Fuel pump question
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Senior User
Joined: Apr 2005
Posts: 453
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From: medford oregon
Fuel pump question
I just got done replacing the front tank and internal fuel pump. It all seems to work fine except yesterday I had to crank it over for a long time before it fired. I checked the filter and there was not alot of fuel in it when I was trying to start it. When its running the amount of fuel coming into the filter is really no more than a dribble. I went out this morning and checked the filter and it was full, kinda weird. This is all on my new tank setup by the way. I have a Mallory 4070 electric pump just sitting around, is this something I would want to put inline to help the pumps or just a waste of time. Thanks for any tips.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Have you checked to see that the pump is getting voltage while cranking. I'm not an expert on this, but I believe there's a oil pressure switch that is intended to kill power to the pump if the engine isn't running. But, there's a bypass for that while cranking. So, if the bypass isn't working you wouldn't have power while cranking and it would be hard to start.
As for adding a pump, I wouldn't do that until I knew I had a problem it would fix.
As for adding a pump, I wouldn't do that until I knew I had a problem it would fix.
Old School Hot Rodder
Joined: Feb 2006
Posts: 6,472
Likes: 11
From: Exmore, VA
I think Franklin2 posted the 1985 fuel pump circuits in here before. I have the 86 circuits on my website, but 85 is different, I think there is an extra relay. The small blue fusible link at the starter solenoid/relay is the cranking bypass for the system, it directly powers the fuel pump, change over valve wiring. Jumper it to 12V battery power, then test the system.
FWIW, the change over valve is only powered through the pump feed wiring, and has a history of problems. Where did you find a pump? several people recently have said they couldn't find a good source.
BTW, it is an extremely low pressure pump, 2-3psi I seem to remember, someone asked about it recently.
FWIW, the change over valve is only powered through the pump feed wiring, and has a history of problems. Where did you find a pump? several people recently have said they couldn't find a good source.
BTW, it is an extremely low pressure pump, 2-3psi I seem to remember, someone asked about it recently.
Posting Guru
Joined: Jan 2013
Posts: 1,933
Likes: 0
From: VA
It could help reduce risk of vapor lock in certain climates. If you do this, you'll probably want to put in a fuel pressure regulator too because having the pump inline may increase pressure past where you need it.
Thread Starter
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Senior User
Joined: Apr 2005
Posts: 453
Likes: 1
From: medford oregon
I think Franklin2 posted the 1985 fuel pump circuits in here before. I have the 86 circuits on my website, but 85 is different, I think there is an extra relay. The small blue fusible link at the starter solenoid/relay is the cranking bypass for the system, it directly powers the fuel pump, change over valve wiring. Jumper it to 12V battery power, then test the system.
FWIW, the change over valve is only powered through the pump feed wiring, and has a history of problems. Where did you find a pump? several people recently have said they couldn't find a good source.
FWIW, the change over valve is only powered through the pump feed wiring, and has a history of problems. Where did you find a pump? several people recently have said they couldn't find a good source.
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