I’m standing at a gas station, so I’m in a bit of a hurry to get the car started again. The issue is the injectors not clicking when trying to start.
I’ve had this issue before, and the previous times it has been solved by leaving the battery unplugged for about 30 minutes, but not this time. I left the battery off for about 30 mins but the car still won’t start. All injectors click with WOT and ignition on, but no continuous clicking when trying to start.
Inertia cutoff is checked, but the pump is running.
I think it’s related to the ECU, hence disconnecting the battery resets the memory.
Has anyone had the same issue, and is there any trick to get it working now?
I’ll try to wait 60 minutes with the battery disconnected but no one knows if that will help
Try not only disconnecting the battery but connecting the leads together (with at least one off the battery of course!) This will discharge any capacitors and sometimes helps on modern cars.
With no injector clicking at all, it is either a dead ignition (the signal goes to the ECU from the coil, there’s a bullet connector on the water rail, should produce a click every third time with the ignition on).
Do you have spark while cranking?
Or it is an ECU problem. I wonder why it would click on full throttle, since the injectors click, even if the AFM flap is closed. Fuel pump running doesn’t have anything to do with injectors. The injectors can get disabled with the throttle closed, but ONLY above a certain rpm, above cold idle speed.
Does anyone know whether the starter relay (oblong silver can on the bulkhead) has any say in ECU operation? I know that it powers the pump and it might do more than that…
At least it’s still daylight, I know the gas station feeling. My fuel pump had disconnected itself and we pushed it out of the way in the dark. Good luck!
The ECU does take a “cranking signal” from the starter relay. How this signal is used, I’m not positive.
It’s written the the ECU slightly enriches the mixture whenever the engine is cranked, regardless of any other conditions or inputs. I’ve always assumed that’s how the cranking signal was used.
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Dir you check ignition with a spare spark plug, Rasmus - always carry a spare plug for ignition quicktest…
Both the ignition and injection is triggered by the ign amplifier - but the ignition is more sensitive to amp failure. You may have a heat sensitive amp - and waiting for it to cool down may indeed restore function.
And while the V12 has a hybrid digital/analogue ECU; I consider the usual method of restoring computers by disconnecting power to restore the ECU as pure hoodoo…
In addition; cranking WOT is unlikely to start the engine even with the injectors clicking - it bewilders the ECU. Certainly; the book advises WOT cranking, stating ‘if the engine then starts - no further action is required’.
But as you have this as a recurring problem - pursue a possible ign amp failure?
Rasmus,
I personally think that disconnecting the battery had nothing to do with solving your problem.
It’s not like modern cars, the ECU in our cars has no memory, no adaptive features and no reset.
When you turn the ignition off all power to the ECU is cut off.
I think it was the time factor, something cooled down and started working again.
Unfortunately, first and outmost culprit is the ECU.
Had the same problem but opposite, my ECU would work only when warmed up, impossible to start but when it did it run absolutely perfect.
Ignition module or the coax wire could also cause such problems as it communicates with the ECU via the coax wire.
The cranking signal plus WOT cuts fueling totally - being the cure for flooding - at least on AJ6 and subsequent. The X300 had a glitch whereby a brief start such as rolling out of the garage without full warm-up could flood the engine if attempting to start it again shortly afterwards.
The cure was to crank at WOT, since the ECU recognized that full throttle was never required for a dead engine crank so it cut fueling to remedy flooding.
During cranking the excess fuel was cleared and during the process at some point there would be an approximately correct amount of residual mixture and the engine would stumble into life if the accelerator was lifted (thus restoring injector fueling as WOT was abandoned).
If the engine did not catch, the drying out continued for as long as WOT was held. When, after 10-20 seconds or whatever the starter was rested, the now dry engine would start as usual with foot off the accelerator and fuelling resumed.
The same issue has occured once before, it was after I accidentally bumped the car into 1st gear from 2nd, which revved the engine to over 6000rpm. When trying to start the car again nothing would happen, so I had to have it towed (over 500 euro) and when it arrived home I tried starting it, nothing, unplugged battery and waited 30 minutes afterwhich it worked just fine.
When listening to the injectors they were not clicking, but I have no idea why.
As Aristides writes I don’t believe the ECU has any protection features like modern cars, but it still wouldn’t allow the car to start after it revved so high.
Causation versus correlation can sometimes be difficult to sort out.
Neither the ECU nor the engine should be fazed by 6000 rpm.
My gut intuition…which I’m not asserting to be foolproof…is that the ECU has come obscure fault; a weak solder joint, loose/corroded connector pin; something along those lines. Diagnosis by substitution might be in your future.
Yeah, I have a second thread going where a rought idle is being discussed, the cause of which is unclear. The plan is to get injectors cleaned this spring, and go from there, checking compression etc.
Someone has been back there before, when I first inspected the ECU to check if there is any vacuum there part of the hose seemed to have been replaced, and the cover was missing screws. There are so many untold stories with this car, but so few explanations…
We have far more explanations than answers! Is it a manual conversion or OEM? Later cars had different ECUs for manuals to cure stalling/vacuum issues. Does sound like a dry joint.
Can’t see why not, Rasmus - if the engine stood it without bursting a gut; I can’t see overreving causing any ECU complication…
A common feature of your problem is ‘waiting’ to cure the non-start. This will equally cool down an overheated ign amp/coil, and/or dry out a flooded engine.
Injector action is caused by ign amp, as is ignition. You may have injectors without effective sparking - but the other way around is less likely - check ign with a non-start…
So, just took the car out for a spin and there seems to be a new issue.
When under load or with no acceleration the car is smooth, but when I give it just a tiny bit of gas the car violently jerks, like it is shifting into 2nd gear or something. I tried cruising in 2nd but the problem still persists. I remember reading about a similar issue on an XJS which, if I remember correctly, was caused by a bad ECU, but I can’t for the life of me find the thread.
