Carb problem, wont stay running.

jax911 · 07-21-2011, 05:13 PM

Replaced the CIS on my 3.0 with a set of Zeniths (lets not talk about why just yet) yes rebuilt with new venturis, jets, etc. carbs came off a running car one year ago. Install went great pumped in some new gas through new filters, car started and ran great for about 30 secondsand then seemed to starve for fuel and died, gave it 3-4 pumps fired up ran for maybe 10 seconds then died again. I then waited for about a half hour while trying to process, 3-4 pumps of gas fired up and ran for about 30 seconds again and the died again could not keep it running.
Seems like it is starving for fuel, where should I start?

dipso · 07-21-2011, 06:31 PM

It's a fuel delivery problem.
Check for a kinked line or maybe even the pump.
Something is disconnected or bent.

Joe Bob · Joe Bob's Garage

Carbs have a baseline set up?

Return line or not?

5 PSI pump or CIS pump with regulator?

Clean fuel filter?

dipso · 07-21-2011, 07:28 PM

Ah hah! Eureka!

I think you have your inlet and outlet fuel lines crossed.

1QuickS · 07-21-2011, 08:43 PM

OK, I'll play. The air correction jets and the fuel check valves for the accelerator pumps are interchangeable, did you get them swapped during the rebuild?

Also, fuel getting to your accelerator pumps means fuel delivery to the fuel wells, there's a small chance of your idle jets getting blocked with crud or old gas in the jets. Clean out the idle jets.

I assume you tried to keep engine running by pumping accelerator after it starts?

jax911 · 07-22-2011, 01:40 AM

Thanks for the response everyone.
Fuel delivery to the carbs does not seem like the problem, its somewhere inside.
I tried running it again and same thing. First time I could hear and see gas coming out of the sqirters and started nicely but then (ran out of gas) stalls. The second time I tried doesnt look like theres as much gas coming out of the squirters and runs only for a few seconds. Could this be a float problem, either stuck or wrong level?
I checked the jets and all looks clear.

1QuickS · 07-22-2011, 07:13 AM

If this is a new installation then I suggest you have a look at my Tech web page for guidelines for initial setup and starting:

Weber Carbs Technical

Have you checked that fuel delivery pressure is 3 to 3 1/2 psi? Have you checked float levels, these are best set on a running engine but until then check them with engine off. If fuel pressure is too high you may be getting a way too rich idle mixture and killing engine that way. The CIS fuel pump delivery pressure is way too high for carbs, PMO sells a regulator that will solve this issue. It could be that initial starting is with less than fully filled float bowls and second starting attempt the fuel pressure is beginning to flood the bowls and enrich the mixture to a point that it won't burn.

You will need to get a float level gauge and an air flow meter (I like the STE the best of what I have tried) for your future tuning efforts.

Again, the air correction jets and the fuel valves for the accelerator squirters may be swapped, if you rebuilt the previously running carbs then it could happen, one type is a check valve and the other is a metered jet.