Fuel pumps... WTH???

Could be that the engine is building up pressure inside at higher speeds, but pressure leaks down by the time you're able to measure it. At this point I'd consider one of those stealth electric pumps. Just take the arm off the stock pump and make a sheet metal plate to go between it and engine block. Dummy up the connections or alter the pump and push fuel through it with the electric.

Red20 wrote: Well, if you're ever in Oceanside these days, you'll see my yellow 1969 screamin' down the I-5. It was originally a 290 SST car. It seriously had only 16k well documented miles on it when I bought it in Hawaii a couple years ago for $2,000. Maybe when I rebuild my overdrive tranny it'll go from screamin' to talking in a raised voice. And I'll frequent the gas station a little less often... I'll dig the fuel pump out of whichever parts bin I put it in tomorrow. Good luck!

16k miles for $2k? What a find!

maximus7001 wrote: Having 2 AMC cars with 258 6 cylinder daily driven for decades I can tell you that the alcohol ate every fuel pump so far. The longest I have ever got out of one is 4 years. The original 49 year old dual action pump on my 68 Javelin 290 just started leaking in april. It is a very reliable design. I sent it out to Then and now for a rebuild. Did you ever solve the oil leak from the vent hole issue?

No, that's the problem I'm still chasing. I haven't had any problems with them leaking fuel.

Yep Josh, I got your message and have sent the funds.  My mailing address (in case you can't open the message) is:

Cameron Earnshaw
10715 E. Valley View Drive
Cornville, AZ  86325

Thanks again for all your trouble!

Cam

Here's an interesting thread from a hot rodder forum.  Though the car is a Mustang, the basic design of the fuel pump is the same as ours.  If you do some searching on Goggle, you'll find this oil leak problem is extremely common with pumps of this design.  I haven't been able to find an original '69 Carter M-4656S pump to take apart to see how the oil seal is designed, but I just took apart an Airtex 905 pump that was manufactured in 1986.  The design of the seal in that pump looks exactly the same as the current Carter, Airtex, Precision, etc.  I don't know if they use the same seal material now as they did back then-- or if maybe this problem has been going on for years-- but the design seems to be prone to leaking and we don't have the choice of different designs like we used to. 

The solution these guys came up is clever-- exactly the sort of thing I was considering-- but they've already done it.  Would be nice to know whether it held up over time.

http://www.hotrodders.com/forum/carter-edelbrock-fuel-pump-carb-problems-212139.html

One thing they mentioned, but didn't follow up on, was perhaps the vent holes are too small.  I had wondered this myself.  Seems to me that if that were the case that it would create a vacuum in the cavity as the diaphragm moved in and out, and that could perhaps draw oil past the seal at high RPMs.  I have an extra pump here, so I'm going to make the vent holes larger to see if I can learn something.  If that doesn't work I can still use the pump to try the mod the Mustang guys did.

Edit:  The original vent holes were 3/32" and I'm drilling them out to 1/8".  Will follow-up to let you know how that worked. 


Edited by CamJam - Oct/06/2016 at 5:03pm