1984 CJ8 Alaskan Postal - 4.0/AW4 install, have a few questions - JeepForum.com
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Unread 07-25-2012, 06:34 PM   #1
JeepScrambler
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1984 CJ8 Alaskan Postal - 4.0/AW4, questions about fuel pumps and A/C wiring

I am in the process of installing a 4.0/aw4/dana 300 combo into one of my '84 CJ8 Alaskan Postal Scramblers. The 4.0 is currently installed, just waiting on the AW4. I do have a few questions.

First; is regarding the fuel pump. I am trying to decide between the E2000 external pump or going with an internal tank mounted pump. My question is, will the in tank fuel pump/sender from a 87-90 YJ with the 2.5 4 cylinder work with the factory 20 gallon CJ tank? Is the pick up and everything the correct length? I have read to make the YJ sender work with the CJ gauge, two wires need switched? Is this correct? If so, which wires? If the 2.5 YJ pump/sender will not work with a CJ 20 gallon tank I will likely just go with the external mounted fuel pump.

Second; does anyone who has done the 4.0 swap know if the ballast resistor and relay used for fuel pump feed wires on the XJ harness is necessary for proper fuel pump operation? Or can this all be eliminated and simply supply 12 volts to the fuel pump? It is my understanding this ballast resistor was not used on the YJ's or the earlier Renix injected XJ's.


Third; is regarding the 4.0 XJ A/C system with the CJ underdash unit. What wiring is needed from the XJ and CJ harnesses to make the system work? I am assuming I will need the XJ compressor and dryer wiring, but what about the wiring from the CJ underdash unit to turn the XJ compressor on? Thanks to Dubs1856 for finding the correct fitting to make the XJ/CJ hoses work!

Fourth; for those who have done the OBD1 swap, did you retain the diagnostic port near the main computer from the XJ, as well as the transmission diagnostic connector that was located under the dash near where your right knee would be in the XJ? Are any of the under dash plugs or plugs under the hood necessary?

Thanks for the help!

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Unread 07-25-2012, 09:48 PM   #2
kschitoskey
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4.0 swap

I put a 95 4.0 in my CJ from a cherokee. I bought a wiring harness from Hesco. Well put together and simplified the swap considerably. I have 2 sending units in my tank - one for the original CJ gauge and the other for an in-tank fuel pump. I was worried about vapor lock. I am very happy with the upgrade.

I haven't hooked up my under dash A/C to the 4.0 just yet - I'll be watching this thread with interest.
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Unread 07-27-2012, 12:09 PM   #3
JeepScrambler
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ttt.... anyone who has done the 4.0 swap have any insight to the questions or provide a source that does?
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1985 CJ8, '85 CJ8, '85 CJ7, '84 CJ7, '84 CJ8, 2-'84 CJ8 AK Postal Scramblers, '82 CJ8, '82 CJ8, '82 CJ8, '53 CJ3A
'02 Dodge Ram 2500 4x4 Cummins HO 6 spd
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Unread 07-27-2012, 12:52 PM   #4
levergun
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Ok. I did this swap in my 88yj a while back using a 93 zj motor.

First I did the e2000 but didn't like it. After 2 burned up I switched to the in tank pump. No a 2.5 sender won't work as IIRC the 15 gal tank in the 2.5 has a different mounting flange. I think it was round vs square or something like that. I silly cut the foot of the stock pickup and used a short piece of FI rated hose to connect the 93 pump to the pickup tube. Make sure you replace all rubber hose with FI rated hose and clamps. Or if you decide to use the e2000 place it as close to the tank as possible. Also make sure you use a FI fuel filter.

2nd- I am not using a ballast resistor in the fuel circuit. I have 12v from the relay going direct to the pump.

3rd- I'm not positive what wiring but it should be as easy as power from the dash switch to the pressure switch then to the compressor clutch.

4th- on mine the dtc is located near the PCM. I didn't touch any of that wiring so it still works. I also found the cel output wire and connected it to one of my not neccesary dash lights so i can do the key trick making pulling odes really easy. As far as the trans dtc is concerned I eliminated mine as I'm running a ax15.

Hope some of that helps. If you have any other ??? Or need a better answer let me know.
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Unread 07-27-2012, 01:34 PM   #5
JeepScrambler
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Thanks for the replies and info so far!

As for the YJ 87-90 2.5 4 cylinder in tank pump/sender, I could have swore I had read this was a direct swap into a 15 gallon CJ tank. I think there was possibly some difference in the pick up tube length; can anyone confirm this? Also, would this YJ sender swap directly in a 20 gallon CJ tank? I had thought the YJ's used a different sender/pump between the 2.5 and the 4.0 equipped YJ's and the earlier 4.2 equipped YJ's had the same style of tank as the 2.5 models? Does that make any sense?

From what y'all are saying and my understanding, I can eliminate the ballast resistor, just make sure the main pump feed wire and pump priming wire are hooked to it.
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1985 CJ8, '85 CJ8, '85 CJ7, '84 CJ7, '84 CJ8, 2-'84 CJ8 AK Postal Scramblers, '82 CJ8, '82 CJ8, '82 CJ8, '53 CJ3A
'02 Dodge Ram 2500 4x4 Cummins HO 6 spd
'05 Wrangler Unlimited Rubicon Sahara Edition (0002 of 1000), 6 spd, hard top, stock, 38K miles
'06 Grand Cherokee "Overland"
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Unread 07-31-2012, 06:15 PM   #6
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I will likely be going with the E2000 external pump, mainly for the simplicity of changing if/when it fails and not having to drop the tank.

One question I do have is with the twisted purple and white w/black tracer wires. There was two sets of these wires which used to come from the bulkhead connector; one set ran to the ECU (purple wire to pin 26 and the white w/ black tracer to pin 46), the other set ran to the transmission diagnostics port which was originally mounted in the cab of the XJ below the dash near where your right leg would be by the front of the console. Since the bulk head connectors will no longer be used, do I need to splice the purple wire from pin 26 and the white w/black tracer wire to the other set running from the transmission diagnostics port?

In this picture you can see the transmission diagnostics port and the twisted purple and white /w black tracer wires

Other set of these wires running from the ECU connector. Do I need to connect these from the ECU to those running from the transmission diagnostics port since their connection at the bulkhead has been eliminated?


Also, does anyone know what these plugs from the stock XJ harness do and if I need them? They were all three inside the cab of the XJ and ran through the firewall near the gas pedal. I know the top plug is the transmission diagnostics port. The smaller square one at the bottom I am pretty sure ran to the gas or brake pedal though I don't know what it controlled. The more rectangular plug in the middle I have no idea what it is for! Anyone have any insight?
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1985 CJ8, '85 CJ8, '85 CJ7, '84 CJ7, '84 CJ8, 2-'84 CJ8 AK Postal Scramblers, '82 CJ8, '82 CJ8, '82 CJ8, '53 CJ3A
'02 Dodge Ram 2500 4x4 Cummins HO 6 spd
'05 Wrangler Unlimited Rubicon Sahara Edition (0002 of 1000), 6 spd, hard top, stock, 38K miles
'06 Grand Cherokee "Overland"
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Unread 07-31-2012, 06:58 PM   #7
levergun
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The big one looks a awful lot like the one that plugs into the gauge cluster IIRC.
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Unread 08-01-2012, 08:16 PM   #8
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Anyone who has done the 4.0/AW4 swap know on the transmission diagnostics port wiring or what the remaining plugs are for?
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1985 CJ8, '85 CJ8, '85 CJ7, '84 CJ7, '84 CJ8, 2-'84 CJ8 AK Postal Scramblers, '82 CJ8, '82 CJ8, '82 CJ8, '53 CJ3A
'02 Dodge Ram 2500 4x4 Cummins HO 6 spd
'05 Wrangler Unlimited Rubicon Sahara Edition (0002 of 1000), 6 spd, hard top, stock, 38K miles
'06 Grand Cherokee "Overland"
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Unread 08-04-2012, 07:34 PM   #9
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Bump for the weekend crew!
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1985 CJ8, '85 CJ8, '85 CJ7, '84 CJ7, '84 CJ8, 2-'84 CJ8 AK Postal Scramblers, '82 CJ8, '82 CJ8, '82 CJ8, '53 CJ3A
'02 Dodge Ram 2500 4x4 Cummins HO 6 spd
'05 Wrangler Unlimited Rubicon Sahara Edition (0002 of 1000), 6 spd, hard top, stock, 38K miles
'06 Grand Cherokee "Overland"
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Unread 08-05-2012, 11:15 PM   #10
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Still looking for some clarification, anyone who has done the 4.0/aw4 swap and made their own wiring harness using the existing CJ and XJ wiring know?
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1985 CJ8, '85 CJ8, '85 CJ7, '84 CJ7, '84 CJ8, 2-'84 CJ8 AK Postal Scramblers, '82 CJ8, '82 CJ8, '82 CJ8, '53 CJ3A
'02 Dodge Ram 2500 4x4 Cummins HO 6 spd
'05 Wrangler Unlimited Rubicon Sahara Edition (0002 of 1000), 6 spd, hard top, stock, 38K miles
'06 Grand Cherokee "Overland"
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Unread 01-15-2014, 10:04 PM   #11
JeepScrambler
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Quote:
Originally Posted by JeepScrambler View Post
I will likely be going with the E2000 external pump, mainly for the simplicity of changing if/when it fails and not having to drop the tank.

One question I do have is with the twisted purple and white w/black tracer wires. There was two sets of these wires which used to come from the bulkhead connector; one set ran to the ECU (purple wire to pin 26 and the white w/ black tracer to pin 46), the other set ran to the transmission diagnostics port which was originally mounted in the cab of the XJ below the dash near where your right leg would be by the front of the console. Since the bulk head connectors will no longer be used, do I need to splice the purple wire from pin 26 and the white w/black tracer wire to the other set running from the transmission diagnostics port?

In this picture you can see the transmission diagnostics port and the twisted purple and white /w black tracer wires

Other set of these wires running from the ECU connector. Do I need to connect these from the ECU to those running from the transmission diagnostics port since their connection at the bulkhead has been eliminated?


Also, does anyone know what these plugs from the stock XJ harness do and if I need them? They were all three inside the cab of the XJ and ran through the firewall near the gas pedal. I know the top plug is the transmission diagnostics port. The smaller square one at the bottom I am pretty sure ran to the gas or brake pedal though I don't know what it controlled. The more rectangular plug in the middle I have no idea what it is for! Anyone have any insight?
Bumping this post, finally back to the wiring on the postal Scrambler. Still trying to sort through this portion of the wiring. Anyone know if the transmission diagnostics port is needed (or if it would even function if I spliced the wires back together since the originally ran through the bulk head). Also trying to figure out what the other plugs are to and if they can be removed. Thanks for the help!
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1985 CJ8, '85 CJ8, '85 CJ7, '84 CJ7, '84 CJ8, 2-'84 CJ8 AK Postal Scramblers, '82 CJ8, '82 CJ8, '82 CJ8, '53 CJ3A
'02 Dodge Ram 2500 4x4 Cummins HO 6 spd
'05 Wrangler Unlimited Rubicon Sahara Edition (0002 of 1000), 6 spd, hard top, stock, 38K miles
'06 Grand Cherokee "Overland"
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