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Fuel pump?
Posted: 29 Apr 2025, 15:32
by Welshclimber
Hi all, engine cut out while driving on the weekend and now won't start again. I'm thinking that the fuel pump might be the issue that there's no fuel getting through because it's turning over fine. Does anyone know of an easy way to check it? It's the mechanical version. I've taken it off and pressed the lever underneath and no fuel comes out but that's as far as I've got with it. Could also do with checking if the fuel filter is blocked I think.
Re: Fuel pump?
Posted: 29 Apr 2025, 15:47
by Smiffo
Pour a little fuel ( like a tablespoon or two in volume ) into the top of carb by taking the intake manifold off.
If it starts, then it’s a fuel problem.
If not, then electrical.
Re: Fuel pump?
Posted: 29 Apr 2025, 20:48
by Welshclimber
Before I even got to that I took the fuel line off between the pump and the carb and turned it over, plenty of fuel coming out of the pump. So must be electrical? Any ideas where to start?
Re: Fuel pump?
Posted: 29 Apr 2025, 20:54
by tobydog
For it to cut out suddenly whilst driving sounds possibly electrical; hall sender and ignition amplifier come to mind. I would check for a spark as well as fuel filter issues. Won't hurt to try some petrol or Easy Start as previously said....
Re: Fuel pump?
Posted: 29 Apr 2025, 21:00
by Welshclimber
Thanks, I’m not familiar with the hall sender and ignition amplifier, where can I look for those please? And what’s the best way to check the spark plugs? I did change them last year
Re: Fuel pump?
Posted: 29 Apr 2025, 21:08
by Welshclimber
Smiffo, please could you let me know specifically where the petrol should go to do this? I’m still learning my way around the engine bay. Do I take the 3 bolts out on top of the carb?
Re: Fuel pump?
Posted: 29 Apr 2025, 21:16
by Smiffo
Yep, that’s it.
3 nuts on the flat plastic bit on the top of the carb.
Underneath you see two chambers. Pour into one of those, so the bowl in the bottom half of the carb gets some fuel in it.
Don't go overboard though - just a couple of table spoons. You just want to see if it fires up for a few seconds.
Re: Fuel pump?
Posted: 29 Apr 2025, 21:22
by Welshclimber
Awesome thanks, I’ll try that tomorrow, kept some fuel from earlier testing to do it.
Now reading up on the electrical bits…
Re: Fuel pump?
Posted: 29 Apr 2025, 23:11
by tobydog
Welshclimber wrote: ↑29 Apr 2025, 21:00
Thanks, I’m not familiar with the hall sender and ignition amplifier, where can I look for those please? And what’s the best way to check the spark plugs? I did change them last year
Did you check the gaps when you fitted them?
Take care not to touch anywhere around the HT cap. You may get a painfull shock.
If you have a spare plug, take an HT cap off of one plug, connect it to the spare plug and ground the metal body of the plug to the engine and turn the engine over with the ignition/starter by someone else while you observe the plug to see if it's sparking. If you don't have a spare plug, take one out and do the same.
Again:
Take care not to touch anywhere around the HT cap. You may get a painfull shock.
Re: Fuel pump?
Posted: 03 May 2025, 14:28
by Welshclimber
Ok so tested the plugs and one wasn’t working so just changed all 4 to be sure. Tried a tablespoon of fuel straight on the the carb too and no luck. So as far as I can tell we have spark and fuel? Anything else you could suggest please would be most welcome!
Re: Fuel pump?
Posted: 03 May 2025, 21:13
by Smiffo
Hmmm.
Assuming new plugs have right gap etc, either fuel is stale ( E10 left too long ) or weak spark perhaps.
Easiest to check is fuel by just getting a couple of pounds worth of fresh.
Outside of that I would make sure good voltage exists at the coil and the terminals don;t look furred up, and then be into trying my good spares of coil and TCI, leads and dizzy cap one at a time.
If you have those, great, if not, wait for someone to advise a possible testing procedure before buying them.
Re: Fuel pump?
Posted: 04 May 2025, 08:28
by Welshclimber
Cheers. Fuel is ok it’s e5 and fresh fuel.
I don’t have spares to test but the ignition coil ohms reading isn’t what it’s supposed to be. I’ve put a fresh thread in the electrical section for that as I could do with knowing how to test the amplifier too.
Thanks for your help
Re: Fuel pump?
Posted: 05 May 2025, 18:18
by Welshclimber
Got hold of some easy start today and sprayed it on to the carb while turning over, it did start to catch for a second or two. Would this still indicate that it’s the ignition coil? I can’t seem to find the grey sticker one in stock anywhere! Is there any issue in fitting the green sticker type?
Re: Fuel pump?
Posted: 06 May 2025, 17:24
by Smiffo
I think green and grey sticker are interchangable, yes.
My understanding is one just gives a more powerful spark, so assuming everything else is good, I don't think it would matter much.
The easy start being used to get it firing is odd though.
Just trying to think this through a min. It doesn’t run on fuel, even when added into carb bowl, but starts to fire with easy start?
If yes, when you push throttle down, you get a squirt of fuel come out of the nozzle on the carb?
Re: Fuel pump?
Posted: 06 May 2025, 17:37
by Welshclimber
Good to know on they can be interchangeable. Interestingly, Brickwerks aren’t stocking any at the moment as the quality has dropped since the manufacturing has moved to South Africa.
So yes, it’s definitely catching for a second with the quick start spray, but not with fuel poured in to hell the carb. You can hear the fuel move when you press the throttle. I could check the visually too though with the top of the carb off to be sure?