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Odd No Start / Flooding perhaps?

 
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Tiny  



Joined: 10 Apr 2006
Posts: 500
Location: London, UK

PostPosted: Sun Oct 01, 2017 7:38 am    Post subject: Odd No Start / Flooding perhaps? Reply with quote

The problem is it's Cold cranking without any sign of firing.

I checked for vac leaks. All OK. I have fuel and spark getting OK.

I pulled injectors and checked fuel spray and flow. Jumper the fuel relay and when lifting the plate just a little i could see that no. 2, 3, and 4 had a nice cone spray, but no.1 had a pointed dribble.

The are all flowing evenly into the bottles on the test.

So I replaced injector 3 and 1, thinking it would move the dribble to no.3...but no. 1 behaves exactly the same again with the dribble. (If i lift the plate higher then they all spray as they should.)

So then get this. I re fit all injectors nice and snug. I tried to start it again, and it just cranks and cranks. I pulled plug lead no.1 and put a spare plug in and rested onto top of motor to check for spark...Turn the key and the damn thing starts up on 3 straight away.

I replace the lead onto plug no.1 and the problem returns again. Unplug it, turn the key and the engine fires!

I've found some threads with similar-ish sounding probs but just wondering if anyone had some suggestions?

I've checked cold and warm fuel pressures with the gauges, and it is within spec.

Any ideas welcome please!? =] Cheers all.

Tiny
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Mike9311  



Joined: 14 Dec 2004
Posts: 638
Location: Chicago-ish

PostPosted: Sun Oct 01, 2017 7:58 am    Post subject: Reply with quote

Ok you win odd problem of the day

Just a thought...

Did you check your distributor cap? Say there is an internal short that only shows its ugly head when cylinder 1 attempts to fire under compression but when you fire a test plug out of the cylinder it has less load on 1 and it fires the others? A possible arc over occurs because its easier between Cyl 1 and another Cyl when 1 is under load (compression). 2 cylinders would then be not functioning when everything is together. In other words you see a spark out of the cylinder but the quality isn't good.

A spark plug gap tester (visual gap) would be great for this. You can control the gap size and see if arc is the same between cylinders.

I am basically saying there is an issue between two cylinders, 1 and another, that only happens when everything is together. Not so much when more energy is available when 1 is out of the cylinder
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1980 931 ...off with the cobwebs
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1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
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1980 924 NA (R&D lightweight)
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Tiny  



Joined: 10 Apr 2006
Posts: 500
Location: London, UK

PostPosted: Sun Oct 01, 2017 9:11 am    Post subject: Reply with quote

That's pretty neat thinking there! Thanks. Great stuff.

When I pulled the cap, I could see some carbon deposits on the copper posts inside, so I cleaned them up, BUT I do have other caps laying round to test with.

When you say spark plug gap tester, do you mean one of these? I have one of these things:



Thanks again. Will update tomorrow
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Mike9311  



Joined: 14 Dec 2004
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PostPosted: Sun Oct 01, 2017 12:26 pm    Post subject: Reply with quote

Exactly like that but I am not sure that one is adjustable. Might do the trick anyway

Will be interesting if this is the problem
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1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
1982 931 WB wana-be GTR race car
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Tiny  



Joined: 10 Apr 2006
Posts: 500
Location: London, UK

PostPosted: Thu Oct 05, 2017 6:01 am    Post subject: Reply with quote

I pulled the CSV and tested. It's working fine.

So then I pulled the spark plugs and saw that they were all fouled pretty bad with carbon soot. When I looked a little closer, the light bulb in my head went on...

The plugs are pretty new, and when I installed them I figured I would close the gap down. (This is the first time I've ever tried this, because the Haynes says 0.7mm) Out of the box they seem to be around 1.2mm.

I don't think closing them down was a good idea.

I replaced them with another set and it started ok and so went for a drive. All seems great.

Is it possible that I have dumped a load of fuel in the oil from continual cranking>? I have read other posts saying that it's a good idea to change the oil after an occurrence such as this.
What do you think?
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morghen  



Joined: 21 Jan 2005
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Location: Romania

PostPosted: Thu Oct 05, 2017 6:41 am    Post subject: Reply with quote

Check the level...if you didn't exaggerate with lifting the plate with the injectors in and cranking too much you should be fine. Depends on how old the oil is and what type. I use Motul 300V Competition and that accepts a certain amount of fuel in it while still keeping its properties.
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Mike9311  



Joined: 14 Dec 2004
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Location: Chicago-ish

PostPosted: Thu Oct 05, 2017 6:43 am    Post subject: Reply with quote

That is totally possible. However that all depends on how much you actually tried starting it. I wouldn't worry about a few minutes but if a lot more time, I would likely be on the side of caution and change oil. What most people worry about is the lack of oil on the individual cylinder that has the issue, since its being actively washed off by fuel from above.

...But that is great news that it is all figured out!
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1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
1982 931 WB wana-be GTR race car
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Tiny  



Joined: 10 Apr 2006
Posts: 500
Location: London, UK

PostPosted: Mon Oct 16, 2017 4:11 am    Post subject: Reply with quote

It is still flooding when I try to start it from cold.

Is there ANY way to adjust it so that it doesn't flood on cold start?

I realise messing with the Air/Fuel Hex-nut in this manner is not ideal BUT I can't think of any other way to alter how much fuel is being delivered.

Help! =]
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Tiny  



Joined: 10 Apr 2006
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PostPosted: Thu Oct 19, 2017 9:23 am    Post subject: Reply with quote

Update:

I read a cool post on here by a regular poster, where the advice was to pull one of the lines from the fuel distro to an injector, and then with the fuel relay bridged, to adjust the air/fuel screw just up until the 'eeeek' noise arrives and fuel starts to flow from the distro, and then back it off just a little till is stops, and use that as a starting point.

I did that, put it all back to together and the thing fired right up instead of the continual cranking.

The allen head Air/Fuel screw needed about 2 full turns clockwise to get to this position, by the way.

In addition to this, once started up I had to quickly adjust the air bypass idle screw (as it was always wound nearly all the way in just to get the car to idle correctly.) IwWound it out a few times and now it seems to be idling as it should again. The cold idle, and cold idle response to blipping the throttle seems stronger too.

I'm gonna get the CO tester, and timing gun out tomorrow and continue setting it up.

By the way i also re-tested cold-control, and system pressures, just to make sure / double check all was within specc, and it is.
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