So how I got here, My 1995 4Runner 3.0 manual died while I was driving. That was a indicator for me to start changing out things( haven’t changed these particular things since I got it 4 years ago)I replaced alternator first which was able to keep me driving for couple days then It happened again, died while driving. So I changed my spark plugs and fuel filter. Now when I go to start the engine it goes on then slowly dies out again. What’s your thoughts guys? I’m soon to change my timing belts, water pump, and fuel pump.

 

Welcome to YotaTech.

Almost everyone here will tell you that "changing out things" will bankrupt you long before you ever solve any problem. You need to diagnose your problem, and then fix what you found. And that's why you came to YotaTech.

The only way an alternator could contribute to "died while driving" is if you let the battery go ALL the way dead. Unlikely, since you were able to start it, but it would have been very easy to diagnose. And you could have kept your (probably) perfectly good alternator.

While there are approximately 6.02 x 10^23 possible causes of dying, "starts then slowly dies" is the classic sign of a VAF-COR circuit problem. It's the easiest thing on your 4runner to diagnose. Jumper FP to B+ in the diagnostic connector. If that clears it up, you now know where to look.

If that doesn't do it, you might have a clogged fuel filter or weak fuel pump. The appropriate pressure gauge (e.g., ) will tell you for sure; the gauge costs less than either a pump or filter change.

Your timing belt (not belts) and your water pump are not causing your 4runner to die. There is no maintenance interval for the timing belt (in standard service). But if you have more than 150,000 miles, sure, go ahead.

Good luck!

 

when I check Fp + +B do I do it with the key on? And if it ready does that mean my sensor is good? ( what’s the voltage it should read?) and just to clarify, if it doesn’t read anything it’s the sensor? And if it does it could possibly be my fuel pump or filter? I’ve already changed out my fuel filter so to narrow it it would probably be my fuel pump if that’s the case..

 

Sensor?

FP goes direct to the fuel pump. B+ is, well, B+ (battery) with key-on. So with key-on, jumpering (not measuring) FP to B+ forces the fuel pump to run (you should be able to hear it). Ordinarily, the fuel pump is driven by the COR; it's closed with the key to STArt, and held closed by the FC switch in the VAF. Jumpering bypasses all that.

 

So will trying this determine if my sensor is bad? I’m new to all this and i could sounds like a spinning wheel. The procedures you gave me will determine if my sensor is bad if the fuel pump runs?

 

what sensor? use a paperclip, with one end in each of the terminals listed above. the terminals are under the flip cap of the diagnostic box on the passenger inner fender. it's the small box to the right of the large box in this picture. it has "diagnostic" on the cover, iirc.

 

I'm with wallytoo. What sensor are you (do you believe you are) talking about? (Okay, I understand English isn't everyone's first language. Heck, sometimes I wonder if it's anyone's first! Try to describe as best you can what you want to know.)

 

im sorry! I figured it out. I jumped Fp and +B and it started and stayed on. So does that determine my fuel pump needs to be changed or some of the wiring toward the fuel pump need to be looked at?

 

continuation, so after doing the jump I opened up where my fuel pump is located. I unplugged the connector to see is there’s power running through, I used my multimeter. It reads 0.07 volts! Isn’t suppose to be 12.0V? If this is the cause please let me know! Thank you

 

Why would there be 12v at the fuel pump if the engine isn't running? If your rig runs okay with the jumper in, your problem is in the VAF-COR circuit. Almost certainly not in the Fuel pump part past the COR. Since we seem to talk about this issue about twice a week on this forum, why don't you try searching for it first? Come back if you still have questions.

 

Im doing my research and replying back to this at the same time. I’m a first timer at this and only looking for help. What I meant to say is that without the jumper and the key turn ON the plug reads 0.07v. With the jumper in and the key ON it reads 12v. But I’ve read others post and their saying it could be the EFI. But what do I know? I appreciate your help. Aloha

 

With the jumper in...it reads +12VDX...

Right. That's exactly what the test contacts are for. When the test contacts are jumpered, you are applying +12VDC (battery voltage, normally labeled... B+), directly to the fuel pump (Fp). With the key in ON. This bypasses the VAF and COR circuitry. This tells you, if you hear the fuel pump running or see fuel pressure on an add-on gauge, That the fuel pump, and it's associated wiring, is good. So, if the VAF contacts close when air is flowing through it, it holds the COR energized, allowing the fuel pump to operate. If the air stops flowing, like when the engine stops in an accident, the COR de-energizes, stopping the fuel pump, preventing a continuous flow of fuel to a possibly broken fuel line. It's a safety feature, and a very good one to have.



SO: If you know your fuel pump operates properly, having verified it with the B+ to Fp jumper, which bypasses the COR and VAF circuitry, but it doesn't operate when starting or running the engine, either the COR contacts in the VAF aren't closing properly, the COR isn't energizing correctly when the VAF contacts close, or the wiring between the two is bad.


Being a simple ON-OFF type switch, the contacts in the VAF are simple to check. Take the plug off the VAF, find the contacts Fc and E (refer to picture above), and ohm across them. DO NOT unscrew the plug from the VAF! It has a wire bale holding it on, nothing more. Just like nearly every plug on these tricks. They either have a wire bale, or the have catches in the plastic of the plug. Should be open, or infinite ohms, just sitting in one place with no air flowing through the VAF. They should read closed, or very low ohms, like less than one ohm, with the vane inside the VAF open, even very slightly. Easy to just stick a finger in from the air filter side of the VAF, and press gently against the vane to open it.

IF the VAF contacts read good, chance are it's the COR gone bad somehow. A coil (it has two: one for start, one for run) has burnt open, or a pair of contacts has either crudded up so bad, no trons can get through them, or a wire inside has broken. It's also possible that a wire to or from the COR has broken, but I would put my money on the COR. Relays don't last forever, after all. I've had to replace mine, a few years ago. Just exactly what was wrong with it, I don't know. I determined it had failed using the trouble shooting described above, and replaced it. Sure enough, it was my problem. A $60.00 relay, at the dealer, but if it only fails every 25 years, not too bad


Does this help?
Pat☺

 

Thank you so much! Very very helpful. Exactly what was going through my mind but you explain the detail which echelon a lot. I just recently purchased the COR so I’m just going to slap that on and see. If not then I’ll the following steps you provided. Thanks

also to clarify, when the jumper to Fp to +B is connect. I’m able to hear the fuel pump and able to start my truck and have it running. I let it ran for 10min. So it could be the COR

 

That was very in-depth Pat!

Ill just add a little. It's faster and safer to have them pull the air tube off the back of the vafm then push the vane open with a screwdriver and the pump should run.

You didn't touch on STA not reaching the COR, or cab rot letting water into the ECU/COR area.

Eugene you should check the voltage at the pump while the COR is removed as a sanity check that the 0.7v leak is in the relay and not the harness.

 

thank you.
what’s the STA? Also I do have rot above my windshield it drips onto my stick when it rains, is there any fuse/ relays around that area?

also may I please have a more in depth on checking voltage at the fuel pump while COR is removed? I’m assuming key ON, COR removed and then checking with multimeter the fuel pump?

Last thing I want to understand, the VAFM method( pushing the cane with a screw driver ) that’s with key ON?

I’m just double checking may sound obvious but getting replies back from you guys may take a while. I ask the most stupidest question but I just want to understand quick.

 

If you look at the schematic I put up, the first picture, you can see that STA is the key in STArt position. You'll notice that it goes to the COR's second coil, L2, allowing the COR to be energized and provide power to the fuel pump during STArting.
Once the engine begins running, the VAFM vane opens (air flowing through the VAFM to the TB), closing the contacts of the switch in the VAFM. This provides a ground to the COR's primary coil, L1. As long as there's air flowing, the COR thus stay's energized. It gets power, B+, from the "Main Relay", which is held energized by the power provided by the key in the IGN, or ON, position. Since it gets the ground for the L1 coil from the VAFM, the engine needs to be running, air flowing, to energize the main coil, L1.

Remember to check the grounds for the COR, and fuel pump as well. They're just as important as the source of power. No ground, no complete path for current flow, no path, no worky, see?

Easy enough to do the check of the fuel pump voltage. Pull out the COR, and read the voltage at the fuel pump, key to ON. It should be roughly 0 VDC. The +0.07 you got before might well have been an error in the meter. They're not perfect, and can sometimes give a very slightly erroneous reading. Like say +0.07 VDC when there's actually nothing there. It may also be a slight bleed from another circuit somewhere. Very slight. Unlikely, though. In my little pea brain, I'm thinking it just an meter error.
If it's not +12.00 VDC, or like 11-14 VDC somewhere, but is actually +0.07 when you measure it, I would call that definitive.

The leak around your windshield is a fairly common problem with these trucks. The trim strip is a trap for any water that falls on it, and since it can hold the water against the metal under it, it rusts through. The leak you SEE, may not be the only one. Examine the area of the ECU/COR, as well as the fuse/relay panel under the other side kick panel, carefully. Especially behind and under things, where rust may be hidden, but affecting the components. Rust can be sneaky!
Check any ground points in those areas for rust under them, too. The metal of the body, as well as the contact screwed onto it, both must be CLEAN. No sign of any corrosion. If there is, clean it up. Fine grit sandpaper works very nicely. A little dielectric grease will help keep the corrosion from coming back. It's not magic, but it can help.
Check wires and connectors for any breaks, or corrosion. It can sneak in under the insulation at the end of a wire.

I am glad my rambling is some help!
I wish you good luck!
Pat☺

 

You would have to be close to a pretty powerful radio transmitter to get 0.07v on an unhooked wire. Hooked to a make shift battery (dissimilar metals in electrolyte). Or maybe some other strange case I'm not thinking of. Oh there's one using an old analog meter with out zeroing the meter with the zeroing knob while touching probe to probe.

My concern is the plug/harness the COR hooks to is damaged. There are two common failures. 1: it's full of water mud or other detritus. And #2 it's been over heated..

Plastic is normally an insulator, but if you overheat a connector it starts to melt and burn this turns it into a conductor (carbon).

 

im going to check my VAF now. Installed a new COR and pump. And still does out. Going to use the method above to check the ohms on the VAF. I’m hoping that’s what’s wrong cause I’m so tired of looking and guessing aha. And I’m still trying to understand the wiring situation on my runner as we speak. But learning definitely on the way.

 

so I checked my VAF with my multi meter. You said it’s suppose to read infinite( when number pop up?) and it’s doesn’t! My setting on multi meter was on 2k ohms.

 

There's a lot of pins on the VAFM.

You're looking primarily measuring from pins Fc to E1, when looking for the fuel pump. The ground that is applied when the truck is running to hold the COR energized, allowing the fuel pump to run. When the vane of the VAFM opens, even a little bit, when air flows through the VAFM to the throttle body, the switch inside the VAFM, between pins Fc and E1, should close, applying ground to the COR's L1 coil, energizing the COR. Pin E1 goes straight to ground, and pin Fc to the COR.

Thus, with everything shut down, no air flowing, the engine not running or even trying to start, the ohm reading between pins Fc and E1 of the VAFM should read infinity. Note that different meters use different means of indicating infinite ohms. Just turn the meter to whatever ohm range you want to use, the lowest scale is good but any scale will work for testing a switch. Hold the two meter leads not touching anything, and look at the meter to see how your particular meter indicates "infinity" ohms. In other words, an open switch. That's on the VAFM, not the cable, just to be absolutely clear. When the vane is opened, even a small amount, by pushing on it gently with a finger or screwdriver, the switch should close, and thus read 0 ohms.

So, place one lead on pin Fc, and one on pin E1. Polarity is not relevant when testing a switch. Ohms are the same whatever polarity is used. You're essentially looking at two wires. When the switch is open, the two wires aren't touching each other. When the switch closes, the two wires are touching each other, to put it simply. When the vane is closed (no air flow), the switch is open, infinity ohms. When the vane opens, the switch closes, 0 ohms. Anything other than 0 or infinity is incorrect, and thus, the switch inside the VAFM is bad. Switches can develop corrosion on the contacts, so when it's closed it can read something other than 0 ohms. Something higher than 0, but probably lower than infinity. It still indicates a bad switch, if it's above 0 ohms with the switch closed.

Does that help?
Pat☺