Re: 50 Clipper Project - Fuel pump issue help needed

Posted by HH56 On 2019/5/29 10:08:38

A few possibilities. One many have had issues with is the tanks need to have a vented cap. Modern non vented caps will allow the pump to pull a partial vacuum in the tank and stop flow but that usually takes a few minutes of running before the vacuum is enough to equal pump suction..

Another issue is the condition of the steel line. If it has been crushed or rusted somewhere or developed pinholes the pump cannot pull fuel or can only pull air. The short rubber hose connecting the pump to the steel line is a known issue if it is the old original hose. Age can deteriorate the inner lining and block flow. Can you remove the hose at the fuel pump and blow air thru the line to hear it gurgling in the tank? Also, if the line was completely empty it can take a lot of cranking to bring fuel to the front. Have you verified fuel is actually at the pump?

When you say the tank was cleaned am assuming it was taken to a shop and any rust particles completely removed? If not there could be some debris floating around that broke off again just from handling and suction has pulled it into the area where the pickup opening is located and has blocked the fuel line inlet opening. A worse scenario is using one of the sloshing compounds and then having the tank lay flat while that stuff dried. The depression in the tank bottom where the inlet tube sits can fill as the sloshing compound puddles and if it dried many tanks have been affected because the sloshing compound hardens and blocks the inlet opening.

If there are any filters make sure they are clean. Microscopic and tiny rust particles can quickly block any filters and even the screen in the base of the pump. The old (and optional) ceramic filters usually located next to the carb can look clean and air can be blown thru but if fuel has dried in the glass bowl a few times varnish can clog the filters to the point that fuel cannot get thru.

Last is the pump rebuild. Sometimes things happen even from reputable vendors and the pumps themselves are the culprit.