GasTurbine

I'd like to begin by stating that this site and its members are amazing and so helpful. I have read so many threads over the years on here. I have been a ghost till now, because (probably due to my ill fated search attempts) I cannot find a solution to my current issue. I will probably list too much detail in some areas and not enough in others because I am by no means a mechanic, I can though follow directions and guidance.

I purchased an 86 model 4runner with a 22RE. It has a manual transmission. When I purchased the 4runner, the previous owner told me that it was only used for getting to and fro his hunting camp. He then went on to say that he normally used a fuel additive in between seasons. He confessed to not doing so this most recent time and led to his current issue. Wouldn't run. His neighborhood mechanic guy said that it was the fuel system and that he needed to replace the injectors and filter. He bought the parts but said he didn't know how to replace them and wished to sell it. So I took a chance and gambled that this was its only problems and bought it since it had only 97k miles. My uncle and I installed the injectors, fuel filter, dropped the tank and cleaned it, and tested the fuel pump. Fired right up!! I drove it for a few weeks maybe two months and had a problem. I'm an engineering major and had to leave for school. In the months away, my uncle had friends look at it but they couldn't/can't figure out the problem.

The 4runner will start up every time you crank it. Run for a moment then die. You can crank again, it'll idle great, start choking and then die. So we thought the fuel system despite most of it being new. We replaced the fuel lines. Their hypothesis was that it was the MAF sensor, I bought an used one and replaced it, problem persists. They then decided it was the coolant temp sensor. After replacing the MAF, I obtained a pdf FSM and performed the resistance checks between corresponding terminals and had everything check out. I even checked another 4runner's MAF to confirm my readings. Using the FSM i read that the coolant temp sensor checked out as well as the cold start (or tempt time, Ive seen both names) switch checked out, since they are side by side. Well the people with more know how said the coolant temp sensor, and seeing as though it was $15, I replaced it. Problem persists. Following a thread, I cleaned one of the MAF sensors and tried it, same thing.

Here comes the big break in the case, which I believe will allow some of y'all to hopefully diagnose my issue...

We decided to see if it was the MAF sensor's wiring harness. While using a test light on each of the terminals, we noticed a sound when it was plugged into terminal #2 (green wire), we realized it was the fuel pump. We tried starting it while holding the test light on that terminal, and viola! It runs! Will idle as long as you hold that test light on that terminal, rev as long and as hard as you'd like. Remove it and it chokes out and dies.

Here are some addition things:
After it initial died on me, the buzzer to let you know the door is open would continuously buzz. If you mashed in the button located in the crack of the door it would cease and if you wiggled and wiggled the key around while in the ignition it would cease, but would come back if slightly moved. In order to remain sane we removed the buzzer. This leads my uncle to believe there is an issue with the ignition (wiring possibly?). I could be wrong, but does the test light and probe make a short when used? As in, when i use it on that 2nd terminal is shorts it, and therefore bypasses something to all the 4runner to run.

My theory is that the ecu has two stages for the Fuel Injection system. 1. The prime the system and get ready to crank. 2. Hey Im cranked and ready to roll. I feel as though something in my initial stage is hanging up or not allowing me to carry into the stage of normal idling and running. I only say this because it will crank every single time, then just choke down and die. also, shorting that 2nd terminal in the wire harness will allow it to run indefinitely.

Ive checked the fuel system fuse (located passenger side in fuse box, 25amp) The fuse is good and the there is power to the terminal location.

I would greatly appreciate any guidance or light shedding on this issue. I would love to be able to take my 4runner out for a spin again.

osv

the coolant temp sensor that the ecu uses to control the engine is a lot more than $15, you probably replaced the temp sensor for the temp gauge.

you definitely want to check the circuit open relay:
http://www.4crawler.com/4x4/CheapTri...ORelayLocation

ignition switches on these things are marginal, they can be replaced, i'd look at the cor first, then maybe the ignition.

my '86 had been sitting for nearly a year, while I replaced the motor and the front axle... when it tried to start it, it barely turned over... I turned the headlights on bright, and it started right up, hasn't been a problem since :-0

probably needs that ignition switch replaced.

GasTurbine

Thanks for the direction. Any clue as to why shorting that second terminal will allow it to idle and run?

I am going to explore the circuit open relay tomorrow and ignition switch. I will report my findings.

I'm pretty sure that's the coolant temp sensor. Based off of yotatech threads and the FSM. The other part you mentioned is called the temperature sending unit, which sends signal to the guage in the dash. Or so that's my understanding.

I heard replacing the ignition switch can be tricky, any tips?

Thanks again for some guidance. I'm so ready to drive Lil red again one day haha

osv

I think that the air flap has to be open slightly to trigger the cor/fuel pump... given that you've already replaced the unit, i'm at a loss to understand what could have turned the pump on there... bizarre.

the 4runner electrical system can be pretty finicky, as you are seeing.

I've never done the ignition switch... I believe that the coolant temp sender for the ecu has a two wire connector, and it's a green connector, front of the intake manifold, 89422-12010 is the part number, about $60:
http://personal.utulsa.edu/~nathan-b...36electron.pdf

GasTurbine

Yeah,that's the part I replaced. Coolant temp sensor. And they run $15 at the local part stores.

Here's an update and depression...
I read that post and others on the car. I ran a jumper on that fuel pump plug on the driver's side so that it would run when the key was moved to the on position but not cranked, it did just that. I was doing this so I could listen for the cor. Well before doing that I wanted to see of having that jumper would allow the 4runner to run. So I cranked it without the jumper and like usual, it cranked sounded normal,idled for a few seconds then died. I reconnected the jumper and it did the same. It would crank and idle fine, but after time or if you attempted to give it any gas, it would die.

First question, why would shorting that 2nd terminal on the maf allow the pump to run with only power (not having to be running) just like the jumper, however it would keep running and you could work the throttle without any issues as opposed to the jumper? Hmm

Well my grandpa showed up to help and I shared all of this with him. I went to show him the fuel pump jumper and its plug however the pump wouldn't kick on... Well now the 4rummer won't attempt to crank and the fuel pump won't run even when shorted. None of the efi elements appear to be getting power. However I can cut the headlights/wipers on. I don't understand why they get power but now the others don't???

Sigh, feels like I take half a step forward and four backwards.

osv

no way that $15 part is genuine Toyota, but if it works, who cares!!

is there enough power to follow the troubleshooting steps in that 4crawler page? see if it helps.

if not, there must be another problem, something common to those parts... if it's a manual transmission, there will be a switch on the clutch pedal, that won't let the truck turn over until the pedal is depressed.

see if that thing is working? I'm not sure that you should permanently short it out, I seem to remember hearing that the ecu on some vehicles uses the input from it to help control the fuel injection... probably not a big deal, tho.

GasTurbine

It is manual. Yes, I wouldn't permanently short it, I was just doing so as part of the test on the c.o. relay. I'm gonna pull it off and check resistances but that article says that'll just tell you that the part is good, not if.you're having issues. I checked the switch and it appears good as well.

Also, that jumper allowed the fuel pump to run with only the key being in the on position. No clutch. Nothing. It was doing just that. Then when I tried the second time, nothing. Now I only get power to assecories and etc, nothing in the fi system. I checked the fuses. They're good.