Well guys, after all the years of building POS toyotas, i have finally come to the jeep side. Last week i picked up a cherry 1990 Jeep cherokee for 1200 bucks. Old man owned, 209k miles, 4x4, 5 speed, 4.0l i6. I completely love the thing especially during this crazy snow storm we are havin up here in the north west

Anyways, for 1200 bucks of course it needs a little attention. First i am not getting any hot air. I have replaced the thermostat, flushed the coolant, burped the system as well as i can, and still nothing. I know it is clogged because the in-line to the heater core is hot, and the out line is cold. Is there any special way to blow the core out? I would rather not replace the core if i dont have too. from what i understand its a pain just like any heater core

Next, im having some fueling problems im guessing. It starts up and runs rough. Puffs black smoke and sputters. Idle bounces around a lot. while driving it seems okay, but once i gear down and come to a stop sometimes it wont idle and just dies. But then starts right back up when i turn the key? I replaced the fuel filter, put fresh 92o gas in it, and have run sea foam through it. After running it, i pull the cap off the test port on the fuel rail and it doesnt hardly squirt out. i would expect a stream to come shooting out but it just kinda bubbles out. Could my fuel pump be failing? could the computer be sensing the low ammounts of fuel and countering for that? It seems like that would explain the rough idle and huffing black smoke? Let me know your thoughts any help will be appretiated! Ill post a few pictures soon!

Thanks

MikeP

 

Well first off welcome to CF!!!!!! As far as your heater core try taking the hoses off and putting your garden hose in one end and blowing it out. Hopefully someone with a renix system can help out with your fuel.

 

Welcome to the dark side from another former Yota wheeler. Kinda sounds like a fuel pump issue to me but I don't know Renix stuff all that well.

 

black smoke is a sign of too much fuel running rich

 

as for the heat see if this valve moves when heat is selected and check for vacuum to the small line

 

Actually I already replaced that small valve. I tested the old one too and it is still functioning correctly. As far as running rich this just started happening yesterday. Since I've gotten it, it hasn't done this till yesterday, my rail pressure is really low so I'm thinking it has to be my fuel pump. When I'm driving you can tell its not getting fuel cuz it surges, and when u come to a stop or put it into neutral it either falls on its face or it just flat out dies. Anymore ideas?

 

did you check it for vacuum at the little line when you have heat selected and is air blowing strong out the vent

 

A fuel preesure gauge will tell a lot.....should be able to pick one up for 20.00



http://www.harborfreight.com/fuel-in...ter-92699.html

 

Wewlcome to the Cherokee Forum!

The lack of fuel pressure is from a leaky/worn check valve in the fuel pump. As far as I know, it will only affect startup. When I start mine, I turn the key on and wait for the pump to stop turning and the system to pressurize. A lot of guys install a check valve in the fuel line to fix this, but its not critical. I would also suspect either a vacuum leak to you fuel regulator, or the regulator its self. Make sure you replace the o-rings with new ones and a little motor oil helps them go in. Leaky fuel rails make for hot engine fires.

Could be your TPS too, 89 and 90 XJ TPS's go bad if you look at them funny or it could just be out of adjustment. Adjusting a TPS takes about 1-2mins. Take your incoming power(about 5V, mines at 4.79) and multipy it by .83. write that number down and turn the sensor till the signal voltage matches that at idle, when warm. Theres a bunch of writeups on how to do it and they say to divide the incoming volts by signal and the result should be between .835 and .825, but if you just multiply .830 and your incoming 5V, it does the same thing, just easier, because you have a target to aim for. Leave it plugged in while doing this and insert your probe wire into the harness along the wires on the sensor side, not the harness side(that way if you FUBAR the harness, you can just get a new one witha new sensor). You want the harness with 4 wires in it even though one is blanked out.

X2 on the fuel gauge, if you follow the test procedure correctly, you can diagnose most fuel problems

Other than a last ditch effort with a hose, if the heater core is blocked, you gotta yank the heater core. It just a tedious process pulling the dash, a lot of unhooking little harnesses, but not a nightmare. Good luck!

Keep us updated, we'll get you going right

Hi from across the river btw!

 

i have a 90 and mine idled and ran the same found it was the o-ring on the fpr i replaced it and it solved the issue's good luck and welcome to the renix family

 

Where is the fpr located? And by fpr I'm assuming you mean fuel pressure regulator? And as far as the tps sensor goes I'm gonna replace the sensor reguardless if its out of adjustment or not seeing as how you look at it wrong and it fails. Back to the o-ring on the fpr though, that wouldn't affect my fuel pressure would it?

 

Im having the same heater core problems as you mike. Im going to try to put the new heater core in today, so ill let you all know how it goes. I got my Haynes Manual so wish me luck.

 

how long was the jeep sitting? check the plug wires for any cracks and if the spark plugs are fouled, and see how the dist. looks inside too. when you flush the heater core do it forwards and backwards until clear,then either use rad flush or clr and pour in and crimp the hoses and let soak for about half hour or so,then flush it out both ways again until clear. and what the other guys said too. if your not sure how good the part is,probably the best thing to do is change it,chances are its the oe from the factory in 90.

 

You could have an injector that is sticking open. That would explain it not holding fuel pressure and also over fueling.

 

Had the same problem with heat in my Jeep- inline hot, out cold, and getting no heat.

pulled both hoses and flushed, reverse flushed, and flushed again til it was clean. Got a lot of black deposits and rusted orange coolant that I had throughout my whole cooling system out. Used a compressor and shot some air through the hoses too. I dont advise this though...you might end up with a soaked passanger floor the next morning if youre not careful. Some people use chemical flushes too. I didnt, but if you do just read the instructions carefully.

I cranked mine up after flushing it with water and air and she was pushing hot hot heat, with both in and out heater hoses hot to touch.

Good luck.