Weber DGV carb help......one just quits!

[MikeyZee]

Hi All,

My son has a 72 240z with a L24 and dual Weber DGVs. We have been having issues with these lately. I have rebuilt these carbs and after they were rebuilt they worked great for about 3 days. When we installed them after they were rebuilt we also put on a new filter and replaced all the soft fuel lines under the hood. The fuel filter appears to be a newer one so I didn't replace that one but I did add an electric one back by the tank. What will happen is that the front carb will just stop spraying gas at random. Maybe it will run for 2 hours maybe 3 days maybe 20 minutes. On Saturday the front carb decided to quit spraying gas. The temp was maybe mid 70s. We had the car towed to a friends house and swapped the front and rear carbs. ok....the one that quit still would not work on the rear but the front worked. The next day I took apart the top of the carb that failed the day prior. Blew out the fuel inlets and was able to get fuel spraying from it....yee haw! Both carbs were spraying. I made sure timing and idle were set (auto 1050 in p). I used the synchrometer and dialed in the carbs. After about 15 minutes the front carb stopped spraying. Hmmm? Maybe there is crud in the line that feeds that carb. I blew all the hard lines out with compressed air. The fuel in the line came out and about equal amounts of air from the front and rear feeds. Again I took the top off the troubled carb it was full of gas (it was on the first carb too). I sent some compressed air through it and again got it working for about 20 minutes. Then the front carb quit spraying again. It's always the carb I have in the front position. The screens in the carbs had nothing in them blocking flow either. I have also tried it without the electric pump with the same result. I have ordered a new mechanical fuel pump on order and plan to criss cross the lines that go to each carb......that is the next step. Has anyone had this issue? Any other troubleshooting advice? Maybe a fuel pressure reg/guage would help?

Thanks for any help or advice!