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  #1  
Old 03-04-2002, 10:32 PM
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vkykam vkykam is offline
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Evaporative Emission Control System

I'm referring to the system that traps the gasoline vapours from the tank, stores it in the charcoal canister, and then uses it up.

Anyhoo, service manual says to test the system, remove the fuel filler cap, blow into the line that goes to the tank to check that there's no obstruction (i.e. that air can be blown through), and blow into the line that goes towards the engine, to make sure there's no leakage.

Well, when I blow on either hose, I can't blow into it. What could be wrong? I wonder if this is why there's "excessive" pressure buildup inside the gas tank, as it can hiss for 5 or 6 seconds as I remove the gas cap for refuelling. I am also suspecting that this might be causing my hard start problem, which only happens when the engine is "luke warm", and takes 8 or 9 cranks before the engine rotates without the assistance of the starter.

Help?

VK
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  #2  
Old 03-04-2002, 10:56 PM
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Re: Evaporative Emission Control System

Quote:
Originally posted by vkykam
Anyhoo, service manual says to test the system, remove the fuel filler cap, blow into the line that goes to the tank to check that there's no obstruction (i.e. that air can be blown through), and blow into the line that goes towards the engine, to make sure there's no leakage.

Well, when I blow on either hose, I can't blow into it. What could be wrong? I wonder if this is why there's "excessive" pressure buildup inside the gas tank, as it can hiss for 5 or 6 seconds as I remove the gas cap for refuelling. I am also suspecting that this might be causing my hard start problem, which only happens when the engine is "luke warm", and takes 8 or 9 cranks before the engine rotates without the assistance of the starter.

Help?

VK
First off, I can only think of one evap hose between the canister and fuel tank. The other two are fuel supply and fuel return. If you can't blow through the evap hose, which, BTW, must be a heckuva lot of fun, it may be that the rollover valve is stuck closed. (you didn't roll the car over on its top to do this, did you? ) Pressure build-up in non-vented tanks is not abnormal, most gas caps will warn you of the possibility of pressure blow-back if the cap is released too quickly.

I highly doubt that this would be the cause of any hard start problems, no matter what temperature. If you're thinking rich mixture/hot engine = hard start that would most likely occur from a dribbling injector, and that's not uncommon at all. I've replaced three injectors similar to the SVXs in the past couple weeks for the same reason. (Nissan Maxima, Mercury Villager, Chrysler LH something) Once the engine starts do you need to 'clean it out' a tad before it runs right? (raise the rpm/goose the throttle)

Beav
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Old 03-05-2002, 06:53 AM
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vkykam vkykam is offline
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Re: Re: Evaporative Emission Control System

I guess I'll have to have the injectors tested one day. C'est la vie.

On the subject of the roll-over valve. IF it's stuck closed, would it be a problem? You know, other than the fact that I won't be able to drive upside down?

Service manuals says if there's a problem with the evaporative emission control system, that a rough idle "could likely" be the cause of it. In your experience, could it? I'm also trying to hunt down a rough idle that cropped up in the past week or two, which I think may be the MAF or the TPS.

Thx, Beav.

VK



Quote:
Originally posted by Beav


First off, I can only think of one evap hose between the canister and fuel tank. The other two are fuel supply and fuel return. If you can't blow through the evap hose, which, BTW, must be a heckuva lot of fun, it may be that the rollover valve is stuck closed. (you didn't roll the car over on its top to do this, did you? ) Pressure build-up in non-vented tanks is not abnormal, most gas caps will warn you of the possibility of pressure blow-back if the cap is released too quickly.

I highly doubt that this would be the cause of any hard start problems, no matter what temperature. If you're thinking rich mixture/hot engine = hard start that would most likely occur from a dribbling injector, and that's not uncommon at all. I've replaced three injectors similar to the SVXs in the past couple weeks for the same reason. (Nissan Maxima, Mercury Villager, Chrysler LH something) Once the engine starts do you need to 'clean it out' a tad before it runs right? (raise the rpm/goose the throttle)

Beav
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Old 03-05-2002, 07:15 AM
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It's my experience that 90% of rough idle complaints are a bad vacuum hose - cracked, split or fell off. 5% are a bad spark plug &/or wire (no wires on SVX.) I'll leave the last 5% to weird stuff - highly unlikely. If you had a TPS or MAF problem you'd more likely be experiencing other problems. Always start with the basics - air, fuel, spark.

If I were you I'd change the spark plugs and PCV valve, if not done in the last 20-30,000 miles. Look over the vacuum hoses closely, sometimes a good ear is better than a good eye here. If you can't quite put your finger on a leak, try using a spray of carb cleaner while the engine is running. No need to soak the engine with it, just a light spray (use the straw in the nozzle) along vacuum hoses and manifold seams is enough. DON'T spray it into/onto something that's likely to cause a fire (spark plugs, alternator, hot exhaust, etc.)

The rollover valve keeps gas from draining through the vent hose if the vehicle ends up on its roof. No use adding injury to insult. Theoretically it could cause a rough idle, but highly unlikely. Most of the problems I see with evap these days is a hose that's fallen off or a missing gas cap. You might check to see if the steel line has been crimped by a jack or such. If you disconnect the line at the canister and the tank (or maybe better yet the rollover valve) you should be able to blow through it fairly easily.

I'm not trying to scare you or cause unnecessary expense but a leaking injector can lead to some nightmares. However, if you're having rough idle AND warm start problems check the plugs, etc. first.

Beav
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  #5  
Old 03-06-2002, 05:57 PM
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vkykam vkykam is offline
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Beav,

Thx much for the info.

Plugs are on order, I'm going with the NGK Iridium plugs. I've had the Bosch Platinum's in there for about 30k miles, so it's due anyways, along with the fuel filter.

I'm glad you reminded me about vacuum leaks. I've acutally had a leak on the hose going into the air box next to the throttle body. I did "goop" it real good the last time (the air box is cracked), but I think I'll be removing the box this time and do the repair from the inside instead. It'll give me a chance to clean the throttle body as well (probably much need too).

VK
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