Good info! I am trying to wrap my head around how the Ecu could be bad since I am getting the pulses according to the noids. That’s the only signal needed to fire the injectors isn’t it? Other than the frequency and duration of the pulse I don’t see what else could be missing.

I will check the voltage drop to the ecu as you mentioned tomorrow. I did put the meter on one of the injectors and I believe it was 13.8 ohms. I like the idea of trying to simulate a pulse with a battery to see if I can hear the click before I pull everything apart. I had 12 volts at each terminal on the injector connectors. Does the computer ground out one of these terminals for each pulse? Sure hope I can find something causing this problem so I can get this thing going again.

 

The injectors ground thru "#10" & "#20" pins on the ecu, they are all spliced together in the engine harness. A high resistance bad connection here won't be able to carry enough current to fire the injectors but will light an LED without issue.

 

I never considered that the resistance could be too high to fire the injectors even though the lights flash. I did the 9 volt check and hear it click. It’s audible without the engine running but I doubt if I would hear it while running. I might try again tonight. Roughly where in the harness are the Toyota splices for the ground circuit? Should I try to ohm the wires from the injector connector back to the Ecu connector to see how much resistance there is before tearing into the harness?

 

I am also having trouble finding a pin out diagram for my Ecu. Mine has 12, 16 and 26 pins. All the diagrams I see online start with a 10 pin connector. The ones I see online for my model are different. I have 89661-35830 Ecu.

 

At 12/4=3ohms your meter isn't accurate in that range. Add in you know at least one of them reads in the 14ohm range and it's not helpful to measure. And that ignores that it's not a loaded circuit and once it starts trying to flow current a bad connection goes even higher resistance..

The splices are right about the middle of the harness under the intake. That spot where it's at the low spot of the dip and can collect water..

You can throw an amp clamp on the ECU lines.

A 9v battery maxes out in the 30-50ma(0.050a) range, so it definitely didn't open all the way. They pull about .75-1 amp each normally.

I'm not saying this is the problem just pointing out why your noid light might be giving you a false sense if security..

What happens to the voltage on the ground side, LED based test light on #10 #20 connected to ground?

Did you check the fuel volume returning to the tank or clamp off the return line and check the pressure and engine response yet?

 

Left corner..

 

Thanks again for helping guys. My father in law passed away yesterday so I have been out of town. I did clamp the return line when this first started and did not notice any difference. Spent a little time this afternoon pulling the upper intake to get to the injector wire splices and went ahead and pulled the fuel rail while I was there. I can check the flow rate to the rail easily now. Fuel rail and injectors did not show any obvious clogs. Splices don’t look bad either but I will go ahead and solder and reseal then while it’s apart. Anything else I need to check while it’s apart?

 

Well since you're in there what you're looking for is, "the green crusties", corroding copper turns a blah green color and gets brittle and stiff.

As for redoing them you need to exercise some caution here with the solder you need a low acid high lead solder, auto and aero space are exempt from.the rohs regulations.

If you are taking these crimps apart you'll notice they overlap 100% under the crimp.

You need clean shining copper on both ends, 100% overlap, don't over squish the crimp or over heat the junction when you apply the solder.. I digress there are threads for.this.

..
OK so the fuel supply to the rail isn't something we have benchmark's for, what we have is a bench mark for the fuel volume coming out of the regulator which you can cross-reference with the fuel pressure in the fuel rail. From memory you should have about 35-45psi in the rail and 500ml/cc coming out of the return line to the tank.

...
You have the fuel rail and injectors out, spend the $20 and buy the servicing kit, new screens new seals and new tips aren't going to hurt it and ensure you're not going to have leaks when you put it back together.
..

 

The past week has been really busy but I did check the flow rate on my lunch break. It comes out to about 40 gph coming out the fuel filter. I believe the stock pumps are around. 50-60 gph so that sounds reasonable after going through the filter. Guess I will try to temporarily hook up the fuel rail with the injectors in place and pulse them manually to check for spray and pattern on each injector. If everything looks good I will dig further into possible electrical causes.

 

Guys I still have not located the splices on my injector ground(white with red stripe) wires. I have 4 separate wires leading from the injectors over to the fender well and all the way up to within about 10” of where it goes into the firewall. Do I need to keep unwrapping the harness or could these be spliced inside the cab? The splices on the black/red wires that go toward the drivers side look good so I hope I find a problem with these grounds.

 

I have an update if anyone is still following this. I got creative and tested the injectors tonight. I hooked the fuel rail to the fuel line loosely on the engine with the injectors clamped into the rail. This way I can observe each injector to determine if they are spraying. With the key in the ignition I have 12 volts hot on each injector plug so I connected all the injector plugs. I disconnected the ecu connectors and tied into #10 on the harness to ecu connector. I jumped the fuel pump to power it and used the end of my lead to tap on the bumper to simulate ground pulses. All injectors sprayed. I swapped into the #20 connector and all the injectors sprayed again. By doing it this way the power was traveling the full length of the hot and grounds in the harness. I think this means the injectors, the fuel supply and I believe my wiring harness should be good. Does this sound right? Am I off on my reasoning? Knowing this where else should I look? Maybe weak spark after running for a few seconds? It runs good on ether spray but that might ignite with a weak spark easier than gas only.

 

Definitely perplexing. Next thing maybe test the coil/igniter? Wiring all good at the igniter?

https://www.yotatech.com/forums/f116...gniter-287857/

 

This part in the middle doesn't make sense, can you elaborate? You're providing ground by touching a wire connected to #10 and #20 at the ECU and the injectors fired? Using this same fuel rail rigging without the wires, the ECU fully connected, if you pull the distributor and spin it's shaft the ignitor and injectors should fire.. The only thing I can think of off hand is it might need to hit a certain RPM, for example the ignitor controls the Ignition up to 500 rpm then the ECU starts using the IGt (trigger) IGf (fired) feed back system.. We're kind of in a grey area here..

Still a bit curious if the engine harness at the ECU might not be grabbing the male lugs of the ECU tight enough. Did you backprobe the #10&#20 at the ECU with a test light (LED based) and observe it trying to fire the injectors? You can try that with and without #10&#20 plugged into the connector body. If it doesn't fire the injectors but does a low amp test light AND (yeah big and) has a firm connection to the ECU male lug the driver circuit inside the ECU isn't providing enough current sink (bad ECU..)

 

Spark quality is a really simple test with the right tool, this simple device connects between the coil output and a ground and you wind out the knob on the scale to about 120kv then observe the spark and quantify the color..

You can get away with stabbing an incandescent test light near the open end of the wire. You shouldn't notice much difference between 1/2" and 1" air gap..

Don't get shocked =P

 

Basically I disconnected the harness from the ecu and connected to #10&20 on the harness with an alligator clip. Then used the other end of my alligator clip wire and tapped a grounded surface to simulate the pulses. It let me see the injectors spray and also allowed me to run the current through the harness. I was unsure if I could get the ecu to send the pulses with the intake off and sensors unhooked. I will try it by using the starter next to see if they still spray. At least that will determine if the harness has a good connection at the ecu.

 

This is all good info guys. I am learning this as I go and have limited time each day so I am having to take my time on it. I have a test light but will have to check to see if it’s led. I will also have to look into the test for proper spark as I am not familiar with anything other than pulling a plug and observing the color. I am also still trying to get a better understanding of how the igniter plays a role in powering the injectors and how the igf and igt signals work. I will have to see if there are simple tests I can use to check these. Thanks guys!

 

Little update. I pulled the distributor, hooked the computer back up and spun the the distributor gear. I am getting two fires of the injectors for each turn. Sounds like the igniter fires four times per turn also. Pushing the flap door while spinning and I do get fuel spray from each injector. If I keep spinning the gear it keeps pulsing the injectors so I think the wiring and splices are ok.

 

I put everything back together to see if spraying out the injectors and adding new filters and seals made any difference. Good news is it looks like I managed to get it back together correctly. Bad news is it still will start, run for a second and die. Playing around with giving it a little throttle while starting and I noticed it would run a few seconds after the csi shut off but it is chugging like a single cylinder is firing. I would guess 10-20% throttle when it will do this. Does this point to anything specifically? I will see if I ca load a video of this.

 

Youve gotten a lot of good advice so far, way more than I can catch up on atm. I know you said youve sprayed hoses to find leaks but in my experience, this technique isnt as effective as most people think. Ive made a diy smoke machine to test for air leaks and ive tracked down and eliminated some bad misfires that carb cleaner and starter fluid couldnt locate. Look up videos on youtube for how to make one.

Sounds like youre being really thorough. Theres no magic bullet, just testing and process of elimination. Everything you learn pays off!

 

I am going to try to revive this thread. Life kept me away from the truck for a bit but worked on it last week with the help of a retired Toyota mechanic and was able to use a good running truck to try swapping out some components.

a little background is this truck was running fine one day and when I went out to move it a few days later it would only run for a second and then die. It does this over and over never runs more than a second or two at the most. It always starts right up and runs like it should till it just dies. I replaced the fuel pump and fuel filter. Have mid 40’s psi pressure and once the engine starts it drops to around 37 psi once the fpr gets engine vacuum. I also tested for flow by filling a can and calculated it to approximately 40 gallons per hour at the fuel rail.

This Saturday we swapped out the afm, the coil, the ecu, the fuel pump circuit opening relay and any other relay we could find associated with ignition or efi. Nothing made any difference. The truck will continue running if you spray carb cleaner in the air box so it does not appear to be timing or spark related. A noid light on an injector shows the injector pulses to continue as long as you keep spraying in the air box. The ground on the intake is clean and tight I have previously pulled the fuel rail/injectors and removed the distributor and have confirmed they all appear to be clicking and spraying some fuel. I can’t say if the spray volume or pattern is good but I would expect it to be enough to at least run even if it ran poorly. I also checked the injector wiring splices and could not noticeable corrosion. I just can’t come up with anything that seems to be the culprit. This week I am going to test out a new ignition switch just to make sure it’s not causing the issue. Does anyone have any ideas where else to look? This thing is driving me crazy. I am about to the point of tearing it back down and temp running all new wires to the injectors from #10&#20 for the ground pulses and maybe even running new temp hot wires to the injectors just to eliminate the harness as an issue.