Here's my problem. I keep blowing the diaphragm on a Purolater fuel pressure regulator. It's happened 3 times in 10 days.
The 1st reg lasted about 6 months. It was installed before the fuel filter. When it blew, I got a new one and kept it installed that way.
3 days later, it blew again. This time I changed out the fuel filter, installed the reg AFTER the filter, with the return line to the tank going around the reg of course. I replaced all the rubber fuel lines w/new ones, checked for flow through the metal return line by blowing through it. I found that I could blow through it pretty easy, but with the gas cap on, it would build a slight amount of pressure and blow back to me . With the gas cap off, no blow back. I have seen pressure build up in the gas tank of every? car I've put gas in at some point or another, so I took it as normal.
Today, 6 days later, having driven my Jeep maybe 10 miles total, it blew again. I have doublechecked every reg to make sure it was routed right.(in/out-wise) My fuel pump is the stock mechanical type. the carb is a MC2100. The metal fuel lines, supply and return, are not crushed or kinked anywhere. My engine(258) doesn't stumble or miss at all as the reg is spewing gas all over the intake/exhaust. My engine is cleaner than it has been in years, but I still think this is not an optimal situation. Anybody been through this before or got any ideas?
Thanks, Shell

edit: first the obvious question... do you have the regulator plumbed for the correct direction of flow. Just making sure.



This time I changed out the fuel filter, installed the reg AFTER the filter, with the return line to the tank going around the reg of course.

how is it plumbed ? is it like this?

fuel pump -> Filter ->
Tee
-> one leg off tee returning to the tank
-> one leg off tee to the regulator then -> to the carb?

I'd put a pressure gauge on the return line. Make sure the regulator can regulate down from that pressure.


This is just a guess, but can the regulator handle back flow without blowing the diaphragm?

With a very hot engine, if the needle on the carb can hold more pressure than the regulator can handle for backflow, and, if backflow harms the regulator then this might be the problem. Like I said, this is just a guess. I don't know how fuel pressure regulators work:rolleyes: I just know when they don't work :bender:

It's easier than you think to put it on backwards, one of my friends put his new electric fuel pump on and thought, okay, OUT of the tank and IN to the motor....uh, nope. We love making him feel small in the pants over that one. What's the temp outside when this is happening? What about the tank vent?

1.It's easier than you think to put it on backwards, one of my friends put his new electric fuel pump on and thought, okay, OUT of the tank and IN to the motor....uh, nope. /first the obvious question... do you have the regulator plumbed for the correct direction of flow. Just making sure.


I have doublechecked every reg to make sure it was routed right.(in/out-wise)

2.It is plumbed like this: Fuel pump>Filter that has return line port in back of it as well as a supply to carb port. The return line bypasses the reg.>reg>into carb.

3.What's the temp outside when this is happening? What about the tank vent?

It is Africa hot in south Louisiana. "I will rebend the metal supply line from the pump as far away as I can from the intake/rad. hoses, etc. Right now it has an inch or so of clearance."
Just how well is this tank vent supposed to work? -With the gas cap off, no blow back. I have seen pressure build up in the gas tank of every? car I've put gas in at some point or another, so I took it as normal. - "I will replace the gas cap." Is there another vent on the stock '83 CJ-7 gastank? I don't remember seeing one when I changed the sending unit about 2 yrs. ago.

4.With a very hot engine, if the needle on the carb can hold more pressure than the regulator can handle for backflow, and, if backflow harms the regulator then this might be the problem. Like I said, this is just a guess. I don't know how fuel pressure regulators work I just know when they don't work

My 258 consistently runs on the cooler side of warm. If needle seat pressure was the problem, wouldn't it have surfaced before? The first reg I had on there lasted 6 months.

I'll do what I mentioned earlier in quotes in this response and see if it helps. I'd like to hear from someone who's had this happen to them, and thanks for the response. -Shell

B/T/T
Anyone else?

Do you have a charcol canister installed so the tank can vent?

If you do it sounds like its clogged and the tank build pressure and pushes it back through the lines to your regulator instead of out to the canister