renix issues

[discosteve]

just got an 86 mj, 2.5 5spd. 4x4. been sitting a year and ran when it was parked. so, itll crank and hit but then instantly die. itll only fire for about 1-2 seconds before dying. every once in awhile itll fire and rex to the moon without touching the gas. with starting fluid itll fire up just fine but if you touch the gas it dies. the fuel pump is working, and there is fuel coming out of the injector. ive tried unplugging the tps and cranking unplugging the map sensor. and cranking after plugging the tps back in. nothing seems to change it. i havent got a chance to check fuel pressure as my tester kit is at work. any ideas? i work on brand new gm`s and really old mopars. mid 80s tbi stuff is a little out of my element. thanks

 

[87manche]

rev to the moon says vacuum leak or boned IAC to me.

after it dies do you still have spark? If no spark it is a critical engine sensor killing it.
check the reference voltages. Y

 

[discosteve]

thanks, i will try that. i got it to stay running with starting fluid and i could even rev it a few times. but as it peter`d out it acted as though it wasnt getting fuel. but... prior to using starting fluid it had evidence of gas coming out of the injector. hmmm. i will most definately try what you suggested, but i think ill also check fuel pressure tmrw. ill keep results posted.

 

[cal]

Does the 2.5 have a ballast resistor?

 

[87manche]

Does the 2.5 have a ballast resistor?

I don't believe so, at least not in 86.
that was a TSB addon in 88 with it going into the production line for 89, IIRC.

Have you done a fuel volume test?
it sounds like a fueling issue if it hits on ether after it dies. If you have spark you should have injectors, so I'd assume a fuel regulator/pressure/volume issue.

might want to pop the vacuum line off the regulator, see if there's fuel in that line. if so, diaphragm in the regulator is hosed.

 

[discosteve]

ill try that. havent touched it since my last post. work, moving the gf into her new place. then sitting with her in the ER. (she fine). but ill be back at it maybe sat morning if nobody else needs their crap fixed. its tough being a mechanic all day then working on cars every
night. never get a chance to fix my own crap. ive been thinking it was a fuel issue. i went ahead and ordered a fuel pump but i still want to do more testing

 

[discosteve]

Tested the fuel pump. Wasnt hardly putting anything out. So i replaced the pump, strainer, and filter. Now itll start and run but it will not idle on its own. When it gets down in lower rpms it acts as though it runs out of gas. Sortof like a bad accellerator pump in a carb. Im thinking of checking the fuel pressure regulator. Also ill check the map sensor and tps. Earlier it made no difference when i tried cranking with either one unplugged but now with the new fuel pump and i know itll start im curious to see what difference it makes.

 

[87manche]

I'd pull the IAC and have a look at how nasty it was.

if it sat forever chances are the IAC is stuck in it's bore. You know the game.

 

[old_man]

Tested the fuel pump. Wasnt hardly putting anything out. So i replaced the pump, strainer, and filter. Now itll start and run but it will not idle on its own. When it gets down in lower rpms it acts as though it runs out of gas. Sortof like a bad accellerator pump in a carb. Im thinking of checking the fuel pressure regulator. Also ill check the map sensor and tps. Earlier it made no difference when i tried cranking with either one unplugged but now with the new fuel pump and i know itll start im curious to see what difference it makes.

Drain all the old gas out of the tank. Put 5 gallons back in along with a can of BG44K. It sounds like your injector dried out and clogged up, along with the fuel filter and the fuel pump took a hike due to crud in the gas.

 

[discosteve]

the gas had already been drained out. along with all the other fluids and the battery stolen and the cats cut off. it has 7 gal of fresh gas in it. i was suppose to work on it tonight but other peoples junk cars get in the way.

ive been thinking of checking the egr. of it is stuck open then that could be the cause of it not wanting to idle. idk, ill let you know what i find next time i get to it.

 

[87manche]

you should be able to see the egr valve move if you apply vacuum with a mityvac or similar.

might as wel just unplug it. Parts are unobtanium and it doesn't make much difference to the ecu.

 

[discosteve]

egr valve is stuck. unhooked it and it didnt make a difference. removed the 4-hole vacuum block behind the throttle body and replaced it with 4 seperate vacuum lines. truck will start and run now but still no idle. comepletely removefd idle soleniod so it wouldnt rev to the moon. it wont idle and you can slowly work the throttle to rev it up. \still acts lkike a carb weith a bad accellerator pump. im thinking fuel pressure regulator has a bad diaphram. i ordered a trottle body reseal kit. tried sparying intake and vac lines with starting fluid while my dad kept the truck running and it made zero difference.


im drunk

 

[87manche]

im drunk

lol.

you should be able to grab the valves shaft and yank it back closed.

assuming it's stuck open.
or just make block off plate for the intake and replace the manifold with a non egr one. That's my plan, cause I'm not swapping intake manifolds.

 

[discosteve]

finally tinkered with the mj tonight. had a spare map sensor so i swapped it on. didnt make a difference. so i took the throttle body off and checked the diaphram on the fuel pressure regulator. it looked fine, no splits, no dirt, nothing. im thinking that there is something not reading right. im leaning towards the tps.

ive got it to where it starts everytime and will only stay running if you work the throttle revving it up. but as you start to rev it, it cuts out, its halfway when you let off the gas that it starts to actually try to rev and stay running.

after working on really old cars and really really new cars all my life this mid 80s junk is throwing me for a loop.

"nothing a complete overhaul cant fix"..... lets just hope it doesnt get to that point

 

[discosteve]

ok, i swapped the tps and it made a difference. tore the throttle body apart and added new gaskets, fuel regulator diaphram etc. went ahead and slapped a new map sensor on while i was at it.

now the jeep fires up, still doesnt want to run but will if you work the throttle.

if you happen to get it to stay running while you floor it the engine will bog down, clear itself out, and rev with the throttle like normal for a bout 30 sec. then itll go back to not wanting to rev up or stay running. ive went over the entire vacuum line system mutliple times and cant find anything bad or hooked up wrong.

i have a hunch that it may be the fuel injector itself. but im not sure, ran out of time tonight to mess with it.


new parts include, fuel pump, filter, vacuum lines, tps, map sensor, throttle body gaskets, fuel pressure regulator, replaced corroded wires on tps.

 

[cruiser54]

Got a catalytic converter on it that might be clogged?

You should be able to observe teh injector spraying.

What's the ground cable from the firewall to the back of the head look like?

 

[scottmcneal]

What's the ground cable from the firewall to the back of the head look like?

This is a great place to start. Make sure they are ALL CLEAN and SHINY. I would clean mine once a year, just to make sure it always ran.
Good luck and hope it works out for you.
:cheers:

 

[discosteve]

Ground wire is clean. There is no exhaust, 2ft straight pipe. I'm seriously thinking on trying an injector, it can't really a be anything else.

 

[scottmcneal]

No muffler, just 2' coming off the header?

 

[discosteve]

No, just 2ft under the truck. Probably 3-4 ft total. Looks like somebody crawled under and sawzawd the cat and muffler off.