Non-Start: Have Fuel & Spark

XJ40
1

Hi all, currently looking into a non start issue. I’d started the car up in the morning (Started no problem) and left it running outside, when I came back 2 minutes later, it had died and now will not restart.

Summary below of what has been checked:

  • Cranks over fine
  • Fuel to the fuel rail
  • Injectors pulsing
  • Spark from the coil
  • Spark at the plugs
  • No codes on the VCM
  • Does not start on easy start
  • Checked all fuses, all ok

Any suggestions on where to look next? It’s an '89 3.6.

Thanks,
Callum

2

Have you tried to see if it will run for a few seconds with starting fluid? Revove air filter open throttle plate, spray starting fluid into intake manifold, crank starter…oh. Is that what you call easy start? If nothing with starting fluid time to check ignition timing and a compression check.

3

Callum welcome to the forums, when you state that the engine turns over fine does it sound ‘normal’ i.e. there is compression? These engines can suffer from both ‘bore wash’ (indicated by lack of normal compression bumps while turning over) and flooding.
The normal trick with bore wash is a small amount of oil down each cylinder and try to fire up.
If its flooded then its a case of flooring the accelerator pedal and just keep cranking until it clears the petrol out of the cylinders.

4

Callum, you didn’t mention if the crank position sensor, cap and rotor have been checked.

5

Hi Robin,

Yes, it turns over as I would expect, albeit making absolutely no attempt to fire.

Do you think that the engine could be suffering from bore wash and/or flooding bearing in mind that the engine was running prior to it cutting out and now not restarting? When I started it that morning it started no problem at all.

I wasn’t with the car when the engine stopped running so unfortunately can’t give any indication of how that happened i.e. suddenly stopping, spluttering then dying etc.

Thanks for your help,
Callum

6

Hi Joe,

I have spark at the plugs so can safely assume that the distributor cap and rotor arm are working.

Also, it is my understanding that I won’t have either spark or fuel injector pulse if the CPS is faulty, both of which are present. To me this suggests that the CPS is okay. The rev counter also rises to circa 100rpm when cranking, further ruling out a CPS issue.

Thanks,
Callum

7

I would take out a spark plug and check to see if it’s wet, if it is re-insert and try starting as if it was flooded.

8

Hi Kris,

Yes, starting fluid = easy start, this did not help. I have confirmed that I’m getting fuel to the injectors and that they’re pulsing electrically.

Timing and compression I will check but it seems strange that either of those could be the fault considering the engine was running perfectly well. If something has gone drastically wrong with the timing or compression I wouldn’t expect the engine to crank over as per usual.

Cheers,
Callum

9

Thanks Robin, I’ll try that and report back.

Thanks,
Callum

10

Not a lot you can do with the timing on these engines its set off the CPS and reluctor wheel, the distributor is just that, twisting it one way or the other will not change a thing unless you go so far that the rotor is too far from the contact that the spark cannot jump the distance.

11

Yes, it’s my understanding that the ECU gets its data on when to fire the injectors and ignition solely from the CPS when starting up.

The fact that I have fuel and spark leave only 3 possibilities left in my mind (Apart from flooding as you mention Robin):

  1. No / not enough air getting through to the cylinders. Not sure how this could be possible considering the engine was running, I can’t see any obvious air leaks or disconnected hoses. However, I will check to see if the butterfly is still able to turn, maybe this is broken but it sounds unlikely.
  2. No / not enough compression. Again, unlikely as the engine was running prior to it not starting but I will check to rule it out.
  3. Incorrect timing. Since we know that the CPS is working (As we have both fuel and spark) is it possible that there’s an issue with the reluctor wheel? I’ve seen one case on this forum where the woodruff key was damaged on the crank pulley/harmonic balancer assembly causing play in the pulley. If the reluctor wheel is loose or in the incorrect position relative to the crank and therefore valve timing, it will give incorrect data to the CPS, causing the ignition and injector timing to be off. Do we think that this is a possibility? Should there be any movement in the crank pulley assembly?

Thanks,
Callum

12

No the crank pulley should be tight on the nose of the crank.

13

Hi Callum Coolant temperature sensor? Or iacv valve? Regards

14

Hi James,

Do you think that a faulty coolant temperature sensor or IACV valve could stop the car from starting? Is this something that you’ve experienced before?

Thanks,
Callum

15

Hi Callum yes I had to replace my cts recently on my 88 xj40 but there was an error on the dash, symptoms were car would start then when I parked somewhere hard to start eventually no start so replaced cts all good. Iacv can also prevent starting i would spray the plug with electrical cleaner and check the gasket, hope this helps

16

what colour is the spark at the plugs? strong blue or orange?

2 Likes
17

That’s a good point Larry, doing some further testing today, the spark I’m getting doesn’t look awfully strong. Occasionally, I’m now getting no spark at all (Battery is on a charger so not low). What do you think the likely cause of a weak spark is?

Thanks,
Callum

18

Faulty ignition on relay? 1994 Jaguar VDP No Spark - #185 by Jag.Man

19

Can be rotor going high resistance also.

1 Like
20

Hi Mike, thanks for the suggestion, to rule this out I swapped it with a different relay which did not fix the issue.

Thanks,
Callum