Yes that is the issue and yes I have had starter contact issues if it was an issue of intermittent failed crank attempts then $20.00 starter contacts would have been my first suggestion.

However with as much money as you have already thrown at it go ahead and throw a temp. sensor at it as well this may very well fix the issue and the only real test I know for that one is throw another on.

seriously though it sounds like temp. sensor or vapor lock.

 

A question out of my own ignorance, how do you explain vapor lock on a EFI vehicle? I have never heard of it on an EFI system.

 

I found this on ttora and also think this is a place to look!

faulty ground between ECM & Engine or some where in the start process

DIELECTRIC GREASE is your friend

I have fixed many start issues by just going through and pulling wires cleaning and
applying Dielectric

so if you do a temp sensor and clean up and grease all electrical connections "ESP. grounds" on the whole truck I feel that this would be your next best step as far as I see!

from there we are talking diagnosis of the ECM and start system! meaning signals to and from every where! NOT FUN !!!

 

Thanks. I'll look deeper than I have into ground and connection points.

 

usually leaky injectors or just some how air in the fuel line that creates a gaseous pocket.
the vapor line to the carbon box, or return line to the tank being clogged creating excessive pressure vapor locking the fuel system creating a hard start situation!


just threw that out there for some thought

but I am thinking between that and the contacts and temp sensor you should find your problem

 

If I wa in your situation right now I would start with pulling all wire connections and using alot of dielectric!!

Then I would verify that I have an open fuel return line!
The fuel constantly runs a loop. The Pump pumps 5-10lbs more pressure than
the regulator retains removing any vapor in the line.
So if the return line is clogged this may be the issue!
to unclog run use an air compressor and blow air down it with the gas cap off!

and Then I would replace the temp. sensor!

see what happens when each is performed.

 

The return line is definitely clear. Temp sensor will be changed tomorrow if it's in stock. I will be checking all connectors and grounds today. Thank you.

 

Ok so I just reread your orig. post and it says you already did the temp sensor,
your last post said your return line is clear here is the location of the ECM wiring

http://www.ncttora.com/fsm/2000//Rep...ine/index.html

terecm.pdf

at the moment I am just throwing this out there

Your Welcome this is a pain for you I know!

 

Well, I went through all grounds and connections yesterday. Cleaned and tightened all grounds. Applied dielectric grease to all connections. Still no good results. I ordered my BR-3 scan tool today. Hopefully I can pick up my problem with this.

 

You said all this includes the ones on the ECM and fuel pump/o2 sensors?

 

Yep. I have even switched out the circuit opening relay in case of faulty contacts.

 

I like your input Eddie Lee, very thoughtful. I'm dealing with the exact same problem right now. I haven't done much other than replacing the plug wires and fuel filter. I did read about a recall for the 2003-2004 4Runners to fix this issue, there was a problem with the grounds in the main wiring harness. So I am inclined to believe that poor grounds could cause this issue. Noise in the wiring due to poor grounds would cause interference in the tach signal (I have first hand experience with this on my Megasquirt'd Corrado). Rather than chase down a bad ground myself, I will probably bring it to the dealer.

Coolant temp sensor is another good idea and one I haven't considered yet. The ECU certainly needs to know the correct temp to determine proper injector pulsewidths during cranking. This is actually a very sensitive moment for an engine.

I don't agree with vapor lock, knowing what the OP is dealing with. This issue can happen in the hot or cold. Vapor lock would indicate the the fuel has gone through a phase change and has turned into a gaseous state. These gas vapors would have to exist in the injectors to prevent starting for a few seconds. I bought my 4Runner this winter and had this problem in very cold weather. I don't think the ambient temperature was hot enough for the fuel to reach its 'vapor pressure'. Remember, it would take a quite a leak (injectors or fuel line) to drop the pressure to atmospheric conditions. It would then take some heat soak to get the fuel to vaporize..............................but as I type this I realize that the PUMP could be leaking back to the tank. The one-way valve could be broken. Even with a good FPR, if the fuel rail is dropping to atmospheric conditions as soon as the pump stops running, the fuel in the injectors could be hot enough to vaporize. And this could happen whether it's 10 degrees outside or 90 degrees in the shade.

The only way to test for this is by connecting a fuel pressure gauge in series right before the fuel rail. I looked in the bay and my 2001 looks like there is a spot to disconnect but there are fittings and I'm sure a special Toyota part number for this gauge.

I know that some vehicles have after-run logics relayed to temperature/pressure switches. Heat + low fuel pressure = fan and fuel pump are turned on after the engine is shut off. This keeps the fuel pressure high enough to prevent it from dropping to its 'vapor pressure'. Not sure if the 4runners have this. Dont have any schematics.

RBH, if you get this gauge, I'll rent it from ya.

 

Eddie, just looked at the pdf's you linked to. Thanks for that. Will be helpful to know what the techs are going by. I see that Toyota has actually referred to a couple Vapor Pressure sensors. This is pretty cool since I've only seen this in engineering/aerospace text. In order for a "sensor" to accurately detect Vapor Pressure, it must know the pressure and the temperature, so it is basically a multi-sensing device.

Perhaps the fuel pump is fine. Perhaps, in the unpowered state, it is allowing no more pressure drop than the next 4Runner fuel pump. Maybe this vapor pressure sensor is not telling the pump to stay running after the truck is turned off. Because in reality, this heat soaking state is the only period an engine would refer to a vapor pressure sensor. Remember, heat + low pressure = phase change.

This could be a good reason for the intermittent behavior, electronics can be like that somtimes.

 

I hope that you both get your rigs on the right side of working!
I am leaving tomorrow for Ohio and a Gathering and will most likely not be around a computer for some time.
Please update us as to the fix that gives you the desired result so some one in the future will benefit from all your new found knowledge!

Happy wheeling!!

 

I received my BR-3 scan tool. I have determined that my MAF sensor and ECT sensor are accurate. This tool is a lot more basic than I thought it would be. It's a cool too to have around, but seems very basic.

It may be con incidence or may be my issue, but I didn't have starting issues for a week. I bought a different brand of fuel last week. I normally burn Shell fuel only, but I bought Marathon brand last week and no problems. Shell recently started advertising Nitrogen enriched fuels. I wonder if this is the difference causing my issues? I may just be reaching for anything at this point, but it is a strange coincidence that my problems became apparent again the same day I re-fueled with Shell fuel again. Hmmmmm.......

 

Hey, the Actron CP7838 fuel pressure test kit will allow a schraeder valve to be installed at the end of the fuel rail. I will cleaning my IAC valve this weekend and if that doesn't work I will buy the gauge for further testing.

 

Hmmm, I was betting ECT sensor. My 97 had the exact same issue and it turned out to be ECT. Did not set a hard code, but did set a pending code.
Was the truck not starting when you checked the sensor? It may be intermittent.
One thing you might also want to look at, when it's not starting, with key on engine off is the check engine lamp illuminated? I've seem efi/main relay's go bad, in this case the ecu will not power up.

 

The problem is still so intermittent that I can't get it to do it with my scan tool connected.

 

Well, I finally had the timing light hooked up when my problem occured. I have no fire when I have the starting problems. I also have a consistant spark on one wire and inconsistant spark on the other plug wire. I ordered an ignitor. I hope this solves it once and for all.

 

Hey, my check engine light doesn't come on when the key in On position. It starts but just takes longer than it should. I keep a camera in the truck so I took a quick pic as seen below. This is with the key just turned to 'On'. Can I get a confirmation that I should have the light on, indicating that the ECU is powered. If the ECU isn't on at this time, then the fuel system isn't priming so it will try to start on 10 psi or so, depending on how long it sits.