ok i will start with an intro, 86 4 runner, 22re, manual trans. bone stock all original. I bought it for my son months ago and it had 278k and ran decent so we pulled the engine and dropped in a new 22re due to milage and had the injectors rebuilt.
now, new engine is in, starts up and runs perfect 100%. for only 2 complete seconds. as in counting 1thousand1 1thousand2, dies.
now, ill give you my diagnostic run down (career mechanic with certifications all the way from briggs, john deer, detroit diesel, cat, honda, chevrolet, ford, etc) but im not the best ecm guy.
1-no the distributor is not 180 out
2-yes it has new clean fuel
3 new filters
4 new TPS
5 all fuses and relays have been verified
6 the MAF is opening and sending proper signal to the CO
7 the CO is sending proper signal to the FP ( fuel pump)
8 the fuel pump is opening and sending 42lbs pressure to the fuel rail KOEO
9 noid lights flash on all injector plugs
10 CSI (cold start injector) works.
11 3 injectors =3.59ohms and one is at 5.50ohms on the 20k scale
now. since it only runs for 2 seconds then dies i assume the CSI is priming it but the injectors are not spraying even though there there is pressure and noid lights flash.
yes i have also tried jumping the FP in the engine bay plug to make it run nonstop and still dies in 2 seconds so we know its not the pump or that whole circuit cutting out.
BUT if i stand and give it a shot of carb clean in the MAF it will keep running perfect so this is why i think the EFI driver in the ecm is not working ?
so my questions,
1 is there something in the MAF that sensing the carb cleaner makes it keep running?
2 how do i test the fuel injection driver in the ecm,
3 or am i on the wrong track beating a dead horse and its ignition dropping after 2 seconds?
You haven't mentioned the number 1 possibility, which may cause some of your "electrical concerns". I wouldn't be surprised if your problem is actually quite simple.
The air flow meter is crucial in the early Toyota EFI systems (that utilize an AFM).
There is a "STA" circuit, which is the starter circuit - which overrides the EFI system from it's "safety" (I'll get to this) and ignores some values - particularly the air flow meter - which allows the fuel pump to run without the engine running.
Running for 2-3 seconds indicates to me that there isn't anything wrong with your ignition system - if there was a fault, it wouldn't run at all.
Instead, my assumption is fuel.
The air flow meter is crucial to the fuel pump. It's a safety feature - in that if something happens to the engine (causing it to shut off) then the fuel pump shuts off.
The air flow meter, especially after just starting (and at idle) is sensitive - and anything like a crack in the tube between the AFM and the throttle body, or even a very mild vacuum leak, can be enough of a leak to allow air to enter the engine at idle, and close the AFM enough to shut down the fuel pump.
However, when the STA circuit is started, it will run the fuel pump - and most likely after you return to a "run" position in the key, there is just enough fuel in the system to keep it running for 2-3 seconds. I've seen it time and again.
You can test this by simply going to the diag port and jumpering 12v to the fuel pump port. It may run, but not well. If it runs longer, find the problem in a vacuum leak or the tube (many times the crack is hidden, hard to see, or on the underside where you can't see it).