Very Odd Behavior From My 4.0l i6
07-06-2017, 08:53 AM
#1
Newbie
Thread Starter
Join Date: Sep 2013
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
Very Odd Behavior From My 4.0l i6
Hey guys, recently ran into an issue I wanted to get some opinions on. I've got a 1995 XJ, engine is brand new with 500 miles on it, and I've ran into what I had thought was a crank but no start issue. The twist is it cranks oerfectly fine just won't get that last bit to actually start, but when I let off the key (don't turn back, just stop cranking) the jeep rumbles into a start with a semi rough idle. The guy who swapped my engine didn't put new plugs in it (for some reason(-_-) so I swapped all 6 plus the plug wires, seems to have slightly improved the spark. Cap and rotor were done 3 years ago, but only 1000 miles ago (don't know if that matters). Starter is brand new, fuel pressure at shraeder valve is good to go.... I'm struggling for ideas here other than a possible relay failing (that'll be fun to find) or a lose wire, possibly ground somewhere. Any help or ideas would be very appreciated!! Thanks in advance!!
07-06-2017, 02:05 PM
#2
CF Veteran
Hard to guess on an issue like this, but I would be concerned that the starter is pulling the system voltage down too low and its causing other unrelated ignition problems (for example, relays can fail to switch if the voltage is insufficient) But then when you release the key and the starter stops putting the load on the battery, and the other systems get their appropriate voltage, and since the motor still has a few spins to go, it starts.
Have you monitored system voltage across the battery terminals while cranking to see what happens?
Have you monitored system voltage across the battery terminals while cranking to see what happens?
07-06-2017, 04:59 PM
#3
CF Veteran
Join Date: May 2012
Location: Lost in the wilds of Virginia
Posts: 7,964
Received 952 Likes
on
767 Posts
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
I agree with Jordon. Some voltage measurements are easy to do, and check those battery connections and cables.
07-07-2017, 10:28 PM
#4
Newbie
Thread Starter
Join Date: Sep 2013
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee
Haven't pulled any voltage measurements yet, I honestly was completely stumped and didn't know where to start. I'll focus on voltage in the morning. Also checking grounds, for some reason that keeps popping in my head, as it was a new engine put in and a lose ground kind of makes sense here. I'll post what I find out, thank you for the ideas. Any more to check while I'm under the hood are more than appreciated.
