California smog a tad better than I thought?

[Clone TIE Pilot]

According to this thread ....

https://gbodyforum.com/threads/gn-sending-unit-for-lt1-swap.60711/

.... the LT1 has the same problem? He says (post #4) that the LT1's original tank had an on-tank vent valve, in addition to the usual vapor canister line.

The LT1 went OBDII in 1996, so maybe 1992-95 don't have this feature. The LT1 only acquired a crank sensor in 1996 because OBDII required one. But that would mean if you want SFI you'd only have two years, 1994 and 1995.

I know there aren't any LT1 truck motors, but until now it has been on my broader list of possible swaps. More nit-picky complications swapping in California?

Are you absolutely sure about this gas tank thing being a problem? As I understand it, in California the vapor canister is technically considered a feature of the vehicle being swapped into, not the engine being swapped in, even though the engine purges the canister. The same would presumably be true of an on-tank vent valve, even more since the engine has no role in the on-tank valve's operation.

I don't know how OBD1 LT1s are set up, but I do know that OBD2 engines use an enhanced evap that pressurizes the gas tank, then uses a pressure sensor on the tank to monitor it. If there is a leak anywhere in the evap system, the gas tank pressure will drop setting off the sensor, which sets off the SES light. This is why leaving the gas cap off on a OBD2 cars sets off the SES light, the computer thinks there is a leak. The enhanced evaps are much more tightly sealed than G body evap systems, even using A/C style O ring seals. Of course stock G body gas tanks do not have provisions for pressure sensors or designed to be pressurized, but the law does not consider this as deleting the gas tank sensor from any OBD2 engine is illegal. The Erod is the loophole as it does not come with enhanced evap, just plain evap, there is no pressure sensor to delete.

One of the biggest sources of pollution from a car is light hydrocarbons escaping from the gas tank as the car sits, even when its not running. This is why they make such a big fuss over it. Engine swapping laws were written years before OBD2 came out. Over on LS1tech, there are horror stories of guys doing complete LS1 swaps into G bodies in CA, but are still failed over the gas tank pressure sensor. One guy ended up selling his LS1 and buying a Erod kit which passed.

 

[jiho]

I don't know how OBD1 LT1s are set up, but I do know that OBD2 engines use an enhanced evap that pressurizes the gas tank, then uses a pressure sensor on the tank to monitor it.

Well I think you're right, and that would kill *any* OBDII swap. Thanks.

I'm betting 1992-95 LT1s don't have this feature, since they don't have crank position sensors. Anyone who actually knows, feel free to speak up.

 

[jiho]

From: https://www.obd-codes.com/p0452

"P0452 EVAP Pressure Sensor/Switch Low

"This diagnostic trouble code (DTC) is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may be slightly different depending on the model."

(Guy who wrote it is a mechanic, hence the "repair steps" part.)

 

[gthmcty1]

Pay $150 and your good for 2 years!!

 

[jiho]

Until the perp gets busted, anyway. May depend on who's up re re-election.

Meanwhile, without a swap you can run your G-body tank forever, because that's what GM built. The rules say you can't make emissions worse, but in cases like this you can't improve them either! An LS would improve emissions, while lacking the LS tank setup would not make them worse. But there's one nagging little bureaucratic technical detail that says you cannot reprogram the LS PCM to ignore the pressure sensor fault.

And if you "opt" for the E-Rod, that's closer to $15,000 than $150.

 

[jiho]

So from what I can determine, it appears no Gen II LT1 ever had a tank pressure sensor, and the truck motors got them for '97. So it looks like a lag of a year or two after OBDII on that. But you'd have to double check whatever you're looking at because it could trip you up and I wash my hands of it.