New emergency fuel pump will not pump

[subford]

I am trying to install an emergency fuel pump to turn on and bypass the main fuel supply system if the main fuel pump dies on the road.

I have installed what I think should work but the new fuel pump will not pump any fuel with a full fuel tank.

With this installed the generator will run OK and the main fuel system is running the engine (460) OK but if I turn on the new fuel pump and pull the main fuel system relay the engine will die and not restart.

The Airtex # E8446 pump is a Rollervane type, 12 Volts, Inlet/Outlet size 5/16” with a pressure 105-115 PSI & flow (GPH) of 50-60.

I have clamped the fuel line to generator after the “T” on the generator side and that did not help.

Here is a diagram and photos if that may help.

Thanks







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[LVJ58]

Pulling the main pump relay may interrupt sensor input to the PCM/ECM, preventing ignition and/or injector function, not sure.

Your injectors only require 30 t0 45psi, 105 to 115psi from you external pump appears a bit excessive.

Also in looking at your diagram of fuel lines & connections, could the external pump be pulling fuel out of the genset fuel line and pumping it back into the tank through in-tank output pressure line?

Just a thought, and best of luck getting your issue resolved.

[subford]

Quote:

Originally Posted by LVJ58 Pulling the main pump relay may interrupt sensor input to the PCM/ECM, preventing ignition and/or injector function, not sure. Your injectors only require 30 t0 45psi, 105 to 115psi from you external pump appears a bit excessive. Also in looking at your diagram of fuel lines & connections, could the external pump be pulling fuel out of the genset fuel line and pumping it back into the tank through in-tank output pressure line? Just a thought, and best of luck getting your issue resolved.

The stock fuel pump is rated at 100 PSI and the fuel pressure is reduced to 32-45 by the fuel pressure regulator and it should do the same for the new pump.
There should be a high pressure check valve in the stock pump but it may be bad. So pumping back could be what is happening and am trying to think of a way to test this as all the lines going back to the tank are steel.

[Bob King]

subford:
Looking at your diagram with the regulator in the return line, how does it have any effect on the fuel rail pressure? I would think the reg. would have to be in the supply line ahead of the fuel rail. I'm no mechanic, just trying to figure it out.
Bob

[subford]

Quote:

Originally Posted by Bob King subford: Looking at your diagram with the regulator in the return line, how does it have any effect on the fuel rail pressure? I would think the reg. would have to be in the supply line ahead of the fuel rail. I'm no mechanic, just trying to figure it out. Bob

All Fords have the regulator (and I think other makes also) between the return line and the fuel rail. How else would you regulate the pressure.

Go to this link for more information on how it works:
Player3B

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[LVJ58]

Quote:

Originally Posted by subford All Fords have the regulator (and I think other makes also) between the return line and the fuel rail. How else would you regulate the pressure. Go to this link for more information on how it works: Player3B /

But isn't it the purpose of the fuel regulator to regulate the fuel pressure entering the fuel rail to the injectors. If the in-tank pump puts out 100 psi would it not need to be reduced by the fuel regulator prior to entering the fuel rail/injectors?

Seems logical, but I could be wrong as often I am--

[subford]

Quote:

Originally Posted by LVJ58 But isn't it the purpose of the fuel regulator to regulate the fuel pressure entering the fuel rail to the injectors. If the in-tank pump puts out 100 psi would it not need to be reduced by the fuel regulator prior to entering the fuel rail/injectors? Seems logical, but I could be wrong as often I am--

No the fuel rail is an tube that goes all the way around to all injector and putting the FPR on the fuel rail with its out let to the return line would be the same as if you put the FPR between the supply and return lines.



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[LVJ58]

OK, I give up then... and again I wish you the best of luck getting your external pump to work.

[Lt46]

I'm thinking even though the Airtex is rated @ 100psi it is not @ the source, but downstream from it. It is not being supplied fast enough, in other words it may pump @ 100psi but will not draft gas out of the tank fast enough to supply that volume at that pressure.

[a k]

You sure your not pumping it back thru the original fuel pump back into the tank instead of going to regulator? Might need a check valve on the outlet of the tank fuel pump.

[koda59]

When you pull the main fuel relay are you sure you still have electrical to the emergency fuel pump?

[subford]

Quote:

Originally Posted by koda59 When you pull the main fuel relay are you sure you still have electrical to the emergency fuel pump?

The emergency fuel pump is wired to its own relay and you can hear it run.

[subford]

Quote:

Originally Posted by a k You sure your not pumping it back thru the original fuel pump back into the tank instead of going to regulator? Might need a check valve on the outlet of the tank fuel pump.

That may be the problem and I will have to come up with a way to check that.

[mpaton]

Quote:

Originally Posted by subford That may be the problem and I will have to come up with a way to check that.

A simple check on the fuel pressure should reveal that.

If it turns out to be the case, then unfortunately, your aux fuel pump will have been back flushing any crud in your normal fuel filter back to the normal pump and the tank.

Also, without a check valve in your aux pump line, the same could happen with your aux filter, although as the engine seems to run with your aux system in place, there probably is a check valve in your aux pump.

There are also 3 fault codes that the ECU can set to do with monitoring of fuel pump current. These are unlikely t ocaue a check engine light however.