Engine trouble - any ideas?

[crofty1984]

Hello All, I'm on the beg for some advice:

I have a 1984 Sealine 22 with a 3.8ish litre Volvo Penta petrol V6 (AQ175A).
I've seen the engine run fine, but it cut out after a brief time. Then it just plain old wouldn't start.
It's had new plugs, dizzy cap, condenser and points. It did run, but cut out, the plugs were a bit sooty, leading me to believe the (auto) choke was being left on.

Anyway, further inspection shows no spark any more, so I replaced the coil and now have bright blue sparks!
I cleaned up the plugs and put them back in. Fired up almost instantly - yay! Set it to 1900-2000 rpm fast idle as the book says, she sat there, then gradually struggled and died and wouldn't re-start. It did almost try once or twice. All this took about 30 seconds from first firing to death.

I don't think it's the choke any more, I've actually seen it disengage after a couple of seconds, plus, it wouldn't soot up and die in 30 seconds, surely?

I've taken the plugs out and you can literally tip them upside down and pour fuel out so it's getting fuel. There's definitely a spark there and it's happening at the right time and place, or surely it wouldn't run smoothly when it does run?

I've had it running for a max of 5-6 minutes, and restarted it half a dozen times before it died the first time (pre-my replacing the coil).

Now I think it could be the fuel. It's definitely getting there and there's definitely a spark, so why isn't it burning? I know the tankful's been sat in there for a least a year. Could it be that? It wouldn't surprise me if the previous owner accidentally shoved a gallon of water in there - he didn't seem to be the most methodical of people. Could it be that I'm lucky enough to pull through a slug of good fuel from time to time from the mess in the tank, but normally, I just get rubbish through?

This weekend's plan is to see if I can get it to run from a jerry can of fresh unleaded.

Any advice would be welcomed.

Thanks,
Dan

 

[Ripster]

On the basis you have petrol and not some other mix being fed through!! Have you tried taking the air filter off? or making sure its defo getting a good dose of air through (pipe not collapsing/pinched) Just a thought...

 

[oGaryo]

water in the fuel or just plain old stale fuel with reduced octane content... empty the tank or run from a remote fuel tank containing fresh fuel. obvious i know but the dizzy was clamped in place, right? not drifted out of timing with engine vibration??

 

[volvopaul]

The power loss could be an inlet manifold leak, try tighteneing up the vertical bolts on both heads, if the engine is fully raw water cooled I have seen cracked inlet manifolds and leaking gaskets that leak water into the cylinders via the manifold, is it def petrol thats wetting the plug and not water?

 

[oGaryo]

The power loss could be an inlet manifold leak, try tighteneing up the vertical bolts on both heads, if the engine is fully raw water cooled I have seen cracked inlet manifolds and leaking gaskets that leak water into the cylinders via the manifold, is it def petrol thats wetting the plug and not water?

Could it also be leaking risers Paul?

 

[markcw]

To test the fuel in your tank, take a small amount of petrol about a large table spoon and find a safe place. poor pecky in a bowl, now from a safe distance light the fuel, if it goes up with a wooosh fuel is fine, if the fuel smolders and burns slowly fuel not good,

Your plug should contain no fuel the petrol is vabouized with the air to produce a mist in the cyclinders, the normal colour of a good burning plug is a dark grey plug tip, light grey is to lean and black sooty and oily is to rich. What you say could lead to the float needel in your carb getting stuck and petrol contiue to get pumped into your cyclinders as the float needel has not shut the flow off. also try reduceing you idle mixture leaner to see of any inprovement is made, have you checked and cleaned your high and low fuel flow jets in your carb?.
remove your flame arrester and hold the choke flap open my v6 required no choke at all even from cold, also check your vacum hose to your carb a vacum leak will cause a poor running engine

thirdly.
electronic or mechanical fuel pump you could have a dieing fuel pump, if you have the black cyclinder type fittied, normaly carter or v/P is it noisy, if yes this is the start of your fuel pump failing like mine did quickly.also on the fuel pump you may have a filter mesh on the inlet side fuel line, is this blocked?

Timeing is take from TDC at cyclinder 1, piston 1 begining the compression stroke, inlet and exhast valves shut to check this remove the rocker cover and watch the valves raise and lower untill you see both valves closed ie fully raised, piston 1 should then be a TDC and plug lead one connected to a postion on the distributor and setup so the arm is in a fireing contact.
Is your spark plugs leads located correctly at the distributor, also in your distributor you have advance cams under your points or spark module, is the cams able to move correctly and are the springs springy and not seized solid.

from your comments i would say you have a fuel issue as the engine runs but dies off hope this may help

mark

 

[crofty1984]

Thanks for the advice everyone. Thought I'd confirm what it was in case anyone with a similar problem googles this thread.
It was indeed fuel. It ran fine through a couple of gallons of unleaded out of a jerrycan.
I caught some of the old fuel that dribbled out and it was brown! Not red-diesel coloured, like really strong tea. So one of (many) problems solved.