Mechanical Fuel Pump -fuel delivery question- need advice

[Tim]

May 16th, 2022

Good morning, everyone.

I ran into this situation while starting up my 1968 1600 roadster a couple of weeks ago. I changed the oil and oil filter, fuel filter near the right front relay and the inline filter just prior to the carbs. When replacing the fuel filters, each contained significant amounts of gas. I put the new (2) fuel filters in place and tried to start the car. It would not start. I could see that the mechanical fuel pump was not pumping gas into the new filters. They were dry. The car ran perfectly well when I put it away last October. I did the following: 1.) I took my small electric air pump (auto tires, basketballs etc.) and reverse blew out the fuel line between the fuel filter and the gas tank. I could hear the gurgling in the gas tank. I assumed the fuel line is clear (enough). 2.) I took gas and filled up the fuel line between the right front fuel filter and the fuel pump. 3.) I took gas and filled up the carbs and fuel line in-between the inline fuel filter and the carbs. 4.) I started the car up and it ran rough for about 30 seconds or so then settled down to a comfortable throttle adjusted idle of about 1000 rpms. After driving and warming up the car, it will idle nicely at 750 rpm.

MY CONCERN IS: 1.) I noticed that the two new fuel filters have virtually no gas as a reservoir in them. I sort of expected that the filters would be full of gas. 2.) I noticed that the gas going into the bullet in line filter (just before the carbs) does not fill the filter, but you can see the gas enter the filter in spurts not as a steady stream. My first thought .... how is there enough gas to feed the carbs. Does this sound or look correct? Am I looking at a mechanical fuel pump failure? Am I better off to buy a new pump or will a rebuild kit suffice? Is there a way to check if the pump is working properly?

Any advice, suggestions or prior experience would be appreciated.

Thank you, Tim

[Habitat.pat]

Tim, the fuel filters have no way to vent the air in them other than through the fuel lines so the in line filters will generally stay empty as long as you don't disconnect them & prime them with the outlet pointing up or at least turn the filter so that it is vertical while the engine is running to get the air to be pushed into the carbs & vented. The filter mounted on the body in the engine compartment, either the plastic one or the glass one has its outlet on top of the filter so it will push the air through the system with time. I've never worried about having the fuel filters full but it doesn't hurt to fill them.

Peace,
Pat

[spl310]

Is the filter that is at the r/f of the car a sediment bowl type or a replaceable inline type?

[OU812]

Hi.. My experance with fuel pressure.. 1966 SPL 1600.. New pump... filter... lines. Problem was that the fuel system, fuel tank filler neck ----- to ------ the machanical fuel pump was sucking air. Replaced rubber hoaes and the gasket (#1 problem) at the fuel filter bowel (glass one). I used low pressure (3 or4 psi) at the fuel tank filler neck..Disconect at the machanical fuel pump and plug off the fuel line. Applied low air pressure to half tank of fuel in the tank.... and look / smell for wet spots in the fuel line system, with fuel coming out. The few rubber hoase and the filter gasket get hard over time. After all that... reconect the fuel pump line,,,,, disconect the fuel near the carberarors and put the end in a container to catch the fuel coming out, when you turn the key to crank (start) the engine. Should have fuel if fuel system has supply and good tight lines, The job is easyer with two people. And dont forget the top of the fuel tank.... fuel gage sending unit... This is what I found..... took me about three weeks one night at a time working on it. Where I started at was.... adjusting the carbs. It wasent the fuel pump. I found that I didnt have enought fuel at the carbs so I could adjust. Hope get back on the road and gives you some help. OU812

[Tim]

May 17th, 2022

Thank you for the information. Yes, the filter on the right front is plastic disposable, as well as the bullet filter I added just prior to the carbs. I drove the car yesterday and everything was just fine. I guess I was just surprised that the filters retained such a small amount of fuel in them. I was expecting the fuel filters to be full. This prompted my concern that the fuel pump was failing. I found it interesting that such a small amount of fuel was being pumped, yet the car ran just fine. Yet why did it not start right up as it had for the past years. I suppose I should drive it and deal with it when it quits. I am open to any suggestions.

Thank you,
Tim

[OU812]

Hi Tim My fuel glass filter has been half or better.... at all times... never seen it full..only when I clean it. OU812..