97 ZJ misfire cylinder #1 and never starts the first time. - JeepForum.com
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Unread 05-25-2013, 12:27 AM   #1
JeffBratcher
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1993 XJ Cherokee 
 
Join Date: Feb 2013
Posts: 12
97 ZJ misfire cylinder #1 and never starts the first time.

I recently purchased a 97 GC and have had a few issues with it.
4.0 I6 175K Selectrac auto tranny
Recently replaced starter(old one died), 120A alternator, cap, rotor, plugs, wires. Cleaned idle sensor(was idling at 2500 rpm!), sea foamed intake, gas, and oil-changed oil after a 100 miles or so. I was getting misfire cyl 1 with CEL. It seems to have cleared up after all this, but still idles a bit rough at 5-600 rpm, and it never starts the first time. Any ideas? Fuel pressure is about 50 at idle, and I installed a new FI on cyl 1, which was a slightly different size and caused bad leaks. So then I switched 1 and 2 and CEL is gone, but I think the sea foam did the most work. Cyl 1 spark plug was much dirtier than the rest, and I suspect dirty valves was the issue.

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Unread 05-25-2013, 06:27 PM   #2
rjbruzan
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2004 TJ Wrangler 
 
Join Date: May 2008
Location: Lake in the Hills, illinois
Posts: 2,004
The starting problem is most likely the anti-flowback valve in the fuel pump assembly. A 300 part but if you get in the habit of cycling the key before starting it should last a long time.

Ron
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Unread 05-25-2013, 09:37 PM   #3
JeffBratcher
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1993 XJ Cherokee 
 
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Quote:
Originally Posted by rjbruzan
The starting problem is most likely the anti-flowback valve in the fuel pump assembly. A 300 part but if you get in the habit of cycling the key before starting it should last a long time.

Ron
Hmmm I have found that key on, key off, and then start works very well. Thanks for the info! My old XJ with the same motor has a fuel pump that I could hear when I turned the key on. It runs a few seconds until it builds pressure then is quiet until you start the engine, then if the gas tank was around half or more empty you could often hear it running. This one seems to build pressure only when the engine is running and I thought that may be the issue. Different fuel supply all together though it seems.
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Unread 05-26-2013, 02:03 PM   #4
Avionic1JN
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1991 MJ Comanche 
 
Join Date: May 2013
Location: Cleveland, OH
Posts: 25
Absolutely true on the fuel pump issue. I've had a mercury that went another 25k with a bad check valve in the pump. Your said it cleared the CEL! sooo... no more misfire?
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Unread 05-26-2013, 05:40 PM   #5
JeffBratcher
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1993 XJ Cherokee 
 
Join Date: Feb 2013
Posts: 12
Quote:
Originally Posted by Avionic1JN
Absolutely true on the fuel pump issue. I've had a mercury that went another 25k with a bad check valve in the pump. Your said it cleared the CEL! sooo... no more misfire?
The CEL has not come back on in a week or two. It does occasionally go from 750 RPM to 500RPM, and a little rough, at idle. Well, it is 16 yrs old. I am getting over it - I am just staying on the safe side in case it is signs of a real problem. The idle sensor was a little rusty when I cleaned it, so that may be all it is..
Thanks for the reply!
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Unread 05-27-2013, 04:22 PM   #6
Avionic1JN
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1991 MJ Comanche 
 
Join Date: May 2013
Location: Cleveland, OH
Posts: 25
Quote:
Originally Posted by JeffBratcher View Post
The CEL has not come back on in a week or two. It does occasionally go from 750 RPM to 500RPM, and a little rough, at idle. Well, it is 16 yrs old. I am getting over it - I am just staying on the safe side in case it is signs of a real problem. The idle sensor was a little rusty when I cleaned it, so that may be all it is..
Thanks for the reply!
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