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Electric fuel pump with two tanks HELP

akchambo

Newbie
Joined
Jan 11, 2003
Messages
8
I’ve recently completed the explorer serpentine conversion but I am now having a fuel issue. The engine starts with 5 psi but then peters out and psi goes to zero. Currently, I have the fuel pump mounted on the frame just in front of the auxiliary tank thinking this would allow to be fed from either tank. However, regardless of which tank I’m on it has the same result. I called Cater fuel systems and the believe it’s the pump placement and recommend with 24” of the tank and lower than the tank. Please provide your thoughts on placement. I would like to still use both tanks. They recommend separate fuel pumps with a switch to supply power to the appropriate pump. Thoughts?
 

jamesroney

Sr. Member
Joined
Sep 11, 2007
Messages
1,914
Loc.
Fremont, CA
I’ve recently completed the explorer serpentine conversion but I am now having a fuel issue. The engine starts with 5 psi but then peters out and psi goes to zero. Currently, I have the fuel pump mounted on the frame just in front of the auxiliary tank thinking this would allow to be fed from either tank. However, regardless of which tank I’m on it has the same result. I called Cater fuel systems and the believe it’s the pump placement and recommend with 24” of the tank and lower than the tank. Please provide your thoughts on placement. I would like to still use both tanks. They recommend separate fuel pumps with a switch to supply power to the appropriate pump. Thoughts?
Nonsense.

Your pump placement is fine. You are sucking air, or have a restriction. You could mount a Carter P0470 pump on the front bumper, and as long as it has a leak free connection to the tank...it would deliver fuel.

Remove all of the nonsense between the inlet of your pump, and temporarily connect a new hose to a single tank with fuel in it. I'll bet it will work just fine. Sometimes the tank select valve will suck air...but won't leak fuel. It's baffling, but it happens. Some select valves also let you pick the wrong position...and block flow.
 
OP
OP
akchambo

akchambo

Newbie
Joined
Jan 11, 2003
Messages
8
Thank you, I’ll look to make the suggested changes in the morning. Assuming this corrects my condition, how would one successfully tie in both tanks?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
35,392
I've had the Carter pump mounted by the master cylinder and by the driver's headlight and they both worked perfect. This includes brutal summer heat in AZ.

As stated, sucking air or a restriction. Possibly a bad pump.

Where are you getting power from? Just making sure you are getting good power, not pulling it off ignition or something else.
The selector valve getting a bad O-ring and sucking air is common.
When you loose fuel pressure, take the hose off and put into a container and power up the pump. Freeflowing, what do you get?
 

ntsqd

heratic car camper
Joined
Jan 30, 2005
Messages
3,551
Loc.
Upper SoKA
It is easy to try to think of vacuum as being the same as pressure, just in the opposite direction. That is the path to headache, it doesn't work like that at all. It should be simple, but vacuum is complicated and somewhat difficult to explain. A pressure fitting assembly that will hold 100 psi can leak under not much vacuum. Truth be told, everything leaks under vacuum to some degree. I've seen vacuum pull helium directly thru 1/4" thick 316 stainless steel, defining what is an acceptable leak and an unacceptable leak is crucial.
Sorry, too many years working around high vacuum systems and leak detectors.

If the tank vent isn't flowing freely the pump can't get very far. Try it again with the cap off.

Some fuel hoses are great under pressure, but will collapse under vacuum. Inspect all of the rubber hoses when the pressure has dropped to 0 psi to see if any of them have been sucked flat or partly so.

Not that it's likely a problem this time of year, but modern fuel has a dramatic lowering of the light ends boiling point when under even a small vacuum. Which is vapor lock.
 
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