still having trouble with my 88 xj

as some of you know from other posts i had some trouble from time to time with long starts....hot or cold. Awhile ago it started jerking a few times and died in an intersection. it jerked as if there wasn't any gas real quick and died. no mater what it would not start.
Here are both my old posts.
http://www.naxja.org/forum/showthread.php?t=944427
http://www.naxja.org/forum/showthread.php?t=947592

so far this is what i have done and still won't start.

I checked the presure release valve at the front of the fuel rail and gas does spray out.
Air filter is good
New plugs
New wires
New Cap and Rotor
Replaced the coil with one i know forsure is good.
New Crank sensor. pretty sure i can't screw that but if there is any other tricks for re-intallation please let me know. Is there anyway to screw it up...lol ?
Good compresion.
Motor turns over.

Things that i know still need to be fixed but i don't think can cause it to not start are:

Neg ground wire from bat need to be replaced. i hooked up a temp ground by using jumper cables and conecting them to the motor. still didn't start.

Only thing i can think of is that i found a broken part on the drivers side of the motor just above where the oil pan starts to slope down. I thought this might be the oil pump but I am not sure as I can not find my manual at the moment.

Any Ideas ? The motor does crank over just won't start and I have had this thing sitting in my driveway for a few months now and i am starting to get verry fustrated with it.

Thanks

:skull1:

jolly_rogger said:

Only thing i can think of is that i found a broken part on the drivers side of the motor just above where the oil pan starts to slope down. I thought this might be the oil pump but I am not sure as I can not find my manual at the moment.

Click to expand...

That is the Knock sensor or the CTS(coolant tempurature sensor) The Knock sensor is lower on the block near the motor mount, the CTS is towards the front of the engine about midway up the block.

You do not have to have the knock sensor, if it is the CTS you need to fix it or it will never go into closed loop(when you do get it started).

I'm thinking your problem is the Synch sensor in the distributer. I replaced my dist. with a reman unit for around $50.

You really do not have too many more things to replace, MAP, O2, CTS, MAT.

Have you checked the connection to the ECU to make sure it is tight and clean. It is located below and behind the cigaret lighter area, pull the lower dash out to get to it. You will see the ECU.

how do you take out the Synch Sensor ? Or do i have to replace the whole distributer ? what years are interchangable with a 88 4.0 ? how ofter does the ECU go in an xj ? Will the CTS stop it from starting ? Where and what is the MAP and MAT ? will they stop it from starting aswell ? i know i need a new O2 sensor but as far as i know it will not stop it from starting and running. thanks again

what exactly does the knock sensor do for the engine ?

Are the spark plugs firing?

haven't tested them but i just replaced them and just about everything else like i stated above and there is fuel to the fuel rail so i would assume they are not., otherwise it would start right ?

The knock sensor retards the ignition timing when a knock or ping is detected.

i was having trouble with my 88' xj too...... until this morning when i sold it and bought a 91 xj. renix- goes forever but you never latch the hood because there is always something to fiddle with!!!

Try seeing what exactly isn't there. Spark or fuel.

You said you have fuel coming out of the fuel rail, but have you actually tested it's pressure? Should be around 30 PSI.

Also, for spark, take a spark plug, and insert one of the connected wires to it and ground the spark plug against the block. While it cranks, have someone watch the plug and if it makes a blue spark, you obiously have spark.

Once you narrow it down to either fuel or spark, you are on a much better track to getting it going again. Apologies if you've already done this.

By the way, you can also take the air filter tube off of the throttle body and drop a few splashes of gas into it, then try cranking it over. If it starts up - you have a fuel problem. Did this with a 94 dakota. It can backfire though haha.

jolly_rogger said:

how do you take out the Synch Sensor ? Or do i have to replace the whole distributer ? what years are interchangable with a 88 4.0 ? how ofter does the ECU go in an xj ? Will the CTS stop it from starting ? Where and what is the MAP and MAT ? will they stop it from starting aswell ? i know i need a new O2 sensor but as far as i know it will not stop it from starting and running. thanks again

Click to expand...

Yes you can replace the synch sensor, but while you are at it you should rebuild the distributer with new seals, gear, shaft etc., thats why I say just put a reman in it unless you just like to tinker. I think 87-90 use the same distributer if you want to find a used one. Pull off the distributer cap and see if there is any oil in the bottom of the distributer housing, if so replace the distributer. If you decide to replace the dist. I can give you some tips to keep you from having any issues when you are ready to start it up after the replacement.

The ECU is not a common issue, I would look at all of the connections before I would worry about the ECU.

The CTS will not keep it from starting, it will only keep it from going into closed loop after warm up. It is located on the drivers side of the engine, to the front of the motor mount and about mid-way up the block.

MAP sensor(manifold absolute pressure) is located on the firewall just above the valve cover. It will cause driveability issues.

MAT sensor(manifold air tempurature) or(air charge tempurature) is just like the CTS, only affects closed loop. located on the top of the intake near the master cylinder.

TPS(throttle position sensor) located on the throttle body can cause shifting issues, poor driveability, etc.

IAC, (Idle air control) located on the throttle body(looks like a round can), an output device that controls the amount of air allowed in the the TB for cold and hot idle. If it is stuck all the way closed it may cause some starting issues.

O2 will not keep it from running but can cause many driveability issues and poor mileage.

Knock sensor, located on the drivers side of the engine near the motor mount, only senses valve ping/detonation and when it does it retards timming. it is not needed if everything is running good and you use good gas. Later models do nat have a knock sensor.


Do you have the RENIX FI manual? It goes into full detailed description of each of these sensors/outputs and is a great diagnostic tool.

The sync sensor wouldn't cause a no-start though. It would cause it to start a little bit late, but if the ECU doesn't see a signal, it will wait for a few seconds, then randomly select a cylinder sequence.

That's out of the renix fuel injection manual, not an opinion.

I've had trouble with very very difficult cold starts when my MAT was disconnected. Wouldn't hurt to disconnect it and see what it does.. Sorry if you mentioned it already, but does the engine have spark when cranking?

i haven't tested the fuel pressure as i do not have a fuel pressure gauge (it's on my to buy list). A reman dist is another $150 locally where i live (kelowna, BC Canada) so i am going to have to wait or go buy one from a wrecker.

Try this. Unhook fuel filter, shake all gas out, and reinstall. Try cranking it over, then check pressure at rail to see if any squirts out. It would cost less than a pressure gauge. I bet the pump is shot. Having changed 4 out in 6 months on an 87 and the way discribe the jerking. Easy fix. Get rid of it and get a HO (just my opinion). I have had way less problems since i got rid of it.

Try this. Unhook fuel filter, shake all gas out, and reinstall. Try cranking it over, then check pressure at rail to see if any squirts out. It would cost less than a pressure gauge. I bet the pump is shot. Having changed 4 out in 6 months on an 87 and the way discribe the jerking. Easy fix. Get rid of it and get a HO (just my opinion). I have had way less problems since i got rid of it.

Click to expand...

4 in 6 months?! What brand of pump are you buying, and from where? Did you replace the filter sock when you did it?

k i spent several hours today on the F'n thing and it is still not starting. i went to a wrecker and got a Distrib and installed it. Now this is my first time installing a distrib but i am pretty damn sure it's right. checked the spark by pulling a plug and hooking it back up to a wire and putting the end up to bare metal and to the engine block and i saw no blue spark infact i saw nothing, Maybe i did the test wrong. so where do i go from here ? i also replaced my negative bat cable and all batery leads. if this damn thing doesn't start soon i'm gonna get it towed to the middle of nowhere and and have a big bbq. please help !!!! if there is anyone in My Area that can help me please come by this weekend and i'll provide the beer. Kelowna, BC Canada. thanks again everyone and please keep the ideas coming.

i replaced my fuel fillter just before it died for good and it did start a few days after my initail tow home but not since then.

just checked to see where i have voltage too and so far i got volts up through the wire between the coil and distrib but i couldn't do any more checks due to it getting to dark outside. so there is power through the coil and up to the distrib.

Pull the coil wire at the distributor, and install a spark plug. Ground the spark plug to the block, head, whatever and crank the engine over. If you have spark, look at the cap, rotor, wires.

all of those where installed yesterday with brand new parts all wires the cap and rotor aswell as new plugs. If i messed up the install of the distrib could the timing me so far out that it would stop the plugs from sparking ?