VTToy

my 92 pickup with a 22re wont stay running . I put in a new fuel pump but that didn't help it seems to be getting gas but only when the key is turned all the way to start I'm getting gas all the way to the intake i'll let off and it will run somewhat but rough and just spit and sputter . I've checked battery cables , grounds [even added extra grounds to make sure its grounded] vac. lines , fuses but know luck . I don't hear the pump run and I know its not pumping fuel when the switch is just turned to the on but I was told that the pump will only come on when the key is turned to start when its cranking over but when I let off it seems to spit and sputter and die out . what do I look for/do next ? HELP please ! this is getting to be a headache ! Thanks

wallytoo

iTrader: (1)

the pump only runs when the key is in "start" position? how would these trucks operate if that were the case?

prior to the engine running, the pump begins operating with the key at "start". assuming it starts, the pump remains running when the key is released to "on" position. if yours does not do this, someting is not correct.

arlindsay1992

iTrader: (8)

Fuel pump will only run when the key is in the start position, or when the key is in the on position AND the AFM senses air flowing through it. This means if the engine stalls the fuel pump shuts off. If you recently had the AFM unplugged and forgot to plug it in, the truck will start then die every time.

VTToy

nope anything we unplugged got plugged back in . what I mint I guess to say is it will only stay running for a second [ if that] after the key is let go of it just spits and sputters and wont take any gas if you try and give it some , say like if you try and feather the gas peddle to keep it running . checked fuel lines seem good no leaks , its getting gas an spark cheeked the vacuum lines , checked the flap in the airbox these are just a few things ive been told to check .

scope103

You have the CLASSIC symptoms of a VAF-COR problem. ONE of these problems, as arlindsay1992 points out, is a disconnected VAF.

So let's see if you have a COR-VAF problem at all. Jumper FP to B+ in the diagnostic connector. This forces the fuel pump to run with key-on only. If your truck starts and runs now, you've found the problem area.

You say the VAF connector is in, but that still leaves the COR, the VAF itself, and all the wiring in between. Get out your multimeter.

VTToy

Not to sound to dumb but I'm not 100% sure what the VAF - COR [ everbody seems to have or call things differently ] and also pics [sorry] and what I'm suppose to jump . some of this stuff I know some I'm not sure of and want to make sure I'm doing it right . Ive gone over and checked what I know and my son has looked it over once and anything I know he unplugged got plugged back in . Thanks for your help

Terrys87

iTrader: (1)

The COR is located behind the passenger speaker.. The VAF (Vacuum Air Flow Meter) sometimes called the AFM (Air Flow Meter) located above the air filter. When cranking the motor, the gate in your Air Flow Meter moves and energizes your COR (Circuit Opening Relay) that energizes your fuel pump. Basically the COR is your fuel shut off if there is an accident so that the fuel pump does not stay running if the motor is not running.

You can jumper FP/+B and that will energizes the fuel pump (4th picture in link) https://www.yotatech.com/forums/f199...l#post51760299 and will tell you if your fuel pump is running.Key will need to be on for this test.

A simple check that I do to see if the fuel pump is running with the jumper in and key on, is to take a container and with the fuel hose coming off of the fuel rail and attaches to the fire wall or inner fender, depending on where your Fuel Return Line is located, and see if it will fill a quart container in about a minute or so. It wont really tell you if you have enough pressure but will tell you if the pump is putting out enough fuel.

If the truck will stay running with the jumper in then you are going to have to start checking out that circuit. Some have left the jumper in just to get around the problem. Leaving the jumper in is bypassing your safety of the fuel system.

I would check that your gate/flapper is moving in your AFM. The only time I have ever gotten a code for the AFM is when the cable was not plugged in. I have had some very baddd AFM's in the past and never gotten a code.

wallytoo

iTrader: (1)

either buy a service manual, or read an online version of one. then you won't sound to [sic] dumb. it will have the information, and diagnostic procedures.

scope103

The VAF is either a "Volume" or "Vane" Air Flow meter (Toyota refers to it both ways) http://web.archive.org/web/201003261...92volumeai.pdf I don't think there is any vacuum involved. "Volume" is to distinguish it from a "Mass" air flow meter, which is different technology. You can call it an AFM if you want (but not MAF).

The COR (Circuit Opening Relay) has two coils, so it is initially closed by the ignition switch to STArt, then held closed as Terrys87 points out when the switch in the VAF closes. (If the start coil in the COR fails, you could probably still start it, but it would take a little longer because the fuel pump wouldn't start until there was enough air flow).

Terrys87 suggestion to check for fuel flow is good (and easy); just be sure you're disconnecting the return line (rubber hose with a plain-ole hose clamp) not a high-pressure line (bolted). I use the output from the Fuel Pressure regulator with a clear vinyl 6mm (1/4") hose to a container. I get about 1/2 liter/min, but there's no spec on that. IF you open one of the high-pressure connections, you MUST replace the two crush washers. Cheaper than dirt, but only available from the dealer. The low pressure side (return line) is much easier.

VTToy

will try this this weekend if it stops raining out . my son did disconnect the fuel line from the fuel rail and cranking it over it looked good seemed to be pumping out pretty good .

Terrys87

iTrader: (1)

So many abbreviations, I got the VAF as Vacuum instead of Vane or Volume. I goofed that one up.

It sounds like you eliminated the fuel pump. Fuel pumps tend to give one or two warnings before they stop completely in my experience. I dont see the COR being bad as it is a solid piece of equipment from my experience.

If the problem is in the VAF,Fuel Pump, or COR circuit. I would be looking really hard at the VAF. It will not throw a code if bad from my experience. I have seen several bad one. Make sure the gate is moving freely. Sometimes they can get sticky and take a while to move and that can cause a delay in starting and if the VAF is really bad a truck will run like crap.

A test I have done with the VAF is while some one cranks the motor, I will remove the air tube from the Plenum to the VAF. While the other person is cranking the motor, with a wooden dowel or similar tool, I will move the gate, simulating that the air is moving the gate. The higher the rev of the motor, the further I move the gate. It is not the best test but by me moving the gate a few seconds before the other person cranks the motor and by how far I move the gate gives me an idea of the VAF is functioning correctly.

You will need a Haynes Manual. I think it is in Chapter 6, but it will give you some resistance checks to do on the VAF. Those checks are great to see if you have a bad VAF.

A new VAF is a couple of hundred dollars if I recall correctly and the last time I checked on line or in a parts store. I have bought several from the bone yard for around $50. Since most bone yards do not warranty electrical parts, Take a meter and a manual to the bone yard and do the resistance checks before purchase. It is an easy test to do and will save you a few bucks. Make sure the gate moves freely before purchase.

I am just going by what you are describing and if the problem is in the mentioned circuit I suspect the VAF. It could be something else but the computer does not pick up codes for the VAF unless unplugged from my experience and a bad VAF can make a truck run terrible.

VTToy

Do I want to just pop it off the air cleaner and move it from the end ? that's what I did before to see if the valve/gate would move . I know its getting fuel all the way up to the intake we have checked that . it just seem that once you crank it over and you get it to start it'll just run ruff as hell for a brief second and then just shut off it wont take gas and seems to shake [motor] bad . i'll have to wait till I can get somebody to give me a hand might be a few days . Its a bitch when your disabled and its your right hand that's bad and your right handed ! sometimes things you used to be able to do your self now takes help from someone else hate it ! .

Terrys87

iTrader: (1)

Take the air tube completely off. You will need to move the gate in order to make the computer think it is running. As you increase the Throttle, try to move the gate to allow more air to flow. You are trying to simulate that the tube is still in place. Leave the VFM attached to the air cleaner.

The reason I do this test is to see if the VFM might be the issue. I have done this test enough times that I can nearly mimic the meter and the Throttle to where the truck nearly runs smooth. It is not the best test but it works for me. Before I did this test, I would do a resistance reading on the VFM and see the gate is moving freely.

A bad meter will make one run terrible. By the way your sounding, I think your fuel flow is in great shape and dont think it is the issue. Vacuum leaks is a big problem for these trucks and could be something that is causing you problems.

I have worked on many of these trucks and the conditions that I find them is bad. Many of the original parts. If I was working on this truck at my house and not know any of the history of it. First I would check compression and see if the Timing Chain guides are good. Then I get my plugs, cap, rotor, and rotor bug at the dealer. I get my Denso wires off of ebay. A fuel filter and air cleaner from the parts store.

Clean and test all of your sensors per the manual. Many say you need a factory manual. I have a FSM but use my Haynes much more then the FSM. It is just as good and more easily available to get access to then an FSM. Dont waste your time with a Chilton. Your sensors most likely will be dirty. I would bet your TPS is worn out and original. Same for your O2 sensor. The Idle Control valve may need replaced or at least tested. All other sensors just need to be cleaned with a brass tooth brush. There is a test for the coil in the Haynes that is very good for checking the Primary and Secondary of the coil.

Then I would pull the Intake System and the EGR and remove all of the carbon. Clean and replace the vacuum hoses as needed and all the ports to the plenum. Re assemble and install the tune up parts. Set the timing per the manual including setting the valves. By the time you get the motor warmed up and then shut down then get the valve cover off and start setting your valves, the motor is too cool. Some set the valves 1/1000th closer then the manual says. I do use 7 and 11 instead of 8 and 12 as the manual calls for on the valves.

The above may seem obvious but I have had to work on trucks where just common maintainence was the issue. More then once. Many original parts were an issue. Some like the VFM is just worn out or leaks. Make sure there are no major air leaks and replace the Intake gasket from the head to the Intake. Any leaks there and you will have issues.

I just turned 50 the other day and it is getting harder for my old butt to get around on these trucks. Sometimes there is no getting around without a helper for starting a truck while you are under the hood.

On my Wife 88 Runner build link below in my signature on the first page, I tried to make my build thread a reference for several of the problems that I have found in these trucks such as dirty sensors and clogged EGRs. It might take some time but going thru the links or to the post will show the problems I have found and how I go about fixing them without having to do a lot of searching on the site for them.

VTToy

Terrys87 , I was hoping to tell I've tried what you said by now but haven't been able to . This weather is driving me nuts ! rain just about every day and when it doesn't I have no help. hopefully with in the next week I can try it looks like some better weather ahead and I'm hoping the days my wife has of will be nice and she can give me a hand .

yngbuck19

My CEL is on due to the AFM the part above the air filter. The engine idles badly after a few minutes of running but goes away after I give it some throttle above idle RPM. I will be changing out the AFM this weekend with a Reman. from Cardone bought it on Amazon for about 100 bucks cheaper than the auto parts store without a core charge. The AFM in the truck now is the original from the factory I believe. 122k mi. on the clock now.

VTToy

Well i'm back to work on the truck I've gone through the vac lines and all seem good , got a used AFM and that didn't change anything truck still doesn't want to run . it'll barely run for a very short sec and just dies out crank it over again and it just does the samething . its getting gas we went through all that i even putin a new fuel pump checked to make sure its getting a spark and that seems good and strong . Is there anything else besides the AFM it could be ? a sensor ? and which one ? i went through the fuses all seem good but the alternator fuse [ which i need to get a new one ] could that do it ? doesn't seem like it would but ?? anything other sug. would be great help , thanks

VTToy

Ok , I know the fuel is going all the way to the rail but what I was wondering if I should still try the FP to +B jump ? if I do and it runs would that mean its likely the EFI relay or the circuit opening relay ? or something else all together ? I did try another complete AFM unit that's suppose to be good [was told it was on a running truck] gone through the vac lines again , checked spark at coil and at plug .cant find any bad wiring , grounds seem good . New parts so far , fuel pump , fuel filter , coil , plugs and wires , injectors and sure theres prob. something else . I also have checked the fuses all are good but the alt fuse { think that's a 80amp fuse } . can hear the pump kick on when switch is turned on so should I try the jump or go back and look for something else ?

scope103

So far as I can tell, you only determined that fuel was going to the rail WHILE CRANKING. If the switch in the VAF isn't holding the COR closed, the fuel pump stops as soon as you let go of the key, and the engine stops running.

Jumpering FP to B+ is SO easy you should have done that long before you started changing parts. B+ is powered through the EFI relay, so if jumpering works it's not the EFI relay at fault.

VTToy

so what should I try next ? if I try the jump [ FP to +B ] and it starts and runs , then would it be the COR ? or something else .

RAD4Runner

Answer:
You haven't done it yet? Don't be scared. Then tell us what you see, hear, feel, smell.


Search C.O.R.