I have a 1999 RV with an F53 chassis.

I have had problems on my last three trips ... ECM died, coil, coil, ....

Last trip another miss started (another coil most likely). I am also having a strange problem of the idle going up and down at random between it's normal 800 rpm's and 1200 rpm's.

With 110K miles on the RV and 40K miles on the plugs I decided to change everything .. getting tired of paying $200 to change one coil while on vacation.

So, 10 new MotorCraft coils, new boots, new springs and new MotorCraft plugs ..... and 4 hours (I did use nickle anti-seize and di-electric grease).

While changing this I also found a couple of vacuum lines that look iffy so I replaced them at the same time.

WOW ... what a difference. Idle is rock solid, no miss ... great.

But now ..... there is a loud "sucking sound" from the engine.

I traced it down to a line that runs from the manifold to ?????. When I put my ear to it, you can clearly here the sound is coming from this tube. It looks like it has been replace at some time (looks like fuel line).

Then there is a larger line running from ??????? to two plastic boxes placed back along the frame.

The larger line is literally falling apart, but it does not seem to be leaking. I am going to replace it in the next few days.

So my questions ....

1) Is it normal for this large sucking sound through this tube? Did I just not notice it before?

2) What is the ???? device that the small tube goes into and the large one comes out off? Is it working? Should it allow this much air in?

3) What does this large tube do ( what are these two plastic boxes under the RV along it's frame)? I did not get a chance to see if anything comes out of these (maybe to the tank)?????

I have included two pictures. The first shows small vacuum line (red) going from the manifold to the ???? device (this is where all the noise is coming from) and the larger tube (green) going from the ???? device to the boxes under the RV. You can see the new coils and some new vacuum line (I used 1/4" fuel line) on the left.

The second picture shows the ???? device and the lines coming in and out. Behind the ???? device can be seen the cruise control device (yellow) and the cable comes out of it.

Thanks so much ..... Mike

 

I'm not familiar with the RV configuration but what you have pictured appears to be the EVAP valve and the hoses going back to the charcoal vapor canister.

 

I am heading back under the RV this morning to trace the larger line back.

The charcoal canister makes sense ... but just before the canister there is a Tee in the line. I need to find out where the other line goes.

So does it make sense that there would be enough air rushing through the small line going to the manifold to make my "sucking sound"?

I could only listen when it is idling but it seems the sound was constant. Should the EVAP valve be letting this much air in all the time or could it have failed?

Thanks ..... Mike

 

I love this forum ... you guys always set me on the right track.

OK, so the "larger line" does go to the charcoal canisters (two in a row) and to the gas tank (vent line).

So it looks like I still have two questions:

1) if there is a hole in the line ( or a bad gas cap or bad canister or ???? ) can the system suck too much air and if it does will it give me some kind of error code (trouble light on my dash)?

2) Can I test the EVAP by unplugging the electrical connection (it looks like this is a normally closed valve ... can someone confirm this) thus the "sucking noise" should stop. My only fear here is that I will get a trouble light and I don't have a code reader to reset it.

Thanks !!!!!!!!!!!!!!!

Mike

 

Your truck may or may not throw a code for EVAP failures, like "insufficient flow" and the like. It may not have the sensors to tell, or it might not throw a code even if it does notice a problem.

The idea for the EVAP system is that while running, the PCM will open that big valve (unknown device) to purge the charcoal canister of any gas vapors, and burn them by routing them into the intake manifold by the smaller vacuum hose (red line). When the engine is off, any vapors that come out of the tank (under low pressure) would go to the charcoal canister and be stored. Once the engine is started the PCM will again use engine vacuum to purge the canister of any vapors.

You shouldn't be able to hear it, at least, I've never heard one standing near any. And it shouldn't be doing it all the time.

There's usually a purge solenoid, and a flow sensor. Not sure what that thing is you named the unknown device, but it sure looks like it could be the solenoid (valve)

 

You are awesome!

I did not know how this works.

Yes, the first answer put me on the right path.

The device is listed (check Autozone and Rockauto) as "Emission Control Canister Purge Solenoid" and is listed as "Vapor Canister Purge Solenoid/Valve allows fuel vapor flow from the EVAP system".

It looks like there is no flow sensor in this line since the vent line goes into this solenoid and then directly into the manifold (with a small vent line off the solenoid going somewhere). There is only two wires going to the solenoid.

I have the engine heating up right now. I will pull the wires off in a few minutes and see if the valve shuts. If it does not, I know there is something wrong with it.

Thanks so very much for explaining how the system works!!!!!!!!!

I am very old school .... my "every day" vehicle is a 86 4x4 F-150 (manual everything) that has been stripped of every vacuum line, air pump and such. I am very lucky I live in a rural area and the local mechanics say as long as I still have a catalytic converter on it, they will let it pass it's yearly inspection.

Thanks so very much again !!!!!!!!!!!!

Mike

 

Well the valve must be working.

I pulled the wires off the solenoid and the noise stopped ... put them on and it starts so the computer must be telling the valve to open.

Funny, the sound is loud.

I had the engine hatch open and the RV was running. When I opened the door (to enter the RV from outside) first thing I noticed is not the engine noise but this sucking sound.

Anyway, looks like I don't have a problem ... or if I do it is a broken line from the solenoid to the canisters or gas tank.

Thanks so much for all the help!!!!!!!!!!!!!

Mike

 

Cool, at least you know what you're looking at now

I think the emissions for your year and size of truck means they didn't have to monitor the flow, so no codes get thrown (which kinda sucks).

Not that your small-town mechanics aren't helping you out, but even here in Metro NY, my 2001 F250 doesn't need a sniffer test, no OBD-II scan (it's only OBD-I) and it's just basically a safety check - no emissions whatsoever.

So in reality, you're good for an inspection even in the big city as long as the cat looks like it's there - except maybe in California

 

Keep looking for the real source of the noise - the valve could still be bad - internally venting the vacuum to atmosphere, for example. It kinda looks like a diaphragm being so big and round.

Gas vapors not being properly purged can be bad in an RV

 

I never let things go. I will definitely keep looking around.

I am a machinist by trade and as such a true fanatic when it comes to "doing it write". Heck, it took me a week to decide on what kind of anti-seize and how tight to set my new plugs at (yes, I used a torque wrench on them).

Just FYI .... You may or not have seen pictures of my RV project (I have posted here before asking questions).

I have stripped it, cut a new door and built my own wheelchair lifts so my wife could travel. She was paralyzed from the shoulders down in a diving accident when she was 12. She had never traveled as she needs care ever 4 hours.

Here is a link to the project: https://mcsele.shutterfly.com/2299

Thanks so much again!!!!!!!!!!

I am sure I will be back with more questions!

Mike