Power loss

Post by **egsj** » Wed Dec 31, 2008 3:13 pm

My traveller's losing power from time to time. It was a bit scary on a dual carriageway last week when I was going at about 60 mph, flooring the accelerator in fourth gear, and then dropping in a matter of seconds down to 20 mph, then to a trickle. Luckily, I was able to pull over safely - and was very glad to have had hazard warning lights recently fitted! Being a newbie with little very little technical knowledge or confidence, I called out the RAC. Their chap (very helpful and thorough) suspected the fuel pump and spent an hour cleaning and reassembling it. The mog carried on fine. Two days later, the same thing happened. The Christmas closure was over and I was able to get a new fuel pump fitted. But the power loss has happened a couple more time since - not as dramatic, just a draining away from 60 to 50 to 40 or so. Could this be a carb or coil problem? Or could there be fuel tank debris intermittently clogging the system (maybe from the car having been run on near-empty at some point) and being sucked through from the fuel tank?

I don't supsect my alternator or battery as each of these is new and the problem pre-dates my having changed them. And the engine itself is only four or five years old.

I'll be popping to my good local specialist mechanic in a couple of days, but I just thought I'd air the problem here first to see what theories come back...

Happy new year to all!

Jamesy

Post by **dalebrignall** » Wed Dec 31, 2008 3:44 pm

did you have a look at the filter in the pump,that will tell you if you are getting muck from the fuel tank.as you look at the pump,put your hand underneath you will feel a brass nut,undoo it and the filter should come out.

Post by **egsj** » Wed Dec 31, 2008 3:55 pm

Useful tip. No, I haven't. I'll check that. Thanks.

Post by **PSL184** » Wed Dec 31, 2008 4:46 pm

Check the fuel level in the float chamber next to the carb. It may be the valve sticking and stopping fuel from entering the chamber intermittantly. You can usually blow these out with an airline to remove any muck and debris.

Post by **crossword** » Wed Dec 31, 2008 5:36 pm

This sounds very similar to a problem which I've had several times , it has always been OK after cleaning out the muck in the float chamber . On my most recent occasion I removed the carb , separated the dashpot assembly & blew air down the jet assembly . I have also added an inline filter between pump & carb which should remove muck before it reaches the carb . ( As should that in the pump .)

Good luck with it.
Andy

Post by **Peetee** » Wed Dec 31, 2008 5:58 pm

Could be carb icing up.
If you have a standard air filter check the assembly is sound and there are no gaps to let air pass. If you have a sports filter like a K&N or chrome pancake then it is more likely to occur.

Post by **bmcecosse** » Wed Dec 31, 2008 8:46 pm

Could be vacuum developing in the petrol tank -if the filler cap breather is blocked. Next time - try taking the cap off and listen for a hiss as air rushes in. Otherwise - could well be carb icing (more likely on cold/wet day) - or just a loose connection on the coil or dizzy.

Post by **simmitc** » Thu Jan 01, 2009 12:54 pm

Does it sound as it it is mis-firing when it slows down? If it is still firing on all four cylinders then it's likely to be fuel, but if you're losing 1 or two cylinders then I'd suspect the ignition side, or even a valve problem.

Post by **egsj** » Fri Jan 02, 2009 11:26 am

There's no misfiring sound, so I guess it's a fuel issue...

Thanks to all of the above for extremely useful advice. I'll run all this by my mechanic and work through the possibilities. It's great to be learning new stuff, and invaluable to have a supportive site like this.

Happy new year to all!

Jamesy

Post by **simmitc** » Fri Jan 02, 2009 12:23 pm

A couple more ideas:
Check that the piston in the carb is moving freely: Remove the air filter and peer into the carb. You'll see the bottom of the piston. Using a finger, raise it all the way to the top and then let it fall back. It should be a smooth, free movement with no jerking or rough spots. I had a piston sticking once, and it gave the symptoms you describe.

When you get the power loss, does the car run freely and the engine speed up when you declutch? Just an "off the wall" thought, but a brake sticking on would make everything slow down. Do you have standard drum brakes or has it been converted to discs?

Post by **egsj** » Fri Jan 02, 2009 12:52 pm

As I recall, de-clutching didn't make any difference. The car's had the disc brake conversion.

Post by **simmitc** » Fri Jan 02, 2009 2:18 pm

With discs and servo it is essential to modify the master cylinder by removing the "top hat" washer. If this isn't done yhen the brakes can come on by themselves, which would certainly slow the car down! Once the engine stops and the vacuum is released, all goes back to normal. However, if the car rolls freely and de-clutching makes no difference to the engine speed then it's unlikely to be the problem here.