Hi,
I'm hoping to get some advice from the experts here. Thanks!
1995 XJ6

Over the last 2 years I've had a crank-no-start condition about every 3 months. I've replaced battery, spark plugs, coils, cleaned throttle, camshaft sensor (that really needed replacing), crankshaft sensor, O2 sensors, ECU, cleaned ECU harness pins, fuel pump (tube had come out), fuel filter, fuel pump relay.

Estimated Stats for starting the Jag:
60% of time starts up great, immediately and runs perfectly
20% of time starts up, RPM goes way down to 500, then returns to 900 after almost stalling
18% of time starts up, almost stalls but I give it a little gas and runs great
1% of time cranks, won't start at all (no gas smell) even after trying multiple times.
1% of time cranks, stalls, then won't start...possible flooding condition (smell gas)...or possible bore wash
---at least 10 times I've had to keep cranking over a 30 minute period to get it to "catch" by pressing the gas pedal... then car is OK
---sometimes it sputters as it tries to catch, then vibrates... but eventually it runs great.

This has happened in all weather and warm/cold engine conditions. One time I took it to the shop they found the fuel pump tube out and replaced the fuel pump while at it. Then it happened again and they put it another fuel pump (for free)
But new fuel pumps hasn't solved the problem...and the shop is out of solutions (don't know of any specialists).

Other thing I've noticed: high Short-Term Trim Values
"A positive fuel trim indicates that you're running too lean (too much air)" so the ECU adds more fuel to correct. My gas mileage is only 20 miles per gallon on highway.

Here are the OTC codes (depending on ECU used) . Yes, I probably need a new catalytic converter.

P0158 HO2S sense circuit high voltage... cyl 4, 5, 6 (B bank), downstream (2)

P0420-catalyst effeciency below threshold bank 1
P0430-catalyst effeciency below threshold bank 2

P0123 Throttle Position circuit output voltage went above the sensor's expected voltage specification range (on one ECU without TPS adaptation)

Possible things to test:
--other important relays maybe failing occasionally? should I replace all of these 22-year old high-power relays?
--fuel pressure regulator - may be ruptured ( cold related ) and bypassing all that fuel back to the pump leaving little for the fuel injectors . Check for the vacuum line on the regulator ?
--fuel pump electrical connector sockets, fuel pump ground
---fuel pump relay connecor
--Papa Indy 1 connector dirty or wet Connector pin 4 with the White / Pink wire as this is the power source for all spark plugs . For spark plugs power ( not control ) fuse # 12 / 10 amp Right Engine Fuse Box . For injector power it comes out of the ECM Controlled relay # 5 located behind the right headlight fuses # 5 / 5 amp and # 11 / 20 amp Right Engine Fuse box .
--ECU harness / ground poor . Clean the grounds along the upper firewall in the engine compartment
--idle control unit sticking
--erratic intertia switch
--lazy fuel pump
--leaky fuel injector
--EGR valve
--Vacuum leak(i've sprayed WD-40 around but haven't found any leaks)
--Exhaust clog
--Water getting into fuel

What is the most likely culprit? This car is used alot, often for short drives, and has weathered some very cold winters.
It is "almost" dependable... but I've been stuck a few times crossing my fingers until I get it going. And I've had a few tows.
Thanks for any more suggestions.

 

First thing I'm going to do is replace all injectors and the fuel pressure regulator, as I found very inexpensive replacements and the originals are 23 years old. I don't have my hopes up it but can only help... I hope somebody could prioritize the tests for me

 

Someone once told to me to quit troubleshooting it and just fix it . I'm not saying that to be a smart ellic , I prefer information for troubleshooting . .

There is some merit to the statement in that just try something with the information you have .

There is also some merit in the other items you mentioned .

A target to shoot at would be the fuel check valve for the starting sequence observations . Did you notice the time between engine shutdown and the failure to start next time .

Injector cleaning with a low effort tank additive .

Instead of getting fuel pressure readings and the effort to do that might just spend the time and money to install a external to the tank a 2nd fuel line check valve that Al Roethlisberger thought about a couple of weeks ago

 

Your list are all good things to check. I'd start with the easiest and most common issues which are often coil or crankshaft position sensor if they are original. Their age doesn't mean they've gone bad, and it would be ideal if you can test before just throwing parts at the problem, but these are common problem areas.

That being said, I've replaced my injectors, coils, and much of what you've done and still can't solve the a similar problem. Although it is possible our symptoms are similar, the cause certainly could be different. It sounds like my scenario is much more pronounced than yours, and has had it laid up for about 6 months. To be honest, my patience is running out.

https://www.jaguarforums.com/forum/x...-p13b0-192634/

I've been noting a lot of these "crank no start" and "dies at idle" issues popping up over the last couple years, most with no clear resolution and many with the original poster just disappearing.

So I'm wondering if there is one, or few, common causes associated with age/use that we'll eventually determine once enough owners troubleshoot this to conclusion.

The following was supposed to be the "mother of all no crank" threads:

https://www.jaguarforums.com/forum/x...ngines-120221/


Good luck and let us know what you find as you walk through troubleshooting.

In my case, I thought it was almost definitely heat soak related. But what is getting soaked and failing? ...that I haven't found yet. But then again, it tried to die and stalled several times this evening after being started for the first time in 24 hours so heat wasn't an issue tonight. *sigh*

.

 

Hi madijag,

There are lots of possible suspects, and sometimes issues like this can be caused by multiple systems having fallen out of spec. Probably the single most common cause of cranks-but-won't-start is low battery voltage while cranking. If the battery voltage seen by the ECM falls much below 11 volts while cranking, the ECM will not trigger the ignition to fire. You mention that the car is "used a lot, often for short drives." That's a classic scenario for a battery to not receive sufficient recharge to make up for cranking depletion.

Many auto parts stores will test your charging system for free. See if one in your area has a Midtronics charging system tester that can test voltage while cranking and can check the alternator output and diode health. It doesn't matter how new your battery is if it is not being properly charged or is an incorrect type or capacity.

Related to low voltage while cranking is corrosion or looseness at battery power connections and ground points. Locating and cleaning all these connections is time consuming, so I would personally begin with the ones associated with the starting and engine management circuits. You can find their locations in the manual at the link below:

Jaguar X300 Electrical Guide 1995

The ignition switch has a separate contact for the Body Processor Module/starter, so it is possible for the starter to crank but other key circuits to not receive power. One clue would be if the instrument cluster lights do not illuminate when you're suffering the problem.

Another thing to watch for when the problem occurs is whether the tachometer reads about 200 rpm while cranking. If not, suspect the crankshaft position sensor (CKPS) (or its wiring, since your sensor is new).

The Ignition Positive Relay in the right-hand heelboard fuse box provides ignition-switched power to the fuel pump relay.

A failing fuel pressure regulator (FPR) and check valve are common causes of extended cranking, but typically, if the fuel pump is healthy, they won't prevent the engine from starting. However, at this age, it would be advisable to replace the FPR as a matter of course. The check valve is in the fuel tank plumbing, but you can add a new one in a flexible section of the fuel feed hose somewhere between the fuel pump and fuel rail.

Your lean running without codes could indicate a problem with the Idle Air Control Valve (IACV) such as carbon build-up preventing the valve from closing. Another suspect is the EGR valve, which if stuck open behaves like an intake air leak. Cracked exhaust manifolds can inhale unmetered air that misleads the O2S. A smoke test might help you find any leaks but it won't necessarily tell you if the IACV or EGR is stuck.

You can do a rudimentary check of your cats with an inexpensive infrared thermometer. With the engine running and at operating temperature, check the temperature at the inlet end of each cat, then at the outlet end, taking care to read sections that are not covered by heat shield. The temperature should be significantly higher at the output (100 degrees F give or take). If the outlet temp is the same as or lower than the inlet temp, the cat is not functioning properly. Downstream O2S readings can help confirm the diagnosis.

Is the drain tube in the fuel filler gaiter clear? If water pools in the gaiter in heavy rain or in a car wash, it can make its way past the fuel cap seal.

Cheers,

Don

 

Thanks. One possible scenario is that injectors are leaking into cylinders (that is why I'm just replacing them). That would lead to sometimes flooding and/or bore wash. And pressing the gas pedal during startup makes it clear out (or worse when it doesn't work). If I didn't ever had to press the gas after startup then maybe I wouldn't get into a flooded or bore-washed situation.

I'll replace the Ignition Positive Relay also just because its less than $10... any others to replace for the 23-year preventive maintenance schedule?

The alternator cranks out a high 14 volts, but the volt needle does go below 11 V sometimes on startup. I've had the no-start problem happen after a very long drive (when the battery was probably totally charged) but that might have been when the fuel pump hose was falling off.

 

will see about adding check valve near the fuel rail. any idea what size hose that is?

 

Al may have that information as he looked into it before and my suggestion would be at the tank so the line from from the engine to the tank won't empty requiring a longer period of time to charge up to the correct pressure . This would depend on whether the fuel drains out through the back replaced with air ( or not ) .

 

On the XJ40/4.0L AJ6, the fuel supply hose is 8mm I.D., so 5/16 inch hose barbs fit. I assume the hose on the X300 is the same but haven't measured. Locating the check valve near the tank is better, but I've done it both at the tank and rail on the same car and couldn't tell any difference in actual performance.

I've used inexpensive check valves from McMaster-Carr (mcmaster.com). Just choose a valve with a low opening pressure (1 psi or lower) and fluoroelastomer seals to resist petroleum/gasoline.

Cheers,

Don

 

Something happened recently that is making it more frequent (3 days in a row now). On random occasions, it will start for 1 second then completely die. This most commonly occurs on re-starting warm engine. It doesn't matter if battery is fresh (or even connecting 2 fresh batteries in parallel). After 5-20 start attempts times it decides to start and runs great.

Getting it to start may be correlated to me fidgeting with the fuel pump relay connector or fuel pump wires. Or just trying 5-20 times. Very hard to find a pattern.

Other times this happened it would crank for a long time without ever doing anything...recently it runs/ignites for a second but then dies suddenly (as if it had a hard spark or fuel shutoff).

 

This sounds like it could be vapor lock. If the fuel pressure regulator and/or check valve allow the fuel pressure in the rail to suddenly dissipate when the fuel pump is shut off. The sudden loss of pressure allows the hot fuel in the rail to boil into vapor. The vapor can pass through the fuel injectors, but when mixed with air constitutes such a weak Air-Fuel Ratio that combustion isn't possible. Allowed to cool, the vapor condenses back to liquid and all is well.

Cheers,

Don

 

The start for a bit then stumble points to the second phase of the fuel pump on - off - on sequence . That third sequence is the Crankshaft sensor seeing engine rotation and enabling the fuel pump to turn back on for the duration of the drive . The CKPS will not throw a CEL code at this point of failure from what I have read from others as it fails in stages before total failure .

The physics of the vapor lock is deep , deep in meaning but possible from a chemical engineering point of view . There is nothing you can do about this aspect in hardware design ( and it's relevancy in X300 history of X300 issues from what I know ) and it's understanding but there is something you can do with the fuel pump pumping regulation . And I highly respect the experience Don B. has on the mater that I don't have . If you want to get into this aspect of the fuel pump control I'm game as the fuel pump control circuit was modified on M'Lady Penelope as I bought her and failed in the craftsmanship of the repair . So I went thought all of this . Pin 16 of the RS3 connector for me but will determain for you .




In order that physics be enjoyed it first must be obeyed . Dr. Richard P. Feynman Phd . Nuclear Physics Cal. Tech .

http://www.feynmanlectures.caltech.edu/info/My .

Mom said I need to go to bed now

 

UPDATE: these last 4 days I've been able to "recreate" the no start condition daily by:
1) start car cold...usually no problem
2) drive 10 minutes
3) turn car off, wait around 30 minutes
4) start car again. it starts and stop immediately. after a bunch of attemps, sometimes holding gas all the way down, it starts very rough. runs VERY rough for a minute then all is OK. Try starting again and it starts and runs perfect. No gas smell, more of exhaust (but no white smoke).

So I guess I have some combination of flooding, cylinder bore wash, and/or vapor lock happening depending on car temperature/length of time between drives. I'll be changing the fuel pressure regulator and injectors in a few days to see if that helps. Then changing as many important relays as I can.

 

I actually installed the check valves inside the fuel tank, while I was replacing the fuel pumps (2, XJR). The check valves were installed in the fuel line as it exited the fuel pumps.

Here is a link to the check valves I used:

https://www.jaguarforums.com/forum/x...2/#post1870043

.

 

UPDATE: this morning (60 degrees) it would crank and not fire at all. tried 5 times, nothing. pedal all the way down, nothing. went to front of car pressed on all the relays by the passenger headlight, just for kicks, then it started perfectly without any stutter, and ran great.

Drove for 5 minutes to a store, and stopped engine. Tried starting 15 minutes later, started perfectly. So the problem is not just a hot-start issue... whether pressing on the relays matters is anybody's guess but I now just reseated all relays and went ahead and sprayed contact cleaner on everything I could find. We'll see if that helps.

 

RE: fuel check valve near pump... is that easy to do without moving the tank? i was going to just put it before to the fuel pressure regulator.

 

The check valve should be installed between the fuel pump and the fuel rail. Ideally, it would be close to the fuel tank, but I found that installing the check valve in the fuel hose on the inlet side of the fuel rail worked just as well.

The fuel pressure regulator is on the outlet side of the fuel rail.

Cheers,

Don

 

Just jotting down stats...when the gremlin appears (seems like 15% of time now):

Maybe 1 out of 4 times ...If engine totally cold: cranks for long time, with no firing. Gets going maybe after around 7 tries

If enging warm: will crank, start and die after 1/2 second (maybe 15% of time). I have to repeat this around 10 times before something happens... by then I've jiggled the fuel pump relay or swap other relays but can't pinpoint if any of it matters.

I've found no correlation between this happening and the time-between drives, engine temperature or outside temperature. It really seems random.

When it starts, sometimes it just hums perfectly. But recently, it will sometimes run VERY rough (as if half the cylinders aren't doing anything) while I try to pump the gas to keep it alive. I smell alot of exhaust but don't see it. Restarting engine after 1 minute of rough running often makes it work perfect.

No other symptoms once engine is running well, other than low fuel efficiency (20 mpg highway) & O2 sensors show high output but sometimes oscillate just fine.

For the last 2 years, pressing the gas a bit while starting would make the gremlin almost never appear... now it seems like it doesn't help. The car has made up its mind before I turn the key if it's going to run well or not.

At least now that it's happening more often I hope I can try to pinpoint if it's a fuel, spark or vacuum issue.

 

UPDATE: after receiving a batch of 5 relays (ignition relays, standard relays) I replaced a few (like the fuel pump relay, ignition positive relay in front, ignition positive relay under RH heelboard, ECM Controlled Relay, Auxilliary Relay, ignition Coil relay). The problem hasn't happened in 2 days (after happening for 7 days in a row). Coincidence or not, I'm crossing my fingers.

 

Fingers crossed for you as well....

I've also replaced both fuel pump relays, and the "ECM Controlled Relay" and have three more new relays ready to go.

I planned to replace the "Ignition Positive Relay" in the right engine bay fuse box, and the right heel board.

Which relays are you calling the "Auxiliary Relay" and "Ignition Coil Relay"?

There is an "Auxiliary Positive Relay" in the trunk fuse box. Is the the "Auxiliary Relay" you refer to?

I don't find an "Ignition Coil Relay" except for the the XJ12.

Thanks!

.