JohnCapoccia

I did a Gen III LS conversion in my FJ62 LandCruiser and I'm in the process of achieving California Air Resources Board certification. My EVAP monitor is not ready, I've done the drive cycles and put over 5000 miles on the vehicle. The company that built my harness and flashed my PCM did not include the fuel tank sender wiring. They told me that's not necessary to get the EVAP monitor to fire. I've read in many places that for the EVAP to fire, the fuel tank needs to be between 1/4 and 3/4, so I sent my PCM back and asked them to enable the fuel level. Here's my question - Can I "trick" the PCM by wiring in a resistor to emulate a 1/2 tank fuel level? I've determined that the sender is at about 550 ohms at the half way point. I don't need this to drive my fuel gauge, I've got the original Toyota sender for that. I'm just trying to avoid adapting the GM sender into the fuel tank. I'll just keep the tank between 1/4 and 3/4 until the EVAP monitor gets to the ready state, and after that, does it matter that the tank would be reporting as 1/2 full when it's not?

Thanks in advance for your help! - John

bczee

iTrader: (12)

I saw on guy that just stripped out the level sender from the assembly connected it up and just move the lever around to the correct level. Just hid the level sensor.

So, most likely you can just trick it as needed.

BC

JohnCapoccia

Yeah, I thought about that too. Maybe use a variable resistor. I tested a potentiometer that I had laying around, I can dial it in to 500ohm but it's very sensitive. Maybe I can find one that more closely mimics the range of the sender. It would be cleaner, I could mount the **** somewhere under the dash.

supra8

What about using this fuel sender converter to take the Toyota sender signal and convert it to a signal that the pcm likes?
https://www.summitracing.com/parts/cin-sn34

JohnCapoccia

Interesting... I looked at their website to see if I could download a manual to see how to install it. Couldn't find anything so I'll give them a call tomorrow. It sounds promising!

JohnCapoccia

I called Classic Instruments. They said the FuelLink device is not appropriate to send a signal to the PCM. Oh well, it was worth a shot.

KENS80V

iTrader: (16)

The evap system includes the purge solenoid (at engine), vent solenoid (near fuel tank), the vapor canister, fuel level signal and finally the fuel tank pressure sensor. It may never get to the "ready" state if it isn't receiving the signals from the various items I mentioned.

JohnCapoccia

So how does one test for those signals? I thought that lack of a signal would trigger a DTC. I believe the referee tested the evap system. He didn't write me up for any deficiencies other than the two monitors that weren't firing. I got the other one to go, I just need to get the evap going now.

KENS80V

iTrader: (16)

The company that flashed your PCM might have turned off the DTC lights for certain evap conditions (the sensors not connected). Not sure what model year and make you are using as a base tune.

JohnCapoccia

It's not likely that's the case. They regularly do PCMs and harnesses for smog legal California applications. I've sent the PCM back to them twice to check and recheck.

Krom

why don't they just flash it so the monitor shows ready?

JohnCapoccia

That's a possibility. I'm more or less trying to do it the "right" way. If I can get the monitor to fire, I'll go ahead and install the sender in the gas tank. I don't want to go through that if it isn't going to work.

In California, you are allowed to pass with one monitor failing to start, so long that it's the EVAP monitor. But another land cruiser buddy had his fail for that reason. The ref that he went to said that for a conversion, all monitors must be running, despite no documentation whatsoever to support his argument. (I definitely won't go to that ref). So plan A is to fix it so it works properly, plan B is to see if the ref will let it slide, and plan C is to do what you suggest.

But that's not even my main problem. The ref failed me because I installed corvette manifolds, because they fit better. They are considered "best practice" on land cruiser vortec conversions, because the exhaust dumps in the middle avoiding interference with the frame. Dozens have been approved in California with this configuration, but obviously I went to the wrong ref.

69 Ghost

What you need to do is run a LS evap system as wired and then wire your gas tank and gauge through the PCM. You can do this as long as you are using an older PCM but may need to get a Van PCM so that it has the gas circuits in the system. It does not matter if you have a 0-90 ohm gauge and sender and you can even mix em up. The newer blue/green OS's don't work quite the same way as the older ones and you may need a 50 or 100 ohm resistor inline to the sender and then program the rest. The gauge can stay the stock. Also you will need to make sure you have a sealed tank because there is a pressure sensor and if does not hold pressure it will think it has a bad cap. When you get it wired and setup you will have to program the gauge to calibrate it to what ever you decide to use for your sender and your gauge.

JohnCapoccia

Got it. I'm all wired up, the PCM is enabled for the fuel tank readings, and I've got the sender from the donor truck that's mated to the engine/PCM. Right now, just for an experiment to see if I can get the monitor running, I've wired in the sender at the 1/2 full position (it's just taped up under the hood). The good news is that it's trying to monitor, It's thrown a P0446 code a few times. It never did that before I had the pcm reflashed to enable the fuel tank reading. Research shows that vent valve is susceptable to clogging, there's a GM bulletin that describes the problem, and instructs to replace with an improved design. Just before re-flashing the PCM, I took a 4WD trip on the Mojave Road, where there were some pretty nasty sandstorms, which could explain the clogged vent valve. Anyway, I've ordered the improved vent valve, and I'll do a correct install of the sender in tandem with the toyota sender that drives my dashboard fuel gauge. If that doesn't work, I'll take it to a local emmissions specialist for troubleshooting.

JohnCapoccia

This is the best article on the EVAP system I've seen

http://www.jagrepair.com/images/Auto...%20Article.pdf

jonathan_ed3

iTrader: (4)

John, did you get this working?

It seems like so many EVAP conversion threads go unfinished/updated.

I'm trying to make an LS1 Purge control work with my Honda charcoal tank.

Some threads say that you only need the level sensor and pressure sensor for the DIAGNOSTIC EVAP self-check, but then others are saying you need them for the PCM to ever actually open the purge control.

I basically want to kill all the diagnostic functions and just have the PCM open the purge solenoid to vent vapor as necessary.

I haven't been able to determine if the two ideas are joined at the hip. Can I truly have functionality without diagnostics? I haven't been able to determine this.

I think it's important to clarify that I want the system to actually WORK, not just pass a test that will get me street legal.

JohnCapoccia

Jonathan,

No, I'm not there yet... Very frustrating. I agree, I've read hundreds of threads on Evap issues, it seems that NONE of them ever report resolution! Here's where I'm at: I've had my PCM reflashed so that everything is supposed to be working/monitoring. I still can't get the EVAP to start even after installing the fuel level sender. I started getting a P0446 code, which indicates a clogged vent valve. This tells me that the system is working, or at a minimum, trying to work, as you've described your concern. I've replaced the vent valve and solenoid with a new one, and it was good for about two weeks before throwing another P0446. My next step is to either relocate the valve/solenoid back closer to charcoal canister, or run a larger hose from the canister to the valve. Right now, I'm re-using the toyota hardline from the old, existing system, but it's a small diameter compared to the GM one. Maybe the PCM doesn't like that???

Of all the stuff I've read over the last six month, the only resolution is to make sure that the system isn't throwing codes, then keep driving it and eventually the monitor will start. So, I'll go ahead and tweak it to see if I can get it to stop throwing the P0446. My next step was to take it to an emmissions control specialist to see if he can figure it out.

So, I really can't answer your question with authority, but I *think* the system is working, so long as there are no DTCs. But maybe someone more knowledgeable will chime in.

69 Ghost

The evap is supposed to work with the tank level between 1/4 and 3/4's full. You need to have the level sensor and the pressure sensor going to the PCM. This is not hard but I believe you also need the newer style canister. The best approach is to use all GM LS style pieces. The canister should be near the tank not in the engine compartment like the older cars. Those only worked on vacuum. I have mine fully functioning and working no problem. One last thing is the tank should be approximately the same size or the tank size needs to be close. I think there is a portion that uses the pressure relief time to throw the code.

JohnCapoccia

Ghost, I have installed all the original parts from the donor car, except for the vent valve/solenoid, which I replaced with the upgraded part number. The upgraded vent valve has a remote filter. According to the GM bulletin, the original one located under the car by the gas tank clogged too easily (DTC P0446), so GM now recommends the upgrade with the remote filter placed above the transmission. I have the fuel level sender installed as well as the pressure sensor, and the PCM is flashed to accept the input from both. There's nothing I can do about the size of the gas tank, it's 23 gallons. I don't know how that compares to the donor truck, which was a 2004 Silverado 1500. The size of my tank is flashed into the PCM, so hopefully if the difference is material, it's accounted for properly. As I said in the previous post, I'm going to move the vent valve/solenoid back closer to tank, and HOPEFULLY that will get that monitor going. Any other suggestions? I'm really at my wits end with this.

69 Ghost

John I pm'd you. More info is needed. It is probably your OS programming and your fuel sending unit. If everything else is good. My guess is that you get it with a full tank.