Power loss

[kevtherev]

yes they wear.
the shorter they get the less of a stroke the pump makes.
at speed this would be more noticeable as the fuel delivery is critical... at lower speeds it would or should recover but if the pump is not delivering and the pushrod is worn it might not.
I would start eliminating things, starting with fuel delivery, then move on to electrics...or we could be bouncing around theories for a while

[vanisveryrusty]

Thanks Kev
I have ordered myself some bits anyway:
Fuel pump and pushrod, upstand.
Fuel filter
HT Leads
Plugs
Distributor Cap.

Plus a clean out of the carb, and a check of the choke mechansism

If that lot doesnt fix it I shall be very surprised !!!!!!!
Shall start with the fuel side due to tank being disturbed.

[vanisveryrusty]

Well I know what its not :
HT leads
Distributor cap
Rotor arm
Timing
Coil
Plugs
Fuel Pump
Carb settngs and choke etc.


It runs Ok when cold, then when its warm, after a short while it starts backfiring badly and max speed drops to 10mph.

Any ideas?
Valves, springs, headgasket ?
Guessing but at a loss.
Compression test a good idea as a next step ?

[BOXY]

Could it be a cracked inlet manifold opening up as it gets warm?

[mark]

^^^^whs......or its loose or gaskit is u/s or ign amp. start it and spray wd40 or similar around the in's and listen for a change in the engine note, for the back fire. other for power loss.

mark

[Ian Hulley]

The little cone filter in the fuel inlet is a likely candidate ... our's was very mucky even though I change fuel filters regularly (and free to remove and blow out with WD, canned air or similar)

Ian

[vanisveryrusty]

The little cone filter in the fuel inlet is a likely candidate ... our's was very mucky even though I change fuel filters regularly (and free to remove and blow out with WD, canned air or similar)

Ian

Thanks Ian but that one was clean.
Still stumped.
Thanks for the manifold leak ideas, ffolks.
Will check that.

[vanisveryrusty]

^^^^whs......or its loose or gaskit is u/s or ign amp. start it and spray wd40 or similar around the in's and listen for a change in the engine note, for the back fire. other for power loss.

mark

Thanks Mark and a fe questions for you :
What gaskit ?
Inlet manifold gasket?
Or head gasket ?
Or possibly both............?
What does the ign amplifier do ? never even considered that in the scheme of things.
This happens at high revs when stationary, or under load up hills.
Once it has started it doesnt go away until its all cooled down again.
Plugs are very sooty and yet carb mixture is correct, Co2 checked et.

[kevtherev]

All the vac pipes ok
including the servo hose?
now suspecting a weak mix after the choke is off.

[vanisveryrusty]

Thanks for the input Kev,
All the vac pipes are OK, no signs of leaks,
The carb was Co2 checked with the choke off and it was OK, that was at idle.
The fault, however appears only under load or high revs.
weak mixture = misfire, yes I can follow that,
What really stumps me is that the plugs are very sooty ,straight after fitting, and i ould expect that on something running rich not lean.
The carb was set up by a very well known carb specialist, so I am 100% happy the actual carb is OK.
This idea of a cracked inlet mnifold opening up when it gets hot is interesting though.
Get a fair amount of condensation and smoke out of exhaust also.
No signs of overheating.
Compression test tomorow.
Any ideas welcomed.....................

[mark]

carb/ manifold, head/manifold and if still in doubt give the vac pipes a spray, when the ign amp is breaking down it is almost always as described

mark

^^^^whs......or its loose or gaskit is u/s or ign amp. start it and spray wd40 or similar around the in's and listen for a change in the engine note, for the back fire. other for power loss.

mark

Thanks Mark and a fe questions for you :
What gaskit ?
Inlet manifold gasket?
Or head gasket ?
Or possibly both............?
What does the ign amplifier do ? never even considered that in the scheme of things.
This happens at high revs when stationary, or under load up hills.
Once it has started it doesnt go away until its all cooled down again.
Plugs are very sooty and yet carb mixture is correct, Co2 checked et.

[vanisveryrusty]

Cleaned the ignition amplifier contacts ( waiting for a new one )
Cleaned the ignition amplifier to coil contact on the coil end ( waiting for a new coil)
Topped up the oil from the minimum mark with pint that was under the rear seat, ( no oil warning light showing when driving)

Did the same route as yesterday................................... no symptoms at all.

Oil too low, causing hydraulic tappets to not work properly, causing misfire or partial seizure of valves etc...................... ?
Or was t the cleaned up contacts on the amplifier and coil?
Or will it come back

Thanks for all the help so far anyway.
Hope the information might help others.

[kevtherev]

Re sooty plugs
a weak spark, mixture or misfire will cause sooty plugs.
any poor burn of the fuel mixture will result in soot at low rpm/cold engine.

Plug colour is only really of any intrest at high rpm after a longish run.

[Ian Hulley]

I would be considering the coil too
A poor coil will get hot..and then the spark gets weak and intermittent, causing power loss

I'd still be considering the above ^^

They tend to break down when hot and/or under load .... early or late coil ? I have a spare late type here in darkest Derbyshire you could borrow to test if that helps ?

Ian

[vanisveryrusty]

repeated post. deleted.