Bleeding the fuel line...

-
7

7milesout

Well-Known Member
Joined
Feb 17, 2017
Messages
407
Reaction score
101
Location
PTC
You guys who've been messing with your cars for years probably know this and maybe have done this already. But I'm learning. And I thought this was another cool trick I learned so I'll share. Hope it's not redundant. I just replaced the fuel sending unit on the mighty Scamp. Just prior to the replacement, I ran the tank empty while carrying a gas can with me. I was near the house and just splashed some gas in it and went home.

Pulling the sending unit out was nice with no gas in the tank. However, after completing this repair, I through another splash in the tank and cranked it up to drive to the gas station. With only a splash in the tank, the fuel pump didn't pick it up. And it ran out the gas it had in the carb in the driveway. She was done. I emptied another ~ 1 gallon into the tank, still no go. I took the gas can to the gas station and got 5.5 gallons. Emptied that in there, no go. I started freaking out thinking maybe the sending unit had a protective cover over the fuel pick-up that I didn't notice and didn't remove.

I went and watched a youtube video and based on that I did this.

I pulled the fuel line off at the fuel pump and blew some low pressure air into the line, and into the tank with the fuel cap ON and tight. It had no gas in that line anyway so this wasn't hurting anything. I had a son stand at the fuel cap and tell me when he heard air hissing out. When he said he heard it, I quit blowing air in the fuel line and just stood then bending over holding the end of the fuel line and waited. I thought it wasn't going to work but after about 5 or 6 seconds fuel came flowing quickly out the line so I jammed it back on the fuel pump. Turned the starter and blam, fired right up. What a slick trick! The extra air in the tank pushed down on the fuel and forced the fuel into the pickup / sending unit and on down the line.

I was so frustrated prior to this, because I had cranked a long time and was concerned I might have damaged the fuel pump running it dry. On a side note, the fuel gauge works now due to the new sending unit. And the maybe 6 inch fuel line that connects to the sending unit and up toward the top of the tank is leaking (and badly). So now I'm going to run the gas down to empty, or near empty (shouldn't take long the way it's leaking), and then replace that line.


7milesout
 
Lets hope you didn't blow the sock off the sender. It happens.
 
You should not have to do this, the pump should prime. What pump are you running?

If this is a "stock" setup, the suction hoses (sender and pump) could be collapsing, in fact there's a whole list of things. Dirt in the pump, etc
 
The air I blew in there was very low pressure. I doubt it blew the sock off. But I'll check it when I empty it out again and get back up under there to change that fuel line. It's a stock type set-up. The sender is brand new, I doubt it would be collapsing.

Weird now that I think about it. I put just a splash in it to get it home. The whole line should have been empty then ... maybe. But it picked it up. But this time, it wouldn't pick it up for nothing. Dern. Now you've got me concerned that maybe the new sender has an issue.

Would you guys quit knowing so much? :lol: It makes a guy very nervous, and makes him feel dumb too. :eek:
 
Well for one some of use have "been there" and hate to see a guy repeat. In the 70's some guy came into the hobby shop with ?? with a huge dent under the tank. I got the big idea.....told him to wrap up a rag and plastic bag and blow it back out with the air hose. Of course NOW the pickup tube is "feet" off the bottom LMAO
 
Now I'm skeerd to run the car out of gas. Afraid a splash won't get picked up. It seems to have blown through the first 3/4 of a tank in a day. I don't know if it is inaccuracy of the new sending unit, or if the full tank "pushed" fuel through the sending unit, and up the cracked hose, where it promptly drained the tank. But the tank didn't drain much the first night (I had a bucket under it). So I don't know. Gonna just keep going I guess, I don't quite believe the sending unit yet. I'll pull it back out when I change the hose to make sure everything is ok.
 
The aftermarket senders aren't right to the gauge. Common condition.. Gauge shows approx' 1/4 tank then only 7->8 gallons fills it. Two options... add the Meter Match Module to the aftermarket sender circuit or send a OEM sender out for restore.
 
Once the gas in the line gets to the area above the rear axle, it's a downhill route to the fuel pump. After that, the gas is then automatically siphoned out of the tank to the fuel pump.
 
Them meter match modules are a bit ... spensive. I'm going to have to check the trash and see if the old crusty sending unit is still there. I wonder how much it is to de-crustify the original unit?
 
Leaking fuel line wont pull gas. It will pull air quite nicely though. Especially if it was dry. Now that pump and line have fuel, it will pull more than what is leaking.
It has more lift with less air in the line.
 
Tooljunkie said:
Leaking fuel line wont pull gas. It will pull air quite nicely though. Especially if it was dry. Now that pump and line have fuel, it will pull more than what is leaking.
It has more lift with less air in the line.
Click to expand...
Gonna replace that line ASAP.
 
Your sending unit pickup simply doesn't go down far enough.
 
I wonder how much it costs, and what company out there refurbishes original sending units?
 
7milesout said:
I wonder how much it costs, and what company out there refurbishes original sending units?
Click to expand...
There were a few vendors mentioned including one negative feed back mention in a recent thread. Based on what I've read, The new aftermarket sender along with Technoversions meter match is the less expensive route.
 
Maybe ... but I don't prefer wiring. I stink at it. I generally have to pop fuses until I guess the correct wiring...
 
Yeah, I caught it. AFTER getting it started (that day), and finding it leaking fuel and finding FROM WHERE ... at that time it made sense to me WHY it wouldn't pick up the fuel and start. The pump was sucking too much (only) air.

So yeah ... I'm running the tank down (again), but now I'm scared to run it out of gas. Because even with a gas can with me, it would NOT pick up the fuel with that cracked fuel line, and I'll be left sitting on the side of the road. So, I'm just going to run it down to about 10% left (as best I can figure), and hope I don't take an ethanol-free bath.

At least when idling and sitting still, it's not leaking any more. I'm guess it was leaking pretty heavy before because when I filled the tank, the fuel level was above the cracked fuel line, so the weight of the fuel was pushing gas up the line. And with a crack there, it pushed it out the crack when the rest of the line was full. Now the fuel level is down, so it's not pushing it up the fuel line. I'm going to put about 175 miles on this tank. That should be low enough.


7milesout
 
You must log in or register to reply here.
-

Back
Top