Weber DCZ6 accelerator pumps

[tinbender]

I recently had my electric fuel pump rebuilt, and I have reinstalled it in my 330GTC #9411. My car has DCZ6 carbs. The pump runs and then slows as it has filled up the float bowls as it should. My problem is that when I pump the gas I am not getting any fuel sprayed into the carbs, and so the engine will not fire. I pulled the tops off of the carbs to make sure I had gas in the float bowls and there is about 1" of gas in there. It seems strange that all 3 carbs would have the same failure at one time. Any ideas?

Thanks,
Terry

[DWR46]

Terry: VERY common problem with today's ethanol fuels. The ethanol causes the Pump Delivery Valve (the screw that holds the Pump Jet into the top of the carb body) ball check to stick closed and not let gas flow to the Pump Jet itself. There is a ball in this "screw" and it acts as a one way valve to let fuel flow out of the jet, but prevents air being sucked back in when you close the throttle. When you shake the Delivery Valve, you should hear the ball rattle. Many times, you can open the throttles all the way and then get your hand under the float bowl and manually operate the rod that works the Pump Piston and get the ball to release by cycling the pump a number of times. Otherwise, you have to remove the carb top and Delivery Valve and "unstick" the ball with compressed air. I used to have this problem ALL the time, but finding a source for non-ethanol gas has pretty well eliminated the issue.

[tinbender]

Thanks Dyke. I will give it a try. I have never knowingly run anything except ethanol free gas, but I am taking the station's word for that.

[DWR46]

Terry: Are you using Marvel Mystery Oil? I can't prove it, but it appears to help, and I KNOW it has fuel Pump benefits.

[tinbender]

Dyke,

I am not, but I do use Sta-Bil Ethanol treatment. How much Marvel Mystery Oil do you use?

Terry

[DWR46]

Terry: The recommended amount on the container, 4 oz/10 gal gas. The big benefit is to make the valves in both the mechanical and electric fuel pumps seal better and avoid vapor lock at high ambient temps. It also does actually help with valve stem/guide lubrication. It was originally developed in the 1920s to prevent sticking valves as flathead valves are "upside down" and receive no oil to lubricate the stems.

[Jimmyr]

Like Dyke said the ball in that holding bolt is a problem. While you have the nozzle off to check the ball, also be sure the small squirter holes in the nozzle ends are open and clear, A small wire is an easy check and cleaning tool for this.

[Steve Meltzer]

If none of the accelerator-pumps are working, you are using non-ETOH fuel, and the accelerator pumps worked before the e-pump rebuild, you gotta be sure that what's up stream is working. I know you just had the EFP rebuilt, but I would verify that there is good fuel flow from that e-pump. I believe that Webers like to run about 4 PSI. I'd also run a long bottle brush through the fuel rail...they too, can get corroded, as did the one on my Daytona...tough to make a diagnosis there.

I take an empty one gallon coolant container, lay it on its side, and cut out a large section on the side facing you. Then, i disconnect the hard yellow fuel line that comes from the e-pump from its attached fuel rail. Now, with the ignition OFF, I put the open fuel line in the newly-created open coolant container. Next, have an assistant turn the key to the "run" position and turn on the e-pump via the dashboard switch; you observe the fuel flow into your newly-minted container. You'll soon know if you have good fuel flow.

If your fuel flow is good, I would remove the carb tops, as you did, and clean the squirters, emulsifiers, the little fuel filters, etc within an inch of their lives. Jimmy's idea of a thin wire is excellent, of course, and I also like to carefully blow compressed air the OPPOSITE WAY the fuel flows.

Hope I didn't embarrass myself here, jumping in the same thread as the real pros.
steve

[tyang]

I just had a 365GTC/4 come into my shop that wasn't starting. The fuel flow was fine, but what I eventually found out was almost all the needles at the inlet floats were stuck in the closed position. No fuel was being allowed into bowls at all. The combination of ethanol fuel, and what I believe was fuel stabilizer (the blue stuff) was leaving enough residue on the needles to stick closed. I had to take the carb tops off, and free what was stuck, but eventually got things working again.

I have found simply running these cars for 10 minutes (optimally 20 minutes or more, but in winter, is nearly impossible) once a month or so will keep things for gumming up.

Here's the video:
https://youtu.be/Wr1sOK3wlfk

Tom

[DWR46]

Tom: alcohol is a wonderful solvent. It will flush all the old dried varnish from fuel systems and leave it wherever it ( the ethanol) dries out (needle and seats) when the car sets for awhile. I used to have this ALL the time, but, amazingly, it seems Marvel Oil and non-ethanol fuels have caused the problems to totally disappear over the last three or four years.

[Steve Meltzer]

Is there a downside to spraying ether into the carb? It would provide a quick and dirty way to divide and conquer the holy triad.
I've heard it's bad for the engine, so, it's clearly notta long term solution; only a shortcut. steve

[Fasthound330]

I try to avoid the problem by spending stupid amounts of money on Sunoco Race fuel.

[DWR46]

Steve; Most "starting fluids" are not good for engines due to their tendency to provide "uncontrolled combustion". Also, you may get the engine running, but the accelerator pumps are still not going to work and the car will "fall on its face" when you try to accelerate.

[Steve Meltzer]

Yes, Dyke, I don't write as well as I should, but I only meant to run the engine 1 second to prove the ignition/spark part of the holy triad was present, and could thus be ruled out. If the accelerator pump squirters are AWOL, no amount of ether will save the day. steve

[Steve Meltzer]

Kevin, How do you use the liquid gold? Diluted? If so, with what and at what stoichiometry? Do you have easy access to non-ETOH fuel? steve