Sooty plugs and exhaust, slow to start (+solution)

[Timbo 0]

So I had my VR6 sitting for a while as I did some welding on it. I hadn't started it for about 3-4 months.

 

Symptoms:

• When cold it took ~20 seconds before it started.[/*:m:3o12wqu5]
  
• Rough idle, misfire and hunting[/*:m:3o12wqu5]
  
• Black smoke/soot from the exhaust, especially on overrun[/*:m:3o12wqu5]
  
• If left for at most a few hours and started again, it started straight away[/*:m:3o12wqu5]
  
• Idle fuel pressure normal at 3.5 bar, rising to 4 bar with throttle[/*:m:3o12wqu5]
  
• After stopping engine, fuel pressure dropped to just under 3 bar after 10 minutes (which accordingly to Bentley is fine)[/*:m:3o12wqu5]
  
• Number 6 plug wet with fuel, all other plugs very sooty[/*:m:3o12wqu5]

 

The cause? Number 6 fuel injector was intermittently sticking open. I rigged up some cheap injector cleaning apparatus like

and after a wee while I had the injector behaving again. I also used an ultrasonic cleaner on the injectors and got a lot of crap off them, though I suspect this was mainly from the exterior as opposed to the internals. After I got it all back together, changed sparks and leads, it starts immediately and idles more smoothly than it ever has before. I'm still getting a little soot out of the back but I'm hoping this is just the contents of the exhaust and it'll clear eventually. The car has no MOT and I have a few more jobs to do on it so I haven't had a chance to give it a good run on the road yet, but I'm optimistic. Since I'm a curious little rhino, I also decided to do the fuel pressure test again. After stopping the engine this time, the pressure doesn't drop at all after 10 minutes. In fact it goes up a little bit, I'm assuming because various things cool and the volume of the fuel system decreases slightly. If I come back after 24 hours, the pressure has still barely dropped. So either the test in Bentley is bunk (remember, my engine passed it, despite fuel pissing into one of the cylinders), or it's based on a different fuel system that allows some pressure loss back into the tank.

 

Anyway, just thought I'd post this incase any body has a similar problem; I didn't come up with anything obvious by searching.

[hyland770 0]

thats amazing, cheers for the link to the video, may have to do this and see what happens with regards to my quest for an ultra smooth running engine...