuel level of at least .79 gal over a distance of 200 miles.

Action Taken When the DTC Sets: 1. Fuel gage defaults to empty. 2. Low fuel indicator illuminates. 3. PCM records freeze frame data.

Not sure that PCM will continue testing eVAP system if this sets. I had this issue with a customer who was trying to do a emissions legal swap in CA. He had used a resistor on the fuel level circuit.

jeepnut24

Wow, thats a lot of good information. I think Im going to have to use a resistor in my fuel level system as well. The stock level sender is almost exactly 1/3 the ohms of the GM system.

orrious

You could go about this a couple different ways. I haven't personally done this, didn't need to maintain emissions when I did my swap.

#1 - The stock fuel pump in you YJ doesn't supply enough PSI for a LSx motor, so you'll need a new fuel pump no matter what. I changed my tank out so I could stretch my wheelbase, my original sender wasn't working, and when ordering the tank had a choice of fuel sender rings. I personally chose one from a '05+ TJ Wrangler as it supplies the right PSI and maintained the Jeep PCM resistance. In '05 they bumped up the PSI.

#2 - I assume you want to run your factory gauge cluster, therefore your going to need to run and supply both with the correct resistance, the Jeep PCM (0-90ohms) and the GM PCM (33-270ohms).

Mechanical Solution: Modify the tank to run both sending units, use the pump from the GM. (Painful IMO)

Electrical Solution: Run YJ sending unit (that way you don't have to modify the tank). Change the pump on the sending unit to any one of the aftermarket in-tank fuel pumps that push 60 PSI, (seriously not difficult). This will get the right signals to your Jeep PCM and the right fuel pressure. Only one last peice of the puzzle, scaling the resistance of the YJ sender to what the GM PCM is expecting. Using a "voltage controlled resistor" or "resistance multiplier" in a simple circuit you can apply the multiplier scale.

Hope this helps...

jeepnut24

Thanks, that does help. I hadn't planned on changing the internal pump, but that may be a better option in the long run.

Im also looking at the possibility of swapping out the gauges for aftermarket.

flame

iTrader: (13)

You should be more concerned with the volume that the pump can put out than the pressure. Most pumps are capable of 2X the PSI that it runs at. Doesn't matter how much PSI you have if it can't supply the volume.