77olds

I posted this in Advanced Tech because it has to do with the injector upgrade.

I have a 2000 XJ, 4.0 obviously, and recently upgraded the injectors to the 784 set from a Neon or whatever.

Fuel mileage immediately after stayed around the usual 15mpg, BUT I also had a cracked fuel line that apparently became cracked during the injector swap.

So I figured, once I replace that line and fix the leak, I should at least keep the same MPG, if not gain 1 or 2...

But no, it's the exact opposite. Since I replaced the fuel line, I'd LOST 2-3 MPG.

I don't understand how this is possible... I repaired a fuel LEAK and my mileage got WORSE.

Can anyone help me understand why this could be?

SuperGlue

caused a larger leak?

77olds

I could smell the small leak, now there is no fuel odor whatsoever. I looked all over and I don't see any wet spots where it could be leaking, either.

My theory is that the new injectors are spraying more fuel, but maybe I need to change my spark plugs because it's not all getting burned off...

but if it was running rich, wouldn't it throw a code?

Jeep450r

How long was the fuel line leaking for?

kjc

O2 sensors detect rich/lean condition and send a signal to the pcm which sends a signal to the injectors to adjust. Glad your fuel system isn't leaking, but if you upgraded to a higher flow injector expecting better fuel economy, I don't think that's gonna happen.
I think maybe if you open up the intake and exhaust, it MIGHT help with mpg's with your new injectors. I would suggest you read the in-depth write-up on here by no rdplz regarding injectors.

Thexjfiles

Did you flash the ECU after the injector swap?

77olds

I did.

I wasn't necessarily expecting a major increase in MPG, but everyone who has done the swap said that they gained at least 1 or 2, I was hoping it would at least stay the same.

However I think I may have found the problem.. when I filled up, the pump shut off and the needle was just a hair below the full line on my gauge... I thought that was weird, so I pulled the trigger again and got maybe an ounce more before the pump shut off again. (I never top-off unless the pump shuts off prematurely)

So I thought maybe that's as far as the needle goes and I just hadn't been paying attention...

but yesterday when I filled up at a different station, the needle ended up just past the full mark.

I think that might be why it seemed I wasn't getting the same gas mileage, the tank didn't fill up as far as usual because maybe it was a crappy gas pump.

So I'll measure my MPG on this tank and see what I'm at.

greengoblin

77olds i also did the injector swap and for a few weeks after i my fuel mileage wasnt that great. its due to we reset the ecu and now it has to relearn driving habits. over the summer i was getting 20mpgs. when they went to the winter blend gas i lost about 3 mpgs. so give it time and see what you get