Old Petrol and engine problem

[ronk]

A pal of mine has bought a project car - a 1980's Spitfire. He has started with the engine on its road to recovery.

The engine was lumpy and not firing at all well - It started with some reluctance on the existing fuel estimated to be 25 years old.
Investigation of very lumpy running it was found a couple of inlet valves seized with bent push rods. He had the head fully re furbished and new push rods where necessary.

At this stage most of the old fuel (brown in colour ) was siphoned out and a gallon of fresh petrol added.
The head was re fitted and all the valves gapped etc and the car ran as sweet as a nut - fast forward a week or two he started the car again - LUMPY and yet again, a very stuck inlet valve. It seems to have a hard, black, varnish like residue. (It shows up light on the photo.)

I suspect something in the fuel?
As the cars previous history is not known, my theory is the fuel could be either:-
A Contaminated deliberately at some stage
B Could have evaporated leaving a concentrated residue of additives - Could even be a lead additive ?

Would anyone like to add their opinion please.

I have suggested that the tank is removed, cleaned and the fuel lines flushed before any re assembly.

 

[Owdgit]

Your diagnosis sounds plausible.
Probably worth changing as much of the fuel lines as possible too and a new fuel filter.
Did he have the valve seats hardened for unleaded?
Might be worth checking the compression on each cylinder too that way you'll know if there's any bypass leak from the valves or piston rings, any signs of oil bypass on the head or plugs?

 

[ronk]

He had the head skimmed / pressure tested / valves ground and re seated. It all went together shiney and new.
Compression tested and all four pots were more or less identical with very good pressures.
The picture of the valve shows the build up after light garage running only.

No evidence of oil - piston crowns are clean.
He describes the residue as like thick shellac.

I’ve suggested the tank is removed, drained completely and cleaned - it’s said white Spirit sloshed about with some nuts and bolts does the job. I’ve also suggested back flushing the fuel line.

 

[Owdgit]

It does sound like fuel, is there no evidence in the carb?
You can usually smell contaminated fuel too.
I'd run through the whole fuel system.
Its an SU on the spitfire isn't it? The jets and needle ok/clean? Not worn and is the needle moving freely, might need the dashpot oil changing/topping up.
Seen it on old bike tanks where the old fuel turns to a jelly like substance and if you don't get it all out the fresh fuel can start to dissolve it causing rough running/carb problems.

 

[ronk]

Yes, twin SU‘s all clean- I saw the fuel that was siphoned out and it was a mucky brown colour.

 

[Owdgit]

I'd go through the fuel system.
A quick Google shows that a new replacement fuel tank is around £130, not a lot of money for piece of mind.
Change the fuel lines where possible, new fuel filter, flush the fuel pump and that should rule the fuel system out.

 

[firebobby]

The modern fuels are having an impact on rubber fuel lines, diaphragms etc. Re-check the carbs and make sure they don't have any gum in them. The tank will need a proper clean out and the fuel lines would probably benefit with being renewed.
Try using a fuel can as a temp tank, with a direct line into the fuel pump. Remember the pump diaphragm maybe knackered too.

 

[maxman]

As above with the fuel.Is valve that stuck open,the same one that was stuck open before,if so I would replace the valves in question and the valve guides.Make sure there is oil getting to the top of the engine.

 

[ronk]

The guy says the valves run nicely and it’s this varnish like gunk that sticks the inlet valve open - in all my years of this level of engine I’ve never seen anything like it.

Im sure it has to be something in the fuel as it’s the washed part of the valve that’s gunked up and prevented from returning to seat,

My first suspicion was sabotage - ie sugar in the tank sort of sabotage! He knows nothing of its history.

 

[john-e89]

If it was mine I’d be renewing the fuel lines for definite as well as a fuel tank internal steam clean at worst or a new tank at best, anything is only as good as it’s weakest link, but you know that already. Unless ALL the fuel system is clear and clean you’re chasing your tail.

 

[ronk]

What sort of gunk could cause that ?
I think it might have been sabotaged with something like a can of varnish or the likes - the car had been in a compound for years - who knows why it went there?

The chap told me that there was nothing but the dregs in the tank when he put a gallon of fresh stuff in. He thought if there was anything left it would have been sufficiently diluted - apparently not!

It’s having a good clean out thus time as it’s costing him a fortune for gasket kits! That’s apart from the effort!!!

 

[john-e89]

What sort of gunk could cause that ?
The chap told me that there was nothing but the dregs in the tank when he put a gallon of fresh stuff in.

It’s having a good clean out thus time as it’s costing him a fortune for gasket kits! That’s apart from the effort!!!

Without meaning to sound brutal what did he expect buying a project car Ron...? Time, money, effort, swearing....it’s all there in an old car resto....

 

[ronk]

Oh I’m sure he knew the potential problems. He bought an Mx5 for his previous project.
Cars of this era are more Meccano fortunately and can generally be fettled with spanner , nuts n bolts engineering skill!

 

[Owdgit]

I wonder if the tank has been coated with petseal?
Modern unleaded fuel is known to react with "older " petseal, it breaks it down.
Still think I'd bite the bullet and get a new tank and replace/clean the rest of the fuel system.

 

[ronk]

The more I think the more it looks like a new tank.
We don’t know what the gunk is in the Tank so cannot determine a solvent to clear it.
It would need a ‘scope put inside to ensure it’s clear before I would risk starting it again.

 

[john-e89]

The more I think the more it looks like a new tank.
We don’t know what the gunk is in the Tank so cannot determine a solvent to clear it.
It would need a ‘scope put inside to ensure it’s clear before I would risk starting it again.

Frost do an internal tank strip fluid Ronk for £13, might be worth a shot before going new tank route. :?

 

[ronk]

I will pass that onto him
Lidl did an endiscope a while ago but I couldn’t think of a use - i can now!

 

[Owdgit]

I will pass that onto him
Lidl did an endiscope a while ago but I couldn’t think of a use - i can now!

I'm not a gynecologist but I'll have a damn good look

 

[Crazy Harry]

Clean the valve and reassemble the engine then try with a small plastic bottle / lawn mover type tank fed direct to the carbs with new fuel - if it runs fine then spend some money on new fuel lines; filter and a new tank!

 

[ronk]

Clean the valve and reassemble the engine then try with a small plastic bottle / lawn mover type tank fed direct to the carbs with new fuel - if it runs fine then spend some money on new fuel lines; filter and a new tank!

I think that’s the only way - do it properly but do it once!
It has to be something lurking in the tank - I still suspect sabotage at sometime. Until it is determined exactly what it is there will always be a nook or cranny with some remaining.