loss of power at speed

[pcoleman]

travelling down our local dual carriageway yesterday at around 55/60 mph and started to loose power,not a miss fire as such, but you can feel it's not firing right as there's bit of "vibration" of sorts from the engine and power/speed starts to drop away. You cant power through it as it just progressively dies regardless of gear, managed to make it to the next layby where the engine stopped completely and ignition light came on. Left it a few seconds then restarted the engine, ran clear and proper so waited for a clear section of road in case it died again, and pulled away no problem. Ran ok on the return journey too. Thinking back same thing happened last year when son and heir was driving it, so we stopped and I took over and nothing untoward happened after.

In summary, it seems to fail when first starting a sustained run at over 50 mph for 10 minutes or less, stop and restart the engine and seems ok, very odd. Most of the usual suspects are new or have been recently changed ie. Aldon coil, Magnecor or similar leads, plugs are recent and properly clean/gapped, carbs are refurbished items and diaphragms are ok (checked today) electronic fuel pump and new filters all done last year or so and no crap in them.

It feels like fuel starvation but,as I say, pump is couple of years old and electronic replacement type,ticks away merrily and fills the engine bay filter on start up very quickly. Only other thing is the electronic ignition is an older lumenition type which was on when I had the car 10 years ago so must be >10 years old. Car will tootle about all day long going up and down the gears/speed range but doesn't like to cruise for long.

funds are limited now so dont want to start spending on the wrong things,any suggestions gratefully accepted.

regards. peter

[Paul Roberts]

Vacuum forming in fuel tank? Check tank breather.

[pcoleman]

crickey paul, I was just having the same conversation here !!

[Lingen]

Peter. I suffered from something similar last year, and it turned out to be the old Piranha ignition giving out. I have now fitted a Powerspark unit, and the improvement is spectacular. They are about a quarter of the price of the Lumenition ones, so it is no hardship to buy a spare while you are at it, in case of failure. It is also all out of sight under the distributor cap. And, no, I am not on commission with them!
Mike.

[milothedog]

Peter.

I suffered from something similar last year, and it turned out to be the old Piranha ignition giving out.

I have now fitted a Powerspark unit, and the improvement is spectacular. They are about a quarter of the price of the Lumenition ones, so it is no hardship to buy a spare while you are at it, in case of failure. It is also all out of sight under the distributor cap. And, no, I am not on commission with them!
Mike.

That's a worry Mike, I bought your old one from you as spare when you posted it on the forum for sale to carry around with me Please tell me it's not the same unit I bought from you

Ian

[milothedog]

That's a worry Mike, I bought your old one from you as spare when you posted it on the forum for sale to carry around with me Please tell me it's not the same unit I bought from you

Ian

Going back to your problem Peter, it sounds like a fuel issue to me. If the ignition was effectively acting as a rev limiter then it would recover quickly as you came of the rev's I would have thought.

[pcoleman]

Thanks for the responses guys, I will vent the tank first and give her a spin on Monday, cant tomorrow going see the vulcan fly

[GDPR]

Anyone considered corrosion in the inertia switch causing intermittent fuel pump power? Could do exactly as described . .,,

[Lingen]

No Ian, I can assure you it isn't! That one was binned. The was one you have was rescued off a car that was running perfectly well, but was also being changed to a Powerspark by the owner. He was taking the car abroad, and wanted to carry a spare, and the relative costs were the deciding factor for him.
I still think you should test it though if you are carrying it to get you out of trouble one day. It is now some time since it was in use, and I did say there would be a refund if it was faulty.
Mike.

[Staggard]

Anyone considered corrosion in the inertia switch causing intermittent fuel pump power? Could do exactly as described . .,,

nothingtoadd[1].gifI know this has nothing to do with this whatsoever but I wanted to use the smiley

[milothedog]

No Ian, I can assure you it isn't! That one was binned. The was one you have was rescued off a car that was running perfectly well, but was also being changed to a Powerspark by the owner. He was taking the car abroad, and wanted to carry a spare, and the relative costs were the deciding factor for him.
I still think you should test it though if you are carrying it to get you out of trouble one day. It is now some time since it was in use, and I did say there would be a refund if it was faulty.
Mike.

Thanks for the reassurance Mike.


Ian.

[flying farmer]

Rust flakes in the fuel tank can temporarily block the suction pipe. When turned off the rust will fall off the end of the pipe and sit there just waiting for the next time there is a demand for fuel.

Neil

[Stevekid1]

Peter,
I had the self same problem last year. Every time I got onto a dual carriageway and started doing a constant speed for around ten minutes, the car would suddenly start to loose power and I could not drive through it. In my case the car did not stop running when I stopped the car and would tick over ok but would not rev. After sitting for a short period with the car switched off, it would then start and run ok and if I stuck to side roads where the revs vary more regularly it was ok but ten mins on a dual carriageway and the same thing would happen. I also have refurbed carbs. Turned out to be a dodgy needle valve in the new carbs. Changed both and re-balanced and car has been perfect ever since. Don't rule them out just because their new.

Regards, Steve

[pcoleman]

Thanks for all the help chaps, this morning I've cleared the boot and removed the carpets and boards and think I've found the problem. When the car was restored 10 plus years ago the vent pipe from the filler cap has been connected to the drain hole in the boot floor and the vent pipe on top of the tank has the remains of a short rubber pipe attached which appears to have closed up somewhat. This must have been like this since the resto when a new boot floor was fitted along with new fuel tank, does explain why I sometimes smell petrol in the boot I will re plumb it in new pipe as I cant disconnect the "vent" pipe from under the tank. hopefully test run this afternoon.watch this space

[Lingen]

Sorry to be a spoil-sport, but that is how the pipes are supposed to be. The pipe on the tank must be blocked off. It is only there because the fuel injected estates used the same tank, and that is where the excess fuel from the pump returned to the tank. Block it off with a short length of hose and a short bolt or whatever. The breather and spill hoses from the filler, both go out of the boot, and discharge on to the road. That was fine in the 70s!
Mike.