Code 31 - Evaporative system 86 F-150

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Mar 11, 2005 | 08:36 AM

Trial and Error

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Code 31 - Evaporative system 86 F-150

I recently bought a code reader and tried it out on my 86 F-150, 302, EFI. It stored a code 31 which the book indicates is related to the evaporative control system. I know little about this system. I believe it has to do with recovery of fuel evaporation from the fuel tank by storing evaporative gases in a charcoal container and feeding the gases back into the engine. My question: Will this have any adverse effect on the performance of the engine or is it purely used for enviormental reasons? There is no inspection law in my state so I don't have to be concerned about that. I would like to fix it anyway, however, if I knew what to do about it. I can smell fuel sometimes when I exit the truck but I do not see evidence of a leak anywhere.

Last edited by Trial and Error; Mar 11, 2005 at 08:38 AM.

Mar 11, 2005 | 08:44 AM

felixr

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From: South East Florida

rip it all out if you are in a no emmisions state

Mar 11, 2005 | 08:45 AM

felixr

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From: South East Florida

cause it doesnt hinder your engine at all without it*

Mar 11, 2005 | 09:10 AM

Trial and Error

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Thanks for the advice. I'll do just that. One more question - I have replaced a noisy air pump on this vehicle once but the new one is making a howling noise now. Would it harm anything if I should remove the belt and run it without an air pump?

Mar 11, 2005 | 10:14 AM

felixr

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From: South East Florida

same as above. as part of the emissions system, the air pump simply pumps air back into the exhaust i think . . . fade into the words, you dont need it. dump it

actually, see if someone who DOES need it will buy it from you. i have mine sitting in my cab, it and the rest of truck are both for sale lol

Mar 11, 2005 | 10:16 AM

felixr

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From: South East Florida

if you DO leave it installed under the hood, and to answer your original question . . . no it wont harm anything to have no belt on it

Mar 12, 2005 | 11:18 AM

reamer

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From: Connecticut

Ah Yes the Code 31. Simple fix, and you shoul leave the emissions alone,
To fix a 31 remove the EGR sensor (3 or 4 screws) on top of the EGR valve.
you will see a "chrome" rod coming out of the bottom of the sensor you took off.
Place a dime or a penny into the egr valve. Replace the EGR.
Now the tip of the sensor has been pushed in to the sensor a little.
Erase codes and re-test. no more 31!!!!!!!!!!!!!!!!!!!
Remove the dime or penny you put in and get some "grindable" epoxie. apply some to the tip of the sensor. Let it harden and file it down till you get the specified voltage out of the sensor.
What happened was the computer is looking for a specific voltage fron the sensor.
Early on, some "out of Spec" Egr's got out and the rod goes too low with the replacement EGR's.