Mechanical vs electrical FP

[Doc Dave]

John,
Do you plumb this "booster" fuel pump directly in the fuel line between the fuel tank and the mechanical fuel pump, for example near the frame rail?
Or is it more of a bypass plumbing set up?

[john eickhof]

fuel pump

I place them in line as close to the fuel tank as possible and mount to any convenient hole in the frame. Electric pumps push better than they pull. So try and avoid having it too close to the engine as it won;t work much better than the mechanical one. Fuel will be pulled through it by the mechanical one with no problem when not being used to boost the flow.Plus it's there in case the mechanical pup should fail.

[Doc Dave]

Thanks,
Good information.

[HWooldridge]

I owned an ex-fire truck (M37) that was plumbed that way and which did not have a mechanical pump. However, the electric always seemed to overpower the carb and flood it; I do not know what pressure it was rated for.

It was very handy if I ever ran out of gas and the truck never vapor locked.

[john eickhof]

fuel pressure

electric pumps from carquest are available in different pressure ratings. always use one with output of 4 psi or less and you will not experience needle valve bypassing from pressure.

[HWooldridge]

electric pumps from carquest are available in different pressure ratings. always use one with output of 4 psi or less and you will not experience needle valve bypassing from pressure.

John,

Do you think it makes more sense to use a higher pressure pump with a regulator or just use a 3-4 lb unit by itself? Reason I ask is whether a lower volume unit will keep up with the engine at higher rpm's.

Thx, HW

[Kaiser2boy]

Hmm, I had my fuel pump rebuilt along with the engine over 4 years ago and have had no problems with it.
Its not like I dont use it , The truck gets a good bit of use both on and off road.
The only problem I had was a small leak but that was due to a lose screw.
Maybe I am just lucky.

[HWooldridge]

I finally figured out what was happening here - and it was somewhat unrelated to the pump. When the pump previously went out (and it really did have a ruptured diaphragm that time), I put an inline filter in front of the pump. As I noted in an earlier post, replacing that filter fixed the problem - but only temporarily. The truck started acting up again and turned out the "new" one-month old filter was already clogged. Years ago, I had installed a large, spin-on diesel fuel filter just ahead of the carb but had abandoned it when I rebuilt the pump - so I removed the inline setup and went back to the previous one. Apparently, there is enough trash in the fuel tank that the inlines can't handle it, because I had drained the tank and blown out the lines but there was still enough junk to cause problems.

I am still going to install an inline electric pump but will use it only for priming and when the truck vapor locks - which has happened more than once during our hot summers.