84-460-Project Posted November 23, 2019 Share Posted November 23, 2019 It all started by troubleshooting the AC/Heater/Temperature controls. The truck is defaulting to defrost. Following tips from the forums I traced the vacuum lines from the control knobs in the cab to the engine bay. Half the lines are missing (I think) and there is no distribution panel on the firewall in the engine bay. After doing some more research I believed the problem to be a disconnected air pump. I bought a belt, connected the air pump to the alternator, turned the truck over and expected to pull vacuum. Nothing. Now I'm scratching my head and seeking advice. Is this an air pump? Does the air pump create vacuum for the heater/ac/temp control knobs in the cab? Link to comment Share on other sites More sharing options...
84-460-Project Posted November 23, 2019 Author Share Posted November 23, 2019 One more thing. This is the vacuum hose diagram from this 1984 F250 w/a 460 and AC. All the vacuum lines are missing and I'm having a hard reading/understanding this diagram. Any help is appreciated. Link to comment Share on other sites More sharing options...
85lebaront2 Posted November 23, 2019 Share Posted November 23, 2019 Air pump is for emissions, vacuum is sourced off the intake manifold behind the carburetor. There should be a line from there to a small vacuum manifold on the firewall near the underhood HVAC case. The vacuum line may tee to a small tank after going through a check valve. This may help, I had already updated my HVAC system to a 1996 so the vacuum tank on yours will be a metal can on the fender. Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 23, 2019 Share Posted November 23, 2019 Air pump is for emissions, vacuum is sourced off the intake manifold behind the carburetor. There should be a line from there to a small vacuum manifold on the firewall near the underhood HVAC case. The vacuum line may tee to a small tank after going through a check valve. This may help, I had already updated my HVAC system to a 1996 so the vacuum tank on yours will be a metal can on the fender. Good job, Bill. But there are a few more pics here, just in case: Documentation/Underhood/Vacuum Systems. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted November 23, 2019 Share Posted November 23, 2019 One more thing. This is the vacuum hose diagram from this 1984 F250 w/a 460 and AC. All the vacuum lines are missing and I'm having a hard reading/understanding this diagram. Any help is appreciated. The vacuum diagram on the compliance sticker only deals with emissions related components. Gosh, I wish mine were that simple! But you need the diagram for the climate control. That would be found in the back of the EVTM. Link to comment Share on other sites More sharing options...
85lebaront2 Posted November 24, 2019 Share Posted November 24, 2019 The vacuum diagram on the compliance sticker only deals with emissions related components. Gosh, I wish mine were that simple! But you need the diagram for the climate control. That would be found in the back of the EVTM. Jim. it could be this one: This is the one from the 1990 parts donor truck. It's even simpler now, no need for the air pump as it's sole function was to feed the center of the catalytic converter, also no MAP sensor with MAF. Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 24, 2019 Share Posted November 24, 2019 The vacuum diagram on the compliance sticker only deals with emissions related components. Gosh, I wish mine were that simple! But you need the diagram for the climate control. That would be found in the back of the EVTM. Yes - here's where to find the 1985 EVTM: Documentation/Electrical/EVTM/1985 EVTM. The basic vacuum diagram is show on #32 Vacuum, and the HVAC vacuum diagrams are on #35 A/C Heater. Link to comment Share on other sites More sharing options...
84-460-Project Posted November 24, 2019 Author Share Posted November 24, 2019 The vacuum diagram on the compliance sticker only deals with emissions related components. Gosh, I wish mine were that simple! But you need the diagram for the climate control. That would be found in the back of the EVTM. Yes - here's where to find the 1985 EVTM: Documentation/Electrical/EVTM/1985 EVTM. The basic vacuum diagram is show on #32 Vacuum, and the HVAC vacuum diagrams are on #35 A/C Heater. Great information. Thanks for posting the EVTM. It appears I missing (2) critical pieces: A (5) port manifold fitting and a vacuum distribution block. I have a (3) port manifold fitting on the back of the intake (picture) that feeds the transmission, brake booster and speed servo. I have a (2) port vacuum tree and (3) port vacuum tree both coming off of the coolant line/thermostat housing (picture) at the front of the engine. None of these are creating vacuum. I assume i need to go find a (5) port manifold fitting and a (3) port vacuum distribution block? Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 24, 2019 Share Posted November 24, 2019 Great information. Thanks for posting the EVTM. It appears I missing (2) critical pieces: A (5) port manifold fitting and a vacuum distribution block. I have a (3) port manifold fitting on the back of the intake (picture) that feeds the transmission, brake booster and speed servo. I have a (2) port vacuum tree and (3) port vacuum tree both coming off of the coolant line/thermostat housing (picture) at the front of the engine. None of these are creating vacuum. I assume i need to go find a (5) port manifold fitting and a (3) port vacuum distribution block? If the only thing w/o manifold vacuum is the HVAC system just plug it into the manifold vacuum port on the front driver's side of the carb, as shown in Figure 1 in the Edelbrock installation manual. But, as was said, you do need the check valve/tee and vacuum reservoir shown in the Vacuum Systems pics or your HVAC system will default to Defrost when the vacuum goes away with heavy throttle. As for the ones on the thermostat housing, they are temperature controlled and were part of a complex system to provide vacuum for various emissions systems at specific temps. Since you have an aftermarket carb and no belt on the AIR pump I'm guessing you aren't worried about emissions. In that case I would remove those valves and plug the holes with pipe fittings. Then I'd set my vacuum advance up with ported vacuum from the timed port on the Edelbrock carb, which is the port on the front passenger's side. And if you aren't using the thermactor system we can talk about how to remove it. Link to comment Share on other sites More sharing options...
reamer Posted November 24, 2019 Share Posted November 24, 2019 If the only thing w/o manifold vacuum is the HVAC system just plug it into the manifold vacuum port on the front driver's side of the carb, as shown in Figure 1 in the Edelbrock installation manual. But, as was said, you do need the check valve/tee and vacuum reservoir shown in the Vacuum Systems pics or your HVAC system will default to Defrost when the vacuum goes away with heavy throttle. As for the ones on the thermostat housing, they are temperature controlled and were part of a complex system to provide vacuum for various emissions systems at specific temps. Since you have an aftermarket carb and no belt on the AIR pump I'm guessing you aren't worried about emissions. In that case I would remove those valves and plug the holes with pipe fittings. Then I'd set my vacuum advance up with ported vacuum from the timed port on the Edelbrock carb, which is the port on the front passenger's side. And if you aren't using the thermactor system we can talk about how to remove it. BTW The air pump is just that, a PUMP. only thing that creates vacuum is the running engine. Link to comment Share on other sites More sharing options...
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