Carla

We took my husbands truck to get new tires, it was running fine when we went in but, after being jacked up getting tires it wouldn't start and run. He thought it was low on gas and put some in and it ran for about 40 miles. Then it would start run for a minute and die. He has changed the fuel filter, ran injector and fuel treatment through it, changed the MAF sensor. Checked the fuel pump it has 65 psi. He tested the cor, it was in working order. It will start and run if you force the MAF to open position. He coded it, the only code is 25. Any help or advice much appreciated. Thank you in advance.

scope103

It runs when you hold the vane of the VAF (not MAF; that's a different technology) open, and doesn't run when you don't. What does that tell you?

The fuel pump will run with the key in STA (start), but once you let go of the key it depends on the VAF to send a signal (through the COR) to keep the fuel pump running. So it seems certain your fuel pump is stopping once you let go of the key. So why doesn't the vane in the VAF move when the engine turns over? (that would keep it running) Maybe you just have the induction plumbing disconnected (to get your fingers on the VAF vane), and the airflow is not getting to the VAF.

Was the replacement VAF from a junkyard? Maybe it has a sticky vane.

By the way, this has nothing to do with getting the tires changed.

Carla

My husband got it running yesterday, by jiggling the Throttle body position sensor, it would sit and idle for hours. Got the leaky brake line fixed and tried a test drive, didn't make it out of the yard before it started acting up again. Any ideas? The throttle position sensor tests as good, with OHM meter and placed in a different truck. @Scope 103, no not from junkyard, but Autozone calls it a MAF (mass air flow, as does the Haynes manual) not a VAF, so I dunno, lol! Im just the go between researcher I guess not at all mechanically inclined.

Carla

The truck runs and is even driveable with the FP to B+ jumped. Does that help any of you to be able to help me? lol use the for idiots version language in replies, please.

scope103

Yes (not that you would have known, but jumpering FP to B+ is what you should have done first). You have bypassed the VAF and COR and forced the pump to run all the time when the key is on. But you already knew that. You can start the truck by putting your finger on the VAF vane, so you know the COR and connections are okay, but your vane is not moving. Either you have a sticky VAF (return it), or you have part of the induction piping disconnected so the air flow is not going through the VAF.

So what's going on here? If you get in an accident that breaks a fuel line, you want the fuel pump to shut off as quickly as possible. That's why the truck is designed that way. If you drive around with the jumper in, as tempting as that would be, if you get in that accident fuel will keep pouring out and you will be a "Crispy Critter." You don't want that.

Toyota calls the VAF "VAF". http://personal.utulsa.edu/~nathan-b...33volumeai.pdf Are you going to believe Autozone, Haynes, or Toyota? (no need at all to believe me). Technically, it measures volume. To get mass (which is what the chemistry needs to know) you have to adjust for temperature. So the VAF also has a temperature sensor.

Gevo

Carla,

why did he replace the VAFM (MAF)???

From my experience, don't force the fuel pump to run outside of the ECU's control for driving purposes!

Carla

It tested bad with OHM's meter.

Carla

I totally believed you, just mechanically dumb,lol! remember I did ask for the for dummies version. I'm really sorry. I did not mean to offend you.

Alex904r

Hello, all,

I am having a similar problem but suspect other componets are faulty. 89 4runner, 3.0, EFI. Initially ran for a minute or so and would die. Now it is difficult to get it to run. Tested for spark and found it had none. I read that the Mass Air Flow meter (it does not have an MAF sensor) controls the spark. If this is so, how do I test to determine if the MAF meter is bad. Ideas?

scope103

Sorry to hear that. But you read wrong; the VAF has nothing to do with spark.

1. How do you know you don't have spark? (the right way (and easiest) to test that is with a $20 timing light, a tool you need anyway.)

2. Have you looked in the manual for how to test the coil and igniter?

3. You're right, your truck does not have a MAF sensor. MAF stands for Mass Air Flow, and that's what you don't have. You have a VAF (either "Volume" Air Flow, or "Vane" Air Flow). At this level of sophistication it doesn't matter, but it never hurts to use the correct words when you're trying to describe something.

Alex904r

Thanks for the info. Those are valid questions:
1) I checked the coil/igniter cable for spark while my son turned the engine. No spark. Yes. I do have a timing light just did not use it on that day.
2) the manual I have has refrences for all 4runners, including the 22r and could not locate a section specific to igniter testing...Took it to the local auto parts but they could not help nor could tell me how to test the igniter.
3) Thanks for the correction on the VAF, i know little about them as I never had ANY issues with my 1990, 22 R, which I had forf 11 years. Struggling with toyotas is new...most are trouble-free!
Thanks.

scope103

Try here: http://personal.utulsa.edu/~nathan-b...12onvehicl.pdf
and here: http://personal.utulsa.edu/~nathan-b...12onvehicl.pdf

While even the manual suggests "pull the wire and hold it next to block, look for spark", it's much easier to do the same thing with a timing light. You don't need to disconnect anything or risk a nasty shock. Put the pickup on the wire you're interested in, and if the light flashes you've got spark.

sphealy

iTrader: (1)

Here is a link https://www.yotatech.com/forums/f116...oblems-276982/ from a previous issue I had for no start/short idle and die. Thought it might be possible if it was low on gas and tank had rust. Previous owner ran it out of gas and described very simular issue and gave up on it.

Alex904r

Thanks for the input.

Today, I verified spark, using a timing light as suggested, and learned the spark was there. Disconnected the VAF and operated it manually and, while this appeared to help, it did not solve the problem. It's still runs for a minute and simply dies. As soon as it did, I checked the gas pressure and it was fine so. ..it gets spark, gas but still dies...what the...?! I am back to square one. Does this sound familiar to anoyone out there?

sphealy

iTrader: (1)

Per pervious post you will still have pressure but injectors themselves can be clogged. Only way to know is visual inspection of injector.

Alex904r

THat's a great idea. I shall check on those tomorrow.

Thanks a LOT!

sphealy

iTrader: (1)

Fyi getting to them can be a pain. I would start by looking at the plugs. Mine were soaked with gas because it was dripping threw not being sprayed as it should. You can axcess your gas tank under the rear seat to look for rust to see if it's even a possibility in your case.

Alex904r

Hell, everyone,

Thanks for your input.
Here is the latest on my 89 runner, 3.0, EFI. Fabricated a noid with a little light and electrical wire I had around the house and learned my injectors are "injecting" properly and have electrical spark to the plugs, have good fuel pressure to them; however, engine still dies after a couple of minutes and as I continue to start it, it gets more difficult each time. I will not follow the advice of Sphealy, and check for plug injectors. Does anyone have any other ideas on what this issue may be? Thanks so much!

sphealy

iTrader: (1)

I'm glad you have determined that the injectors are receiving the proper electrical signal but that does not mean the injectors are or are.not clogged. I take no offense you will not take my suggestions. Just to be clear you have not taken my advise. I recommended you start by looking at your plugs to see if they are wet and if so further look into gas tank prior to removing the intake. Also you have failed to mention if you have checked the small but important parts like dizzy cap rotor button. If worn badly they will fail when warm or hot. Good luck with your repairs.

scope103

How did you check the fuel pressure, and what did you get?