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  #16  
Old January 27th, 2018, 17:25
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Re: Renix woes for 1988 XJ 4.0/auto

and really, this is a LOT less problems than the other harness.you guys are a huge help.
i will clean grounds and see if i cant bring it back into spec.
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  #17  
Old January 28th, 2018, 14:08
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Re: Renix woes for 1988 XJ 4.0/auto

ground strap on head cleaned, and on ground on block above the starter cleaned and re installed. not right yet, but closer. Ohms are now under 1.0 from tps to battery neg.
and less than one from body to engine block. volts are the same. still no advance and fuel delivery to run higher rpms.
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  #18  
Old January 28th, 2018, 14:18
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Re: Renix woes for 1988 XJ 4.0/auto

Test your fuel pressure.

With the engine running, see how much voltage you have on either side of the fuel pump ballast resistor.
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  #19  
Old January 28th, 2018, 15:39
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Post Re: Renix woes for 1988 XJ 4.0/auto

Quote:
Originally Posted by cruiser54 View Post
Test your fuel pressure.

With the engine running, see how much voltage you have on either side of the fuel pump ballast resistor.
so when it ran better, the fuel pump was replaced. it has less than 150 miles on the new pump and filter, and i already had the rubber hose come off the pump in the tank. it was holding steady on 35 psi. i can hear the pump when i turn on the key but not start it.
i made a jumper for teh wires on the ballast and that made no difference i could detect. i ll get the voltage -be right back
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  #20  
Old January 28th, 2018, 15:51
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Re: Renix woes for 1988 XJ 4.0/auto

ballast resistor wire voltages are
10.0 v on front terminal
14.0 on firewall side
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  #21  
Old January 29th, 2018, 17:15
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Re: Renix woes for 1988 XJ 4.0/auto

Will it rev high in neutral? If not, you could have a distributor indexing problem. I even had a CPS that would limit the engine to around 1500 rpms once.

What color is the tailpipe. It should have a black coating. If it is light grey, it is running lean.
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  #22  
Old January 29th, 2018, 17:16
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Re: Renix woes for 1988 XJ 4.0/auto

When you crack the throttle, does the fuel pressure change?
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  #23  
Old January 29th, 2018, 21:13
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Re: Renix woes for 1988 XJ 4.0/auto

tail pipe is black. throttle does not go much beyond idle. as iin idle fuel and spark are there but wont rev high. idles fine with a little shake, i can deal with for now. i dont think the fuel pressure drops, gage died and cant re check. but does have new pump and filter.from a year and a half ago.
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  #24  
Old January 30th, 2018, 08:31
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Re: Renix woes for 1988 XJ 4.0/auto

Just reread this end to end

1) You need to confirm fuel pressure and flow capacity is still there to maintain higher engine rpms. Pumps go bad right off the shelf, and fuel lines in the tank come loose.

2) It sounds more and more like exactly what I had last year, The shear pin on the gear at the bottom of of my Distributor shaft was loose (finally broke, sheared off) and I could spin the rotor around by hand. There should be no rotational play in the rotor turning it by hand. Mine had a bout 3/8" side to side just before it broke.

Second the distributor you have may need indexing, I even had to cut the location ear off of mine on the brand new one, like so many others here to index the new one as it was defective off the shelf new, because of OEM Factory Cam shaft mistakes over the years by AMC-Jeep on these jeeps. Did you say you replaced the engine? Distributor?

See if the rotor on the distributor can be rotated rationally or if it has any side to side play in the shaft (bad bearings). If it has more than 1/8" in rotational SLOP, or any side to side play replace it.

Either way, take a used cap and make a cut away view window and follow cruiser54's Indexing the distributor instructions on his website blog. There are no short cuts to his instructions, LOL, I tried. Buy a new cap and rotor and used the old one for making the window Cap tool. Makes the indexing super precise!!! And that makes a huge difference. Contrary to urban legends, the ECU can not compensate for a spark jumping the wrong plugs!!!

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  #25  
Old January 30th, 2018, 10:57
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Re: Renix woes for 1988 XJ 4.0/auto

so before i had to fixed...well 60 percent of the time anyways. it ran good and strong. when it ran bad, i shake the harness and it come back to good. i replaced the harness and got rid of a lot of crap. but now back to no power. the reason not messed with ignition, is this is not an ignition problem. it is a sensor not telling the cpu to deliver problem.
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  #26  
Old January 30th, 2018, 11:03
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Re: Renix woes for 1988 XJ 4.0/auto

IIRC you disconnected fuel/spark to one cylinder at a time with no change? Have you tested each fuel injector pigtail with a Noid light?

Do what you want, If it was me, I would set the Crank to TDC, and pull the cap and see where it is pointing, and see if the rotor has slop in the rotation.

Also the ECU may have an issue if the harness had a short and damaged the ECU.

Have you tried running and driving with the O2 sensor disconnected????

Have you confirmed that the O2 sensor heater is good (about 8 ohms) and that the heater wire, orange has 12-24 volts from the relay???
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Last edited by Ecomike; January 30th, 2018 at 11:06.
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  #27  
Old January 31st, 2018, 04:53
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Re: Renix woes for 1988 XJ 4.0/auto

How's the tube from the throttle body to MAP sensor?

It has to be perfect.

Any change if you unplug the MAP sensor?

How much voltage at the fuel pump wire connector?
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  #28  
Old January 31st, 2018, 11:42
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Post Re: Renix woes for 1988 XJ 4.0/auto

Quote:
Originally Posted by Ecomike View Post
IIRC you disconnected fuel/spark to one cylinder at a time with no change? Have you tested each fuel injector pigtail with a Noid light?

Do what you want, If it was me, I would set the Crank to TDC, and pull the cap and see where it is pointing, and see if the rotor has slop in the rotation.

Also the ECU may have an issue if the harness had a short and damaged the ECU.

Have you tried running and driving with the O2 sensor disconnected????

Have you confirmed that the O2 sensor heater is good (about 8 ohms) and that the heater wire, orange has 12-24 volts from the relay???
o2 is new and works fine. ecu swap and no change
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  #29  
Old January 31st, 2018, 11:43
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Post Re: Renix woes for 1988 XJ 4.0/auto

Quote:
Originally Posted by cruiser54 View Post
How's the tube from the throttle body to MAP sensor?

It has to be perfect.

Any change if you unplug the MAP sensor?

How much voltage at the fuel pump wire connector?
MAP tube is perfect
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  #30  
Old January 31st, 2018, 11:45
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Post Re: Renix woes for 1988 XJ 4.0/auto

Quote:
Originally Posted by Gunter View Post
MAP tube is perfect
ballast resistor wire voltages are
10.0 v on front terminal
14.0 on firewall side
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