Running On 1 Less Cylinder.

[Corey]

I just want some light shed on my theory.

Now…a lot of people say running on one less cylinder is bad, because it’ll flood the cat with fuel.
However, if you disconnect the fuel injector and the coil connectors, won’t everything be okay? Shouldn’t it run just like the newer cars do with cylinder deactivation? The cylinder should just pump air.

My next question is…what happens to the fuel that is still in the fuel rail going to that disconnected injector?
In theory, if the injector isn’t connecting (meaning it can’t let fuel spray out), won’t that cause back pressure in the fuel rail, or no?

Topic

[college man]

In theory what you say about stopping fuel and spark will
shut that cylinder off per say. But you engine will be down
on power and the other injectors will need to compensate for
lost fuel (Lean) which will tell the computer to add more fuel.
Let alone set a misfire code,Lean code and make the engine possibly
knock. Also not good to try and compress air. I’m not for the idea. :blink:

[Daniel]

For your first question: when an automobile deactivates cylinders it also leaves the exhaust valves open. The reasons for this are: a.so the cylinder does not pull air charge from the intake which would throw off sensors like the maf. b. If the deactivated cylinders were still compressing air it would create a huge drag on the motor. c. If the deactivated cylinders are pushing huge amounts of (un regulated) oxygen rich air into the exhaust it could shorten the life of your cat (possibly even detonate it.) Your engine has an air pump that injects air into the cat to burn off unused fuel but, the volume of air it injects is closely regulated by the computer.
As for your second question: The fuel rail feeds multiple injectors. The pressure through the rail is regulated by a vacuum or electronically operated fuel pressure regulator. Any fuel that that one cylinder does not use will eventually be used by other injectors. The regulator would keep the fuel pressure at a constant pressure even if no injectors were operating.
If you want to disable a cylinder, in theory, you could unplug the injector, and remove the spark plug. The open spark plug port should releive any compression drag. You would also want to cap off the power supplies for the plug and injector, with some kind of insulated cap. Otherwise they would arc to the closest ground, which would create a short and blow a fuse.

[Bill]

Engines with cylinder deactivation disables the injector but it also deactivates the valves. These engines have a lot of problem with oil burning especially GM trucks. It tears up the rings for some reason. (I have my theory but that’s for another time).

The fuel pressure regulator takes care for any excess fuel pressure.

[Corey]

Wouldn’t deactivating the valves cause the engine to stall? The sealed cylinder would try to go downwards, but would be closed off. I assume it’d be similar to trying to get the engine to run with the throttle body 100% sealed (closed)?

[Bill]

Because it’s only one or paired cylinders it has no effect.

[Daniel]

When the valves are disabled the exhaust valve stays open, and you only disable the valves for the cylinders that you want deactivated.

[Mark Elliott]

I have a 1997 Dodge Dakota SLT 5.2 L V8 318 Magnum Small Block and was getting back fire though the exsaust pipe caused by cylinder 3. So I unplugged the spark plug wire and the fuel injector on cylinder 3 and the back fire stopped. I did leave the spark plug still in the block and left the fuel injector still on the rail just both unplugged so cylinder 3 would not get spark or fuel anymore. That was 3 year ago it is still running great today. I use it every day even pulling a utility trailer loaded. I only lost a little power not a lot and it does not bog down and can still haul ass. The idle is off and lower than normal but it sure can run. I hear a lot of BS about cause fires and ring problems and other BS and that is all it is, is BS. Cylinder 3 is not Dead and has compression just fine. I am just to lazy and strapped for funds to further diagnose it further plus again it is doing just fine running on 7 cylinders. Dodge build this one right for sure. So all of you saying it is a bad idea to do it or it can’t be done for long or it is dangerous I have news for you that you are wrong for sure. Again it been running like this as a daily driver for more that 3 years. Oh and also I do not burn a lot of oil either just in case you might think that. Also it does not knock or rock around and zero damage to my motor mounts or my front end. Your all just talk because I own it, did it and drive it. That’s the honest truth. I don’t believe talking out my ass like some of these people on the forms. I know now some will just call me lucky and is so hats off to me. See you on the road in my rear view mirror. LMAO. Mark E. down hear in Sunny Florida.

[Author]

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