Coolant temp. sensor?

I'm trying to find my coolant temp sensor cause I think that may be why my jeep isn't starting. Its a 88 wagoneer limited with the 6 cylinder MPI. I looked on the housing but no dice. I found a sensor on the radiator at the bottome and was wondering if that was the coolant temp sensor I imagine it is. But when I went to the auto parts store they gave me a sensor with threads about 1/2'' and the sensor in the radiator has about 1'' threads.

On my 89 xj the sensor is (while lying on back with feet sticking out from underneith the from of the jeep) up and on your left. It is below the exhaust manifold and above the oil pan. There are two sensors there, one is the knock sensor the other is the coolant temp sensor, I believe the cts is the front one. Hope that helps and hope I am correct. I would suggest you download the FSM, I know it is posted in the faq at jeepforum.com's cherokee section.

katarn

There is 2, one for the gauge and one for the computer.

The one for the gauge is a single wire connection screwed down into the head on the drivers side right near the firewall.

The one for the computer is on the drivers side still but down under the exhaust manifold in the side of the block. It larger but I've never gotten a real good look at it.

As for one in the rad, is that maybe one for the electric fan?

Yeah the one in the radiator is for the electric fan. Also what color are the wires for sensor that ties into the computer? Thanks for the help.

The wires for the coolant temp sensor?

Yes, the one in the radiator is for the fan. On older models with the closed cooling system its that 1"dia thread you described. Newer models are smaller and go into the thermastat housing on the front of the engine. Looks like they gave you one for the newer systems. My 1990 has the 1" in the radiator.

OK, hold up.....who thinks the coolant sensor is going to keep it from starting??????

Describe exactly what it does. Does it crank? Do you have spark? Do you have fuel pressure at the injector rail? Does it ever act like it is going to start?

Yes it is getting spark. We replaced the plug wires, the coil, the distributor button, and checked and made sure it was getting spark by pulling a plug and looking at the spark as well as two of my friends stuck a screwdriver in the end of the plug wire and it shocked the $%@@ out of them. It is getting fuel we tested the pressure and with the key in the start position (not turning it over but just in the start position) it got 39 psi on the MPI. So its getting spark and its getting fuel. It will turn over and everything sounds normal it just won't fire up. It will start with starting fluid blown into the intake. It will idle fine but it will blow white smoke out first then it turns black. I belive the white smoke is just clearing out the starting fluid. When I turn it off and try to start it again it still won't fire it turns over fine but no fire. It only starts with starting fluid and not on its own power. I really appreciate all the help I just got this jeep and its driving me nuts that it won't run.

I don't know much about worn out engines but is the black smoke oil? Massive oil blowby?

Have you done a compression test?

With spark and fuel isn't the only thing left compression?

Or maybe the spark and fuel arn't happening at the right times? Mixed up plug wires?


Just throwing stuff out there.

I don't know much about them either but if that was the case would it even start at all with the ether. And also it runs perfect when its going. And I haevn't noticed and oil leaks anywhere.

Did you screw up your firing order when you changed the cap and wires?

We didn't replace the cap and wires but I'll check that out and make sure. Would it run right if the wires were not on the right plugs cause once we spray it with the ether it runs fine?

You could still get a hit with starting fluid if some or all the wires were hooked up wrong but I would expect it to run.

Sounds like you not getting fuel or your fuel is bad. Someone put diesil in the tank?

You mentioned you had fuel pressure in the fuel rail..... Maybe something electrical with the injectors. Check the harness connectors, engine ground, .....

Good Luck.

list of sensor could-be's: coolant temp, tps, map, shorted injector, cam sensor, bad ground near dipstick,

in the case of sensors... unplug one at a time and try starting it. when it starts and stays running..you have found it. the RENIX system can substitute readings for a missing sensor but it does not have self diagnosis. it will not recognize a faulty reading. only a missing one.

measure each injector with an ohm meter should be around 12 ohms.... more than 20 or less than 10... its bad, as is no reading.

Thanks alot everyone I'll see what I can do tomorrow and let ya know.

The only sensors that can cause a no-start situation are the crank position sensor, cam position sensor, and MAP sensor. Other sensors such as the O2 sensor, coolant temp. sensor, throttle position sensor, and manifold air temp. sensor can cause poor running but will not prevent the engine from starting.

On that note if its not the sensors then what else could be the problem I'm banging my head against a wall here. Thank for the help though everyone. Keep the ideas coming.