Dodge1934 Posted December 30, 2017 Share Posted December 30, 2017 I`m finally getting around to cleaning up my original fuel pump on my 1919 Mclaughlin. The fuel pump is a stewart fuel pump. I`m trying to understand how it works. |I have attached pictures and hopefully they are sufficient for those who know to advise me. There is a "plunger that goes up and down into one of the openings on the top of the pump. I assume this plunger is supposed to block a flow of air or gas as the float goes up and down. I think there should be a small spring that would fit on the punger at the bottom end to keep the whole sealed when the plunger is up.It appears to me that without the spring the hole is never really sealed at all. There is also a collar on the plunger which would hold the spring from going to high . several questions 1 Is there supposed to be a spring on the plunger 2: if yes to above.... would a ball point pen spring work or would it be to strong 3: any other words of wisdom to offer on what you see Link to comment Share on other sites More sharing options...
keiser31 Posted December 30, 2017 Share Posted December 30, 2017 Check this out....it may help.... Link to comment Share on other sites More sharing options...
Guest Posted December 31, 2017 Share Posted December 31, 2017 See post 6 and 10 especially. Link to comment Share on other sites More sharing options...
Friartuck Posted December 31, 2017 Share Posted December 31, 2017 Based on my experience with my vacuum tank, yes there should be a spring. Think about how this operates: 1. Some fuel is needed in the outer chamber (tank) to get the vehicle running which creates vacuum (hence prime via the filler plug on top to prime if needed). 2. Vacuum draws fuel from the tank and deposits it into the inner chamber. The flapper on the inner chamber is pulled closed. As the float rises, it applies pressure onto to the vacuum line and now permits the fuel built up in the inner camber to gravity feed into the outer chamber (tank). Without the spring there would not be enough pressure placed on the pin to make a good seal. As the float lowers, the process repeats. Note: since there is a vent to atmosphere. I find today's fuels evaporate quickly. Priming is a necessity. Suggest purchasing or making a special funnel with the appropriate threads to screw into plug hole. Link to comment Share on other sites More sharing options...
Dodge1934 Posted December 31, 2017 Author Share Posted December 31, 2017 Thanks for the input guys I will digest all this and get back if I have further questions Thanks again Link to comment Share on other sites More sharing options...
robert b Posted January 2, 2018 Share Posted January 2, 2018 (edited) There is NO spring on that pin , it must be free to travel up and down as the float rises and falls . The two long springs cause the levers to over center and trip the valve to switch from vaccum to air vent to allow the fuel to flow from the inner tank. The conection on the out side of the tank there is a vent only and no fuel is any were neer it . It vents the outer tank always and the inner by the valve , the free movment is there to allow the over center work of the levers and springs to work in relation to the float level and fuel height in the inner tank . The vaccum is closed by the inner plunger and brass seat in the tank top ,this is also controled by the spring and levers action. Bob Edited January 2, 2018 by robert b (see edit history) Link to comment Share on other sites More sharing options...
Mark Shaw Posted January 2, 2018 Share Posted January 2, 2018 Stewart%20Vacuum%20System.pdf Link to comment Share on other sites More sharing options...
Dodge1934 Posted January 2, 2018 Author Share Posted January 2, 2018 10 hours ago, robert b said: There is NO spring on that pin , it must be free to travel up and down as the float rises and falls . The two long springs cause the levers to over center and trip the valve to switch from vaccum to air vent to allow the fuel to flow from the inner tank. The conection on the out side of the tank there is a vent only and no fuel is any were neer it . It vents the outer tank always and the inner by the valve , the free movment is there to allow the over center work of the levers and springs to work in relation to the float level and fuel height in the inner tank . The vaccum is closed by the inner plunger and brass seat in the tank top ,this is also controled by the spring and levers action. Bob After reading up some of the other information supplied here I agree Bob. I have the thing pretty much cleaned up and ready to reassemble. The inner plunger controlling the vacuum seems to be in order but I am less convince the vent line ever seals as the float goes up and down. I don't see an easy way to check either. I agree there is no indication a spring would ever be required. Thanks for your input Link to comment Share on other sites More sharing options...
Dodge1934 Posted January 2, 2018 Author Share Posted January 2, 2018 1 hour ago, Mark Shaw said: Stewart%20Vacuum%20System.pdf Great information Thanks for sharing Link to comment Share on other sites More sharing options...
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