Low R1 fuel pump pressure

I assume he's checked things like the rubber fuel lines and the filter?

He might also try disconnecting the fuel line going from the pump to the tank, put it in a gas can and check the pressure again.

Jeff DeWitt

billslark wrote:

I would expect that the pressure would be less with a fuel pump that has a return line to the tank. I'm not sure what the specs are but the question I would have is, are you measuring the pressure with the return line blocked off?

JT

billslark wrote:

ON A CAR WITH A RETURN LINE 1.5 P.S.I. SHOULD BE NORMAL. BOB KAPTEYN

My stupidity is showing, but does an R1 Lark fuel pump have a return line to the tank? That's what I believe you're saying.

Bill Pressler

Yes it does. The return line come off the top of a GF-97 fuel filter (glass bowl) and runs parallel to the feed line along the frame to the gas tank. The return line is the smaller of the two lines. The purpose is to divert excess fuel back to the fuel tank and reduce the chances of a vapour lock occuring.

Allen

billslark wrote:

Jet-Thrust fuel pumps. According to the manual the pressure should be 5.5 to 7 lbs. at 1000 rpms. Then it says that if the pressure is low you should do a vacuum test on the inlet side and it should show 10 in.. Also, there was a variation on the fuel return line theme. Some of the later made Jet-Thrust cars had the new style in line filter, not the glass bowl type. Those cars had a tee right on the fuel pump and that is where the return line started. The stated purpose for the return line was to relieve fuel pressure in the line to the carburetor so that when the engine was turned off there would be less tendency for the engine to flood when it was restarted hot.

The fuel pump tests for R1&R2 engines is in the Avanti manual as Tim describes. All tests are written up for early versions with the return line from the pump. Measurements are done at the inlet to the in-line filter, after the "T" for the return. The corresponding point for later Avanti's, or "R" series Larks & Hawks, with the GF-97 filter; would be after the sediment bowl. I can add: There's a volume test. A pint in 15 seconds or less, with the engine at idle, running on fuel in the carb. Pressure is @ 1000 RPM, straight into the gauge - not at a "T" in the fuel line, like a permanent gauge would be. The GF-97 has a .050" restriction at the return port. Although Stude claimed return flow cooled the fuel delivered to the carb, there probably isn't enough to help much. Mostly, it functions as a "vapor diverter", and bleeds off pressure to the carb when the engine is shut off, preventing flooding. Mike M.

All new pumps available for the Stude V8 are actually pumps designed for the Chrysler 318 engines. The arm comes out straight and has one bend near the end. When you push down on the arm it will move easily for quite a distance before resistance is noted. These pumps will work fine for normal driving but when you put the hammer down it starves the engine. These pumps are made by Master and have a problem with the pivot pin comming out and bad oil leaks developng in the area of the pivot pin. Carter also markets a pump for the Studebaker V8 but it ia also a Master pump repackaged by Carter. The only difference is that it is marked "made in canada" Same 318 pump,same casting mold etc and the pin comes out even faster. Has anyone ever develloped a solution for this such as loctite on the pin? There are Loctite formulations out there that do not set up hard and the pin could still be driven out later but seal the pin in and stop the oil leaks. I invite comments from the experts. If anyone knows of articles or posts written about this,please contribute. Bob Kapteyn

I seem to remember somebody (Calvin?) putting a dab of JB weld on both ends of the pin. Sounbds like it would work pretty slick.

Mark (Faulty memory R us) Dunning

Airtex pumps are made by Master