Kracker

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 john deer, detroit diesel, cat, honda, chevrolet, ford, etc)
1-no the distributor is not 180 out its dead on.
2-yes it has new 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 cold start injector KOEO
9 noid lights flash on all injector plugs
10 CSI (cold start injector) works.

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 signal. or the signal is dropping after the CSI primes.
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?
thanks

millball

An inductive timing light ought to be able to show whether or not the spark cuts out as its dying.??

Kracker

ok ill check that

scope103

Are you watching the fuel pressure, and the noid lights, as it starts and then dies? The VAF-COR issue (very common) you refer to would show up as adequate pressure on start, then rapidly falling when you release the key, until the pressure is low enough that it dies.

If you have lost the IGF signal from the igniter, the ECU will cut off the injectors, AND throw code 14. It's a stored code, so you need to check, but since you've done most everything else in order I assume you have done that. Even without a code, if you can get a noid on any injector (they all fire together) it would be worth watching it as it dies.

Following the principal of doing the easy stuff first, I'd second millball and watch the spark with a timing light. Even before that: check for codes. Then plumb in a fuel pressure gauge and watch that. Then wire up a noid light (even a home-made one) to watch the injector pulse.

PS Whatever I know about the operation of these trucks, I am NOT a hardcore techie.

Kracker

i now suspect the NE or IGF circuit, checking those now. trying to find a diagram to see which ones they are at the igniter

scope103

You could search this forum for "igniter."

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

NE doesn't go to the igniter, it goes to the ECM, which generates the IGT pulse to the igniter.

Continue being methodical with your diagnosis. You don't want to be "sure" its the IGF circuit, just because that's the latest thing you've heard.
https://en.wikipedia.org/wiki/Medica...nts%27_disease

Terrys87

iTrader: (1)

Even if the noid is flashing on the injectors, that does not mean enough signal is getting thru to fire the injectors. I had an 86 where the crimps in the harness was so corroded that it could not fire the injectors but would pass the signal to lite the noid light..

Since you say your motor running is running for a couple of seconds at a time makes me think the AFM is not hooked up.

I am sure Igniter do go bad but I have worked on hundreds of these trucks and really have not had one to fail. The one that did fail was exposed to the weather.

What I went thru for Non Firing Injectors https://www.yotatech.com/forums/f199...l#post51897320

wyoming9

iTrader: (1)

Your talking fresh rebuilt engine or used long block ??.

Poor quality injector refurbish??

Like Terry said those injector harnesses tend to get quite brittle and corroded with age I wonder with moving things around degraded them even more . This would be my Top pick!!!

Then it is quite possible a pin might have got bent or even broke off all it would take is just one.

Kracker

igf at the ecm... i dont know if im looking for voltage or what at ecm?

scope103

Posters on this forum sometimes provide links to valuable information, rather than clutter the posting with stuff well-explained elsewhere.

As I said in that post, I was able to read the IGF signal with an oscilloscope, but NOT with an LED.