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Unread 02-19-2013, 06:38 PM   #1
aldersonfilm
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Can you run without an ECU?

Is it possible to still start and drive if the ECU is damaged or missing entirely?

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Unread 02-19-2013, 07:25 PM   #2
mtwask01
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Only if you retrofit to a carburetor. The ECU is the brain of the fuel injection system and is absolutely necessary. If it is damaged, it may still run and drive depending on the severity of the damage, but if missing entirely, it absolutely will not run.
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Unread 02-20-2013, 11:35 AM   #3
sAe23
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You'd probably have to change the distributor too, and who knows what else...

OP, why not just unplug it and see for yourself ?
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Unread 02-20-2013, 12:31 PM   #4
Pats94
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Go to a carb, distributor set up. If you have a auto thats going to need to be addressed.
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Unread 02-20-2013, 04:56 PM   #5
tjwalker
It's the crank sensor!
 
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Gotta know.....why are you asking?
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Unread 02-20-2013, 06:38 PM   #6
aldersonfilm
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Haha this was purely a curiosity question. I pulled the battery cable while the engine was running to check the alternator, but I then heard that this can damage the ECU. Just making sure, I didn't do that.
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Unread 02-20-2013, 10:57 PM   #7
Reptile
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Quote:
Originally Posted by aldersonfilm View Post
Haha this was purely a curiosity question. I pulled the battery cable while the engine was running to check the alternator, but I then heard that this can damage the ECU. Just making sure, I didn't do that.
So you ignored a warning that it could damage your ECU and still proceeded to do it??

Sure it'll run without a ECU, I don't see why not, at least on a downward slope. Say, why don't you cut off some random wires and let us know what you get away with?
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Unread 02-21-2013, 12:14 AM   #8
aldersonfilm
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Didn't hear it could damage the ECU until I had already tried pulling the cable. Seems to be running fine though.
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Unread 02-21-2013, 04:26 AM   #9
Hudson
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Get a multimeter and check the alternator that way.

Your battery should be at like 14.55 DC volts with a good alternator. (With engine running obviously). With engine off it should drain down to like 12.55 DC volts and not much lower.

Most auto stores will test alternators for you for free if you don't have a multimeter.
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Unread 02-21-2013, 05:43 AM   #10
Kettles
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I dont know why the cable off would damage the ECU, unless the voltage regulator was bad and without the battery it somehow started generating excess voltage. But not knowing the specifics on how it works, I cant say either way if that would happen.

But I do know, if the alternator is functioning properly, the engine will run without a battery and it shouldn't hurt anything (not start mind you, but you probably knew that). The ECU controls everything, if its not there/not working, nothing works.
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perfect depends on how far away you are when you look at it:D
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It's a 4.0 ... as long as there's something in the crank case that isn't coolant I'm sure it will still run forever.
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Unread 02-21-2013, 09:33 AM   #11
tjwalker
It's the crank sensor!
 
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Below is a link to a good article that explains why you should not remove a battery cable on a running engine. I've fixed a couple of vehicles where it fried either the computer, the alternator, or both. Doesn't happen all the time, but why would you want to take the chance when the charging system can efficiently be tested with a simple meter.....

http://www.troubleshooters.com/dont_...ct_battery.htm
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Unread 02-21-2013, 05:10 PM   #12
Kettles
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Quote:
Originally Posted by speedbucket View Post
perfect depends on how far away you are when you look at it:D
Quote:
Originally Posted by Millermagic View Post
It's a 4.0 ... as long as there's something in the crank case that isn't coolant I'm sure it will still run forever.
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