• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

86' 740 EVAP System Questions

W

waynegarbo

New member
Joined
Jul 18, 2018
Location
Fresno
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?
 
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.
 
86' EVAP System Questions

ZVOLV said:
Did you fail smog for evap?
Click to expand...

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.
 
EivlEvo said:
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.
Click to expand...

What is a grill flow regulator?
 
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.
 
PCH said:
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.
Click to expand...

Ok this is what I needed to hear. Therefor my car is ready for Smog.
 
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:
ZVOLV said:
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.
Click to expand...

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
 
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.
 
ZVOLV said:
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.
Click to expand...

Not sure what this is but I don't have this on my car.
 
waynegarbo said:
Not sure what this is but I don't have this on my car.
Click to expand...

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.
 
waynegarbo said:
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
Click to expand...

How do you open it to check the thermostat?
 
waynegarbo said:
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?
Click to expand...

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...
 
EivlEvo said:
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...
Click to expand...

Ok thanks I'll check it out.
 
You must log in or register to reply here.
Back
Top