My 1996 XJ6 cranks but won't start.....I have changed the crank sensor....fuel filter & installed new spark plugs.......when the key is turned I can hear the fuel pump turn on.......I am going to change the fuel injectors as well........any other ideas what the problem could be?

 

First and foremost, YOU ARE NEW, so welcome to our side.

Secondly, DONT PANIC, also DONT throw things at it, your wallet will suffer and that is silly.

I am assuming it was running and died for some reason that is not mentioned.

Under the bonnet (hood for some) on the RH side is a fuse container, and in that container is a BLUE relay. That is one of many ignition relays on these, BUT this one supplies the 12v power to the RED wire of the crank angle sensor, SOOOOOOO, make sure you got 12v in that wire. This relay is well documented as causing NON running.

Secondly. You may well be hearing the pump whirring, GOOD. BUT, the hose on top of that pump has a habit of blowing off, so the pump pumps, but the fuel just sprays around inside the tank. An easy check. Crank the engine for a couple of seconds, it dont start, we know that, then CAREFULLY crack the 2 nut hose connection arrangement at the rear of the fuel rail, and observe it you have a "spurt" of fuel, or a "dribble" at best.

SINCE FUEL SPILLAGE WILL OCCUR, PLEASE TAKE THE REQUIRED SAFETY PRECAUTIONS.

If you get a decent "spurt" as you "crack" that fitting, the fuel supply/pressure can be assumed OK for the moment. If you get a dribble/zero, then you have NO fuel pressure/supply, and the tank will need to be removed to address that hose.

There may well be other things wrong, but generally with these engines it is something simple.

Once we know the results of the fuel, and 12v presence in that RED wire, more options will be forthcoming.

 

You should see the rev counter read about 100-200rpm when the engine is cranking strongly. If you see no response from the rev counter, then the Engine ECU is not powered up, or is not getting a signal from your new crank sensor.

If the 1/2 engine speed sensor (also know ans the cam position sensor, thought it is mounted where the distributor used to go on anAJ6 engine) fails then the engine may not start unless you let the engine crank a long time. Without this sensor the engine ECU cannot distinguish TDC firing from TDC non firing for each cyliner. The ECU will "guess". If the engine does not start after many seconds, it will "guess" the other TDC. It has a 50/50 chance of guessing right first time.

There may be some way to check the electrical function of the hall effect sensor used, but I'm not an electrical engineer, so I don't know how this might be done.

 

Thank you guys great info

 

Sorry to bring this back from the dead but I am new to the forum I have watched from afar but have encountered an issue I was hoping you all could help me with.

My car is doing something similar. I have a no start issue, I have fuel to the rail but no spark. My first thought was the crank sensor but it seems to ohm out within range.

I saw you posted about the relay in the engine compartment to the right with the fuses. How do i determine which wire to check for power 12v?

I had an engine speed sensor code but cleared it and it has not come back yet in all the cranking.

I have a 1996 xj6 vanden plas

 

There is a very good chance your OBD code is telling you what is wrong! - the CKPS, at the front of the engine reading the crank pulley.

A good clue is whether the tach reads 200 - 300 rpm as you crank, like XJRengineer said.

 

My 97 xj6 decided to crap out while driving at first it seemed it was the alternator died due to the lights going bright as I attempted to keep it from stalling by giving it glass as I felt the stall coming on. As I pulled in to the parking spot it stalled and since will not start. I have replaced the fuel filter after noticing a lot of sputtering and thought that did the trick apparently not. The transmission limp mode light comes on while its about to stall. And now it will try but no turnover as if its a fuel issue. Any thoughts?

 

Yes, the transmission fault indicator and the stall are both symptoms of the bad CKPS reference in this thread! The tranny fault (if you were to read the codes) is POSSIBLY that the transmission shaft speed detector does not agree with the engine speed as determined from the CKPS.

 

-- this was my problem. thanks!

 

Ok, gentlemen and ladies, I apologize for resurrecting a virtually dead thread but I'm stumped. I picked up a /96 XJ6 (North American model) yesterday from a co-worker. Naturally aspirated 4.0L I-6. Drove it home without a huge issue. It was surging a bit but I think it was because the boot to the throttle body was poorly installed and it was getting more air than the PCM was reading from the mass air flow sensor. I just fixed that this morning.

Anyway, I parked it in my heated pole barn and was going through it. Now it won't start. I've scoured the troubleshooting in these threads and I'm confused. Here's what I know:
It cranks and the battery is at 95% or more. I'm keeping a trickle charger on it for now.
There is fuel at the fuel rail. I cracked open the fitting at the rear of the fuel rail and it was spurting a strong stream.
I don't think I've activated the security system. I locked and unlocked the doors with the key and can hear the security system disarm.
I have spark. I pulled a coil and plug, grounded it and had my boy turn the engine over and can see spark at the gap.
While cranking I can see that the tachometer is showing about 200 RPM. This leads me to believe that the crank position sensor is good....but is it really? Before throwing $100 at a new sensor I want to be sure that it truly is bad. I don't have an oscilloscope so I'm not sure how to test it.

Any thoughts? I *think* I've covered all the easy stuff that has been discussed in other threads.

 

Watch the voltage meter on the instrument cluster for voltage sag during starter rotation

If it drops below 11.4 volts the ECU does not have enough power the run properly

You can read this with a hand held meter on the LH engine fuse box large lead in cable terminal



The first power to the ECU is through fuse X on the RH engine fuse box that needs the king relay in its corner to close properly

You can swap this relay with the one on the left side as in this side it only runs the horn

After the ECU gets its first power it command the large ECU controlled relay to close and bring second power to come into the ECU and certain engine sensors including power to the fuel injectors to open in their timed sequence




You can put your finger on it and feel for it to click

You can swap that one for a same part number relay such as A/C clutch

These relays can be hard to remove a sealed with a O - ring but penatrate spray helps



You can swap the fuel pump relay with the one on the inboard most position as this one is a Acc relay

The way the crankshaft position sensor and fuel pump relay work together is ....



The engine has a Cam position sensor code P0340 that is more refined of the crankshaft position sensor that is only used in the starting sequence

The engine will start with that connector removed but takes more revolutions

You may have put your engine in a bore wash condition where the fuel has washed the oil film off the cylinder walls thereby not enough compression for a sustained light off

By holding the pedal to the floor and cranking the injectors will be cut off by design and oil from the underside of the pistons can re coat the cylinders walls



Editing

 

Thank you, Lady. I'll get on these items tonight and tomorrow. I'm just stumped. It drive relatively well in the way home.

 

It appears that my cranking voltage is low. The gauge is showing about 10 volts (just above the red indicator while cranking). I did swap the #1 and#5 relays on the right hand side as well as the left side and right side king relay (the blue one) in each box. Still doesn't fire.

Lady, in your last picture of the fuse box in the trunk, you show the red lines as an "OR" scenario. Are you saying to remove the cam position relay and use a jumper in order to get to a bore wash condition? I'm a bit fuzzy here so just wanted to check.
Another thing I just noticed is that you put up a schematic for an AJ16 SC. Is that the supercharged engine and even if it is, will it apply to the naturally aspirated engine?

It feels like it cranks just fine. As I stated earlier, it's showing 200 RPM on the tachometer. But the amount of cranking I've done over the past two days, I should smell fuel. I'm not smelling fuel at all. Is the low voltage condition you referenced a situation where the injectors won't fire?

I'm a mechanical guy...these 'trons are really aggravating to me. LOL

 

The 10 volts is key

The easy things to check on this whether the battery can deliver the needed cranking amps as the battery alone , you would need to remove the battery and have it tested at a small shop or some auto parts stores that have the large old school load testers and not the small hand held ones . You need the large one

Battery shims at the auto parts store to place over the positive battery post to make better contact with the stretched out positive battery cable clamp

The fuse link on the side of the positive battery post terminal nuts coming loose

lets skip the other things for now

There was a X300 in the salvage yard that started one day then the same day was at 9 volts with fully charged vattery and no start but cranks

I.m a dude , my car is the lady

 

Those are easy checks. The nuts on the battery fuse link seemed pretty good but I added a little torque anyway. For the record, if the next guy needs to know, those are 13mm and 14mm nuts.

I checked the terminal end on BOTH the left and right. Basically I was right there and may as well get them both. I believe these are what you were referring to...



She still won't fire. I'm beginning to wonder if it isn't the PCM (or computer, or whatever the correct nomenclature is).

 

I think Lady P is right that the 10v is key. Don't worry about relays or ECU at the moment.


Assuming the battery is good, test the voltage between each of the fusebox +ve studs and ground (try ground direct to the battery, then also to the engine), and between starter +ve cable end and ground. Compare to the voltage to that you see at the battery. They should be more or less the same.

There are 3 bulkhead studs where the battery +ve passes from the cabin in to the engine bay. These can be corroded. Follow the cables back from the fuse boxes and starter to the bulkhead and check them.

Also, check the engine earth ground stud. The engine earth goes from near the starter to the lower part of the chassis. Remove the ends of the earth strap, clean and replace.

Then check your voltages again.

 

Thanks...both of you. I'll make those checks tomorrow after work and report back.

I really appreciate all of your feedback and suggestions.

 

The ECU needs 11.4 volts

The BCM is providing the ground to close the starter relay so that is OK

The other end of the large cables attached to the fuse boxes are carry through terminal post on the firewall , remove the cable and shake the post to ensure the last nut next to the firewall is tight . The cabin / other side of the firewall is another cable terminal end you are ensuring is tight . found one loose before

The same large terminal post is on the right lower side on the wheel well , this is the starter cable before the starter solenoid and is the one of interest

 

The large engine ground strap is best got to from under

Ask me how I know

This strap is 15 mm on the starter mounting bolt and 8 or 10 mm on the frame that can be cleaned with a wire brush and some light bulb grease on assembly

 

I checked the voltage of the battery under load from post to post and from positive to the chassis. Both times I read around 11.0 to 11.2 volts. I also checked the heel plate voltage to ground under the back seat. Same story.

I also jacked the old girl up and removed and cleaned the ground to frame from the starter. Visually it wasn't bad. No significant corrosion and it wasn't loose at all.

One thing that hit me last night...I did use my code reader (a Roadii) to clear the fault codes shortly after I got home with the car on Saturday. I had COMPLETELY forgot that I did that. I was mentally going through what I had done and glanced at my workbench and saw my code reader sitting there and it reminded me that I had done that. Is there a chance I engaged a security feature in the PCM? I did remove the positive battery lead for about an hour last night in an attempt to clear any security issues. That didn't help and it still won't fire.