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primary fuel filter.


Domore

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My 2005 Mack700 as been losing power/motor slowing down when plowing snow.Thought is might be starving for fuel, so one of my guys checked the primary filter and it was half full. Thought that was the problem so we changed the fuel filters. Same problem, checked the primary filter and it is still only half full of fuel. I would think the filter should be full. Open the bleed cocks while truck was running, but nothing come out. Don't understand how the motor runs with a 1/2 full filter.

Truck will idle and rev fine in neutral. But will have no power under load. Truck has a automatic transmission.   Thanks in advance...

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2 hours ago, hatcity said:

you're plowing snow when this happens.  2 thoughts

1) fuel is gelling

2) air intake is getting restricted due to blowing snow

Fuel is not gelling. Truck comes right out of the garage.

We have installed a new air filter and we checked that also. Thanks

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4 minutes ago, fjh said:

plugged tank vent

Thought of that also. But if the vent was blocked, wouldn't there be a vacuum like release when we remove the fill cap?

You said before that the filter being 1/2 full was normal. This filter is the red screw on filter, not the glass bowl type. Why I didn't think being 1/2 full is normal is because it has 2 bleed screws on the top where the inlet from the tank and the outlet to the 2nd filter is. Is there a fuel pump to bring fuel from the tank to the filter?

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  1. another thought- are you filling fuel tank at the end of day and then parking? warm fuel tank then cools overnite. condensation in tank-water in fuel

Success is only a stones throw away.................................................................for a Palestinian

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11 minutes ago, hatcity said:
  1. another thought- are you filling fuel tank at the end of day and then parking? warm fuel tank then cools overnite. condensation in tank-water in fuel

Thats exactly what we do.Normally the last driver will fill the tank and then park it for the next time it's needed. When this problem started we parked it in the garage and changed the filters. The next day we had a storm and we took it out to use. The driver drove about 3kms and had to bring it back and park it in the garage. The garage is heated but the is still snow and ice melting off, so it is possible to be some ice in the fuel line. Is there anything between the primary filter and the tank? Can I blow back through the fuel line?Thanks

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8 minutes ago, terry said:

should be a primary and a secondary filter, on every fuel filter change on this system  that i have done the secondary will be completely full and the primary is always aliitle low, when you drop filters.    terry:D

My primary is only about 1/4 to 1/2 full.

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I think we found the problem. We think it was ice. We removed the fuel lines and blew them out. Primed everything, tried the truck plowing snow and everything seem back to normal. Now my primary is almost full. Guess we didn't leave the truck in the garage long enough before to completely thaw the fuel lines.

Thanks to everyone for their replies.

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