I have had this weird issue the last few days where it will start up everytime, but when it’s cold (mornings) it will idle for about 5-10 seconds then die abruptly. Even with Fp to B+ jumpered, it still happens. I am somewhat familiar with the vaf-cor system, but this seems different. Once the truck is warmed up enough or during the day it starts fine and runs perfectly. Is this something to do with the cold start injector?? Not sure what to test/ how to proceed.
Thanks!

 

how cold is cold? freezing?

you can pull the connector to the cold start injector and hotwire the injector to the battery for a quick second, should be able to hear it click... you can also put a noid light on the wired end of the connector, see how it behaves in various cold start scenarios.

there are also factory procedures for checking the resistance of the temp sender for the injector circuit, much has been written about that.

in the case of my 22re, i think that it ended up being an intermittent failing fuel pump, that finally quit working entirely... i had put a fuel pressure gauge sender on the cold start injector, which helped a lot with troubleshooting and monitoring.

 

it is not freezing. Only like 50-60 degrees. It seems like after i keep trying to start it, after a few times of it starting and stopping, it finally runs fine. I’m guessing that’s because it warms up a little and then doesn’t use the cold start injector. When it’s warm outside during the day, it will start fine no problem every time. Is there something that tells the normal injectors to not run while the cold start injector is firing??

 

sounds like socal weather... my 22re wouldn't start easily in 50ish temps if it had been sitting for a few days.

you can put your finger on the body of the cold start injector while someone is cranking the engine over, should be able to feel it click... per my noid light testing, it only fires for a very brief time at those temps.

agree with what you said; the fact that your engine runs for a short period would seem to indicate that the cold start injector is working... i was able to duplicate that behavior by squirting carb cleaner into the plenum, via one of the hose connections, but with intermittent fuel pressure problems it wouldn't keep running.

i'd expect that the normal injectors should be firing all the time, not dependant on the cold start injector firing, but you can verify that with a noid light.

 

I must have been wrong about my original diagnosis because after work i tried to start it and it wouldn’t want to start at all. Even when jumping the fuel pump. I checked voltage at b+ and then at the COR socket and had none. Later i checked again and had 12v hmm. I also pushed the vaf flap open and i can hear the fuel pump with key on. After trying to start it a few times it would either crank and not start or it would start then die. Eventually i got it going with a jumper on the pump. Weird thing is once i get it started for longer than a few seconds, i can pull the fuel pump jumper out and it will stay running fine.

 

it's in a 4runner, you have easy access to the pump? i wonder when it was last replaced.

 

it’s in a ‘93 pickup.
update: today on my 2 hour commute home, about an hour in it kept trying to die while on the freeway but since in gear it would start right back up. i could hear the COR relay click every time it died. Eventually it started happening to frequently so i pulled over and put a jumper from b+ to fp. this was able to get me home.
this weekend i’ll have time to work on it. hoping it’s something simple.

 

is your CEL/MIL lit when turning the key to "on"?

that was an issue for me when the fuel main relay was failing (water leakage down the a-pillar corroded the relay in the kick-panel fuse block). the CEL wasn't lit, so the truck wouldn't start (but the starter would rotate the engine just fine) even with the Fp & B+ terminals jumped. eventually, the CEL would turn on, and the truck would immediately start.

i doubt your cold-start system has anything to do with your issue. for one, the CSI doesn't pulse like the regular injectors; rather, it sprays fuel continuously if the temperature is low enough AND the key is in the "start" position. and your truck was starting and running. once the key is released from "start" position to "on", the CSI stops injecting (spraying) fuel. it isn't a choke.

 

So now the truck won’t start at all. I can’t jumper the fuel pump from b+ anymore either. I pulled the efi relay and i can jumper the fuel pump if i also jumper terminals 3 and 5 from the efi relay location. How can i test this relay with multimeter? I checked all the blade style fuses in the fuse box they are all good. Where is the ign fuse located? wondering if i should go ahead and replace the relay or if it is a different issue

 

Do you mean you can't jumper the Fp and B+ pins and get the fuel pump to run?

And the fuel pump runs?

That being the case, it sounds like your EFI relay is shot. I would replace it, and work from there. The best way to check it would be to pull the cover off, and visually check the condition of the contacts. Chances are, they are corroded, and you would be able to see the corrosion with no trouble. Even if you're and on old geezer, like me, and need glasses to read.
If the contacts are corroded badly enough to totally prevent operation of the fuel pump, chances are, you won't be able to clean them enough to get the relay to function adequately. THAt'S why I say replace the relay.

If I remember right, and I won't bet I do, the IGN fuse is in the cabin fuse panel, the one behind the driver's side kick panel. Again, though, I won't put money on that.

Is that any help?
​​​​​​​Pat☺