P7M13

P { margin-bottom: 0.08in; } My 98 3.4 4wd 4runner was running fine. Then one day it wouldn't start. Turned over but no start; not even a cough. I towed it to the garage and tinkered with it on and off. Forgot about for a while. A couple seasons later I went out and screamed at it and tried it. It fired right up. Never did figure what was wrong. Ran fine for months and then started misfiring and threw code . Swapped coils, injectors, etc. around and no dice. One injector's ohms were way off, so I replaced it. It ran like a champ for a few weeks with no codes and then one day same thing. Turned over strong but no start. I rarely drive off of my place and run it real low on fuel and fill from jerry cans often, so I figured the fuel pump was maybe due anyway. Plus it has been experiencing an occasional hard start when cold and I was just plain tired of diagnostics. Replaced with a walbro 190, and it fired right up first try. But no typical walbro noise...I thought eureka, fixed AND quiet. Drove it around. Next morning, no workie.


The truck won't start and acts like its not getting fuel. Some starting fluid indicates spark. The EFI relay is working and delivering proper voltage. The pump relay/COR is only getting around 2.64 volts from the ECM. No short on the relay power from ECM, it was clean. If I short the COR relay, the pump starts up with the ignition, BUT it still won't start when turning over. The fuel filter is not clogged. I'm sure cause I took it off and shouted obscenities through it. ECM is getting good voltage, and seems like it's grounded well. IGT1, 2, and 3 ECM to igniter wires are clean no shorts, but no voltage when ignition is on and I probe the igniter side. That doesn't seem right.... Good voltage into the igniter. If cranked and I pull a plug it seems on the dry side.


I'm thinking the injectors are not firing, but with the low volts to the COR, is it all because the ECM is licking itself or is there some mystery short under the intake manifold that will cost 15 cents to solder?Why would it start right up and then next day not if it's not a short? I would have guessed an ECM would just die for good and be done. I've checked all the grounds I can find; everything is tight. When I pulled the ECM and took the cover off, I see no signs of arcing or toastage. It looked mostly clean, dry, and no obvious signs of issue. Not sure where to go from here.

crazypaint

Id try another ecm

P7M13

Update and another question....

Checking the MAF resistance, the E2 and THA only briefly ( like way less than a full second) show an appropriate resistance and then show a short thereafter. Cleaned again and again; most times I probe it it is about the same. But note above voltage from ECU to COR. So question is......Could total MAF input failure to ECU so dramatically affect voltage to fuel related components that the COR voltage is shunted when ignition is on and injectors are killed? Any gurus want to chime in? From here on out I'll be just "buying and trying" parts so any opinions are welcome.....

P7M13

And oh yeah....how in the world can you be running around with a failing MAF with no codes thrown?! Still stumped.

wyoming9

iTrader: (1)

So you have no Mil on??

Yet Engine does not run sounds like a bad ECM.

Then I have had connections test good with a meter that just would not work when plugged together.

Now since you broke the seal on the ECM I really hope you live in the desert if your ECM was good it won`t be now.