Fuel pump
Thread Starter
5th Gear
Joined: Sep 2007
Posts: 5
Likes: 0
Fuel pump
My son and I have an old C3 we mess around with on the weekends for some good father son time. Took it for a drive yesterday and noticed a puddle of gas when we got home. Ran fine all day. Took a look and found a leak where the fuel line from the carb attaches to the fuel pump. We've been trying to get at the nut to see if it just came loose but can't figure out how to get a wrench on it. Do we need a special wrench? Is there a "trick" to get at it?
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
No trick. I can't remember the size but you need to have a wrench on the brass section as well.
If fuel is leaking there fix it properly. If you won't then you run a serious risk of fire. The gas leaks and sprays against the hot exhaust system. A very common cause of fires in C2's and C3's.
If fuel is leaking there fix it properly. If you won't then you run a serious risk of fire. The gas leaks and sprays against the hot exhaust system. A very common cause of fires in C2's and C3's.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Not real likely the nut came "loose". Possible, but not way up on the list. Most of the tube nuts are pretty soft too. Use a flare nut wrench. Looks like a box end, but has a slot opening just one flat of the box and are 6 point. Using a normal open end will possibly just round the nut, leaving you with a bigger mess. I have a crowfoot tube wrench that I can put on the nut, then a 3/8 extension or wobble joint or whatever.
If you can confirm that the tube is leaking and not the vent(s) on the fuel pump, I'd pull the tube all the way off and look at it around that flare for cracks.
Sorry, no real tips or tricks to getting into the tube. I know it's pretty tight around there. Maybe from the bottom or thru the wheelwell?
The nut 9/16 wrench size and be sure to use a backup wrench on the fuel pump side- you can twist the fitting right off the pump.
If you can confirm that the tube is leaking and not the vent(s) on the fuel pump, I'd pull the tube all the way off and look at it around that flare for cracks.
Sorry, no real tips or tricks to getting into the tube. I know it's pretty tight around there. Maybe from the bottom or thru the wheelwell?
The nut 9/16 wrench size and be sure to use a backup wrench on the fuel pump side- you can twist the fitting right off the pump.
Drifting
Joined: May 2012
Posts: 1,353
Likes: 44
From: Calgary Alberta
You can remove this from underneath with the car sitting normally if you have to. Swapped the pump and lines on my 70 this way because I only had one jack and most C3s don't like to be jacked from one side only. Make sure it's not the vent holes in the pump first...that's what mine was and it's the pump checking out of the hotel. If it's the fitting or the flare on the end of the line you need to get a wrench on each...sometimes those brass fittings don't want to budge at all after a bunch of years. Not a nice place to have a leak but you'll get it fixed up, it's not that bad.
Thread Starter
5th Gear
Joined: Sep 2007
Posts: 5
Likes: 0
Thanks for the help. We got a crowfoot on it and verified that it was tight. When we crank the engine, you can definitely see the gas leaking from where the carb line joins to the pump. Not sure what you all mean by "vents holes on the pump". We did verify that fuel was not leaking at either of the other two lines attached to the pump. Are there other places that the pump could be leaking other than the fittings?
Next, we removed the carb/pump line completely to check for cracks. Close inspection did not reveal any cracks in the line.
I am thinking we will purchase a new line and install it to eliminate that as a problem. Do we need to prepare the fittings in any way?
Thanks!
Next, we removed the carb/pump line completely to check for cracks. Close inspection did not reveal any cracks in the line.
I am thinking we will purchase a new line and install it to eliminate that as a problem. Do we need to prepare the fittings in any way?
Thanks!
Drifting
Joined: May 2012
Posts: 1,353
Likes: 44
From: Calgary Alberta
The vent holes on the pump are also commonly called "weep holes"...they are typically not present on aftermarket replacements, but original AC pumps had two small circular holes at the top of the canister looking piece of the pump. These holes would leak fuel in the event of a diaphragm failure inside the pump. This typically puts a lot of fuel on the ground...and it can look like it is coming from the fittings / line as it runs down the side of the pump.
If it is not that...I'd replace the line because possibly it is no longer seating properly in the brass 90 degree fitting that connects the line and pump, and I'd replace the brass fitting itself while you're there to save having to possibly go back there again. Corvette Central has both...the factory hard line for my 1970 was around $30 and the brass fitting was around $5 or something. There is a good thin sealing compound that is specifically for fuel applications, but I can't recall the name of it...white stuff, small applicator.
If it is not that...I'd replace the line because possibly it is no longer seating properly in the brass 90 degree fitting that connects the line and pump, and I'd replace the brass fitting itself while you're there to save having to possibly go back there again. Corvette Central has both...the factory hard line for my 1970 was around $30 and the brass fitting was around $5 or something. There is a good thin sealing compound that is specifically for fuel applications, but I can't recall the name of it...white stuff, small applicator.
Thread Starter
5th Gear
Joined: Sep 2007
Posts: 5
Likes: 0
Thanks! Going out to check on the weep holes now. I already looked at Corvette Central and did find the line for $30 and the brass fitting for $4. If it's not the weep holes, I'll call them to place the order and ask them about the sealing compound.
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Drifting
Joined: May 2012
Posts: 1,353
Likes: 44
From: Calgary Alberta
You don't have to remove the two lines from the frame to the pump. The larger one is the supply from the tank, you'll need to pinch that off carefully to stop the flow of fuel because it is gravity fed to that point. You can use a long nose style vise-grips for this with a little piece of tin or something similar to make it easier on the rubber. The smaller line is the return line, you shouldn't have to mess with that. Make sure the rubber is in good condition...they are cheap to replace if they are worn.
The pump came off my car first before removing the fitting because the fitting was in no mood to budge, and the pump was clearly the issue in my case. I used a regular old open ended wrench to get it off in the end.
The pump came off my car first before removing the fitting because the fitting was in no mood to budge, and the pump was clearly the issue in my case. I used a regular old open ended wrench to get it off in the end.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
The vent holes on the pump are also commonly called "weep holes"...they are typically not present on aftermarket replacements, but original AC pumps had two small circular holes at the top of the canister looking piece of the pump. These holes would leak fuel in the event of a diaphragm failure inside the pump. This typically puts a lot of fuel on the ground...and it can look like it is coming from the fittings / line as it runs down the side of the pump.
If it is not that...I'd replace the line because possibly it is no longer seating properly in the brass 90 degree fitting that connects the line and pump, and I'd replace the brass fitting itself while you're there to save having to possibly go back there again. Corvette Central has both...the factory hard line for my 1970 was around $30 and the brass fitting was around $5 or something. There is a good thin sealing compound that is specifically for fuel applications, but I can't recall the name of it...white stuff, small applicator.
If it is not that...I'd replace the line because possibly it is no longer seating properly in the brass 90 degree fitting that connects the line and pump, and I'd replace the brass fitting itself while you're there to save having to possibly go back there again. Corvette Central has both...the factory hard line for my 1970 was around $30 and the brass fitting was around $5 or something. There is a good thin sealing compound that is specifically for fuel applications, but I can't recall the name of it...white stuff, small applicator.
Thread Starter
5th Gear
Joined: Sep 2007
Posts: 5
Likes: 0
Thanks for all your help so far. Just received the pump to carb gas line from Corvette Central, and we can not find the right way to snake the pre-bent line down to the pump or up to the carb. Before I give up and start disconnecting hoses and parts, anyone have any advice?
Racer
Joined: Oct 2003
Posts: 424
Likes: 9
From: Killeen Texas
I replaced my fuel pump about 3 years back on my '81, and it was a SOB. Had to remove alot of things under the hood and it still wasn't easy. Just one of those time-sucking jobs and nothing easy about it. Good luck.
Drifting
Joined: May 2012
Posts: 1,353
Likes: 44
From: Calgary Alberta
If the old one came off, the new one will go on. I'm sure you're going to have some "why do I do this to myself" moments...Corvettes are perfect for that...but it will go. I sent mine up from underneath. I assume it's just a stock hard line you've got.