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EVAP system problem, 99 STS


hiljak

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Hello all, I haven't been around in while (that's a good thing right?). Anyway, I have a problem with my STS... it's throwing a P0440 code (EVAP) and also a check gas cap message. I changed the cap with a new one from Caddy, same problem is still there.

I can clear the code and the messge and engine light will be off for a day, then their back.

Here's another wierd thing, once that code has been set (and is currently showing the light), I can't get gas with the engine running. It will take some gas into the tank, then spit it back out. Yes, you read that right, it spits the darn gas right back out! I think it may be pressurising the fuel system while that code is set.

How does one go about troubleshooting this?? Thanks guys.

James

1999 STS 65k

1995 STS 127k

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Is P0440 the only code or are there other P codes (like 0442, 0452, 0453)? They could show as history codes but they are still important.

Basically, your evap. system is not able to develop vacuum. Another code would narrow down the potential problem pieces.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Hello all, I haven't been around in while (that's a good thing right?). Anyway, I have a problem with my STS... it's throwing a P0440 code (EVAP) and also a check gas cap message. I changed the cap with a new one from Caddy, same problem is still there.

I can clear the code and the messge and engine light will be off for a day, then their back.

Here's another wierd thing, once that code has been set (and is currently showing the light), I can't get gas with the engine running. It will take some gas into the tank, then spit it back out. Yes, you read that right, it spits the darn gas right back out! I think it may be pressurising the fuel system while that code is set.

How does one go about troubleshooting this?? Thanks guys.

Look in the top of the wheel well and see if the pipe that runs from the gas filler to the tank is corroded, your car is fairly new, it's just a thought, Mike

We have seen these pipes rust

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Hi guys, thanks for the replies.

The other two P codes listed I didn't think were related. One is P1189 which is a bad oil pressure sensor which I haven't had a chance to change and the other is P1617 (history) glow plug short to ground (not sure about that one).

I will check the pipe you mentioned and report back. Are there sensors which could be bad?

Checked the pipe, it looks great. It seems to be coated in an "under coating" type of stuff. No visible rust or corrosion.

Any other suggestions?

James

1999 STS 65k

1995 STS 127k

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  • P0440 - Evaporative Emission (EVAP) System
  • P1189 - Engine Oil Pressure (EOP) Switch Circuit
  • P1617 - Engine Oil Level Switch Circuit
If you mean by "It will take some gas into the tank, then spit it back out"that gas runs on to the ground from under the car, then BodybyFisher is probably right, there is a break in the filler tube. There is a connector from the fillter tube to the gas tank; you might look at that too.

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...

Here's another wierd thing, once that code has been set (and is currently showing the light), I can't get gas with the engine running. It will take some gas into the tank, then spit it back out. Yes, you read that right, it spits the darn gas right back out! I think it may be pressurising the fuel system while that code is set.

How does one go about troubleshooting this?? Thanks guys.

hiljak,

My understanding is not to add gas when the car is running, period...

I don't remember why, but I got the information here...

good luck..

my .02

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....

Here's another wierd thing, once that code has been set (and is currently showing the light), I can't get gas with the engine running. It will take some gas into the tank, then spit it back out. Yes, you read that right, it spits the darn gas right back out! I think it may be pressurising the fuel system while that code is set.

How does one go about troubleshooting this?? Thanks guys.

On your vehicle, there is a check valve (part of the on board refueling vapor recovery) at the base of the filler tube. Sounds like that check valve is stuck closed or being held closed somehow and that is preventing the fuel from flowing to the tank.

Unless you are willing to do some hit or miss tearing things apart, I would run all the symptoms past your local friendly Cadillac dealer service manager. Go right to the top of the food chain.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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