DISREGARD previous post about truck dying and fuel pump not turning on with jumper in. It turns out I had just run out of gas. My bad haha.

Don’t want to drive it with the jumper in though because it doesn’t stay locked in anymore. Any minimal movement would shake it loose kill the pump.

Also wasn’t able to trace the leak yet because I ran out of spray cans, I have brake cleaner but I kinda don’t want to just waste it. Gonna try to find the cheaper brands first.

 

With the jumper in, I sprayed every rubber hose I could see but not once did the idle change. Tomorrow I will go under the truck and try to shoot some carb cleaner from there. Maybe a cut or puncture on the underside got away from be sprayed from up top.

I doubt this motor locked, so a jumped timing may very well be the issue. Ugh.

 

I find it hard to believe that a vacuum leak (as we usually think about it) would be enough to cause this problem. After all, at idle the engine is pulling enough flow through a nearly-closed throttle plate to hold the VAF open. JJGADU's truck can't open the VAF even with the throttle open.

Vacuum gauges are absolutely old-school, but aren't THAT hard to find. https://www.harborfreight.com/fuel-p...ter-62637.html Or that expensive.

It seems we're at the WAG stage, so my latest is that the VAF fc switch is broken. Holding the VAF vane "all the way" open will start JJGADU's fuel pump, but not otherwise. The fuel pump should start with the VAF open the "minimum" amount (like idle). So I'd put key-on, then put my finger on the VAF vane and listen for the fuel pump as I opened it. It should start with only a little opening.

As RJR said, it's hard to imagine the engine would run at all if it's pulling so little vacuum that it can't open a working VAF. Something is going on here that we're all missing.

 

We've seen the armature/switch break or bend in a few of these. Easy enough to check by ear or with a multimeter, connect to the VAFM and see how far you have to push the plate open before it closes the contact (it shouldn't be very much)

 

In post #13, OP did say he swapped this VAFM over to another truck, and that truck ran. Maybe that other truck has Fp to B+ jumper, so I guess it still could be the VAFM, but I have another crazy idea...an obstruction in the intake tube. A dead rat, an old rag, a bunch of leaves...a wasp nest...who knows.

 

Keep in mind, though, that OP has tried two different VAFM's on this truck with the same results, and tried both of those VAFM's on a different truck where they worked properly. If that is the case, it doesn't sound to me like a faulty VAFM.

This is a difficult problem to make sense of, I'll agree with that.

It might be worth checking the PAIR system carefully. In looking at the schematic drawing of the PAIR, a torn diaphragm could provide a "short circuit" from the air cleaner to the intake plenum through the resonator, the PAIR valve, the VSV and check valve, bypassing the VAFM. See the 2nd drawing in the attached file. The tubing involved looks pretty good sized, and could possibly support enough bypass air flow to render the VAFM inoperative.

 

Not all the way open. At first I had the vane propped open a good amount because I wasn’t sure how far it had to go to get the truck to start. Once it was running I could slowly close the vane until it was opened just a little bit to where the engine wouldn’t die.

What is the WAG stage?

 

The other truck did not have the fuel pump jumped.

After settling with the insufficient vacuum idea, an intake obstruction made the most sense to me. When I washed the engine bay down, I did stuff the throttle body with a towel, but it was large and obvious enough that I would not be able to put the intake tube back in if I didn’t remove it. Maybe I had stuffed a rag in somewhere else and forgot about it and was sucked into the manifold? But then wouldn’t the motor be destroyed, at least run like trash, and not hold a steady idle like it currently does (with vane propped open or with fuel pump jumper)?

 

In the morning I will try to follow the PAIR inspection steps in that attachment. Hoping to find something and dismiss the jumped timing theory.

 

Maybe a stretch but, have you checked that the TPS is working and adjusted correctly?

 

The VAFM only has to be cracked open slightly to enable the fuel pump switch to keep the engine running, so your experience indicates the VAFM switch is working properly.

(WAG = wild a$$ed guess. )

This is not a TPS problem.

The suggestion of a plugged air intake is a possibility, but it would have to be coupled with an induction leak somewhere else or the engine wouldn't run at all.

If the engine is running, it is getting air from somewhere. If it's not moving the VAFM, the air is coming in through a different path. It's that simple. Stay focused on that.

 

The tps adjustment and operation is no that critical, if it's out of range in the table to no make sense it uses the "fail safe" table instead.

Something worth checking is that the socket (female) of the plug is tight to the prong (male terminal) on the vafm plug, and there aren't any breaks in the wire. What I'm imagining is a broken wire or loose connection that closes when you take the mechanical portion of the air box off to prop the vane open.. If you put a meter or test light on the FP lead at the diagnostics port, prop the vane open, key in the run position the light (Voltage) will/may disappear while manipulating the vafm orientation or wiggling wires.

 

When you prop the vane open, I assume it's from the air cleaner side, with the other side of the VAFM firmly connected to the intake to the throttle body. When the engine is running, do you feel any air going past your hand while holding the vane open? There should be a noticeable flow, even at idle.

 

That is the exact symptom of the VAFM plug being disconnected. I agree with CO 94 that it may be electrical, the plug not making good contact or one or more bad wires in that harness.

 

If this were the case it wouldn't run when he holds the vane open by hand. That doesn't change the electrical connections at all.

The symptoms are, it won't run unless he holds the vane at least slightly open. When he lets go of the vane, the vane immediately goes back to the rest position and the engine stops. This can only happen if there is no significant amount of air flowing through the VAFM. But the engine requires air to run, which means the engine is getting its air from someplace besides through the VAFM. What the OP needs to do is find that alternate air source. It likely is a pretty good sized hole, like maybe half the size of a fist or bigger. I'm not familiar with the details of the 22re intake plumbing, but on the 3vze there is a large "Y" connection on the underside of the induction pipe just downstream (toward the engine) of the VAFM. I think it goes to the PAIR resonator. If that Y was open, it would be somewhat hard to see, but would certainly cause the VAFM to be bypassed.

 

Engine was bevahing a bit differently today.. VAFM was disconnected from the air cleaner and slightly propped open to run. I put my hand in front of it but was not sure if the air I was feeling was being pulled from the VAFM or pushed from the fan. So I decided to rev it at the throttlebody to feel a more noticeable air direction. But as I revved, the engine would choke. When I let go, it would idle fine. It never did this before. Did I finally fry this VAFM from all the manual opening of the vane?

Anyways, I took the prop off and put the jumper in the diagnostic box. Started it, let it idle, put my hand in front of the VAFM and felt air being sucked. I revved it and it did not choke or anything. Vane opens up when being revved with jumper in.

Also, I still can’t seem to find a vacuum leak. Drenched the fuel return and vacuum in carb cleaner but didn’t get that idle drop that I barely noticed yesterday. Have yet to follow the PAIR inspection instructions.

 

So here’s a new and unusual occurrence.. I wanted to start on the PAIR system inspection so I reconnected the VAFM to the air cleaner. Step 1 as per the inspection instructions on the diagram was to disconnect the No. 1 PAIR hose from the air cleaner and listen for bubbling. Well I tried listening, while engine was idling and while warm after idling. I don’t think I was hearing bubbling both times. So I thought to just move onto the next inspection which was on the PAIR valve. While the engine running still, I reconnected the No. 1 PAIR hose to the air cleaner and the idle dropped to the point where the engine was about to shut off. I quickly pulled the hose off and it idled back up again. Plug it back in and it dies. Definitely didn’t do this before? Could it be this VAFM really broken this time?

Now as for the PAIR valve inspection, it says to apply vacuum to the PAIR valve diaphragm.. Then blow into the pipe? Noobie question, but how do I do this?

 

I should also add that I did check the air cleaner for a blockage, which there was none. No blockage in the No. 1 PAIR hose, atleast from the air cleaner to the resonator, either. The resonator to the PAIR valve however, I don’t know.

Only at this moment did I think that I should’ve probably tried letting the engine run with the No.1 PAIR hose connected to the air cleaner box but with the filter removed. It’s just I don’t understand how the filter would have suddenly caused this.

If the PAIR valve is supposed to be sucking air from the air cleaner, is it possible that I have a faulty unit that is blowing exhaust out instead, which is now being sucked into the engine causing it to die out? What exact component of the PAIR system would cause this?

 

Ok, so been reading that the PAIR reed valve is not working. Is this something that can be repaired or will I need to replace?

Could this be the root cause to why I don’t have a vacuum strong enough to pull the VAFM open? Or is this issue just another byproduct of a different underlying problem?

 

Sorry for the inconsistency guys.

Pickup was behaving differently again today. Yesterday I had mentioned that the truck would die when I would connect the No. 1 PAIR hose to the air cleaner, leading me to think I had a bad pair valve. Today I started the truck with the jumper in and the PAIR hose disconnected because I wanted to see if exhaust fumes were blowing out of it. Although I could smell some exhaust, it wasn’t pouring out or anything. Stuck the hose back onto the air cleaner and it dies. Well, I wanted to show my dad what was happening, so I had him start the truck and watch as I reattached the hose. Instantly it dies. He wasn’t paying attention so we were gonna try again. Pulled out the hose again and noticed that the paperclip I had used as a jumper had fallen out. Even before I could get to the diagnostic port, my dad had already started the truck, paperclip still in my hand. Stood back in confusion. Decided to reconnect the PAIR hose to the air cleaner and nothing happened, unlike previous attempts in which the truck would die instantaneously. It ran for atleast 3 minutes. I did not touch a thing. Tried again, same thing, but it didn’t run as long as it did the first time. Maybe less than two mins the 2nd time around, but I was able to get some revs in before it died. Tried starting again and it was back to turning over then quickly dying.

Jumper back in, started the truck, and it’s back to idling as a normal truck would. PAIR hose was even still connected. Jumper still in, shut the truck off, then started it back up again. PAIR hose still connected. Coated the vacuum hoses in carb cleaner, no change. Let her idle for 10 minutes before shutting her off . And that’s the end of today’s story.