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Unread 08-09-2011, 08:45 PM   #1
SayBye
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No Fire, Where Should I Begin?

I have no fire on my 91 YJ 4.0. Where should I start???? Thanks.

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Unread 08-09-2011, 08:49 PM   #2
Nickabis
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Where don't you have fire? Plugs, distributor, coil? when was the last time you've done a tune up with new plugs, wires, cap, and rotor?
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Unread 08-09-2011, 10:55 PM   #3
cevans87
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no don't start there... start by doing a code scan...

turn the key from the off position to the on position 3 times... on the 3rd time leave it on, and your check engine light will start blinking... count the blinks and then look up the codes... for more information just doing a search on the forum... that's where you need to start to save money...

if you get code 11 which is a blink then a pause then another blink and a long pause.... you have a crankshaft position sensor going bad or a camshaft position sensor going bad
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Unread 08-09-2011, 11:01 PM   #4
Nickabis
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Quote:
Originally Posted by cevans87
no don't start there... start by doing a code scan...
I didn't say start there, I know testing those things for spark are easy but all I wanted was some more info on the no fire from the OP before saying to go spend the cash to through parts at it and giving direction on where to start.
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Unread 08-10-2011, 08:21 AM   #5
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theres no fire in the distributer and plugs, so would that mean i have a bad distributer? or could that mean i have a good distributer and a bad coil?
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Unread 08-10-2011, 08:46 AM   #6
oldtime_ironman
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It's usually a bad crankshaft position sensor, or sometimes a bad coil. BUT look at what cevans said: get the codes from the computer first. It will save you some grief because the jeep computer is one of the best diagnostic tools all by itself!
So why not get the codes and then get back to us?
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Unread 08-11-2011, 09:55 AM   #7
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if the crankshaft position sensor is the one that bolts to the bell housing then i already replaced that last week... my fuel pump wasnt coming on so i thought that was the problem. i ran a power wire straight from my battery to my pump and it came on and ran fine. so theres no fire and the fuel pump isnt coming on without me forcing it on (holding the hot wire to it). but ur right, ill try the code thing when i get home and get back to you.
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Unread 08-11-2011, 10:57 AM   #8
Que89YJ
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Fuel pump isnt coming on is huge. Thats not the crank sensor or cam sensor. I'll be willing to bet you cant check codes because the cel light doesnt come on. If that is the case then:

http://www.jeepforum.com/forum/f12/c...rs-ecu-492597/
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Unread 08-12-2011, 05:13 PM   #9
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Quote:
Originally Posted by Que89YJ View Post
Fuel pump isnt coming on is huge. Thats not the crank sensor or cam sensor. I'll be willing to bet you cant check codes because the cel light doesnt come on. If that is the case then:

http://www.jeepforum.com/forum/f12/c...rs-ecu-492597/
what do u mean by cel light? i turned the key 3 times and the only thing that happened was the check engine and shift arrow blinked one time together, then went off and didnt come back on...
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Unread 08-12-2011, 05:37 PM   #10
oldtime_ironman
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Quote:
Originally Posted by SayBye View Post
what do u mean by cel light? i turned the key 3 times and the only thing that happened was the check engine and shift arrow blinked one time together, then went off and didnt come back on...
I think he means that this is a sign that your ECU (the computer) is a problem
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Unread 08-17-2011, 12:55 PM   #11
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im going to dive into the ecu tonight when i get home...

i have read on here that the computer is powered through the dome fuse? is this correct or did i read the post wrong?
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Unread 08-17-2011, 01:32 PM   #12
Que89YJ
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Yes, you can also check power to the ecu on pins 3 and 9 on the ecu connector with the key on. You should see 12 volts on both pins. If you have power on those 2 pins and no CEL then read the link I posted about the ecu.
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Unread 08-17-2011, 02:49 PM   #13
jeepin100
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no start

I have 89 yj 2.5 has no spark out of wires i have replaced coil,did not fix prob. has anybody had prob. that could direct me? someone said computer? how would i test for that?
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Unread 08-17-2011, 05:47 PM   #14
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the cel and arrow come on every time i turn the key on. so does that mean its not my computer?

checked the ignition coil and i have 12 ohms coming through it...
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Unread 08-17-2011, 06:24 PM   #15
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im confused. my ecu doesnt look like any of the others on here that have replaced the caps. not only that, but the caps in mine are two 220uf and one 470uf. so i dont have a clue what ive got? my jeep is a 91 4.0 yj. heres a pic...
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