This afternoon I was driving my MY94 XJ6 and it suddenly died. A friend help me tow it to my shop. The engine turns over but does not fire.

This evening I went over with a different friend and tried a BUNCH of diagnostic tests to see why the engine turns over but will not start.

I tried spraying starting fluid into the end of mass air meter. No change, will not start on starting fluid.

When the car is turned on, I can hear the fuel pump activating back in the fuel tank.

Pulled the wire going from the coil to the distributor cap and held it at a grounded bolt on the cylinder head. I have a strong REGULAR spark there.

I pulled a plug wire off and checked the spark there. The spark there is less frequent obviously but it does occur. I even pulled a plug and put it in the end of the wire and held the body of the plug against a wire. I got spark there. It’s not as bright as the one on the coil wire but there is spark.

I tried cleaning the contacts inside the distributor cap and the center contact and the end of the rotor.

I had a brand new battery from another car so I tried putting that into the car. Turns over very well but still no start.

Cracked the incoming fuel line coming into the fuel rail and got lots of fuel there when I turned the car onto the run position. Reconnected and tightened the fuel line connection to the fuel rail. Did not actually check the pressure yet. I will do that tomorrow.

Put a noid light into an injector plug and got a regular blink there as the engine was turned over.

Tried cracking the return line off the outlet of the fuel pressure regulator and tried turning the car to the on position so it would cycle the pump. Got a decent amount of fuel out of the pressure regulator.

Pulled one plug and did a compression test with just one plug pulled and got 120PSI on my compression gauge.

Tried disconnecting the wires going to the temp sensor for the EFI but no change when cranking the engine over with that disconnected.

Like I said I will install an actual fuel pressure tester into the system tomorrow to see what the actual fuel pressure is at the inlet of the fuel rail.

 

Do you have any movement on the rev counter when you crank the engine? CPS ok?

Larry
Day 17

 

i second the CPS issue , can happen instantly with no pre-symptoms , try swapping out a known good one from another car , just to prove, just need a 10 mm socket drive , its mounted just above the lower front engine pulley , its best to remove the whole bracket from the block and unplug the loom ( 3 pin ) , as the bracket can break if trying to remove the sensor , mine is a modified bracket for performance and economy , so will look different to yours.

BB


ps CPS= crank position sensor

 

I have a regular strong spark from the coil and the noid light stuck into an injector plug has regular flashes. If the CPS was not functioning, how could I have these things occurring?

 

dunno then , good luck

BB

 

Hi Steve,

Have you checked the Vehicle Condition Monitor for any stored codes? To do so, with the key in position II (ON), without cranking the engine, press and release the VCM button on the trip computer to the right of the steering wheel. Watch for a message in the tachometer/mileage indicator window below the speedometer. Codes appear in the form of Fuel Fault or FF and a two-digit number, such as Fuel Fault 69 or FF24.

I don't think you'd have spark if the CPS failed, but it would still be worth watching the tachometer while cranking just to be sure. Look for about 200 rpm indicated while cranking.

Check the fuses, starting with the ten in the center console fuse box. I seem to recall that one of those 5A or 10A fuses could blow and cause a sudden cranks-but-won't-start condition.

Any chance you got fuel contaminated with water that could have been mixed up with your fuel but settled to the bottom of the tank while you were driving?

The blue Hella relays are all suspects.

Any screeching sounds that might indicate failure of the harmonic balancer?

Check the electrical connection at the MAFS.

Will try to think of other possibilities.

Cheers,

Don

 

I was wondering if it is possible for the toothed part of the crank damper to move and throw the firing signal of the CPS out of time so the spark might not be occurring at the proper point in the engine rotation?

 

I just checked the VCM codes and I have a new code I have never seen before. I have had a "Fuse 1" code for a long time but today when I checked the codes I got the usual Fuse 1 but then after that I got "PAO" which I cannot find in any online XJ40 trouble code reference I have been able to find. Anyone know what a "PAO" code is?

BTW, I had the battery in the car disconnected and on the charger all night. So I don't know if this would have erased any stored coses or not.

 

That is probably the PAD warning, indicating that either the wire embedded in a pad wear sensor has come into contact with a rotor, shorting the circuit to ground, or a wire in a sensor harness is broken or shorted to ground. That shouldn't cause your no-start. But it's possible a blown fuse might.

Yes, leaving the battery disconnected will typically clear all codes.

 

I just finished swapping over to a special fuel rail where I drilled a port to attach a fuel pressure gauge right near the inlet. And when I attached the gauge and cycled the ignition key on and off a few times to get the empty rail filled with fuel, I got around 42 or 43 psi of static pressure. When I cranked the engine over a few times, it settled down to a constant steady 40psi. And it holds that 40psi in the rail afterwards for a very long time.

Unfortunately I also tried placing six cut off soda can bottoms, one under each injector and noted the amount of fuel being deposited in each can after cranking the engine over a few times. I have VERY little fuel gathering in the bottom of each can from each of the injectors.

So then I tried swapping over all of the injectors from a non-running X300 car I also have sitting around to see if those injectors flowed any more fuel when cranking the engine. Same result, very little fuel appears in the bottom of each can under the injectors.
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When the harmonic balancer delaminates, only the grooved belt pulley slips position relative to the crankshaft.

The toothed wheel doesn't move from position as it is bolted to the assembly which is itself locked to the crankshaft with a keyway, so that ain't your issue.

Larry
Day 18

 

So I am guessing that even though the noid light (LED lamp that sticks into the wiring harness in place of an injector) is blinking when I turn the engine over, there is not enough current to actually open the injectors. What would cause that I am not sure.

 

When I worked at the dealer I found a bunch of AJ6 distributor rotors that failed. I always kept a spare in the boot when I owned a 1992 XJ40.

bob

 

Hi Steve,

Your fuel pressure is good.

Just thinking out loud. Sorry in advance if it goes nowhere:

The X300 injectors have a slightly higher fuel flow rate than the '93-'94 ones (220 cc/min vs 210 cc/min) but should otherwise work fine. I ran them in our '93 with no problem. The '93 and later cars use peak/hold injectors that are opened with a large current then pulsed, compared to the earlier "saturated" injectors that were just opened and closed by connecting/disconnecting to ground via the ECM. It's not as easy to test a peak/hold system, but with the ignition on, try measuring for battery voltage on either the Pink/Blue wire or Pink/Black wire at one of the injector connectors. The ECM adjusts for low battery voltage by increasing injector pulse width, but if the voltage at the injectors is too low that could be a problem.

Low battery voltage while cranking is a common cause of cranks-but-won't-start, because the ECM won't trigger the ignition to fire if the voltage falls below around 10.5 volts, but it seems unlikely that low battery voltage would cause your engine to suddenly shut off. What is the static voltage of your battery after trying to crank the car one time? Is it holding well around 12.6 volts?

How did the fuses in your center console look?

I don't think you'd have spark or injector pulse if the ECM wasn't receiving power, but it might be worth swapping the EMS Main relay (light blue, at the far right on the firewall) with the A/C Clutch relay (the light blue relay next to the EMS Main relay). Those blue Hella relays are not sealed against humidity and are known to fail intermittently or suddenly.

Is there no chance of water in the fuel? Is the drain tube in the rubber gaiter around the fuel filler neck clear and unobstructed?

Cheers,

Don

 

A friend and I went to the shop again this evening and I rechecked for spark and I do have a good strong spark at the plugs BUT even when I spray starting fluid into the throttle body with the throttle held open and cranking the engine over. it still DOES NOT FIRE!

Argh!

So I pulled an injector electrical connector off and with the key on but NOT cranking, I have 12V on both of the wires going into the injector plug with the injector electrical plug not connected to the injector.
I.E. I connect a volt meter to each terminal inside the connector individually and then connect the other lead on the volt meter to ground on the cylinder head.
If I crank it over I see this voltage between each wire and ground on the cylinder head drop to 8 or 9 volts but reading voltage across the two electrical terminals in the connector while cranking is very low, like 0.1 volts
Is this normal?

 

A friend and I went to the shop again this evening and I rechecked for spark and I do have a good strong spark at the plugs BUT even when I spray starting fluid into the throttle body with the throttle held open and cranking the engine over. it still DOES NOT FIRE!

Argh!

I am using a nearly new high cranking amps battery from another car to do all of this testing with so I am very certain I do not have a low battery voltage issue.
Now the battery that was in the car when it actually died was not real great but as I said I am doing all of this testing since it reached my shop with this other nearly new larger battery
.
So I pulled an injector electrical connector off and with the key on but NOT cranking, I have 12V on both of the wires going into the injector plug with the injector electrical plug not connected to the injector.
I.E. I connect a volt meter to each terminal inside the connector individually and then connect the other lead on the volt meter to ground on the cylinder head.
If I crank it over I see this voltage between each wire and ground on the cylinder head drop to 8 or 9 volts but reading voltage across the two electrical terminals in the connector while cranking is very low, like 0.1 volts
Is this normal?

BTW, ever since I had the dash and gauge cluster out of the car while I was working on the heating system issues, the speedo has stopped working. However it has been this way for weeks so I doubt this has anything to do with my no start issue.

 

I will try swapping the relays tomorrow. Thanks for the suggestions Don.

 

Did you try another rotor like Bob suggested? Pretty common fail point.

Larry
Day 18

 

But if the rotor was bad wouldn't it be impossible for me to have a good strong spark when I pulled a plug this evening and held it against a bolt on the cylinder head?
But tomorrow I will see if I have another rotor and give it a try.

 

I doubt the speedo issue is related to your no-start. It could be one of the connectors on the back of the cluster. It could also be a wheel speed sensor. The vehicle speed signal comes from one of the wheel sensors (I think it's the right rear wheel but may be wrong), by way of the ABS module, which is mounted on the left rear wheel arch inside the trunk, near the fuel filler neck. Have you had any ABS or BRAKE warning lamps illuminated?

One thought while you're checking the rotor - check the distributor to be sure it is tightened down and can't spin, which could throw off the timing.

Cheers,

Don