Question about running engine with disconnected fuel injector? - Fuelly Forums

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Old 09-09-2008, 10:00 AM   #1
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Question about running engine with disconnected fuel injector?

My little old reliable 94 CX just let me down. It has dropped a cylinder. It only registers 25psi on a compression check vs 165 for the other three. Put some oil in and only registered 35psi, so it appears a valve related problem, or worse yet a piston problem. Anyway the question is would it be ok to run the engine with the injector disconnected or do I need to put a resistor across the connector to simulate the injector being in the loop. I don't want to wash down the cylinder and dilute the oil, while still running the engine till I fix the problem.
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Old 09-09-2008, 01:18 PM   #2
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I think you can just unplug it. Your oxygen sensor readings will already be way off because of the extra oxygen going through that cylinder.

You can go into open loop via unplugging an injector or you can go to the trouble of adding a resistor and then go into open loop because of the oxygen sensor values being way off.

I unplugged an injector on my 87 Integra without any ill effects other than a CEL. My mpg was just about the same as with it plugged in.
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Old 09-11-2008, 07:07 AM   #3
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Well is there anyone out there that would know what type, size and any other info on a resistor to replace the injector, Spec it out, please. It is running ok with the injector disconnected but its in limp mode and has even less power then when the injector is connected, it also is rougher, but oh well its all in the interest of learning. I have another engine to replace this one with so, it just a time thing.

Thanks
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Old 09-11-2008, 07:19 AM   #4
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You could use a digital ohmmeter to test the resistance of the unplugged injector and then get a resistor with a similar value.
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Old 09-11-2008, 11:38 AM   #5
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I doubt you're going to get very far with a 60hp engine running on 3 cylinders. I had a spark plug wire come off on my DX on the freeway and I barely struggled home.
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Old 09-12-2008, 04:51 PM   #6
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yea v8's and 6's can get away with it but when a 4 cyl looses one its major problem
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Old 09-18-2008, 01:45 PM   #7
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BTW The car is running on the three cylinders with the injector disconnected it does 80mph ok but hills are definitely a problem for Fred and Barney. The limp mode only allows 20mph in 1st, 40mph in 2nd, 60 something in 3rd and 80 in 4th and 5th I have'nt pushed past that. Its definitely a little rougher and down more on power with the injector disconnected, but its been doing this for 500 miles and soon I'll have the mpg's to compare to previous mpg's as a 3 cylinder vs a 4 cylinder. Then with the resistor in place I can compare the two in a different senario, as in closed loop as oppossed to limp mode. Remember I have almost no compression in one cylinder, so the engine is alot smoother not having to compress the dead cylinder to 160psi it only makes it to 25psi, big difference. It takes a while to get up to speed.......
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Old 09-18-2008, 02:53 PM   #8
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What about taking the cam off real quick and removing the lifters for that cylinder?

It'd keep the valves closed so your not moving air that isn't burnt and will keep you from wasting energy opening and closing valves on a dead cylinder.

If compression is that low I seriously doubt you'll have an issue with hydrolock, but if you are concerned about that pull the plug and run a hose to a catch can with a breather.
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Old 09-18-2008, 07:23 PM   #9
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Removing the rocker arms is a good idea- but I think the Honda rocker shafts have an oil hole in them to lube the rocker pivot point (at least that's the way my 87 D15 is), so if you remove the rockers, better use some electrical tape and a steel hose clamp to block those oil passages- it would be a shame to seize the cam during this experiment because all the oil was shooting out where the rockers were meant to be.
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Old 09-29-2008, 01:52 PM   #10
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Well an interesting thing seems to be happening now that the resistor is in place. The gas mileage in limp mode with the injector disconnected was approx 40mpg after two partial fillups, because of the gas shortage here in the Atlanta area. With the resistor in place of the injector and closed loop mode the gas mileage was 28mpg and 30mpg after two partial fillups. The engine runs with no limits in closed loop and with limits in limp mode. So that's where I am at, at the moment.
I think I will try disconnecting the O2 sensor and leave the resistor in place so I will be in limp mode. But I would imagine it would give the same results as in limp mode with the injector disconnected.......
Any thoughts/ideas/comments on the above?????
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