Thomas Vaughan
Member
Please can someone watch this video on my Instagram and help me understand why the engine jumps like it does?
Thanks
Thanks
Technical 126p elx newly built engine
- Thread starter Thomas Vaughan
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Technical 126p elx newly built engine
Slight misfire? I assume as revs increase slightly it smooths out.
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Thomas Vaughan
Member
Yes, correct. I'll investigate a misfire. Thanks
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Thomas Vaughan
Member
I've been busy trouble shooting.
Strong spark on both plugs
Fixed warped carb base and carb.
Adjusted float
Dismantled carb and cleaned, fitted new gaskets.
Adjusted tappets
Rerouted return flow line.
Mixture screw out 2 turns
Then I replaced all the fuel lines with clear hose....and noticed that after the fuel pump there are air pockets in the line to the carb. Watch THIS VIDEO
Fuel to the pump, and from the return is steady and solid.
Could it be a damaged diaphragm?
Strong spark on both plugs
Fixed warped carb base and carb.
Adjusted float
Dismantled carb and cleaned, fitted new gaskets.
Adjusted tappets
Rerouted return flow line.
Mixture screw out 2 turns
Then I replaced all the fuel lines with clear hose....and noticed that after the fuel pump there are air pockets in the line to the carb. Watch THIS VIDEO
Fuel to the pump, and from the return is steady and solid.
Could it be a damaged diaphragm?
If possible and safe to do so can you run it from a gravity fed fuel supply straight to the carb in your garage just to prove/disprove if air or faulty pump is the answer.
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Thomas Vaughan
Member
Great idea! Will try that this evening!
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Thomas Vaughan
Member
Tried the direct feed method and messed up. Didn't cap the removed supply line and emptied a liter of fuel over my carpet, the fuel in the jar I was feeding it with ended up going out the open return line also on the carpet. I then removed the fuel pump, dripping more fuel on the carpet, then after disassembly knocked the jar over on the carpet.
Don't work with fuel when tired.
Going in to watch crap on tv now.
Fuel pump confirmed dead.
Don't work with fuel when tired.
Going in to watch crap on tv now.
Fuel pump confirmed dead.
Sorry to hear that. You did note my disclaimer "If possible and safe to do so can you run it from a gravity fed fuel supply"
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Thomas Vaughan
Member
The jar of fuel gravity fed the carb perfectly, but my error was not thinking about the existing fuel lines, disconnected but still attached to the pump.Sorry to hear that. You did note my disclaimer "If possible and safe to do so can you run it from a gravity fed fuel supply"
I knocked the jar over with my foot after placing it safely back on the floor.
Keep the fire extinguisher handy
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Thomas Vaughan
Member
Still uneven idle and dies if I touch the accelerator lightly or close the choke.
Flooring it keeps it alive but doesn't even out the engine.
New fuel pump fitted.
Cleaned, adjusted float, etc, and fitted new gaskets to the carb.
No difference if I...
Remove the fuel filler cap
Dipstick
Air filter
If I pinch the return flow closed
Someone must have an idea what is causing this?
Flooring it keeps it alive but doesn't even out the engine.
New fuel pump fitted.
Cleaned, adjusted float, etc, and fitted new gaskets to the carb.
No difference if I...
Remove the fuel filler cap
Dipstick
Air filter
If I pinch the return flow closed
Someone must have an idea what is causing this?
OP
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Thomas Vaughan
Member
Have you got a clip on strobe timing light, if so try it on one lead then the other and possibly on the one from the coil to see if when the engine kicks it is affecting the spark, just a thought to see if it is a spark issue.
Also, and it may sound odd but see if banging the ignition coil with the back of your hand affects it when running, I had a Ford Zephyr many years ago that did that.
Also, and it may sound odd but see if banging the ignition coil with the back of your hand affects it when running, I had a Ford Zephyr many years ago that did that.
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Thomas Vaughan
Member
Thanks.
I do have a clip on timing light, but it's got electronic timing not a distributor.
I do have a clip on timing light, but it's got electronic timing not a distributor.
Same principle though on HT leads.
By the way some have issues related to electronic ignition.
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Thomas Vaughan
Member
Thanks, I'll give it a go.
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Thomas Vaughan
Member
Another question,
Should the fuel lines and fuel filter be totally full of fuel, with no air?
Should the fuel lines and fuel filter be totally full of fuel, with no air?
Not unusual to see a little air, but if concerned check all the hose fittings etc and older plastic clear braided hose tends to go brittle and hard to seal.
However if you managed to run vehicle with the gravity tank of fuel and issue was still the same then air not the problem.
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Thomas Vaughan
Member
I'm at a loss now.
I've cleaned the carb inside and out
Adjusted the float correctly
Flattened gasket surfaces and new gaskets all round
New fuel pump, filter, lines, clamps.
Checked timing
Checked plugs/spark
After removing the plunger on the automatic idle cutoff valve (which I suspect was dead and always closing the fuel passage) I really thought this would be it.
It now idles without choke but if I even touch the accelerator the engine does.
I really don't know what else to do.
I had my first "sell it and buy something else" moment.
I've cleaned the carb inside and out
Adjusted the float correctly
Flattened gasket surfaces and new gaskets all round
New fuel pump, filter, lines, clamps.
Checked timing
Checked plugs/spark
After removing the plunger on the automatic idle cutoff valve (which I suspect was dead and always closing the fuel passage) I really thought this would be it.
It now idles without choke but if I even touch the accelerator the engine does.
I really don't know what else to do.
I had my first "sell it and buy something else" moment.
As a test with it idling smoothly, if you partially cover the top of carb restricting air with your hand so making it run richer, will it slowly rev up, indicating a fuel/carb issue. Don't completely block carb top as the "suction" will damage the gaskets.
If no joy try slackening the distributor clamp and advancing the timing a little, whilst trying to increase the revs to see if it makes a difference.
Only gently increase revs a little at a time to prevent a backfire.
Sorry I forgot you have electronic ignition, so previous may be invalid, is it "wasted spark" what triggers it and how does it advance the timing? Is there a chance the electronic ignition is faulty?
Try to listen to the engine to feel what makes it sound better.
If no joy try slackening the distributor clamp and advancing the timing a little, whilst trying to increase the revs to see if it makes a difference.
Only gently increase revs a little at a time to prevent a backfire.
Sorry I forgot you have electronic ignition, so previous may be invalid, is it "wasted spark" what triggers it and how does it advance the timing? Is there a chance the electronic ignition is faulty?
Try to listen to the engine to feel what makes it sound better.
