Fueling sucks, not pump/filter. (4age with 30/32 weber downdraft)

[undercoverninja]

Hey guys, I have really bad fuel delivery, it runs lean at high throttle, backfires, surges, etc. Was all tuned and running perfect, had a cracked piston/rebuild, then started having the fuel issues. I have replaced the fuel pump and filter, and inspected the soft lines/fittings, but I'm stumped now.

I'm thinking:
- Fuel pickup
or
- Clogged hardline
or
- Something up with the carby

Anyone got ideas?

[Jim621]

have you tried removing the fuel line from the carbs and doing a flow test on the fuel pump?

[undercoverninja]

Measure the amount of volume/time? I think I'll do that yeah

[Jim621]

yeah, just get a 2L coke bottle and fill it up and time how long it takes..
best to disconnect the fuel line after the regulator to ensure the fuel pump is working at 40PSI or whatever the normal working pressure is.
You should disconnect the starter motor so don't drain your battery as you will need to switch the ignition to 'start' to get the fuel pump to run.

[undercoverninja]

So I did a flow test, it's a carby setup with a facet pump no reg. It took 52 seconds to pump 1l, which seems like a long time considering the pump is rated at 180lph

[undercoverninja]

It has been suggested that it could be timing as well, I check the valve and it's sweet, will check ignition when I get my timing light back.


EDIT: All fixed. Fueling was an issue, but the timing was way out >_> i kinda assumed the mechanic I went to was capable of using a timing light.