The Stovebolt Site Forums The Parking Lot Big Bolts 1972 c50 mechanical fuel pump issues...

so this is the second mechanical fuel pump i have replaced and its because they start leaking where the metal is pressed together.... i guess its cheaply made but where can i get a good quality mechanical fuel pump? Id rather keep everything original as to the fuel system.... dont need any electrical issues keeping me from driving or id buy a new truck haha...

Thanks mike

Rock Auto has several fuel pumps for your 350. i.e. AC Delco, Carter and economy pumps. Sounds like you may be buying the economy pumps. I'd go with the AC Delco or the Carter. Cost difference is mice nuts.

Well im kinda scepical now cuz they look just like the one i got from orileys. But this is my 3rd pump in less then a year..... is there something causing this issue??? All of the fuel pump have worked for a few months then start leaking right where the lower section of pump is pressed to join the upper section theres a "seam" around it where ita leaking from. But the last two were just steadily dripping while the truck was running. This one i noticed yesterday when i noticed a wet puddle on the ground under it just parked and i got down there to smell gas and see an actual drip happening just sitting in park..... and its dripping feom same seam..... are the manufacturers really doing this [censored] of a job or is my truck causing this some how?????

I did find a mechanical fuel pump online that has small bolts going all the way around the pressed seam im talking about and im.wondering if this is the upgraded version due to the leaking seams????

Hy DIY.MechanicMike, the problem is with the pump manufacturing process not you or your truck, the pumps you have been buying are not repairable, the pump you found with the screws around the circumference are repairable and that was the way all the fuel pumps were made in the past. Buy the one with the screws if it is not N.O.S. (new old stock), N.O.S. pumps have diaphragms and check valves in them that are not compatible with todays fuel formulations, hope that helps.

Could it be building up to much pressure because my gas tank is behind the seat, so there isnt much suction going on so the pump is putting all its got into pushing the fuel rather then sucking? And since my tank is higher (more gravity flow) the pump doesnt even need to be pumping all that hard, heck if i kept it at a full tank and never let it go below 3/4 tank i probably wouldn't even need a fuel pump, cause my carb inlet is only maybe 3 inches higher then the bottom of my "behind seat" tank where the outlet is.
Idk im just laying out random things i have thought about causing this.... one other thing i thought is because my truck is so low geared that when on the highway i can only go 50mph max in 4th gear @3k rpm. I usually just cruise at 45 mph and that drops my rpm to like 2500-2800 which i feel better driving at just cuz i like to baby it cuz its my first big truck and id like it to last. And not to mention its a classic haha. It might not be a hot rod but its a classic work truck and that just shows how tough they are to still be around today and working. But just a fyi i dont drive it alot, it might get a average of 50miles per month put on it and some times it doesnt even move like January and February so its not drove alot and in the last year of this type of driving 3FUEL PUMPS LEAKING!!!! WTF LOL this is why im close to going to a electric but i feel the mechanical ones are more tuned into the engine cuz they pump based on the engines rpm but idk it just makes sense it would be better tuned, you know the more rpm = more pump action which = more fuel for more power as you need it. then less fuel when you take your foot off the pedal and slow down. So if my thoughts on this are whack and and electric pump would fix it all please let me know haha

Thanks "3b" ill check on those type then. It looked to be better quality then the others. Orileys will just keep giving me new ones for free and sending the old ones back cuz they dont last longer then the 1 year warrenty so i could just keep on that route for free but 1. Its a waist. 2. I dont have time to be going and doing all that. And 3. The reliability factor. i dont wanna have this happen at the rock quarry or after leaving there with a full load and having to take a fuel pump off on the side of the road togo swap it out haha. Thats just insane.. thanks for the valuable info on the pumps....

So i found a couple that are like the "older style" with the bolts around the circumference. Now the two im looking at are not much different in price but one delivers 80gph free flow rate at 5.7-8 psi and the other delivers 110gph free flow rate at 6.5-8 psi. Now giving my previous information on how my truck is driven and how often and what rpms and such and fully loaded weight at 24,000lbs max what pump would better suit my needs? I have pretty hilly terrain in my area if that matters....

What does the free flow rate even mean? I personally feel the lower flow rating would be better giving im not a racecar and i already have good fuel flow thanks to gravity but your guys' input makes me feel much better about making a decision Haha.

Also i have the original 2bbl Rochester carb for the 350 engine so with that info which delivery rate would best suit my rig? Did a lil looking into the free flow rate and it seems the carb has a bit to so with things.....

The flow rate needed is related to the horsepower the engine is making, it is only related to engine speed in a general sort of way. Any standard type quality pump will keep up with your engine. The high pressure pumps you describe above are meant for racing applications and likely put out too much pressure for your standard tuned carb.

4-5 psi is plenty, 8 psi will likely push gas past your needle and seat. That is not a good thing.

Get a standard Delco or Carter as mentioned above. Don't worry about the rebuildable thing, it is unlikely you will ever need or be able to get parts for it anyway. Crimp together pumps are OK if they are quality built.

Go to a Chev dealer and buy the real deal, or get it on line, but get a OEM quality pump. If O'Riely sells Delco or Carter, you can certainly get it there, or anywhere else. You have learned what cheap crap is worth, don't buy it again.

I never use second line (cheap crap) parts on anything I want to keep working, the good stuff is well worth the small cost of the up grade.

Keep that Chevy on the road! :{)

I found one that is rated 15gph free flow rate @ 4psi max would this work?

Would having one with to much pressure cause it to push more fuel threw then you needed causing a rich burn? And basically a waist of gas?

I think that would work fine, 4 psi is about what the factory specs are for the OEM pump

And yes, too much pressure will overcome the float's ability to close the needle valve. It might be adjusted by lowering the float but there may also not be enough float to ever close off the flow of fuel. The high pressure pumps are made for special applications which you do not have, since you have a standard carb and a standard engine.

So far all good info here. In my experience I have never seen a pump leak at that spot. Usually it is from the weep hole or into the block from the diaphragm.
When you install the new pump make sure the rigid line is supported along the frame. Maybe when you are driving the truck the fuel line is under tension or flopping up and down like a jump rope and tearing loose the pump bottom? Or a steering component hitting a line?
I'm just thinking out loud because 3 failures in a row seems almost impossible. But, you may have stumbled across a batch of worthless pumps too! Good luck!
Mike

This is exactly what I was thinking. Hope you don't have something tied to it or hitting it. Most of the websites say Carter M6624 is the pump you want. You experience is rare for that many pumps in one year. Most pumps, no matter where you buy them, will be Mexico or off shore made. No matter what brand.
Because of the rare situation you are reporting, I must also mention that you may be mistaken about where the leaks are. You may have a bad fitting that is leaking down onto pump. A fitting or hose or tubing that you keep using.

Also, you don't buy a fuel pump for a simple common 350 2bbl Chevy motor by the PSI or GPM. You buy it per the recommended stock application.

I will say that M6624 has a higher PSI than I thought would be correct. But all the vendors say that is the number. That has nothing to do with the crimp seam leaking. It does have something to do with other places leaking or carb flooding/leaking. If you are sure it runs good and the leak is at the crimp seam, buy the Carter M6624 next time.

You may be getting older rubber or Chinese rubber diaphragms that are not E10 rated and there is a weep hole leaking.

Of ALL the vendors I checked, including O'Reilly's, only Rockauto lists a C50. Which does not mean anything, just funny. It's the motor not the truck that needs the pump.

All of the above is stated if you are not keeping any secrets about the motor/carb/fuel system. Please state if you have noticed loss of power, hesitation under load, while pump was leaking.

I don't know if this is true or not. I have lots of theories in my brain sometimes when it comes to analyzing weird issues like yours, but if your gas cap or gas tank is not vented or the tank has intermittent blockage, the pump will pull a vacuum which may break pump diaphragm and then weep. Also if something is causing the diaphragms to fail, gas gets above the diaphragm and in a chamber that is not leak proof and the crimp leaks gas. But these theories do not hold up if truck still has plenty of power during leaking. But on the other hand if the pump crimp is above the diaphragm and diaphragm is not broken, there would be no gas in that chamber to leak. OK, I'm past pill time. Bye, bye.

Hey sorry it's been a while.... But I ended up just swapping one out at orileys again but this time they had to order it in so maybe a different batch like someone said, idk but it hasn't been that long either ..... But I'm for sure it was leaking from the crimped area cuz I was watching it while my truck was running, was not coming out of the weep hole. I did notice one of the times I had hesitation issues and limped it back home and didn't realize it and left again and sure as [censored] lost power In same spot going up a hill and came back and smelled fuel and found the problem. But as of right now I'm good to go as I just returned old one n got a new one from orileys.