92 XJ Limited Edition, will not start. Experienced help needed!!!!

[92XJLimited]

UPDATE: STILL WON'T START!!

So as of today I have replaced the following:

spark plugs
CPS
Engine coolant temp sensor
thermostat

Still no change. Cranks endlessly, but will not start.
After I replaced everything listed above the only fault codes that were displayed were 12 and 55, which as far as I understand should not have any effect on the engine's ability to start. I went through and unplugged and reconnected all the sensor connections. After doing this the fault code 23 started coming up which refers to the MAT sensor. I'm going to get a new one tomorrow, but is the MAT sensor capable of telling the engine not to start? Does it affect the startup A/F mix at all?

 

[bfred]

If your sure you have spark, and its not flooded, try some carb cleaner down throttle body while cranking. it should try to fire. good way to see if its fuel or spark

 

[Blaine B.]

You are right, 12 and 55 mean nothing is wrong......12 = battery disconnected recently and 55 is "end of code list."

I'm not sure what or where the MAT sensor is?

Are you talking about the intake air temp sensor?

 

[Ecomike]

UPDATE: STILL WON'T START!!

So as of today I have replaced the following:

spark plugs
CPS
Engine coolant temp sensor
thermostat

Still no change. Cranks endlessly, but will not start.
After I replaced everything listed above the only fault codes that were displayed were 12 and 55, which as far as I understand should not have any effect on the engine's ability to start. I went through and unplugged and reconnected all the sensor connections. After doing this the fault code 23 started coming up which refers to the MAT sensor. I'm going to get a new one tomorrow, but is the MAT sensor capable of telling the engine not to start? Does it affect the startup A/F mix at all?

MAT = Manifold (intake) Air Temperature sensor
and yes it affects A/F ratio. It gives the computer air temperature data which is combined with MAP data to allow the computer to calcualte actual air density needed to estimate the air quantity (Mass flowrate of air). When it went bad on me I had fits cold starting mine (an 87 Renix). I think mine was stuck telling the computer it was hot all the time cause it always started fine once it was warmed up.

If it has'nt been mentioned to you before, also try holding the gas peddle to the floor (WOT-Wide Open Throttle), that way if it is flooded (which is normal after 30 seconds of cranking and it not starting!) it will tell the computer to stop feeding fuel by closing the fuel injectors, and thus dry out the flooded engine.

Also, if you have been cranking it a lot (sounds like you have) you may have lost compression by washing the pistons with fuel from flooding it. Check the oil and see if it smells like gas, if it does, change the oil and (1). If using WOT and replacing the MAT do not solve the problem check the compression, if it is low (1) add a few drops of oil to the top of each piston (pull the spark plugs for access).

Also, the MAT is a simple variable resistor, it should read (by itself, disconnect it before testing it)
7,500 ohms at 40 F,
3,400 ohms at 70 F
1600 ohms at 100 F
450 ohms at 160 F
185 ohms at 212 F

 

[92XJLimited]

Ecomike,

I've tried everything you mentioned except a compression test. The car is sitting in my driveway so I don't think I have any way of doing a compression test unless there is some home-remedy type of deal to test it. Another question, even if the oil doesn't smell like gas, should I still pull the new plugs and put some oil on the piston tops?

thanks

 

[89xj]

if you have spark and fuel then the timing could be messed up. could be cam sensor(stator), distributor is a few teeth off, plug wires on wrong, timing chain stretched.

 

[92XJLimited]

how do you adjust the timing on XJ's? The plug wire are a possiblity but how do I figure out (in the event they are on wrong) which ones go where?

 

[old_man]

I reread the posts and you mention that the head was not warped. So, you pulled the head? You also mentioned it cranked over rather quickly.

What did the cylinder walls look like? Have you done a compression check? My thoughts are that you overheated and scored the cylinder walls or stuck the rings and now have very low compression. Pull all the plugs and do a compression check.

Replace the plugs with a cheap set of Champions. They may have been wet fouled.

If the compression is fine and you are still getting spark, then spray some starter fluid down the intake while it is cranking. If it sputters, you have a fuel related problem.

 

[ninner]

Get a mechanics thesescope(sp?) and listen to an injector to make sure its opening. A long screwdrive w/ your ear up to the handle will work in a pinch.

 

[Shorty]

it started and ran after overheating-- then changed cap and rotor-- now won't start. I'm guessing either the rotor is not seated correctly (pull the cap and re-install the rotor) or the wires are in wrong locations.

to fix-- pull number one (front) plug and turn engine with breaker bar on the crank pulley. Turn until strong puff of air is felt out of plug hole. Stop turning when air stops comming out and note where rotor on distributor is pointing. This is where the distributor needs the number 1 plug wire attached. Replace the number 1 plug and attach the wire to the terminal where the rotor points. Follow the firing order (clockwise) around the cap (1-5-3-6-2-4) and verify the wires are attached to the correct plugs 1 through 6 (front to back) on the engine.

P.S. check the resistance between terminals B & C on crank position sensor-- should be open circuit ( no continuity between them ) if it's working. You can have someone crank the engine and watch for fluctuations in the resistance if you're using an analog meter, but if you see an open circuit, you can be pretty darn sure the CPS is not the problem.


hope this helps--

 

[skipc]

Since you say it turns easier and takes longer to start the last time you ran it, and now it doesn't, and you have fuel pressure, I dont' remember you saying anything about verifying spark. I doubt any overheating would cause a dead engine - it may run rough or badly, but you'd at least get a kick or two and it sounds like you said it doesn't even do that.

Start with the center wire at the cap. Pull it and check for spark. My guess is that there's none. Run a heavy jumper from a clean bolt head on the block (scrape it around too) to the body and to the coil (scrape there too).

It may be unrelated to the overheating and just be a bad/old ground.

The CPS is the other item that I would focus on. Maybe put a scope on it.

Without spark, the engine will seem to turn easier because the starter can actually turn the engine faster than it usually needs to - it starts before then. If it delayed starting, it would sound like it was going faster. While a bad CPS usually stays bad and keeps it from starting a bad ground can be vibrated into working sometimes before it finally breaks connection.

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