I've been reading some new threads regarding resetting the ECM after an injector install and was wondering if this was really necessary.

I just installed the Bosch III injectors from FIC and the Average city/highway mileage went up from 18.1 to 19.9 mpg Without resetting the ECM.

Since the O2 sensor reads the air/fuel ratio in the exhaust and gives this information to the ECM so, it will pulse the injectors with the correct amount of fuel, why would the ECM have to be reset?

 

when you did the swap did you have the batt. unhooked like you are supposed to?. when you started it back up it did reset.. I just like making sure all residual voltage is out of the vehicle before starting back up.

 

Hey Jon,

I didn't disconnect the battery when I installed the injectors. I knew I should but, I got lazy and didn't want to reset all my stereo settings.

The engine runs Great, and the mileage is up almost 2 mpg! I don't think the ecm needs to be reset for an injector change but, the battery should be disconnected for safety's sake. Thanks

 

What are the negative aspects of not unhooking the battery (other than maybe a fire since your dealing with some raw fuel) when doing an injector swap?

 

I guess if you wan't to work on your engine with the battery on it's up to you. I on the otherhand disconect it as habit. I don't like sparks around fuel. A stupid small spark can ignite fuel vapors so for safety I just do it. Plus I want the ECU dead when restarting.

 

Not to mention the fact that almost every single engine repair procedure in the FSM begins with number 1. "disconnect negative battery cable"

 

Spark + Fuel Vapor + Air = FIRE!!!

 

Skin graphs, hospital, loss of car, maybe home... duh

 

If you're going to do an injector swap yourself, I'm here to tell you that the single, most important thing you can do AFTER disconnecting the battery, is to take the gas cap off and leave it off until you reconnect the fuel rail. Ask me why

 

 

You could end up looking like Richard Pryor did.

 

Are the injectors the same lbs per hr as the ones you removed ? If they are no adjustment needed. The better mileage is due to being flow matched.

 

heres a good article. this will explain why resetting the ECU in important to get rid of the old BLM values stored in the ECU

http://www.gnttype.org/techarea/faq/BLMINT.html

 

I said FIRE in my post. What I was wanting to know is if this could cause problems with anything else other than FIRE. Could not disconnecting the battery cause any electronic or mechanical problems with the way the engine runs?

 

If you're just replacing the stock injectors, and you don't disconnect the battery, there won't be any negative effects on the engines performance.

The reason a lot of members get so, alarmed about issues like this are because so, many inexperienced members working on their own engines fail to use Common Sense.

For example: the member who posted about changing his fuel filter and letting half his fuel tank empty onto his garage floor because it wouldn't stop for 7 hours! All he had to do was cap the fuel line.

When I changed the injectors, I removed the gas cap, relieved the fuel pressure from the schrader valve and capped the fuel lines. There were no gas fumes or puddles of fuel anywhere. I also, don't use any electric shop light and always have a fire extinguisher at hand.

As far as my Original question: Reset ECM after injector install necessary?

After reading the responses, I find that on a Stock injector replacement, it is Unnecessary to reset the ECM.

But, you should Always disconnect the battery for safety's sake.

 

why??? Will that bleed the air out of fuel lines? I just changed injector and it’s running a little rough. I’ve checked everything , it threw a code at first then after I redid the process and double checked. It went off but still running rough
can I remove fuel cap, bleed fuel like a little then start vehicle??
thanks I know this thread is really old but hey 👋

 

Fuel lines are self bleeding, as soon as the fuel pump turns on. Cap has nothing to do with it.

Removing the cap relieves pressure from the tank that could push fuel out of your disassembled fuel rails during an injector swap. Fuel getting pushed out is messy, and a fire hazard.

You have another problem that is causing rough running. Diagnose that problem and don't worry about your gas cap.

 

gotcha. Yeah all I did was swap injectors and now having a little issues. Thinking it’s a vacuum line. Thanks for the reply

 

This falls under the "Runs OK" category. You have new injectors, the system needs to re-learn the BLMs across the board. Might as well give it a blank slate. I have to assume you are replacing injectors because there is an issue. Why do you want to start operating the new injectors with information from faulty injectors? The adjustments don't happen immediately. It has to see the conditions and adjust. It should actually start running better after a few drives as it see all the different load/airflow/RPM conditions.

Are you data logging? Where are your BLMs now? Bosch III's are known to need some Voltage offset adjustments (that for some unknown reason) that are not published. For some reason it seems the Iron headed L98 has more issue with this than the Aluminum headed 'Vette motor.

Is re-setting the radio presets that much of an issue? I mean, write them down and put the back in. This can't take more than 5 minutes and it's about safety.

Yes, other tings can happen. The car has electricity at the ready it in circuits. A slipped wrench, accidentally breaking a wire, or other means that could expose a connection could cause an arc spark. This could cause a fire as mentioned or could short or overload other electrical components. I would say it is rare and just the right sequence of events would have to happen to cause damage. I guess I just watched "Final Destination" too many times.

 

appreciate it man. Yeah my father in law called me late last night and told me to drive it and let it re-Learn. I replaced the injectors because I could hear an air leak and sure enough one of my o rings was cracked. Btw this is a 2003 dodge Dakota 4.7l not a corvette but I couldn’t find any other forums !!! Lol thanks again