Cdmcnr

I have a 86 Toyota 4 runner that I got from a buddy it had been sitting up for quite some time he told me it only needed a gas tank and fuel pump. (Yeah right lol) So I towed it up to my shop put a new battery in it sprayed some cleaner in the throttle body and boom it started right up and ran for a little until the spray ran out so then I installed a new tank and fuel pump new computer because it kept blowing the Efi fuse. After all that it still wouldn't start but it would if I sprayed the throttle body. So I removed the intake and fuel rail remove the injectors and tested them all ok checked wiring harness had to make some minor repairs put it back together and still same thing. Grab a noid light do have pulse very weak though but the funny thing is when I went to start it it and I now do I explain this it when I was turning it over to check the harness with noid light it wanted to really start then when I plugged the injector back up it just goes back to spinning over its very weird. It seems to me like and I don't know maybe the injectors are not pulsing or maybe I'm over looking something. Right now at this point any help would be very much appreciated and ideas thank you for your time sorry for such a long story.

scope103

Do you know if the fuel pump is running? (You can jumper FP to B+ to eliminate the VAF switch and COR.) Do you have fuel pressure at START? (The gauge requires a banjo bolt adapter, but they are not hard to get.) Are the plugs wet when you pull one out?

wyoming9

iTrader: (1)

It also would not hurt to install a new filter after you check fuel pressure.

If it is quiet you should be able to hear the fuel pump run when you jumper it

Co_94_PU

iTrader: (-1)

High resiistence on the ECM ground? Just a shot in the dark guess..

What repairs did the harness need, this might be a clue?

Since you did harness repairs after the computer swap, it may have been damaged also, there aren't alot of tests for those unfortunately. Just the voltage and resistence checks.

And of course my favorite goto answer.. Follow the trouble shooting flow chart from the manual, if it doesn't get you going atleast you'll have eliminated a vast portion of the sub systems as causes, then it's on to really bizzare odd ball things.

Cdmcnr

Hi thanks for the responses and yes I can hear the fuel pump run and I do have fuel coming into the fuel rail. The repair that I made was on the fuel injector harness found speaker wire and wire nuts holding it together but I did do the repairs before the computer swap ( those things aren't cheap lol ) but now today while I was at the shop I did find some shady grounds replaced them with new wire and when I went to start it wanted to for a second then back to normal (aggravating grrrrr) I will say that manual is not very clear on the flow chart if anybody knows where I need to go to get a decent flow chart I'm all ears but thanks for replies I'm going to still keep going at it and any more ideas that you guys have will be really useful thanks again

Co_94_PU

iTrader: (-1)

Engine codes, Vaccum leaks, Igniton system, Ignition timing, Fuel supply, VAFM Fuel pump switch, Spark plug gap, compression check, Air valve, EFI ECM voltage check.

Not sure how the flow chart confused you but there is the condensed version, the other one is much better and specific IMO.

You can use the ECM resistence checks from the 90's model, that verfies the sensors and wiring all at once so you don't have to do tests directly on all the sensors.

stanprophet

This is what I am thinking also, have have fixed a ton of 22re motors with this problem. The ground is in a multi gang ground on the intake.

That light is only drawing like 20-30ma, where an injector will draw much more. High resistance in the ground will create a huge voltage drop as current increases. I would check the grounds at the intake manifold. Use a multimeter, clip the red lead to the crimps on the ground wires, not the bolt. Connect the black lead to negative battery terminal, have someone turn the motor over and see what kind of voltage you find. Anything over about 100mv is bad. You are voltage dropping the circuit under a load, if there is high resistance on the ground, voltage is bypassing the ground and going through your meter.

Just to help some people understand a bit better, you cannot use the ohm meter to measure resistance in a curcuit with any type of load. For example, if the wire to the starter has one little strand connected it will measure good on resistance. But it will be unable to carry any amount of load.

Voltage drop the grounds, it is quick, easy, and very very effective!

stanprophet

I do not use factor flow charts very often, they can often lead you to perform many test that are not necessary. Although it is a good idea to check your fuel pressure, it sounds like you already know that the injector pulse is weak. You already know that it will start with a little shot from a can, so it will run. You know your problem is fuel related.

With KOEO (Key On Engine Off) you should have 12 volts at the injectors. As long as you have power then you know that your issue lies in the ground. Since the ECM controls the injector pulse by pulling the injector control wire to ground, allowing current to form in the field winding, and pulling the pintle off the seat to inject fuel. There is only a couple of things that can be the problem. High resistance on the wire, faulty driver in the pcm, or bad ground for the PCM.

Either way using the voltage drop method you will find the answer quick.

Cdmcnr

do have questions can some one give me an idea where i can get a good wiring schematic for showing grounds for a 86 toyota 4 runner

B-Fake

Not sure if this is all you're after, but here's the grounds under the hood.

https://www.yotatech.com/forums/f116...-guide-194413/

The FSM will have schematics.

Cdmcnr

Thanks big help

stanprophet

If all the grounds check out, double check the resistance on the injectors.

I had a car towed in last week, customer put a fuel pump in about 6 months ago and could not get it to start. It had been to 2 shops and they could not figure it out, so it came to me. The computer was intermittently shutting down and it did not have any injector pulse. I scoped the drivers and even when the computer was working there was no ground signal from the ECM.

We ordered a computer and it came today, put the computer in and had the same problem.

I had originally checked all the wiring, and the grounds for the ECM, they were good. In the process of checking further I had 2 of the injectors disconnected and while cranking it wanted to start. I pulled all the injector connectors and measured the resistance, on the #4 injector, resistance was 1 ohm, where the rest were around 3. Plugged in the other 3 injectors and it fired up.

The injector that was shorted was causing the injector driver in the ECM to shut down. Swapped the old computer back and it would not start, the drivers were damaged by the faulty injector. Luckily the new ECM was not damaged.

If the computer was blowing the EFI fuse, and you have a weak injector pulse this could be a possible cause. This was not a toyota, but was an OBDI MPI system that is all the same concept.

Cdmcnr

Was up have had some great help on here with getting my 86 4 runner going with all the test I have ran came up with a bad solenoid resistor. Now the new problem is cant find the part have come across some used ones one line but when talked with sellers seems kind of sketchy. So now I'm at a point can I by-pass it or what r some options if any.

wyoming9

iTrader: (1)

Well if you bypass the resistor the next thing you will need is all the injectors as well.

It is there for a reason.

Why do you feel uncomfortable with the people you have talked with.

I would have to look to be sure but it may have different part numbers which Toyota is known for.

As long as the resistance value measures the same it should work just fine.

Are you sure yours is open?? I have never seen one fail.Always a first time But I gotta wonder what happened??

Feel free to Pm me as sometimes I can`t reread every thread.

Cdmcnr

thanks for the replies but the reason why im trying to by-pass the solenoid resistor is having trouble finding one toyota discontinued the part so i camr up with a idea wnet to my local radio shack got a pack of 1/2 watt resistor with different ones in it then after some time found the right ones so know when i ohm it im at 2.1 which by the test that i found to check the resistor it is within specs but now have a problem to where ive lost njector pulse so thank god the computer is still under warranty so as soon as i get that going to give it another try but do have one ? for some reason im not getting any fuel through the return lines got it going into the fuel rail and cold start injector but nothing is coming out of the return lines at the tank any suggestions thanks

Cdmcnr

ok guys this is what i got now on my 86 toyota 4 runner new computer another solenoid resistor good grounds. Now when i go to start it it wants to bust off better than before but it wont but will still run off cleaner just fine have checked everything i can possibly think of any ideas on what i may be missing ?

Discombobulated

Your missing a clean question I have no idea what you just said???

DELTA_RIDER-92-PETE

Are you saying that it will run on intake cleaner/engine starter but as soon as its gone it dies like its not geting fuel if so start at the fuel pump an move forward its not getting fuel somehow sounds like to me

Cdmcnr

Ok this is what is going on now since my previous post I've installed a new computer a solenoid resistor new ground wires and now when I go to crank it it wants to start up at first but it doesn't I have 12 volts to the injector and pulse ( of forgot to mention will start up and run if I spray it with ether) I don't understand why it won't start up and run it wants to but it won't confused as hell

crazypaint

Fuel filter might be bad