warf90 Posted January 4, 2010 Share Posted January 4, 2010 I swapped a 4.0 liter AW4 into what was a 4 cyl 5 speed MJ. I have a couple of issues that I need help with. The temperature gauge does not work at all. I am not sure what year the instrument cluster is from. I am guessing an 88 and I got the sending unit for an 88. The guage never moves. When I ground the wire out it still does not move. I had a spare gauage out of another 88 and installed it. Still no luck. The gas gauge does not work. It reads Full all time. Even when disconnect the wire under the bed the gauge does not move. When I ground it, it does not move either. But it is already reading past full. When I did the conversion, I left the dash wiring from the 4 cylinder in the truck. The 4 cylinder was a 89. The drivetrain was from a 90. They are both renix. The last problem I have is when it is cold it runs for about a 1 minute and then it wants to die. I have to give it gas to keep it running. When I drive it cold it stumbles from dead stop. It will only do that a couple times and then it is fine. When it warms up it runs good. THanks for the help. Link to comment Share on other sites More sharing options...
freakjeep93 Posted January 4, 2010 Share Posted January 4, 2010 you temp gauge problem sounds like a sender or mabye your cluster isnt compatible with the newer motor :dunno: . the not running well when cold sonds like its just cold blooded. let it warm up before you take off. :fool: j/k your gas gauge may be the sender being bad. I'm not sure. Link to comment Share on other sites More sharing options...
maddzz1 Posted January 6, 2010 Share Posted January 6, 2010 Did you swap the fuel pump for the 4.0? They are different for the 2.5 Temp Gauge: The engine my have the temp sensor for the idiot light gauge instead of the temp sender for the temp gauge Link to comment Share on other sites More sharing options...
comanche87 Posted January 6, 2010 Share Posted January 6, 2010 :agree: Link to comment Share on other sites More sharing options...
BJA814 Posted January 6, 2010 Share Posted January 6, 2010 I learned that there are multiple temp sensors on the block, one of which is connected to the computer. Could have something to do with your cold running issues? Sounds like the electrical system is all kinds of confused. Link to comment Share on other sites More sharing options...
Geonovast Posted January 6, 2010 Share Posted January 6, 2010 Dash wiring should have been swapped too. Link to comment Share on other sites More sharing options...
warf90 Posted January 6, 2010 Author Share Posted January 6, 2010 I have not had to time to get back to the MJ, but some of the problems that I have is, I do not know what year the cluster came out of. I am guessing that it is an 88. The previous owner swapped it out. I did buy a sending unit for a guage for an 88. I assume thats what I got from the auto parts store. As far as the gas guage not working. I did install the 4 liter pump with the rest of the sending unit that goes with it. The coolant temperature sensor for the computer is there an plugged up. It is a different sensor than the one needed for the gauge. I am still not sure of the running problem. What is the difference between an 89 4 cyl dash harness and a 90 6 cyl dash harness? I did not see anything different. It looked to me that all the connections were the same. It may be the problem, I am not sure. Link to comment Share on other sites More sharing options...
maddzz1 Posted January 6, 2010 Share Posted January 6, 2010 When you swapped the fuel pump did you put in a new sending unit? If you put in an after market sending unit (airtex) then that may be why your gauge isnt reading correctly. Altho it says it is compatible with an MJ it isnt. It is actually a mirror image of the MJ sending unit. There is a pic around here somewhere Link to comment Share on other sites More sharing options...
warf90 Posted January 6, 2010 Author Share Posted January 6, 2010 I pulled the fuel pump/sending unit out of the tank that orginally went with the 4.0 L and installed into the tank in what was the 4cyl truck. The fuel pump/sending unit and instrument cluster were both in my other MJ before I junked it and it did work in the other truck. I guess I need to pull it bad out of the tank and make sure everything look ok with it. Link to comment Share on other sites More sharing options...
maddzz1 Posted January 6, 2010 Share Posted January 6, 2010 Maybe it isnt seated in the tank properly and the float is stuck on the "pan" in the tank. Just something to check. Did you swap the temp sensor on the back of the head or the other one? As for the stumbling when cold: The truck runs in open loop mode when cold and switches to closed loop when it runs for a while. Check your oxygen sensor Link to comment Share on other sites More sharing options...
warf90 Posted January 7, 2010 Author Share Posted January 7, 2010 The O2 sensor is new. I replaced that during the engine installation. I thought the O2 came in to play more when the system goes into the closed loop. Maybe not though. I replaced the sensor for the guage and not the computer. It is the sensor that has the threaded rod on the tip and it was from the back of the head. I am going to pull the sending unit back out and check it. It sure sounds like you may be right about the float getting hung up in the full position. Link to comment Share on other sites More sharing options...
warf90 Posted January 13, 2010 Author Share Posted January 13, 2010 Finally got to work on the temperature gauge problem. I found the purple wire open or broken in between the connector by the starter solenoid and the dash. I temporarly jumped a wire inbetween the sensor and the where the purple wire comes off the ignition switch and the guage functions properly. I think I am just going to run a new wire instead of trying to find the broken wire. OK now on to the fuel guage problem. Still have not figured out the cold running problem. Link to comment Share on other sites More sharing options...
maddzz1 Posted January 14, 2010 Share Posted January 14, 2010 The O2 sensor is new. I replaced that during the engine installation. I thought the O2 came in to play more when the system goes into the closed loop. Maybe not though. I replaced the sensor for the guage and not the computer. It is the sensor that has the threaded rod on the tip and it was from the back of the head. I am going to pull the sending unit back out and check it. It sure sounds like you may be right about the float getting hung up in the full position. Yes, you're right about the O2 sensor in closed loop mode. My bad :doh: Maybe the EGR valve Atleast you got one problem solved Link to comment Share on other sites More sharing options...
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