clogged fuel line?

My M998 was running like it was fuel starved, losing power at highest speed. At lower speeds, it ran fine. Parked it overnight and had a hard time starting it. Cracked the drain cock on the fuel filter, the engine died and will not start. No fuel spurting from the pump or filter while cranking. Therefore, I think I either have fuel line blockage or a bad pump. Perhaps both?

I have the rubber lines off the fuel (lift) pump. Should gravity allow fuel to just flow out of the lower line from the tank? It appears quite dry. Certainly nothing flowing out.

If I remove the fill cap on the fuel tank, should I be able to hear compressed air in the tank if I blow air back through that hose from the pump end? If the fuel line "sock" got sucked up, should I be able to blow it back open with compressed air through that same line?

Is there a location between the fuel pump and the top of the tank that I can break open the fuel line and see if I get any gravity flow? The tank is nearly completely full and I'd rather not dump or drop the tank just yet. I haven't crawled under there to trace the line back yet. Thought I'd ask first.

Thanks!

Matt

Fuel Lift Pump replacement

What the heck... no replies??!!

I tried shop air back up the pump inlet hose and didn't get any hissing from the fill neck. Wasn't sure that would work anyway. Pump was still suspect, not sure of the lines. My tank was very clean when I drained it and inspected it last Winter. Hoses don't look like original, nor decrepit.

So I got antsy and replaced the fuel pump anyway. Reconnected the lines. Fuel pump pulled fuel from the tank and sprayed it out like a mutha.

Cheap fuel pump on ebay. $29 Might buy a spare and keep in the M998.

Removed the pump back plate from the engine. Replacement gasket from Napa: FPG 5182. $1.69. Rock Auto has them for $0.70.

Spackled marine grease on the pump actuator rod. It stayed in place fine while I reinserted the back plate (10 mm socket) and cranked it down. I got lucky, when I quit trying to crank the engine, the push rod was quite recessed. The pump (11 mm socket) was easy to slip into place, start each bolt, then work the pump down evenly side to side. Pretty easy job. Didn't remove the spash shield in the wheel well. Did all but reconnecting the lower hose from above.

Now to work my way back up the lines and try to get out as much air as possible before trying to restart.

DocThrock said:

My M998 was running like it was fuel starved, losing power at highest speed. At lower speeds, it ran fine. Parked it overnight and had a hard time starting it. Cracked the drain cock on the fuel filter, the engine died and will not start. No fuel spurting from the pump or filter while cranking. Therefore, I think I either have fuel line blockage or a bad pump. Perhaps both?

I have the rubber lines off the fuel (lift) pump. Should gravity allow fuel to just flow out of the lower line from the tank? It appears quite dry. Certainly nothing flowing out.

If I remove the fill cap on the fuel tank, should I be able to hear compressed air in the tank if I blow air back through that hose from the pump end? If the fuel line "sock" got sucked up, should I be able to blow it back open with compressed air through that same line?

Is there a location between the fuel pump and the top of the tank that I can break open the fuel line and see if I get any gravity flow? The tank is nearly completely full and I'd rather not dump or drop the tank just yet. I haven't crawled under there to trace the line back yet. Thought I'd ask first.

Thanks!

Matt

Click to expand...

Weekends are sometime slow here. Sorry I have nothing to offer but it sounds like your doing fine!

Doc sorry if it was a truck we were talking about I could likely help you but I know nothing about hummers!
Karl