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Old 07-18-2018, 02:19 PM   #1
waynegarbo
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Default 86' 740 EVAP System Questions

After putting vaccum on the canister purge valve should I hear and feel a significant flow through the evap port and out the pcv port by blowing through it? Or am I doing the "blow"
through test incorrectly?

How do you know if the purge/check valve is stuck?

How do you know if the gas filler neck is out of round?

Is there a roll over valve test?

I don't have a smoke machine, so, carefully, will cigar smoke, through the filler neck evap tube work to test the gas cap? How would I distinguish between smoke coming out of the cap or an out of round filler neck?
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Old 07-18-2018, 02:24 PM   #2
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I'm interested in this as well BUT for my smoke machine I use a...

Paint can. Put in air input on it and an air output on it. Stick some incense in some hard foam in the base. Light it. Wait a hot minute. Hook up to a grill flow regulator and blow air through it. Works great. $20.
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Old 07-18-2018, 05:18 PM   #3
ZVOLV
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Did you fail smog for evap?
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Old 07-18-2018, 07:35 PM   #4
waynegarbo
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Default 86' EVAP System Questions

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Did you fail smog for evap?
No, getting it ready, as, 2yrs ago, the tech passed the evap but said there was a leak and I also have never had any gas tank pressure as I used to when I loosen the gas cap. That concerns me why. It may be cause I took my sending unit out before the smog 2yrs ago. I never really thought I had a good seal as I was trying to jam and fit it in, so, just about two weeks ago I replaced the seal. So far my tank is still not pressurizing. Some say to fill my tank. So I'll try that but hell even with 3/4 tank I still don't hear any pressure release.
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Old 07-18-2018, 07:38 PM   #5
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Originally Posted by EivlEvo View Post
I'm interested in this as well BUT for my smoke machine I use a...

Paint can. Put in air input on it and an air output on it. Stick some incense in some hard foam in the base. Light it. Wait a hot minute. Hook up to a grill flow regulator and blow air through it. Works great. $20.
What is a grill flow regulator?
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Old 07-18-2018, 07:47 PM   #6
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When there is an open in the EVAP system you will usually smell gas either inside the car, under the hood or in the garage (if you park in one). Simply having no pressure escaping the tank when you remove the cap is not an indication that something is wrong.

Back when I was doing pressure tests on EVAP very often the STANT adapter used with the pressure machine had bad fit on many Volvos (mainly 240's) which made it difficult to pass functional test. IIRC we were allowed to actually skip doing the pressure test because Volvo filler neck was not working well with Stant adapters. I don't know if they use revised adapter now or what.
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Old 07-18-2018, 08:15 PM   #7
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What is a grill flow regulator?
https://www.amazon.com/Bayou-Classic...%3A11292772011
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Old 07-18-2018, 10:15 PM   #8
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Quote:
Originally Posted by PCH View Post
When there is an open in the EVAP system you will usually smell gas either inside the car, under the hood or in the garage (if you park in one). Simply having no pressure escaping the tank when you remove the cap is not an indication that something is wrong.

Back when I was doing pressure tests on EVAP very often the STANT adapter used with the pressure machine had bad fit on many Volvos (mainly 240's) which made it difficult to pass functional test. IIRC we were allowed to actually skip doing the pressure test because Volvo filler neck was not working well with Stant adapters. I don't know if they use revised adapter now or what.
Ok this is what I needed to hear. Therefor my car is ready for Smog.
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Old 07-18-2018, 10:29 PM   #9
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Make sure you have the preheat hose and that the thermostat in the airbox isn't stuck open.

How fresh is the cat?

Make sure the ignition timing is correct.

For the evap test they pinch off the line going into the charcoal canister from the tank and apply pressurized nitrogen into the fuel neck and check if it holds with the machine.

Last edited by ZVOLV; 07-18-2018 at 10:57 PM..
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Old 07-19-2018, 12:01 PM   #10
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Quote:
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Make sure you have the preheat hose and that the thermostat in the airbox isn't stuck open.

How fresh is the cat?

Make sure the ignition timing is correct.

For the evap test they pinch off the line going into the charcoal canister from the tank and apply pressurized nitrogen into the fuel neck and check if it holds with the machine.
I don't know what this means: Make sure you have the preheat hose and that the thermostat in the airbox isn't stuck open.

My cat is 2yrs old

Timing good

yes I will make sure they pinch off the larger rubber hose and not the small hard plastic one
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Old 07-19-2018, 02:57 PM   #11
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Flex hose from box. If missing you may fail. Airbox has a thermostatic operated flapper. When they fail, it will always suck in hot air and can fry the MAF. Some block it off mechanically, with rags for example.
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Old 07-19-2018, 04:45 PM   #12
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Quote:
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Flex hose from box. If missing you may fail. Airbox has a thermostatic operated flapper. When they fail, it will always suck in hot air and can fry the MAF. Some block it off mechanically, with rags for example.
Not sure what this is but I don't have this on my car.
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Old 07-19-2018, 08:12 PM   #13
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Not sure what this is but I don't have this on my car.
He's referring to the silvery hose that is attached to a heat shield on your exhaust manifold and runs into a flap on your airbox. That flap is controlled by a small piston thermostat that actuates the flap. The idea is that when the motor is cold, the flap can be open and draw hot air from around the exhaust manifold and once the motor warms up, it can close the flap and draw appropriately temp'd colder air.

I personally think it's an idiotic system. However... if you need it to pass smog then I guess you need it to pass smog.
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Old 07-19-2018, 08:13 PM   #14
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This.

https://www.google.com/search?q=volv...w=1536&bih=732
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Old 07-19-2018, 08:24 PM   #15
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Ok thanks
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Old 07-19-2018, 08:28 PM   #16
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Quote:
Originally Posted by waynegarbo View Post
I don't know what this means: Make sure you have the preheat hose and that the thermostat in the airbox isn't stuck open.

My cat is 2yrs old

Timing good

yes I will make sure they pinch off the larger rubber hose and not the small hard plastic one
How do you open it to check the thermostat?
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Old 07-19-2018, 10:32 PM   #17
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Quote:
Originally Posted by waynegarbo View Post
How do you open it to check the thermostat?
The thermostat is just this thing.

https://www.google.com/search?q=volv...hrome&ie=UTF-8
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Old 07-19-2018, 11:11 PM   #18
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Evo, where is it located. Outside? Or do I take it apart? How do I know it's stuck open? What drives this thing, voltage or vac?
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Old 07-20-2018, 12:53 PM   #19
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Evo, where is it located. Outside? Or do I take it apart? How do I know it's stuck open? What drives this thing, voltage or vac?
It's a temp spring. No wires or anything. It's in the airbox. and connected to the flapper which iirc is on the lower engine side of the box. I'm not certain honestly because none of my cars have ever used it so I'm going from very limited memory.

If you unclip your airbox like you would to change the filter, you should be able to find the flap. That flap should have the thermostat actuate it (iirc it's pretty small. Maybe the size of a medium bolt?) and then the hole on the other side of the flap (which is internal and external (the hole)) would have that heater hose connected to it.

I can't find a great pic honestly...
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Old 07-20-2018, 11:52 PM   #20
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Quote:
Originally Posted by EivlEvo View Post
It's a temp spring. No wires or anything. It's in the airbox. and connected to the flapper which iirc is on the lower engine side of the box. I'm not certain honestly because none of my cars have ever used it so I'm going from very limited memory.

If you unclip your airbox like you would to change the filter, you should be able to find the flap. That flap should have the thermostat actuate it (iirc it's pretty small. Maybe the size of a medium bolt?) and then the hole on the other side of the flap (which is internal and external (the hole)) would have that heater hose connected to it.

I can't find a great pic honestly...
Ok thanks I'll check it out.
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Old 07-25-2018, 05:19 PM   #21
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Ok thanks I'll check it out.
Ok EVO I took the air box out. Yeah my thermostat sits in a molded cylinder in the air box. Yes, when you push on the thermo it opens the flap. The thermo spring cylinders a probe attached to the flap. That spring, I'm not able to remove, hence, remove the thermo.
So I shimmed a piece of rubber hose between the pivot and the housing in the open position and spread some glue over the top of it to keep it propped open.
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Old 07-25-2018, 05:51 PM   #22
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You want it stuck closed so it doesn't stay remain stuck open and suck hot air all the time.
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Old 08-06-2018, 09:26 PM   #23
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Quote:
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You want it stuck closed so it doesn't stay remain stuck open and suck hot air all the time.
ZVOLV-I thought the flap works the way I propped it open. I propped it open to allow vent air in from the larger port facing the radiator?
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Old 08-08-2018, 04:57 PM   #24
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Quote:
Originally Posted by PCH View Post
When there is an open in the EVAP system you will usually smell gas either inside the car, under the hood or in the garage (if you park in one). Simply having no pressure escaping the tank when you remove the cap is not an indication that something is wrong.

Back when I was doing pressure tests on EVAP very often the STANT adapter used with the pressure machine had bad fit on many Volvos (mainly 240's) which made it difficult to pass functional test. IIRC we were allowed to actually skip doing the pressure test because Volvo filler neck was not working well with Stant adapters. I don't know if they use revised adapter now or what.
I did fail the evap test with a gross evap leak reading. I do not smell gas anywhere. I have checked all the lines and fittings. Previous to the fail, I changed my sending unit seal but I do not smell gas around the sending unit. I have done a hand vac test on the gas line(s) to and from the rollover. Vac held. When I did a vac test THROUGH the rollover I get no vac.
I did a smoke test from the canister, and from the rollover. I also blew cigar smoke directly
into the filler. I do not see any leak. But then again it's not professional and the car is on jack stands.
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Old 08-08-2018, 07:16 PM   #25
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Cigar smoke isn't gonna cut it!
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