Loss of power when fuel is low

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Loss of power when fuel is low

Postby Stuart Paterson » Mon Sep 28, 2020 18:14

Hello all,

I've got an unusual issue that I'd like to sort. It's the most annoying kind of issue - one that you can live with but doing so means a sub par experience.
I semi regularly drive a 120 mile round trip in the cappo, meaning I use about half a tank each time. So I usually fill up on the way out and experience the issue on the way home.

With less than 10 miles left - the best leg of the return journey - the cappo starts to lose power under WOT. The issue is repeatable - the car is fine at WOT up to around 5000rpm, then power is cut and the car doesn't want to creep past this rpm. Shifting up a gear clears the issue until I reach the same rpm. It feels like fuel cut, just more aggressive since it's occurring at peak torque.

I had a similar issue last year when I took it to a track. On a left hand hairpin the car would lose all power and take a second or two to recover. It had a full tank at the time. I replaced the fuel filter (some pretty nasty looking, orangey fuel came out the tank side of it) and the issue went away.

So I expect this is a fuelling issue, most likely some rubbish in the tank blocking the inlet.

My questions to you all are, has anyone experienced a similar issue? Any idea what's in my tank? Can I syphon the tank empty out of the filler cap? Or should I cut to the chase open the tank up?
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Re: Loss of power when fuel is low

Postby Ian Linden » Fri Oct 02, 2020 16:44

I agree it's something in the fuel tank. According to the Service Manual, removing the tank looks like a major job. It says you can empty the tank through the filler pipe.

Having done that, I wonder whether you could just remove the tank service hole lid, and clean the tank out with a vacuum line?
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Re: Loss of power when fuel is low

Postby Timothy North » Sat Oct 17, 2020 13:54

I suggest being hesitant to clean the tank out other than by removing it and washing out or having it done professionally.

As Ian says removing the tank is a big job but not actually difficult nor particularly time consuming. I did this myself a couple of months ago.

The rear suspension must be dropped along with the differential. Fortunately the brake callipers can be unbolted and tied out of the way without breaking the hydraulic lines. Thereafter it is a matter of disconnecting the propshaft and drive shafts, disconnecting the damper/spring units at the bottom end and unbolting what is in effect the rear subframe which can be dropped on a trolley jack under the diff. It helps, but not essential, if there are two people doing this, one to control the jack, the other to hold the assembly steady. The whole thing can easily be wheeled away. Dropping the tank is then straightforward.

Removing the tank provides access to the pipework sitting on top and running down the front which is likely to be corroded.

Changing suspension bushes, diff mountings with the suspension removed is a lot easier too.
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Re: Loss of power when fuel is low

Postby Timothy North » Mon Oct 19, 2020 09:55

Having thought about my last post I was wrong in suggesting that the drive shafts have to be disconnected. Only the propshaft needs to be disconnected. I also disconnected the ends of the anti-roll bar so it could be moved out of the way of, I think, the calliper bolts.
I have a photo of the suspension removed from the car but do not know how to attach it here.
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Re: Loss of power when fuel is low

Postby Ian Linden » Mon Oct 19, 2020 13:52

It is a bit involved. I see you have created your own gallery. Open that, and click New Image. Scroll down and click Choose File, then navigate to the image file. Having uploaded the file into your gallery, click the image to expand it, then right-click it and choose Copy Image Link.

Now go to your post, click the Img button above the text box, and paste (CTRL-V) the link into the post.

That should work.
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