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Unread 11-05-2010, 06:24 PM   #1
cumminsgetsome
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1990 4.0 hard starting

Hello, I have a 90 jeep cherokee with 4.0, the problem is it cranks along time before it starts. It does not matter if it is hot or cold. I replaced crank sensor and no difference. I can hear my fuel pump and have tried bumping the key a few times then trying to start it, did not help. I have cleaned the grounds (one on firewall and one on side of motor) not sure what else to do. Any suggestions would be greatly appreciated. Thank you

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Unread 11-05-2010, 07:04 PM   #2
kylexj90
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i have the same problem. I think maybe a o-ring in the fuel rail is bad where the line connects to the rail maybe. ive been trying for so long ive just bout given up.
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Unread 11-06-2010, 06:55 AM   #3
tjwalker
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You have a Renix XJ (87-90) By design, the engine is not going to fire until the computer (ECU) gets a signal from the crankshaft position sensor and measures that signal to indicate that 300 rpms while cranking has been met/exceeded.

Somewhat extended crank times should be considered a “characteristic” of your engine, rather than a problem.

You can upgrade the battery and battery cables--at least 4 ga., 2 ga. better--and buy a high-torque starter.

You are correct in that good grounds are critical, especially for a RENIX!

Other than good basic tune-ups on a regular basis which should always be reviewed, (plugs, wires, cap, rotor, fuel filter) the above suggestions are things that will help optimize start times on a Renix engine.
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Unread 11-06-2010, 07:11 AM   #4
cruiser54
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Upgrading the cables helps as tjwalker suggests. But, the fact is that a Renix Jeep requires the 300 RPM crank signal to the ECU before fuel/spark is provided. I have had good luck by adding a ground cable from the negative battery terminal to one of the radiator support bolts, after cleaning the paint off of course. Napa has a short cable PN CBL#710894 which works perfectly for that application.
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Unread 11-07-2010, 02:02 PM   #5
cumminsgetsome
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Thank you for your replies, I do understand that this motor recquires more cranking, but I have owned a 89 jeep and it did not crank as long as this one, just about everyone around my jeep when I start it comment that they were unsure of it starting. I will try the added ground. I have also heard that you can wallow out the holes on the crank sensor to move it closer to the flywheel to get better signal, has anyone tried this and have it help? Also if the distributor was out of time would this also cause longer starting because of the cam sensor being off?
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Unread 11-07-2010, 03:46 PM   #6
cruiser54
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You can move the CPS closer to the flywheel and it will generate a stronger signal. Make sure the stator/sync generator in the distributor is functional. Then index the distributor. Indexing definitely shortens crank time if it's set properly and it was way off before.Be sure to add the ground. Be sure to clean your throttle body and IAC while you're at it.
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Unread 11-08-2010, 12:37 PM   #7
cumminsgetsome
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What do you index the distributor to? Are there marks? Thanks.
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Unread 11-08-2010, 01:32 PM   #8
cruiser54
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It's a simple procedure to perform and was in a Technical Service Bulletin in 1988 or so. Try searching for it.
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