Air bubbles coming from Fuel pump?

[The_Beest]

Hey All,

Got some issues here... I've been frantically trying to get our truck (77 Power Wagon 360) running well as we are picking up a camp trailer sometime in the VERY near future... Well it's been a task to say the least...

Some background: I changed the plugs and wires last night, the cap, coil, and rotor seem to have been replaced not to long ago, although the cap doesn't seem to fit SNUG on there?? I replaced the fuel pump and filter about a week or 2 ago... and i set the timing to the best of my ability last night as well @ 9* BTDC with 750-800 RPM idle. I also adjusted the mixture screw out (possibly too much, will check tonight). After doing all this work last night, I decided to take it out on a drive... it was running great and idling smooth for most of the trip. Although on hard accel, it seemed to sputter once or twice (timing related or carb?). With the test drive coming to an end, it all of a sudden decided it didn't want to run anymore unless my foot was in it and still it didn't seem to want to hold an idle... especially being in gear with the brakes on...

Now since I changed the fuel pump, after running it for any period of time, there are air bubbles coming into the fuel filter (clear filter) and I have no idea why??? I'm guessing that's NOT supposed to happen? What could be causing it to not want to stay running while in gear with the brakes on? I THOUGHT it was a timing & idle issue but I thought i fixed it....

Anyways, if anyone has any sound advice please let me know, im starting to go crazy here and not sure i'll be able to pick up our trailer before the holiday weekend :(

Also, after tinkering with it it doesn't seem to want to start as easy now... the timing didnt change much (if any at all) before I started tinkering... ANy advice on how to get it to fire right up again??

Thanks,
Devin

[bigblackd150]

I think that your fuel pump may be going, also check for any leaks before the pump to make sure it isn't pulling in air. You may have to check back to the tank.

Vic

[Delray Dude]

Did you replace the rubber fuel lines when you replaced the pump?

Sounds like the air might be seeping in with the old hose.

Other possible bubbling would be the 1st signs of vapor lock - fuel is getting hot and starting to "boil".

If you start the truck when the motor is cold (like overnight cool down) is there bubbles right away? If so, suspect air is getting in somewhere - could be a bad diafram in the fuel pump or leaks in the fuel line hose.

If the bubbles apepar after some run time - most likely due to the heat from the exhaust is heating the fuel in the supply line causing it to boil. Boiling leads to sputtering.

For what it's worth - I try not to keep glass fuel filters on - maybe for diagnoses reasons, but a glass filter could get broken if something hits it and fuell spraying all around a hot engine can make the truck extremely hot all over (if you know what I mean). I'd suggest a nice metal filter for normal running - much harder for something to break it.

[Speed Dragon]

Is the filter before or after the pump?

[The_Beest]

Thanks for your replies!

It would happen when the truck would start warming up so i suspected the vapor lock boiling issue... Altho, I just had the carb replaced a week or so ago due to other issues and that seemed to take care of it??

I see what your sayin about the glass filter but I "think" the one thats in there now is clear plastic? So im not THAT worried about it, altho I do prefer the metal filter, just because...

And the fuel pump is brand new and the filter is after the pump, closer to the carb...

Maybe one of these days ill add a filter before the pump and after the tank....

Thanks again for your replies!

Devin

[Delray Dude]

Good to hear it went away.