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Fuel Pump For B85 With 707


62bmack

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Heres a ball park

Assume the 707 gets about 5 miles per gallon at road speed of 50 mph

5 mpg at 50MPH =10 gal/hr

10gal/hour= 10gal/60 min= .166 gal/min

Hope that helps, you can most likely get the actual GPM from the Mack Museum.

Firemack

Thanks alot that did help. so here is the problem i am having with my truck. She starts fine and idles fine. accelerator pump seems to be responsive but she just runs out ofpower onder a load. I think that the pump i put on is not giving enough fuel?

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62Bmack

I had a similar problem with our B75 Pumper, I added a T in the fuel line and connected a fuel pump pressure gauage to monitor to fuel pump pressure while driving the truck, it ran out of fuel and the pressure dropped going up long hills, I sent the pump out to Kanter (in NJ) and had it it rebuilt for $88 and reinstalled it, since then never had the fuel presuure drop again. Problem solved. Maybe just to be safe send it out for a rebuild now anyway and then you know that is not the problem (if it has not already been rebuilt by a reputable shop). One other item to check is the fuel filter, I did have it run out of fuel with a clogged fuel filter, change that first and see if that is the problem before changing the fuel pump.

Firemack

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62Bmack

I had a similar problem with our B75 Pumper, I added a T in the fuel line and connected a fuel pump pressure gauage to monitor to fuel pump pressure while driving the truck, it ran out of fuel and the pressure dropped going up long hills, I sent the pump out to Kanter (in NJ) and had it it rebuilt for $88 and reinstalled it, since then never had the fuel presuure drop again. Problem solved. Maybe just to be safe send it out for a rebuild now anyway and then you know that is not the problem (if it has not already been rebuilt by a reputable shop). One other item to check is the fuel filter, I did have it run out of fuel with a clogged fuel filter, change that first and see if that is the problem before changing the fuel pump.

Firemack

Thanks alot for the info firemack. Sounds like fuel pump rebuild time. Do you know if the second pump was a backup or did it send fuel at the same time helping to boost pressure?

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62bmack,

Some Mack Fire trucks do have dual fuel pumps, one electric pump at the tank and the mechanical pump on the engine. Our 1954 B75F has only has one mechanical pump on the engine so that is the one I was monitoring as it would run but then run out of fuel when under load.

Firemack

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