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duncan16v

duncan16v

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Posting this for some ideas from wiser heads as to what might be the issue.

Car is a '92 BX 16 Valve - I've owned it since 1996. It's been off the road for years and I recently went through a whole heap of recommissioning maintenance:
  • replaced cam belt and accessory and LHM pump drive belts
  • pulled all the injectors and had them cleaned
  • replaced spark plug leads
  • replaced spark plugs
  • replaced fuel hose and fuel filter
  • changed oil and filter (obvs)
  • replaced O2 sensor
  • replaced ABS module
  • repaired loads of crappy electrical issues
  • overhauled brakes front and rear
  • Spent uncounted hours finding and fixing all the hydraulic leaks, replaced dead spheres etc etc. Except one leak who won't show itself when I'm looking for it. Bastard.
  • Lots and lots of other stuff. Alvadi.com and the Estonian Treasury send me Christmas cards as I catapulted myself into their 'High Roller' category.
Anyhoo. I was ready to go get a roadworthy just before Christmas but that didn't happen for one reason and another, and the car sat for the last couple of months. Yesterday, I fired the car up to warm it up and have a red hot go at locating Schrödinger's leak. Let it idle for a bit then gave it a bit of a rev once it had warmed up. The exhaust spat out some perforated bits of muffler (ohhh nooo), then the engine started idling roughly, and got a lot of smoke or steam from the exhaust. I killed the ignition and started checking the obvious: water in the oil (nope), blow-by in the water jacket (nope), any obvious external symptoms (nope). Pulled the spark plugs - all good except #2 cylinder where the electrode was wet. Refitted the spark plugs and tested the spark plug leads. No spark on #2 - which explains the wet electrode. Replaced #2 spark plug lead - no change. Ran the engine with #2 spark plug disconnected - no change. OK. Next step back is the distributor. Removed the distributor cap and rotor which both look reasonable but have seen better days, but nothing really obvious pointing to a fault on #2. Parts availability in this case made a sad face :-( however did find a cap and rotor for 200 sodding euros. Injector sounds like it's firing OK although that's hard to test, and the wet spark plug electrode suggests there's no shortage of fuel getting to #2.

There are no ECU fault codes and diagnostic checks point to no spark on #2 so has to be something upstream of the spark plugs, and the only remaining culprit is the distributor and rotor (I am assuming the coil is firing as it should) otherwise I would expect a fault code.

Things that worry me:
  • no spark is bad. It's a pretty simple ignition system and I can't find an obvious culprit that's screaming "I'm broken!"
  • The smoke/steam from the exhaust. Where the hell is that coming from? Could simply be moisture in a muffler/resonator maybe? Coolant level hasn't dropped, nor are there signs of exhaust getting into the water jacket (like pressurised coolant) so I'm inclined to rule out a blown head gasket.
  • The issue came on suddenly after I revved the engine to maybe 4000rpm or so

Anyone had a similar issue with a 16 Valve engine or can point to other areas or things to look at?

Thanks
Sad Duncan
 
Pull the lead off no. 2 and hold it near the manifold to see if there’s a spark.

Check the cap for cracks as I’ve heard these engines are really finicky about damaged caps/rotors. Maybe try cleaning the cap and see what happens.
 
I'd be suspecting the distributor cap. I'd test the spark plug by swapping two around and seeing if the fault follows the swap. Then I'd have a very close look at the distributor cap and rotor. They don't fail all that often, but the results can be really odd when they do. I wouldn't worry too much about the smoke/steam/exhaust issue until you got it running on all four again.
 
I agree you need to check the distributor cap. In the 1990s PRV (V6) engines in Pug 605s and Citroen XMs used a Bosch distributor, and I have had a couple of the caps fail. It's very hard to pick - there were no visible cracks or tracks, and I couldn't see any arcing at night.

Best test I found was an old fashioned timing light. Connected directly to the coil it produced a strong flash (obviously also very fast), while connected in place of any of the plug leads the flash was weak and intermittent at best.

Same dizzie had been used in some BMWs, so I was able to get a new replacement without too much trouble...
 
I have been doing a heap of testing and some creatific thinkerizing...

Fuel filter was replaced as part of the decommissioning works, the tank drained, and fresh fuel tipped in. Plastic tank, so rust shouldn't be an issue. Do need a new fuel sender but.
I tested the distributor cap with a meter - it showed a ridoncluous resistance on Cylinder 2. So cleaned up all the terminals and got that fixed. Cleaned the rotor cap as well.
Tested the spark plugs - they all measure 4k ohms which is about right. Swapped in one of the old weird 3 terminal plugs for the purposes of testing - still came out wet.
IMG_3782.jpeg

Tested the spark with a screwdriver inserted in the lead - it throws a humongous spark that's enough to animate Adam, Frankenstein's monster.
Swapped the plugs for #1 and #2 - no change.
Tested an old plug inserted in the lead - gets a healthy spark:
Screenshot 2024-04-08 at 08.57.41.jpg


So: ignition looks healthy (although could still be tracking to ground in the distributor cap - will test using the timing light as suggested).

That amount of spark *should* be igniting any fuel. Noticed that there's no difference in idle between plug connected and disconnected.

So I put my thinkerizing cap on:
  • Plug is wet, so defs getting fuel
  • Spark appears to be there in abundance
  • Idle doesn't change on testing Cylinder 2
  • Maybe that injector is going hog-wild and pouring fuel in. Doesn't seem likely tho'. That would surely produce very different symptoms
  • Pointing towards weak compression, I'm thinking
  • Next step is to get me a compression tester

I really don't like where this is heading :-(
 
Armidillo said:
I agree you need to check the distributor cap. In the 1990s PRV (V6) engines in Pug 605s and Citroen XMs used a Bosch distributor, and I have had a couple of the caps fail. It's very hard to pick - there were no visible cracks or tracks, and I couldn't see any arcing at night.

Best test I found was an old fashioned timing light. Connected directly to the coil it produced a strong flash (obviously also very fast), while connected in place of any of the plug leads the flash was weak and intermittent at best.

Same dizzie had been used in some BMWs, so I was able to get a new replacement without too much trouble...
Click to expand...
Do you have a part number? My usual sources are showing no loner available
 
I'm catastrophising a bit.

The XU9J4 is a wet-liner design. I can't see a path for compression to get to the outside world without pressurising the water jacket so surely can't be a head gasket failure. Maybe 2 to 3? Cracked head?

1712531832439.png
 
Anyone replaced a head gasket on one of these and has top tips?
 
DoubleChevron said:
injector stuck open/pouring fuel in on that cylinder.
Click to expand...
I'd prefer that to the other options... 🙃

I had the injectors cleaned a few months back, so entirely possible that one has objected to being interfered with.
 
Weak compression doesn't necessarily mean a blown head gasket. Could be rings, valves, cracked head, leaking sparkplug or fuel injector seals.

I think it's possible to pull the fuel rail with all the injectors still attached. You'll have to gerry rig the pump to run as there's no priming function on the BX to pressurise the fuel rail. If no.2 injector is leaking then that's probably your culprit.
 
duncan16v said:
I'd prefer that to the other options... 🙃

I had the injectors cleaned a few months back, so entirely possible that one has objected to being interfered with.
Click to expand...
Could a test be to swap the injectors between cylinders and see if the problem follows? (I've never played around with injectors so my idea might be silly)
 
I'm going to pull the injectors - if #2 is stuck open, as a simple test, I *think* I should be able to blow through it.
 
You might need a bit more pressure than just blowing through it. The fuel rail runs at 3bar or 42psi and you may find the injector seals just fine at lower pressures.
 
122psi on Cylinder 2 which seems pretty low, but the end of the hose has fuel on it (this is with a disconnected injector). So a stuck injector is looking more likely at the moment.

Maybe I can stop catastrophising. But then again, it's a Citroën...
 
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