tempermental starting..

[Ecomike]

^^^^ Hmm... The motor is a open system('94), not a renix... Is that what your talking about?

Sorry, I did not realize they went back to the open cooling systems after Renix. On an open cooling system I would replace the radiator cap first.

Then if no change in the temperature cycling look for tell tale signs of a hidden tiny radiator or coolant hose leak that is opening at 210 under pressure and then resealing at 170 F.

Then if no leak is found, search thermostat threads here and then replace the thermostat. Many have had thermostat brand problems and discussed them in this forum already so read up on their history before selecting a new thermostat.

By the way, did you ever change the sticking open thermostat that was sticking open that you originally mentioned?

 

[mrtosh]

Sorry, I did not realize they went back to the open cooling systems after Renix. On an open cooling system I would replace the radiator cap first.

Then if no change in the temperature cycling look for tell tale signs of a hidden tiny radiator or coolant hose leak that is opening at 210 under pressure and then resealing at 170 F.

Then if no leak is found, search thermostat threads here and then replace the thermostat. Many have had thermostat brand problems and discussed them in this forum already so read up on their history before selecting a new thermostat.

By the way, did you ever change the sticking open thermostat that was sticking open that you originally mentioned?

Yup, changed it when i bought it last weekend. Also checked it yesterday when i did the waterpump and the coolant sensor. Guess I never thought of the radiator cap..... Would that cause the temp to fluctuate like that? Also @what temp does the OEM electric fan kick on? On my '89 XJ it comes on around 215-220..

 

[Ecomike]

Yup, changed it when i bought it last weekend. Also checked it yesterday when i did the waterpump and the coolant sensor. Guess I never thought of the radiator cap..... Would that cause the temp to fluctuate like that? Also @what temp does the OEM electric fan kick on? On my '89 XJ it comes on around 215-220..also, I don't know if this will matter, but after playing w/the jeep some, I noticed that when i first started the jeep and turned it to a/c the elec. fan would kick on, then turn off. Even if i turned it to a/c it wouldn't come on. What do you think?

I have seen small leaks from bad radiator caps, hose connections and tiny radiator leaks all make the temperature cycle like that. The size and duration of the leak affects the temperature range seen on the gauge.

I read recently that the electric fan should come on and run while the A/C compressor is running, and turn off when the A/C compressor is off. Not sure what years that was for, may be all of them, but not sure.

The electric fan cycles on/off with the A/C clutch. It is probably too cold for the A/C to stay ingaged right now. But if the A/C clutch is engaged and the cooling fan is not running, then there may be a wiring problem.

There is also a sperate thermal switch control in the radiator itself that cycles the electric fan on temperature. Most everyone in the forum says theirs cycle on at about 220 F, but the Haynes manual, or something I was re-reading yesteday says it should come on at about 190 to 195 F.

I have raised the question in this forum recently about calibration, error and accuracy in the temperature gauges, but I did not really get an answer. I think the old timers here realise that all the Gauges tend to lie (as they call it) a lot, and at different times and they have probably tired of discussing it and learned to just deal with it.

I bought a $20 infrared hand held sensor at Harbour Tools 2 weeks ago and I have been sampling the temperaure at various spots under the hood (not just the coolant temperatures) ever since to get closer, more precise values. I have confirmed that the temperature is very non-linear on the Jeep gauge, and with only three temperatures listed on the gauge (as I recall) anything in between those is a huge guess! Even the labeled values maybe off a good bit.

At some point it takes a certified ASTM thermometer to check all the gauge readings ( even the infrared ones I am getting) to see how accurate and precise they are. At least with the infrared one I have now I get measurements in 1 degree F increments. What I thought was 130 F on my gauge seems to be closer to 160 F.

 

[mrtosh]

K, I noticed this when i was removing my PS pump while doing the water pump. The two fuel lines that go into the rail that have quick disconnect fittings, the hose that connects to them are pretty loose, like they slip right off... Are they supposed to be like that? Is it supposed to be just hose on the coupler like that? I'm wondering if the jeep is getting too much fuel when it doesn't fire right up, or if it isn't getting enough. when it cranks it acts like it doesn't even wanna start then when you stop cranking it catches and kinda sputters before i give it a rev. Sorry to rant. Just feel like i'm :banghead: . Thanks for all the help.

 

[fspell220]

the temp. fluctuation is because you have pockets of air in the water jackets creating hot spots in you motor. You should remove your temperature sending unit to purge the system.

 

[Ecomike]

I know that burping the system is highly recomended, some would say required, but I replaced my radiator, radiator hoses and overflow bottle, left the bottle cap off for a bit while I topped off the bottle with the engine warming up and I never had a problem. I removed the bottle cap twice and toped off the bottle level to the "fill to here" mark on the bottle after the engine cooled down.

Now mine is a closed, Renix 87, not an open, newer, 91+ model. It was 1991 that they went back to the open system, right?

Is the burping more of a requirement on the open, 91 and newer models?

Did I just get lucky?

 

[mrtosh]

I have an '89 XJ too, it's a lot easier to burp. I ran the '94 w/the cap off for a good 15 mins. and filled it up. New cap, still fluctuates. I'm wondering if the temp gauge sending unit is shot??

 

[Ecomike]

I have an '89 XJ too, it's a lot easier to burp. I ran the '94 w/the cap off for a good 15 mins. and filled it up. New cap, still fluctuates. I'm wondering if the temp gauge sending unit is shot??

That is easy to test!:sunshine:, I think.

Disconnect the temperature gauge's temperature sensor and hook up an ohm meter to it. Then run the engine and see if the sensor is seeing a real temperature variation or not.

It still has its own gauge temperature sensor like the older jeeps on the read of the head, right?

 

[mrtosh]

*Update* As far as the fluctuating gauge goes, I found a small leak at the upper radiator hose, where it connects to the thermostat housing. Tightened it, but it still fluctuating quite a bit. W/the hard starts: I did a total tune-up Friday. Changed plugs, wires, cap, rotor. The plugs all looked good. The cap had quite a bit of grim and carbon in it and the rotor was pretty gummed up. It only took about 20 mins., so it was at the point where it would usually take a while to start. fired right up..... Thought perhaps that was the problem. Nope. Low and behold today, fired up great when cold, fine when let sit for about 10 mins, took forever after sitting about 2 hours. Back to square one. I did notice once on the hard start, that after letting it crank for 7 or 8 seconds, then trying again, it cranked over really slow, like the battery was dying, then fired right up. Any thoughts. Previous owner said he changed the CPS. Don't know what sensor to check if any.... TPS, MAP, CPS, ECU, IAC. Could it be a fuel problem? Thanks for the help guys. This forum has been quite a lifesaver.

 

[Ecomike]

Slow cranking is usually a sign that the battery, starter, or starter solenoid is going out. If you have been using them a lot..................... trying to start the jeep while trouble shooting one or more of them may have overheated and may be getting ready to die.

Have you rechecked the new cap and rotor to see if they are still OK, since that fix worked for a while?

I have heard stories of rotors melting, cause unknown....even new ones. Just a thought.

Just for the hell of it, try starting it with the TPS disconected. If it starts, reconnect it before using the throttle, or it will die. I have started mine without the TPS connected when it gave me idle speed problems.

I am currently experimenting with running mine with the IAC disconnected, after I get it set where I want it (another story for another thread). I briefly reconnect it if the temperature changes a lot and I need it for a few minutes of warm up, or I need to adjust the idle speed due to large air temperature changes.

My old buddy, that occasional, random high idle buddy has recently returned to visit his wrath on me!

Curiously, if I disconnect the IAC, at 700 rpm, the engine and transmission perform flawlessly, better than anytime in the last 2.5 years!!! Figure that one out will ya? Even seems to have about 50% more power at WOT????