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'59 American FH: fuel pump mystery |
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pwreimers
AMC Apprentice Joined: Dec/16/2012 Location: Salt Lake City Status: Offline Points: 101 |
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Posted: Jul/19/2017 at 12:09pm |
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-Yesterday, I went to start this car: no fuel to carb. After trying many things (besides changing to another pump), I hooked up a gas can and hose to the fuel pump inlet. The pump would not pull the gas until I 'primed' the line by getting a flow established by suction. Once the hose had flow, I hooked up to the pump inlet, the pump worked fine. Once the pump began working, I reconnected the line to the car gas tank and the pump worked as usual.
-Today, it starts just fine. -This seems to be a summertime phenomena, and it occurs if I have not driven the car for a couple of days, perhaps a week. It also happens on my other '59 American, too. That pump, though, seems to have enough strength to pull the gas from the tank, although I do not let that one sit as long (I use it much more often). -We've had weeks of 95+ heat. Presumably the gasoline has evaporated out of the carb, pump and lines. -While I could begin a habit of starting each car each day to get fuel flow established, I would really like to know if there is something wrong with the one pump. -The 'pulsating' diaphragm on this particular pump was disintegrated last summer. This is the diaphragm on the top of the pump, just above the check valves. I replaced it with a non-fabric-reinforced buna-n rubber piece I cut to fit; this diaphragm is now a bit domed and I should get the right raw material from McMaster Carr to make a replacement. For now, it works. -The gas tank was removed and coated with a bake-on by a reputable outfit here; the product is called 'Gas Tank ReNu' and is warranted. I hate to just replace parts to see if that will work. It may be that another pump will just do the same thing. Any thoughts? Experiences? Thanks, in advance! As usual, Pete
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tyrodtom
AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6214 |
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The check valve in the pump isn't closing tight, it letting the fuel in the line drain back to the tank .
Taking the pump apart again, and removing and cleaning both check valves might help, or if you can get new ones replace them.
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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tufcj
Supporter of TheAMCForum Supporter of TheAMCForum Joined: Jul/10/2007 Location: Watkins, CO Status: Offline Points: 4097 |
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If it's a vacuum wiper pump, I have a rebuild kit with neoprene diaphragms. I bought it for a pump that ended up not being rebuildable due to other internal damage. Kit was $69 + shipping, I'd let it go for less.
Bob tufcj |
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69 AMX
74 Javelin AMX 67 Rogue If you need a tool and don't buy it... you'll eventually pay for it... and not have it. Henry Ford |
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pwreimers
AMC Apprentice Joined: Dec/16/2012 Location: Salt Lake City Status: Offline Points: 101 |
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That's a great idea. It looks like I've got some work to do. I just wish it wasn't 95 degrees out there! Maybe I can test that by putting an inline check valve on the fuel line, just upstream of the pump.
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19692 |
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The in-line check valve should work. I think I'd put it in the line between tank and pump though, close to the pump.
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Frank Swygert
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pwreimers
AMC Apprentice Joined: Dec/16/2012 Location: Salt Lake City Status: Offline Points: 101 |
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Well, this did not work out. Here's the check valve I used, from Grainger: https://www.grainger.com/product/GRAINGER-APPROVED-1-4-Ball-Cone-Spring-Check-4DHY9
It cracks at 1 psi, is made of nylon with a buna-n seat & ss ball. $5 is a very fair price. I installed it just upstream of the fuel pump inlet in the problem car, which worked at idle. Installed in the workhorse car, same result. A little later I moved the problem car and it stalled out. I have to return to that. I needed to get groceries and took workhorse out, which stalled within a couple of miles. I removed the check valve and it ran as usual. All I can figure is these pumps can't handle that upstream 1 psi load. $10 to find that out isn't a real problem, but it's a little surprising. Maybe it's fuel pump rebuilding time? Honestly, the idea of disconnecting the fuel pump line while the motor runs, and timing how long it takes to fill a one quart jar, scares the beejeesus out of me. Is there another way to test the pump performance? As usual, Mystified but determined Pete
Edited by pwreimers - Jul/21/2017 at 1:02am |
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tyrodtom
AMC Addicted Joined: Sep/14/2007 Location: Virginia Status: Offline Points: 6214 |
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You can do the fuel pump test while it's cranking, it won't take long to fill a 1 quart jar.
Use someone inside to turn the switch, or get a remote start switch that hooks to the solenoid, only $10-$15 at NAPA.
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66 American SW, 66 American 2dr, 82 J10, 70 Hornet, Pound, Va.
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7555 |
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i'd just bite the bullet and rebuild the pump (though i too enjoy and learn from experimentation). its unlikely that only that one checkvalve is dead. you only need to build them every decade or two or three.
that pump should put out 3 - 7psi which ought to overcome the 1 psi. i found that two check valves in series interact in weird ways. found that out with LPG where the pressures are much higher. |
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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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pwreimers
AMC Apprentice Joined: Dec/16/2012 Location: Salt Lake City Status: Offline Points: 101 |
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I am a bit embarrassed; your post encouraged me to re-read the TSM, which I should have done in the first place. BTDT? They have two tests and the flow rate one sounds much safer than my imagination!
I never thought about being in the flow path between two check valves. It would be interactive, no doubt; they would have strange manifestations: one opens, the other closes... Sometimes experimentation seems the hard way; hopefully it gives definitive results, whereby only one conclusion becomes known. A good experiment eliminates unknowns properly. You're right: it's just plain rebuilding time...I'll do the flow and pressure tests, though, just to see. I just like that stuff! I do not understand the 'pulsating diaphragm' sitting above the check valves on top of the fuel pump. Does that diaphragm really need to be anything more than a seal to prevent flow from one side to the other? Isn't the flow path on the other side of the check valves? Thank you! Pete
Edited by pwreimers - Jul/22/2017 at 12:14am |
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pwreimers
AMC Apprentice Joined: Dec/16/2012 Location: Salt Lake City Status: Offline Points: 101 |
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Update: during installation of a rebuilt fuel pump, the prior fuel pump (still installed) was used to get the car up the driveway, using my lawn/snow fuel tank and a long hose connected to the fuel pump inlet. After parking the car, I took the hose out of the tank and put it onto the ground to see if the fuel from the carb/pump would drain backwards, indicating the fuel pump check valves were stuck open. I let it sit for a couple of hours while the motor cooled. The hose drained a bit, perhaps an ounce, not nearly enough to empty the pump, the pump bowl and the the carb bowl. I must conclude the check valves in the removed fuel pump are okay. I will test the newly installed pump out by letting it sit for a couple of days to see if the fuel pump works. In the meantime, I'll assemble a pressure gage and a line tap to measure fuel flow rate and pressure and check against the TSM guidelines. Any thoughts are always appreciated, Pete |
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