What is the average lifespan of the diaphragm on a carbed big six that is using 10% ethanol? Do they leak fuel into the engine when they fail, or just quit pumping? Are some pumps better than others? Is it better to replace them on a routine basis, or wait for them to fail? Are fuel pump diaphragms available separately? If so, who sells them?....thanks, jack

 

"Do they leak fuel into the engine when they fail..." I'll answer that one...Yes, they can fail in that manner. If not caught in time, the gas leaked into the crankcase dilutes the oil and lead to premature failure of bearings, etc.

 

These are good concerns I think especially when you are using ethanol in the gas, and the factory manual fuel pump.

Lifespan?..until it fails I guess..
Some better than others?..Choose your own preference..I used to like Carter's..but these days anyone's quality is speculative. I see that both Holley and Edelbrock sell a "racing pump" for v-8's but show no listing for a big 6. Classic inline shows a process of modifying a SBC racing pump to be used.

http://fordsix.com/forum/viewtopic.p...0105e5#p538804

Classic Inlines - Carter Fuel Pump Modification

Certainly worth some discussion..if you're going to change it..it's certainly better to be able to do it when and where YOU want..I always have a spare.(Carter), but I must admit..a modified better quality racing style pump may be a good choice especially if the diaphragms can be changed..

This is an advantage for an electric one of course..if you go THAT route..they generally last longer as a "pusher" than a "puller".(at least frame mounted as close to tank as possible), and make sure it's got a specific pressure for your carb. (Something that gets overlooked when using a manual pump even) But even with their problems..they DON'T risk any gas in the oil. It IS comforting to hear that BBBBBddddtttt when the key is turned on and the pressure builds, especially when you've ran out of gas, dark out, and your battery may be low and it's 10 below.

Good discussion..more research..make decisions

 

Some of the older mechanical fuel pumps had a replacable diaphram, but most of the newer ones, as well as replacement units do not.
Most newer replacement pumps have an ethanol resistant diaphram, been that way for 20+ years.
There isn't an "average" lifespan for these types of things. Some last decades, others can fail in less than a year. Getting a good quality replacement is the key to having one that will last, but even these can have unexpected failures.

 

Mine became weak before it failed altogether and it didnt supply enough pressure making starting harder.

 

Still running the original fuel pump on my 1986 and same with my son's 1984. Unbelievable, but true!