Technical Losing power

[Alex9721]

Hey. I managed to get my car running for first time this year - which was fab, if only for a mo. With a jump start I got the car running but within a couple of miles the power dropped away and the car stopped. I struggled to get restarted. Managed to crawl home and have since changed the spark plugs, air and fuel filter, but car appears to lose significant power within a mile or so - it appeared to start fine on my drive after I did the work and my car's nose was up as I have a sloping drive. The engine appears to labour in second, third and fourth and on a short run and does not maintain power. I think that it might be fuel pump? Would be interested if any advice on whether you think the same, if so whether pump can be repaired - are there kits? or if it needs replaced or any other thoughts on the culprit. Thanks (non mechanic) Alex

 

[the hobbler]

Hey. I managed to get my car running for first time this year - which was fab, if only for a mo. With a jump start I got the car running but within a couple of miles the power dropped away and the car stopped. I struggled to get restarted. Managed to crawl home and have since changed the spark plugs, air and fuel filter, but car appears to lose significant power within a mile or so - it appeared to start fine on my drive after I did the work and my car's nose was up as I have a sloping drive. The engine appears to labour in second, third and fourth and on a short run and does not maintain power. I think that it might be fuel pump? Would be interested if any advice on whether you think the same, if so whether pump can be repaired - are there kits? or if it needs replaced or any other thoughts on the culprit. Thanks (non mechanic) Alex

When you removed the spark-plugs (for renewal) what colour were the plugs that you removed? If they were very black, it might be that the "choke" is staying on and therefore the engine is running very rich. This scenario can also be caused by a punctured float in the carburettor.

 

[Alex9721]

Hi. Thanks for replying. The spark plugs were black but otherwise in good condition. I have tended to keep the choke open a while, closing it progressively as I have found that if I close the choke "too soon", the car idles at progressively lower revs and then stops. Generally, should I look to reduce the choke more quickly - in warmer weather, or try starting with no choke?

 

[the hobbler]

Hi. Thanks for replying. The spark plugs were black but otherwise in good condition. I have tended to keep the choke open a while, closing it progressively as I have found that if I close the choke "too soon", the car idles at progressively lower revs and then stops. Generally, should I look to reduce the choke more quickly - in warmer weather, or try starting with no choke?

Try using the choke for less time----the black spark-plugs would indicate that the engine is running rich. As I mentioned earlier, also check the condition of the float in the carburettor. Modern fuel attacks the solder of a brass float, and if this has happened, petrol will get into the float which will stop floating and cutting of the fuel (via the needle valve) as and when required. You can't really repair a float---so if the float 'rattles'when you shake it (because there is fuel in it), you will have to fit a new float---not a difficult job and can be achieved with the carburettor left in place..

 

[Alex9721]

Thanks for explanation on choke and carb. Really appreciated

 

[Ant Knox]

Thanks for explanation on choke and carb. Really appreciated

If you still have it, try using the hand throttle under the dash centre for warm-ups. The 'choke' can potentially wash out the bores of oil when left open for extended periods on start up, whereas the hand throttle will not.

 

[the hobbler]

If you still have it, try using the hand throttle under the dash centre for warm-ups. The 'choke' can potentially wash out the bores of oil when left open for extended periods on start up, whereas the hand throttle will not.

Word of warning---you must NOT use the hand throttle as a "throttle" when the vehicle is on the move---it is NOT a "cruise control" Only use it when the vehicle is stationary, and out of gear.

 

[Alex9721]

Thanks Ant. I think it still has the hand throttle as the previous owner mentioned it but said I should steer clear of it. I'll give it a try.

 

[fiat500]

Thanks Ant. I think it still has the hand throttle as the previous owner mentioned it but said I should steer clear of it. I'll give it a try.

They might have said that because the internals of the mechanism are a bit crude, and things might get jammed if it hasn't been set up properly.

 

[Noah500]

The hand throttle thingy doesn't act like a modern cruise control because it doesn't 'switch off' if you brake... could be nasty if you tried to use it as such!

 

[fiat500]

The hand throttle thingy doesn't act like a modern cruise control because it doesn't 'switch off' if you brake... could be nasty if you tried to use it as such!

I consider it more to be a "throttle lock". The way I use it is to select the correct amount of engine speed on the foot pedal, and then I carefully put the hand device to catch at that level.

If you examine the way that the two cables interact, the engineering of the hand cable is not really designed to take any strain from the friction of the foot throttle mechanism and return spring. The original spec. cable may have been a bit more resilient, but modern copies (which most cars will have by now) are a bit frail.

 

[Alex9721]

Thanks - appreciate all the posts. Good to have an understanding of how the hand throttle is being used

 

[Ant Knox]

Just to clarify my post, I was suggesting to use the hand throttle for stationary warm-up only! I only use it when i've pulled the car out of the garage and while i'm faffing around with doors, checking lights etc. (Pre-flight checks).
As others have pointed out, it would be foolish to use the hand throttle whilst driving. If you've ever played with it, it's immediately obvious how vague and crude the system is in any case, which should be warning enough!
All the best.
Ant

 

[Alex9721]

Got it. Thanks again

 

[Goldnrust]

I have tended to keep the choke open a while, closing it progressively as I have found that if I close the choke "too soon", the car idles at progressively lower revs and then stops.

This is normal operation. When the carb is adjusted right, I would expect to need to use full choke for a cold start, then after 15-30 seconds you can bring the choke down to around half and you can start driving. Letting a car idle up to temp is not the best way to warm it up (unless we're talking about pre-war cars using splash lubrication and single weight oils).

After a mile or two you can turn the choke off. This will con-inside with hints of warmth coming through the heater, suggesting the engine is getting warm. If you turn it off a bit soon you'll feel the engine just feels a bit flat.

Black plugs do show a rich condition, but if you've only been doing short diagnostic drives, not getting off the choke much, or if the plugs simply haven't been cleaned for a long long time, then it can be a red herring.

When the car starts to loose power, if you pull over and let it idle for a minute or two, does it pick back up and run ok for another mile or two? If it did, that would be indicative of a fuel supply issue, where a weak pump or partially blocked lines/tank do not allow enough fuel flow to keep the carb topped up when working the engine hard, but when the engine is only sipping the fuel at idle then the carb can refill.

If it doesn't then I would suggest checking the quality of the spark once the engine is showing the problems. Some coils when beginning to fail can show up problem when hot only.

I would also suggest checking the valve clearances. If they have closed up, which is not unheard of in these engines, then you might find that the valves are starting to be held open as the engine warms up and the loss of compression is causing the loss of power.

 

[fiat500]

Just to clarify my post, I was suggesting to use the hand throttle for stationary warm-up only! I only use it when i've pulled the car out of the garage and while i'm faffing around with doors, checking lights etc. (Pre-flight checks).
As others have pointed out, it would be foolish to use the hand throttle whilst driving. If you've ever played with it, it's immediately obvious how vague and crude the system is in any case, which should be warning enough!
All the best.
Ant

"it would be foolish to use the hand throttle whilst driving" ......but can be quite amusing in the right circumstances when not on the King's Highway.

 

[fiat500]

I agree with @Goldnrust about the "choke". Maybe it's something about the fact that it isn't technically acting as a conventional "strangling" mechanism, but I find that once I'm underway with the momentum of the road, I can put the lever down immediately with no apparent effect on the performance given that initial speed is obviously quite low.