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It could stop it from starting. Did you try spraying starting fluid in the intake? When I had bad Dual Function Reservoirs, it was more of a running problem, than a starting problem. When you cycle the key to the run position, do the fuel pumps kick on for about two seconds? I would recommend posting your questions in a Ford F-150 forum. You'll get a lot of answers there.

Thank you, John for getting back to me. I really do appreciate it. I wrote this whole thing out and went to go sending it and wouldn't go through I did spray starting fluid into the intake and it did start up but stalled. After that, I replace the fuel pressure regulator I do hear each fuel pump in Each gas tank kick on for a couple of seconds when the key is turned to the on position, I removed the fuel filter and blew through it. That was clear that was replaced about 3 years ago when I seen your video. I was thinking. Could that be the cause of my truck not starting when I select either tank from inside the cab? I could see the gauge going up or down depending on how much gas is in each tank. So I'm not sure now. If that would be my problem, I know there's a high pressure pump, in front of the fuel selector Canister, and then after the high pressure fuel pump is the fuel filter and then on to the fuel rail. I believe now that I'm thinking maybe you would know. Could it be the high pressure fuel pump? Thank you for any bit of information that you could give me ​@@johnd.9145

@@nickpanhead7209 see if you can get a loaner fuel gauge from a local parts store. See what the fuel pressure is at the Schrader valve on the fuel rail under the hood.

I'll try that when I'm at truck again. I did press On the schrader valve. And nothing came out. But I'll stop at an auto parts store to borrow one. Thank you

I would say it's the diverter valve at the back of the engine. You could test it like you tested the bypass valve, it's just harder to access. I laid across the driver's side fender, with my elbow on the upper intake, to reach mine. The divert valve's default position is to send air to the catalytic converter, so if you apply vacuum to it manually, the air should go to the crossover pipe, that runs between the heads. The other test you could do, is to see if vacuum is present at the top nipple on the TAD solenoid, on a cold engine, for about a minute after startup. (Depending on how long engine warm up takes.) Once the engine warms up, the TAD solenoid stops applying vacuum to the Divert Valve, and the air goes to the catalytic converter.

@@johnd.9145 I took all 3 solenoids to clean/inspect them. the EVR one is DOA. I'll do the test for vacuum once I get the EVR one installed. so just start the engine and put a vacuum guage on the top nipple to a guage and see if the solenoid is doing it's job?

@@johnd.9145 I bench tested using my voltmeter and the TAD solenoid looks DOA...not registering any ohm value across the 2 connector pins. Do you know where a fella can snag one of these? E7TZ-9H465-A is the part # :)

Not off the top of my head. Maybe try some forums, in the "parts wanted and for sale" section.

@@johnd.9145 found one I THINK will work on the interweb. has the connector with the groove on the left side. will. see.

photos.app.goo.gl/yjsqJ2ygm1jUY4EX9

The link is a screenshot from the forum, that describes the test procedure.

John, I'm the OP KarlJay. I'm trying to fix my selector valve. The two rods move freely, but the two valves on the other side have lost their O rings. The 0.5 PSI anti siphon and the 20 PSI diverter valve. I'm trying to figure out how to get the O rings back in place. I can't tell if those valves come out from the body or not. I didn't find your part 2, is there any way you can tell me how to get to those two valves on the other side and what that hole nearest the pickup tube is for. Mine is packed with something and I can't tell if it's supposed to be clear or not, your's looks like a clear thru hole. @10:38 I can see a black O ring in the bottom, mine had a green one there and the black one coming out of the valve.

I've never seen those larger O rings successfully reinstalled.

This is the best information I've found on these valves. Keep scrolling down at this link www.supermotors.net/registry/2742/66025-2

No, I couldn't get it apart.

I learned what I know about these trucks on forums. You'll get answers there. I would suggest pulling engine codes. The engine computers have the ability to self diagnose. Once you have the codes pulled, post them on a forum and do some diagnosing before you start changing parts.

Mine did that, next to drivers side next to radiator, clean the ground wires And body where it tighten down, should fix the problem, Should be 3 wires on that part

It's currently back on the blind and fully functional 👍

I honestly don't know. We rented canoes at a campground near where the Juniata and the Susquehanna come together. The owner drove us several miles up the river to a boat landing on the Juniata and we canoed back down.

I think it was 25 feet. It was a small plastic spool of rubber line that the local parts store sold.

The process for testing the in tank fuel pumps is fairly involved. You need a quart container that is gasoline rated. You need two pieces of hose with about a 5/8" inner diameter. Disconnect the fuel line from the back of the fuel tank selector valve. The two fuel lines closest to the center of the truck, are coming from the two in tank fuel pumps. The top hose is from the front fuel tank, the bottom hose is from the rear fuel tank. Put the hose over the end of the disconnected fuel line, coming from the working tank. Jumper pins "A" and "E" at the diagnostic plug, under your hood, near the driver's side fender. Unplug the inline high pressure fuel pump that's mounted on the frame of the truck. With the hose in the container, turn the ignition to the on position. Don't start the truck. The fuel pump should pump 6 ounces of fuel in 5 seconds. If it doesn't, it needs to be replaced. If it does, you need to test the fuel tank selector valve, to see if it is functional. To test the fuel tank selector valve, you disconnect the two return lines at the rear of the selector valve. They're the two lines closest to the truck frame. The top line is going to the front tank, the bottom line is going to the rear tank. Connect two hoses, one to each return Port on the selector valve and run them into the container. Reconnect the wiring to the high pressure fuel pump and reconnect the fuel lines from the fuel tanks, to the selector valve. When you turn the key on, the return line going to the tank you have selected, should pump 6 ounces of fuel in 5 seconds. If it doesn't and the fuel pump pumps 6 ounces of fuel in 5 seconds, in the first part of the test, the fuel tank selector valve is bad.

@@johnd.9145 thank you so much , you are highly appreciated . God bless . That’s all I needed to hear . Preciate you man & Keep up the content 👍🏽

Auto Zone or advance Auto, but be careful with the hard plastic, barbed fittings, they break easy. Also, after several of the Dorman reducers split, I went with 1/4" vacuum line at the metal vacuum tree nipples, then reduced it to 5/32" Id hose. When I put the Dorman brand rubber reducers directly on the metal vacuum tree fittings, they split after a few weeks.

@@johnd.9145 thank you for the advice. I got 4mm vacuum hose to do just as you suggested, go right from the tree. Problem I’m having is I have like 6 vacuum lines that go behind the engine and there’s a weird plug that goes into 5 more vacuum lines, then they go to the tad, tab, etc…I’m not sure if I can just run them straight over and eliminate that vacuum plug or if it’s needed.

Depends on it's function. Does your truck have the under hood sticker that shows vacuum line routing? You might want to ask the question on a F150 forum. My truck doesn't have air or cruise, so there's a minimum of vacuum lines.

@@johnd.9145 ahh ok yes mine has air and cruise both. The lines for cruise and bigger and come right off the tree. I’ll have to surf the forums some. No unfortunately I didn’t see the sticker.

In 1988 F150s there was no filter from the factory. Other years and models did have a filter.

@@johnd.9145I have a 1988 ford f150 lariat, and mine had one. I removed the filter inside of it myself a few years ago. I also have 87 custom F150. So what ever you think, you know just got tossed out the window.

My truck didn't come with a filter in the dual function reservoir. Some did. From what I've read on line, shallow bowl DFRs had a filter, deeper bowls marked "do not remove" didn't have a filter. So yeah, I could be wrong about all 1988s not having a filter. I enjoy working on this truck and learning about it. I'm not angry about it in any way and won't be tossing everything I know out the window.

Nope. Haven't had time.

Glad it helped.

I would try places like Rock Auto, Jeff's Bronco Graveyard and LMC Truck and Amazon.

Where do you blow the air in? I might try this with mine.

@@johnd.9145 So I plugged the fuel inlets for both tanks. Earplugs and electrical tape. Whatever works. And then there’s the outlet that goes to the engine. Plug that one too. And then there’s the two holes in the plastic body. Cover those with electrical tape. Then you gotta remove that valve for the fuel side and I cut up a heater hose and jammed it in and stuck the air hose in the other. Hope that helps. If not maybe I can make a video and put it on my channel.

If you made a video of that, it would be the only one I know of. Thanks for the info.

I made a quick little video. It’s on my channel.

You're welcome!

These fuel tank selector valves are pretty expensive. My best guess, without seeing your truck, is that the selector valve wasn't switching properly before you plugged off the lines. Check out the O ring in the top cover; the O ring that I'm pointing to in the video. Also, it's possible that there is a filter in bottom of your selector valve. I would check that second, after checking the O ring. Here's a link from a forum with some good information www.supermotors.net/registry/2742/66025-2

I would join a forum and ask the question there if I were you. It's difficult to troubleshoot these fuel systems and a forum will give you access to lots of knowledgeable people.

@@johnd.9145 Okay thanks John, i’ll try that out👍

Because these selector valves are expensive, I would suggest joining a forum and asking the question there. Here's a link from a forum. www.supermotors.net/registry/2742/66025-2

It probably could. I'm pretty sure the gears in it are plastic. Mine wouldn't move the blend door, but when I unbolted it and moved the temperature control dial, it would still rotate.

photos.app.goo.gl/mTX5xL6cCZ7dtkit6

The linked photo shows a TAB solenoid. The electrical connection keyway is in the center. On a TAD solenoid, it's to one side.

Thanks for the video John...........very helpful

@@johnd.9145 RockAuto lists the "TAD" as > Intake Manifold Runner Control Valve / Solenoid

Good stuff. Thank you for documenting. Going through a 96 F150 and vacuum and right out of the gate have found no vacuum going to charcoal canister. Hoping the solves the occasional gas smell from gas tanks

Just the temperature problem.

Glad it worked out.

Here's some good information. www.supermotors.net/registry/2742/66025-4

I've read somewhere that it needs to be reseated. The guy that put together that page at super motors is on a couple of F150 forums.

Hope it helps.