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Hi, I have a 1986 E 150 4.9L engine. When driving on acceleration the air would stop blowing from the front a/c vents and go to defrost only then when I let of the gas it returned to the vents. Not long after it would only come out the defrost vents. I changed the oil and noticed a part attached to a rubber hose hanging down near the frame on the passenger side. I have included a pic of the part. The other end of the hose looks like it is attached to a round metal part. Anyone know what it is and what it does? Also, I noticed two small dia. plastic hoses coming through the firewall on the drivers side. The one on the left is broken off so I don't know where it is supposed to go. The
other is partially broken and is attached to a T section that goes to the round air reservoir mounted in the back corner of the fender.
The can is probably a vacuum reservoir to keep AC functioning under low vacuum/high engine load conditions. Engine “supplies” vacuum to the can, AC “draws” vacuum from the can. There’s likely a check valve somewhere.
The above post is correct
The picture you posted is of the canister purge valve (burns fuel vapor from the fuel tank at cruise speed when the valve is commanded open by the processor)
One end hooks up to the carbon canister and the other to the upper intake /throttle body
Your defrost problem
Look for the little black vacuum line coming from the HVAC case area and yes there is a one way valve that fails in that line
Check the vacuum reservoir for leaking (the coffee can on your 86)
Occasionally but seldom will you need to replace the vacuum mode switch
Where is the carbon canister located?
I took a pic of the two vac lines comes from the cab one is completely broken off and I don't know where it connects. The other is connected to the pic that looks like a T connector. And pic of the round canister that that line goes into. Lines coming from cab.
The carbon canister is on the RH (passenger side) frame rail right behind the radiator on those older trucks
They had a tendency to rust out and rot away (the mount) Then they fall off
By the looks of your canister purge valve you have no carbon canister left on the vehicle
No big deal really and a canister can probably be obtained at the wrecking yard cheap
Repair those vacuum lines into the cab for the HVAC to work
Good luck
On my 88, the vacuum line you show that is broken does go to that check valve tee. the straight through connectors are the vacuum line from the firewall and the vacuum canister ball. The line that connects to the tee below the check valve, I couldn't see where it goes but it should be a constant vacuum source. The check valve holds vacuum in the canister and heater system when you are at wide open throttle.
The second connector, there is nothing on mine and I do not know of anything in the dash that requires vacuum except the heater vacuum motors. The connector on mine did not appear to have a hole in it but it was dark and i was using a flashlight. If it does have a hole init and is in fact a spare connector through the firewall, that is interesting to know.
The carbon canister on my 88 is rectangular shaped and is mounted on the frame rail under the passenger seat.
The broken vacuum line... You should be able to remove rubber fitting off of the connector and use a short piece of vacuum line to reconnect it back without changing the whole line..
I just thought a second line that might be needed on some vans but i am not sure about yours.. The water valve that closes off the flow through the heater core. My 88 with a 5.0 and FI does not have one but i believe the 5.8 did.. Not sure about yours but if you do then that second line could be for the heater control valve. It seems a round about way to get there but would save ford adding another penetration through the firewall.
The lines labeled 1 & 2 look like the two small black lines coming out of the cab. The partially broken line in my pic is plugged into the T connector and goes to the Vac reservior. Line 2 is completely broken looks like in the diagram the Green line but it's black. The line at the top labeled Black does go to the engine manifold. Do you think lines 1 & 2 have something to do with the air not coming out the a/c vents? What is the box with numbers 1 thru 9?
Except for being broken at the firewall, line #1 is all correct in the picture. It is connected exactly like my 88, except for one difference. The grommet that comes through the firewall on mine and has a sealing lip around it. yours appears to have been pushed in unless it is just made that way. If line #1 was repaired so that your controls would get vacuum to them, then if the rest of the system in good, then your HVAC vents should work correctly.
As for line #2. If your van has a heater valve on one of the heater hoses going to the heater core that looks similar to one of these https://www.rockauto.com/en/catalog/...ter+valve,6860
Then it needs vacuum from line #2 to control it. If it does not have a heater valve then perhaps like my 88, Ford did not install one and my guess is that the second port is just empty, if that is what it is for...
Is your 4.9 fuel injected or a carb? I am not as familiar with the specs of the 4.9 and the system is a little bit different from the 5.0 and 5.8 engines. My 85 with a 5.0 anc carb uses the purge valve while my 88 with a 5.0 and is fuel injected does not.
As to the canister purge valve, manicmechanic007 mentioned the VECI, vehicle emissions control information label. You should have a decal near the radiator support under the hood with the vacuum diagrams. It is specific to your van's emissions system.
I don't have time right now but will look through my 85 manual and see if they how how the purge valve connects to the engine and charcoal canister. There may also be a line going back to the gas tank from the canister. At least there were on some of the older cars I believe
Gonna say I do not see a canister purge valve in the photo but clearly your van has one
I think you are missing a one way valve where you say there is a tee
I am not familiar with ones that have 2 vacuum lines going inside myself (I believe my 94 5.8 only has one)
Thanks raye321 for the photos and I think only line #1 referenced is outside the firewall with the one way valve (the tee)
Somebody maybe ran another vacuum line into the cab?
Once again only the reservoir and the check valve are under the hood in that diagram the rest is inside
IMHO
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