zogster

Wonder if anyone has a good idea of what's going on here...

I'm having trouble getting started again after a fairly lengthy AOS seal change job, with associated turbo, inlet manifold etc removal and reassembly.

At first the engine cranked but didn't start. I checked/wiggled all the connectors (AFM, TPS, speed and reference sensors, injectors), used contact cleaner... and it then started cleanly, idled smoothly, and died after about 40 seconds. No spluttering or weak running, it just cut out as if I'd killed the ignition.

Since then I've managed to start it a few more times, but more often it cranks without catching. When it does start, each time dies after a short while. And I think that when it;s cranking but not starting, there's just a hint of 'almost catching" for a moment when the engine is no longer being turned by the starter but is spinning for a turn or two under its own angular momentum.

I'll go through the Clark's Garage checklist tomorrow, but in the meantime does anyone have an inspired insight?

Auto_Werks 3.6

Bypass DME relay? I know its not associated with your repairs, but it could be a coincidence.

SummitP

I would guess an electrical connection got damaged when you were doing you aos. You say that it started up after jiggling connectors, that is where I would start. Check your speed and ref sensors and check the wiring specifically, it can get brittle and corroded and lead to no start or intermittent no start conditions.

zogster

Worth a shot... I actually had a couple of sudden loss of power with a single backfire incidents before I did the mammoth troubleshoot. Wanted to change the AOS seals as I'd been chasing a possible vacuum leak and knew the AOS seals were suspect. So it's possible that whatever caused the loss of power incidents before is still a problem.

divil

When it cranks without catching, does the tach bounce? I mentioned that in your other thread and you couldn't check because it was not happening very often. But it's worth knowing, because if it does bounce , that suggests the speed/ref sensors are working

Here's a video of what it would look like:



If it's not bouncing, then you have no ignition signal, and therefore no spark (assuming your tach is wired correctly, I'm sure you'd have noticed it it wasn't). Most common cause is crank sensors, i.e. speed or reference, or both.

If it does bounce, you can probably rule out your speed and reference sensors, but you should still check for a spark since the signal can still be lost somewhere after the DME. If you find no spark at the plug you can try jumping pins 9 and 16 of the KLR together...if you get a spark then, you have a bad KLR. If you still don't get a spark, you might have a bad coil or bad DME.

Do you know if you're getting fuel?

zogster

Thanks for the pointers chaps...

Yes, I seem to have tach bounce when it's not catching.

Just tried again, and it started first time - I'd unplugged and replugged the speed and sensor connectors just for luck before trying. But then it cut out after a couple of minutes. Fiddled with the connectors, swapped the DME - no difference, still no start.

Am now installing coffee in self while considering next move.

zogster

I tried the DME jumper trick, and still no start, so I think we can rule out a DME problem.

But the fact that I'm seeing tach bounce suggests that the speed and ref sensors are good. Hmmmm.

Will get some spark testers and plug those in line, see what that tells me

divil

When you say you swapped the DME, do you mean the DME relay or the DME itself?

zogster

Sorry, DME relay.

I just tried again with spark testers in place, and now it's as if the battery isn't even connected - though I suspect whatever is causing this glitch could well be an unrelated gremlin. It also happened yesterday, and then magically went away after I fiddled with battery terminals and immobiliser connections. I don't think it's the immobiliser, as I just bypassed it and still no juice.

divil

So you get no power to the dash or anything at any key position? I don't know how the immobilizer works, but if you're sure it's bypassed correctly, maybe look at the ignition switch? It provides power to the coil, so an intermittent bad switch could explain your cuttting out/no start issue. Obviously this is a different symptom you're seeing now, but I think that switch is still a common denominator.

zogster

Looks like the no juice thing was the battery ground at the rear. I flexed the ground lead and power came back. (And the immobiliser cuts both the ignition and fuel pump circuits, though not quite sure where.)

Having sorted that... it looks like I'm not getting a spark.

The ignition switch could be worth investigating - I'll have a look at that next.

divil

Well I suggested that as something that could possibly explain both issues, but since your battery issue turned out to be unrelated, I think that makes it less likely. I'd look at a few other things first. If you are getting tach bounce and no spark, try bypassing the KLR. Disconnect the harness and attach a jumper wire between pins 9 and 16, and see if that fixes your no spark issue. The ignition signal goes from the DME to the KLR (and tach), then from the KLR back to the DME, then DME to coil, coil to distirbutor. You just need to find out which link in the chain is broken...

Also check the coil + terminal (black wire) with the key on pos. 1 - it should have battery voltage.

zogster

Thanks Divil.

The KLR jumper thing didn't seem to make a difference. And I do have +12V at the black coil terminal.

One other thing that may or may not help: a couple of times when stepping out of the car after cranking, but with the ignition now off, I've received a small static shock.

divil

No idea about the static thing. This ground lead issue you had...can you provide some more detail about that? Which lead was it exactly? Also, do you have a test light? You could use that to check for the ignition signal at the coil primary:




But I think the grounding issue is worth more investigation too.

zogster

Re. the ground issue - the cable I played with was the short, heavy ground cable from the battery neg terminal to the post in the battery well a few inches away.

I tried a spark tester, as shown, between the coil and distributor cap, and there was no sign of spark. (Though the design of these particular testers is such that while they fit on the spark plugs OK, they won't fit on the centre distributor terminal so I had to use an extra length of wire to make the circuit, so there's another link in that test chain that could be unreliable)