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+--- Thread: Loss of power under load (/showthread.php?tid=4748)
RE: Loss of power under load - "Slack Alice" Simon - 02-08-2020
Maybe a build-up of debris in the fuel pipe?
Put a plastic tube on the end uncoupled from the fuel pump, and blow it back into the tank.
RE: Loss of power under load - Chris KC - 02-08-2020
First thing I'd do is change the points (not just gap them).
RE: Loss of power under load - dickie65 - 02-08-2020
Overheating coil starting to fail ???
RE: Loss of power under load - David Stepney - 02-08-2020
I had a similar problem on the RP a couple of months ago. It turned out to be a choked fuel feed pipe from the tank to the pump. Fitted a new one and the problem disappeared! I understnad that it may be something to do with modern petrols corroding the lumen of a copper tube.
RE: Loss of power under load - Peter Naulls - 02-08-2020
Thank you for the suggestions. I have a day off on Tuesday, so plenty to keep me busy!
Peter.
RE: Loss of power under load - Greig Smith - 02-08-2020
Lace curtain wire - that plastic covered thin coiled wire that Beloved uses to hang lace curtain up behind your main drapes works a treat for feeding through fuel pipes & crankshafts & oil passageways.
Skin the white plastic off it & grip one end into the chuck of your battery drill or hand drill (No electric drills, they are too fast). Run the other end over a grinding wheel to de-burr it & put a bull nose onto it to make feeding it through passages easier. Then pour some paraffin or oil or Q20 / WD40 into your fuel pipe & feed the end of the curtain wire spring into your fuel pipe while running your battery drill slowly.
We now do this on all the crankshafts & engine blocks we rebuild & not just A7's. You will be amazed as to what will come out of the nooks & crannies in a seemingly 'clean' crankshaft. It's an easy thing to do to a fuel feed pipe - let us know what you find
Aye
Greig
RE: Loss of power under load - Peter Naulls - 10-08-2020
Nobody likes a question like this without a conclusion, so here's what I have (or haven't) found.
I stripped the pump and found it working fine - no problems with diaphragm or valves. I blew the feed pipe back to the tank and it didn't seem that there was any great resistance, also blew through to the carb. The following day changed the points and leads but the problem still persisted.
I tried to change the distributor cap but found that my spare one doesn't fit - it's a dizzy rebuilt by the Distributor Doctor and the base plate and cap are a larger diameter strangely. I think a problem here is highly unlikely however.
That leaves the head gasket as the only other thing I haven't checked and I believe the likely cause, however other events have since taken over and I have swapped cars so my special can get a bit of daily use in this recent fantastic weather.
Thank you again for all your input; working through the list of possible causes has been a worthwhile exercise.
RE: Loss of power under load - Nick Salmon - 10-08-2020
Peter - Is it a standard dizzy or electronic?
RE: Loss of power under load - David Stepney - 10-08-2020
Peter
When the RP played up (see my earlier post), I too was almost at my wits end. The problem first occurred on steep and long hills, when the car would 'run out of breath' after a long climb in the indirect gears. At first i thought it was fuel vapourisation. I checked everything, including blowing back the fuel line to the tank which appeared to be clear. Like you, I rebuilt the fuel pump - even had it to bits on the side of the road on one occasion and only changed the fuel line front to rear out of sheer desperation, as everything else (tank, pump carburettor) was either new or overhauled. Once the new line was it, the problem was solved and the car is now going as it should.
Hope this helps you.
RE: Loss of power under load - David Witton - 10-08-2020
Just a thought, try a separate earth to the distributor