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1987 4 cyl MJ Rough running condition


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  • 2 weeks later...

Hey guys.  I decided to take a step back with doing the fuel pressure regulator rebuild, mainly because I need to at least do some of the Cruiser Tips first.  I did buy a rebuild kit but haven't broken the seal on the package yet in case I want to return it.  Yeah, I'm cheap, but I'm also retired and funds are low.  The other reason is, I couldn't detect any fuel squirting from the hole in the TB.  So now I am just doing a few things that need to be done as a matter of course.  Like the other day I replaced the fuel filter and now I'm contemplating dropping the fuel tank to dump out the old gas and install the new fuel pump and associated parts that I already purchased. Question:  should I start a new thread since my troubles are not fuel pump related anymore?  Also, Is dropping the tank that difficult for an old timer?  Thank you for all your comments.

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Nah, you can keep adding to this thread because it’s still a fuel problem so you can change your title to reflect the issue as a whole. As for the tank, put a jack under it, loosen the nuts on the J bolts to the frame and have at. It’s pretty easy to do. Some will say to remove the driveshaft, I have never hard to when lowing the tank but some guys like it removed for the complete and total room there is to work. 

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So now I'm back to dealing with the fuel tank.  I removed the tank albeit a real pain in the you know what, since it was half full.  Got it all cleaned up and ready for the new pump and sending unit that I got a while ago.  As it turns out you are right eaglescout526, there is no top bracket on the sending unit apparatus to hold the pump secure.  Talked to the guy at MTS and he said folks just use zip ties.  I'm not too fond of that idea since it could come loose and fail.  I want this to be the last time in my life to have to deal with it.  I was thinking of tack welding a tab to the fuel pipe to catch the top bracket and secure it with a screw and nut like original.  Does anyone have any other solutions before I bugger the whole thing up?  

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  • jeepogeek changed the title to 1987 4 cyl MJ Rough running condition
  • 2 weeks later...

I finished with the fuel tank items that were previously mentioned.  The truck still runs like crap.  I ordered an REM from nickintime, but I didn't hear back from the guy.  So I really can't do anything till I get the REM.  today I was poking around under the hood and found a green wire near the ICM hanging loose.  While performing the ICM contact cleaning procedure I noticed a spade terminal that didn't have anything attached to it.  So I plugged the loose wire into it.  When I went to start the truck with the key, the truck started in the power on position instead of the start position.  The wiring diagram shows the green/white wire going to the coil/icm.  Does anyone have any ideas about this condition?

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As it turns out, the green wire went to the starter relay not the icm.  Truck starts as usual now.

 

There has to be something simple about this rough running condition.  The former owner's wife told me today that before it died due to the fuel pump quitting that the truck ran smooth.  It sat for months so ethanol may have gummed up the injector or something else in the TB.  Oh well, the REM is supposed to be arriving tomorrow.  Maybe it will tell me something otherwise I will continue pulling apart the TBI and do a rebuild.  If any of you read this and have any suggestions please chime in.

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  • 3 weeks later...

An update on what I've done so far and the truck still runs like me when I get up in the morning...running rich, missing and stumbling.  I have pulled the fuel tank and cleaned it out, replacing all the parts inside and the hoses.  I've also done the ground refreshing and completely rebuilt the TBI including replacing the injector.  I purchased the REM but this old guy (me) can't figure out how to use it aside from pushing the buttons.  I guess I start replacing the sensors starting with the O2, MAP and CP.  Anyone else have any ideas?

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Thanks for the suggestions guys!  I'll look into them.  BTW, everything in the fuel tank is new so there shouldn't be any issues there plus I replaced all the external hoses and the in line fuel filter.  

Shouldn't the REM point me in the direction of the rich running part of all this?  Does anyone know how to use the REM?  I'm having trouble With it.  I'm a 74 year old!  I can get it to work but have trouble toggling here and there.  Then I just get frustrated and quit messing with it.  Remember,  the truck starts right up.  The spark plugs all have he same dry carbon and the exhaust smells really bad.

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9 minutes ago, jeepogeek said:

Thanks for the suggestions guys!  I'll look into them.  BTW, everything in the fuel tank is new so there shouldn't be any issues there plus I replaced all the external hoses and the in line fuel filter.  

Shouldn't the REM point me in the direction of the rich running part of all this?  Does anyone know how to use the REM?  I'm having trouble With it.  I'm a 74 year old!  I can get it to work but have trouble toggling here and there.  Then I just get frustrated and quit messing with it.  Remember,  the truck starts right up.  The spark plugs all have he same dry carbon and the exhaust smells really bad.

Just spitballing here, could your timing be off? 

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41 minutes ago, jeepogeek said:

Does anyone know how to use the REM?  I'm having trouble With it.  I'm a 74 year old!  I can get it to work but have trouble toggling here and there.  Then I just get frustrated and quit messing with it.

Each button toggles through each of the functions for its associated display so you can see four parameters at a time. There is a menu (maybe settings, sorry I don't have mine with me) that you set your truck's info (engine, trans?, don't remember). Your O2 sensor readings should switch back and forth from a low value (0.2) to a high value (4.5), ther is a lso a parameter tha shouls alternate between lean and rich if the O2 sensor is working correctly. This video walks you through its functions 

 

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2 minutes ago, fiatslug87 said:

Each button toggles through each of the functions for its associated display so you can see four parameters at a time. There is a menu (maybe settings, sorry I don't have mine with me) that you set your truck's info (engine, trans?, don't remember). Your O2 sensor readings should switch back and forth from a low value (0.2) to a high value (4.5), ther is a lso a parameter tha shouls alternate between lean and rich if the O2 sensor is working correctly. This video walks you through its functions 

 

That will be helpful when I get mine (an REM is my Christmas present from my grandma. My other grandma is getting me one of Minuit's radios)

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Couple things regarding that.  The wife of the guy I bought the truck from (he is deployed to middle east) told me the truck ran smooth prior to the fuel pump failing.  Then it sat for a few months.  Seems to me if the timing was bad the truck would have run badly then.  The other thing is it starts right up.  However, if the crank sensor is bad the timing would be effected I guess.  That's why I'm thinking of replacing it.  I do not think any of the sensors on the motor have ever been replaced.

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1 minute ago, jeepogeek said:

Couple things regarding that.  The wife of the guy I bought the truck from (he is deployed to middle east) told me the truck ran smooth prior to the fuel pump failing.  Then it sat for a few months.  Seems to me if the timing was bad the truck would have run badly then.  The other thing is it starts right up.  However, if the crank sensor is bad the timing would be effected I guess.  That's why I'm thinking of replacing it.  I do not think any of the sensors on the motor have ever been replaced.

Does it seem to run better at higher RPMs or smoke at all? How long did it sit before you bought it?

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3 hours ago, 89 MJ said:

Does it seem to run better at higher RPMs or smoke at all? How long did it sit before you bought it?

 

 

Yeah, walk me through the upload because I tried to do it with my Iphone and it said the file was too big.

 

 

If you read this whole topic you can find what I've done thus far.  However to answer, the plugs are RC12LYC Champion.  And I've replaced the cables, cap, plugs, all the fuel pump components, and rebuilt the entire TBI.

 

It doesn't really smoke much just rich carbon smokey stink. It stumbles at all speeds. It sat for at least a few months.  

 

I've seen the REM video but it confuses me.

 

 

iphone

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32 minutes ago, jeepogeek said:

Thanks for the ideas and commentary everyone.  Eaglescout526 what do you mean steam clean method?


It’s a crude method utilizing water as a means to blast carbon deposits off the piston heads. It only works on a engine at operating temp. Thinking about it, doing sea foam would be the better choice or even some high octane fuel. 

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