Hi all,

This forum looks like a great place to find help! Any assistance you can give is much appreciated.

Here's some background on the truck in question:

1994 F-150 with the 4.9L engine. It's been used (and abused) by several owners before it came to me.

Two owners ago, someone attempted to modify the fuel injection system and managed to set the engine on fire. It didn't do extreme damage, but it melted some of the vacuum hoses and a few other parts as well. The owner didn't know how to fix the damage he had done, so he sold the truck cheap.

The guy who bought it knew enough to get it running again, but he capped off most of the vacuum hose ports instead of installing hoses. He then sold the truck to me.

I'm trying to hook everything up like it originally was. No modifications. I'd like to replace the existing vacuum hoses and hook up the missing ones.



Here's the main problem. Two hoses on the throttle body have been capped off. Where do they go?



From other photos I've found, it looks like they are joined into one hose, which goes toward the front of the vehicle. Does it go here?



Second problem: Where does this hose go?



Third problem: Is this a wire or a hose? Where does it go?



Here are some more pictures of the engine compartment:












If you need more photos or info, let me know.

Thanks!

 

Second Problem - that hose does not go anywhere, it is an air intake hose for the air pump.

Third Problem - that is a vacuum hose to the recirc vac motor. The hose is white and goes into the passenger compartment where it is controlled by the a/c panel.

 

Thanks! My AC only blows from the defrost vents, would this missing white hose cause the problem?

 

Possibly. I believe that hose has to do with the movement of switching vents or something

 

Great, thanks!

Do you know where the hose goes through the firewall into the passenger compartment? If the original hose was still there, I could figure out how to replace it. The problem with this truck is that I'm dealing with parts that are installed wrong or missing altogether.

Hopefully y'all will be able to bear with me, I've got more questions coming.

 

Yep! He's right. I'm not familiar with the 6's, so unfortunately I can't speak to problem 1.

I would want to take my air control panel out of the dash and look for any remaining vacuum lines. If they have been burned or lost from the engine bay, they may be partially there under the dash. They have to come through the firewall somewhere, but they might not show from the engine bay anymore.

 

Thanks FoxFord! I'll do that. It'll be nice to have A/C out the vents come summer. Down here in FL we get over 100 degrees during August.

The engine runs without those two lines on the throttle body, but it's running a bit rich especially at idle. Maybe the lines have something to do with it.

 

No, the white line is only active when you set control to Max A/C. If you will pull apart the wiring harness where the wires that attach to your blower motor are in, you will find the other half of the white hose. You can see that harness in your very last picture, just to the left of the heater hoses.

If you are always blowing from the defrost, that is a black hose that is also in the same harness as the white hose. It needs to be attached to manifold vacuum.

Looking at that last pic, I can see the little stub of the white hose sticking out, and I can see the black hose heading over towards the engine. Cannot see the other end, tho, to see what, if anything, it is connected to. It should be connected to the vacuum tree sticking out of your intake manifold. There might be a vacuum reservoir in between tho - if so it is on the side of the evaporator case.

 

Now that you posted that, I can't remember when, if ever, my control has been off of Max A/C. I'll try it in a different position and see if it makes a difference.

THANK YOU for circling the items in my picture!! That helps a lot. I was looking in the firewall for the other end of the hose. I didn't think to check the wiring harnesses.

I'll hook up the white hose, follow the black hose and report back with a few more pictures.

Thanks again!

 

I traced the black hose and discovered it was connected to nothing.



However, it's too short to connect to the vacuum tree. So I started looking for places it could be connected. Here's one possible path I found (path marked in blue and red):



The vacuum comes from the vacuum tree through a hose to a canister, then through another hose to a white connector. Could I hook the black hose up there? Am I correct in assuming that the canister is a vacuum reservoir?

I did some more research on Issue #1 (missing lines on throttle body) and found out they are supposed to go to the carbon canister (located under the battery.



Would capping them effect engine operation or make the engine run rich?

Thanks!

 

The Six that was in my truck is long gone so I cannot comment on your canister hoses. My truck's Six was replaced with a 460.

WRT the a/c line, you can use that vac reservoir as you have shown, but it's not for that. That reservoir, often referred to as the "coffee can", is for the air pump control hoses IIRC. The vacuum reservoir for the a/c is attached to the side of the evap case as I showed in my pic. It does not have in and out ports, only in. You hook up the line from the vac tree to a tee, one side goes to the vac reservoir and then you hook the black hose to the other side. The tee in your pic will work.



I recommend you go to eBay and purchase an EVTM for your truck. That stands for Electrical & Vacuum Troubleshooting Manual. It will help you sort all this out with wiring and vacuum diagrams.

 

Your pictures and instructions are helping me more than diagrams would.

Once I get the AC reservoir and the black hose hooked up to the vacuum tree, what should I hook up to the "coffee can"? Are there more hoses I need to find?
Thanks!

 

This is why you need the EVTM. My truck has 460 and so those hoses are all different on mine.

 

The vacuum system isn't too complicated, though it seems so.

From the tree on the manifold there should be:

One line to the fuel pressure regulator

One line to the MAP sensor

One line to the coffee can vacuum reservoir - one line out from the reservoir which feeds the AIR system solenoids in succession (meaning t-junctions) and the EGR solenoid, each solenoid then has a line going to the appropriate check valve or the EGR.

One line to the HVAC check valve (the side with the diaphram), one line to the HVAC reservoir (from the 90 degree port on the check valve), and the one line from the remaining check valve port feeds the HVAC system (passes through the firewall in the bundle on the passenger side, also where the white line comes out) If you remove the passenger side kick panel in the cab, and look under the dash you will find a number of vacuum lines for the HVAC system. As they are more or less protected from the elements they are probably in good shape, you just need to replace the supply line and the white line that are damaged from life in the engine compartment. As already stated you will need to pull apart the bundle that passes through the fire wall. You may be able to use a junction fitting with what is left of the lines or you may need to replace them entirely.

You will also have larger diameter hoses that provide vacuum to the brake master cylinder and the PCV check valve, (may come from another fitting on the manifold).

For your EVAP System -
in the engine compartment you should have one line from the fuel tank/s going into the Vapor Canister and a line going out of the Canister to the EVAP Purge solenoid, and then a line from the solenoid to a small fitting on the Throttle Body. This system collects fuel vapors and then under certain conditions those vapors are drawn into the throttle body.

The other two larger fittings on the throttle body are for coolant lines.

 

Thanks R&R! I checked the vacuum system with your description and here's what I have:

"The vacuum system isn't too complicated, though it seems so.

From the tree on the manifold there should be:

One line to the fuel pressure regulator - Got that.

One line to the MAP sensor - Got that too.

One line to the coffee can vacuum reservoir - one line out from the reservoir which feeds the AIR system solenoids in succession (meaning t-junctions) and the EGR solenoid, each solenoid then has a line going to the appropriate check valve or the EGR. The previous owner bypassed the coffee can and hooked everything directly to the vacuum tree. I'll put it back like you describe it here.

One line to the HVAC check valve (the side with the diaphram),
one line to the HVAC reservoir (from the 90 degree port on the check valve), and the one line from the remaining check valve port feeds the HVAC system (passes through the firewall in the bundle on the passenger side, also where the white line comes out) This was all disconnected but I'll hook it up like you describe.

You will also have larger diameter hoses that provide vacuum to the brake master cylinder and the PCV check valve, (may come from another fitting on the manifold). I have one to the brakes, but not to the PCV.

For your EVAP System -
in the engine compartment you should have one line from the fuel tank/s going into the Vapor Canister and a line going out of the Canister to the EVAP Purge solenoid, and then a line from the solenoid to a small fitting on the Throttle Body. This system collects fuel vapors and then under certain conditions those vapors are drawn into the throttle body. Will it affect the performance of the engine if I just cap off the fittings on the throttle body?

The other two larger fittings on the throttle body are for coolant lines."
Got it.