WOW this board is getting slow...

Looks like I have a blown diaphragm since even with the new 30 psi rate 454 pump, I can only get about 9.5 psi with the adjustment run all the way in. My only remaining hope is trying the new filter I have, but the one in there is not old, and the gas in the tank seems clean (checked while changing pump and sock was in very clean condition, though I know that is no proof, so I'm changing it just to see).

Anyway, I've seen posts where people talk about diaphragms, including one that is thicker than the typical TBI diaphragm, but no sources or part numbers that I could find. The board being so slow also makes it difficult to do searches with all the threads that have to load, so I'm hoping someone can give me an idea where to get ANY diaphragm that will work. Looks like none of the kits come with that piece. The dealer and 2 parts houses tell me the only thing I can do is order a new regulator assembly, but that's a big chunk of change just to get the diaphragm.

If I can't find a source, I guess I'll just have to get an in-line or something. Surely there is some source for these things...

 

when the diaphragm blows i believe it will puke fuel in great volumes. did for me anyway. there is a spring available from top down solutions that allows more FP than stock F body spring. also there is a orange spring that i believe will get you over 20 easily. that is one used in VAFPR and possibly in a high pressure TBI application. my aeromotive FPR has 2 springs one like 10-20 and the other 20-50.

 

Thanks, but I've already "upgraded" to a spring that supposedly allows 5-40 (IIRC?) psi adjustment. And it was running about 14.5 when I first installed and adjusted it. Then I started seeing < 10 psi readings and thought the OEM style pump, apparently known for not being able to maintain more than 15 psi, was too close to "dead head" and was giving up. So I swapped in the 30 psi 454 pump I had already bought but not got around to installing. Same pressure, so now I'm only guessing, but the diaphragm seems the most likely culprit...

Problem is, I can't find a single parts house that can get me a diaphragm by itself or a kit that contains one (acording to the guys I spoke with). The only way I can get one, it seems, is by buying a complete regulator assy from GM just so I can get the diaphragm.

 

diaphragm is available seperately. i purchased seperately about 2 years ago when i ruptured 2 from what i thought was too high FP. i did a search for "fuel injection parts" and found a company. i might have receipt at home. when the diaphragm fails gas comes pouring out of the cup bigtime. i think something else is the issue. i went to a TPI pump to get 20+ FP not a TBI application. the 1995-1996 454 pump should hold 30+ FP all day. that i believe is the first application for high press TBI. what year application was your pump??

the diaphragn has no relationship to FP. the spring does. is it possible you have wrong spring?

 

That's the pump I'm running, made no difference in pressure.

I've been working toward that same conclusion on the diaphragm and spring. I originally thought diaphragm and didn't think it would leak due to the close after market cup I have, but then I remembered that is has to be referenced to atmosphere (or vac) and that the leaking fuel would poor out that hole, and it's not, so probably not the diaphragm. I know I put in the spring that was rated for 5-45 or whatever, but I wonder if the spring is bad, has since broke, weak, or whatever. It was maintaining about 14.5 for the first few hours, but then fell off, so I'm not sure. I'll be checking that spring before doing anything else I guess.

Thanks again…

 

Well, true enough, it wasn't the diaphram.

Finally got of my laziness and replaced the fuel filter, as expected, no change.

Took off the TB and gave it a once over. Looks like maybe the spring just bound up. I backed it off a bit, ran it in again, and it went way past where I thought it was bottomed. Ran it to bottomed, backed off about 6 turns (about half way in from where it seems to have hung) and installed it. 22 psi right steady. MAN THAT THING IS FLOWING SOME FUEL NOW! Injectors were still seeping after shut down a bit (a few drops) and the bores were full wet. Probably gonna have to back it down a bit but at least it wasn't something serious. Never expected or thought about it binding in the FPR bore (or whatever it really did).