Put my new fuel pump in this afternoon and its like night and day. Before the engine ran really rough around 2k at low loads and it had a hot cammed idle with a really bad periodic hiss/pop sort of sound. I never did measure the pressure but I knew from a fact that the stocker got plenty of fuel past the regulator. Still, though, that was no guarantee that it was working properly. The pump mustve been pulsating real bad.

Runs great now. No funky idle, not rough around 2k. Runs like a completly different car.

I took the stock pump apart and it appeared to be fine inside. The commutator and brushes had some miles on them but nothing that would stop it from working properly. The proof is in the pudding though. The walbro made all my problems go away. Further proof that the stock fuel pump is little more then unadulterated garbage.

 

What psi are you running w/new pump?

 

Stock, but when I swap some vortecs on I plan on going up to around 20-25 psi. The pump itself will go up to around 110 psi.

 

Sounds good man. Told you those stockers are crap!

 

Good to know! I wholesale those pumps so I can get mine for DIRT cheap (and I don't even have to wait for it to show up, we got like 60 of em in back!) I'm almost positive a have a decent amount of crap floating around in my tank, so it wouldn't be a bad idea to take it off and clean it out, then throw the new pump in...

 

So does that mean you can get us the TGO discount on a new one?

 

You have a tax ID and business license?

 

I do send me info!

 

No, but I assume you do Fuel pumps for everyone, lol.

 

I would also be interested in getting one if you do wholesale them to members here. Let me know Thanks

 

20-25 psi on tbi? i thought the injectors could only handle 16 or so

 

1995-1996 truck TBI is factory spec'd to 32 lbs. i was running 20 lbs all summer but just dropped it to 17.5. i think higher pressures over 32 are no problem. never heard of a high pressure TBI injector failure???

 

Did you have to drop your rear end to get to the pump? Was it in the fuel cell? How hard was removal and insallation on the pump? I am a newbie so all this stuff is kind of new to me

 

lol, look for my post about fuel pump down a little bit on the boards... i just did it.. You dont HAVE to drop the rearend, but its easier to unbolt the shocks and take out the springs... that will lower the rear enough.. you do have to take off the panhard bars, the muffler and all the heat shields. and yes, its on the top, in the middle of the tank. once you drop the tank, the pump removal and install is EASY... just dont bend your fuel level sender like i did... its not fun to fix... i didnt make mine terrible, but its a little off... it took me about 4 hours after i got the muffler off

https://www.thirdgen.org/techbb2/sho...hreadid=299545 <--- thats my post, lots of good info in it

 

The stock pump is what limits that PSI. Like it was said earlier some later 454 TBI trucks ran 32 PSI of fuel pressure with a 4.3 injector. I think it was mainly to keep the engine from vapor locking as easy.

I helped tune a old school LT1 spec 350 using TBI w/305 injectors. We used the regulator pod for a 94 chevy truck 454. 32 PSI of fuel pressure and right at 370 hp.

 

mmmmm i have a fuel pressure regulator on my throttle body from turbo city, with it all the way in i have 16 psi with the stock pump.............im going to put in a 190 lph walbro this weekend, do i need to hookup the gauge and all to adjust or can i leave the regulator the way it is? its such a pia , i have a gauge that i put in place of the fuel filter to get the reading then i have to yank it and put filter back in, unless there is an easier way i dont know of........ this is news to me, i was told after about 16 psi the injectors would start to pop and could fail, and you guys say your running 32 psi?

 

The injectors them selfs will take as much pressure as MPFI injectors, it's the injector pod gasket that could fail. Like mentioned ealier, GM ran 32 psi so I'm sure we would be fine running that much.

 

The diaphram in the regulator could potentially fail as well. The diaphram is exposed to the full fuel pressure at all times.

 

so on a 305 tbi setup what would be the safe setting? i thought it was around 16 or so, what would the walbro 190 put out with the regulator screwed all the way in? apparently the stock pump is 16 psi

 

Youd end up dead heading the pump if you cranked it all teh way down.

I dont know what the stock regulator would be but with my replacement holley I calculated the max safe pressure before the spring gets within .060" of presses solid to be around 17 psi, which is pretty close to what the actual was. Around 21 psi, the spring pressed solid and the pump dead-headed.

 

im sorry i dont know what you mean by dead heading the pump, i gather your saying if i left it the way it is i would be running about 21psi? and according to most of you this is ok?

 

i just found this
http://www.diy-efi.org/gmecm/faq/tbi_fp.html


is he correct in saying you cant get your pressure any higher than 15 with the turbo city regulator?

 

Dead heading the pump is when youi block all the return flow. This will cause the pressure to come up to the max that the pump can deliver.

With a holley high pressure spring for their aftermarket tbis or a spring from one of the later BB tbi regulators, you can get at least 30 PSI or more out of your stock regulator.

 

A MPFI engines regulator diaghram can fail too. I would be more worried about the TBI gaskets, but I have seen MPFI engine use very similar gaskets on fuel rails and are running at 60 PSI, so I would not be too worried on the TBIs fuel holding ability. I have only heard of one diaphram failure and it was on a TBI running 48 psi in a supercharged 2.8 S-truck with an older diaphram (original?). When the new diaphram was installed, along with new O-rings and gaskets the TBI held 48 psi no problem.

An assortment of various transmission springs comes in handy when trying to manipulate the TBI regulator to a different pressure.

 

well im going to shoot fot 16 idle and 22 wot, seems to be what most run

 

One of the things that concerned me was that the system was only designed for up to around 12 psi origionally with the first units so its sort of unclear how much pressure they can really take before it blows out. If it blows out with teh stock regulator, itll spray fuel all over.

By transmission springs your referring to accumulator springs? I always wondered if those would be the right dia.

 

ummmmmm,these guys that are running 22 wot , is that with aftermarket injectors? i did have the stock ones replaced with flow matched ones from turbo city, however just being flow matched makes me think they are the same as stock...

 

Stock ones should be fine for higher pressures.

 

i blew two GM regulator diaphragms. one was old with 65K and 10 years on it i replaced that and instantly blew a new one. i had unknown high fuel pressure with a 1985 vette delco pump and stock FPR and stock spring. i did not listen to board members about using a FPG. lucky me it happened while i was watching for it. talk about a fire hazard! moved it back to 13 lbs and used a VAFPR but that is another story and another mistake. BUT VAFPR did not blow diaphragms.

 

I really need to go back and look at a pressure regulator again, I swear that the diaphram is on the return side of things, there for there should be very little pressure on it. The only pressure would be whats needed to push the fuel back to the tank.

This is how I see the system setup. The fuel comes in and is exposed to the injectors and the regulator. The regulator has a metal plunger that actually pushes on the opening that allows fuel to bypass to the tank. The diaphram is around this plunger and on the return side of the plunger. Once the fuel is past this plunger there is nothing restricting it from returning to the tank, there fore there should be no pressure. Ronny, I can't really explain why you blew diaphrams. I know when I dead headed my system I spiked the fuel pressure into the 50's for a few seconds with no problems. I would expect the pod gasket to be the weak link. Seeing that GM ran 32 psi on some of the truck TBI's I would think that 32 would be a safe number to ASSume.

Like Ronny mentioned I think VAFPR are a crutch and I haven't heard anything good about them from people that DIY tune. I'm sure they help the guys that are just trying to tune with them exclusively.

Are the VAFPR's that top down sells GM pieces? I was thinking that they were used on some big block applications. If they were has anyone ever looked at the bin that went along with it to see how GM tuned around it?

 

The fuel pressure regulator diaphram is exposed to the full fuel pressure. The port at the top of the regulator in the pod is the return port. There is a side port that leads to the injectors and dumps excess fuel to the daphram. The force from teh spring keeps the seat on the diaphram against the return port untill the pressure over the diaphram exerts enough force to exceed the spring force, and teh diaphram (and seat) moves back, allowing fuel to return. You can even calculate what the resulting fuel pressure will be.

 

yea i aggree with Dim. the rip in diaphragm was preceeeded by fuel all over top on intake. i assumed a gasket. nope, the diaphragm. now here is the odd thing. in both instances the phragm will hold the pressure(unk amount) with key on, when starter engages it ripped. that was wierd. lets assume i had pressure set to near max pump will allow. what FP does a 1985 pump apply at max? maybe 50? as it is a TPI pump. ithink stock TPI is about 25 or so?

 

Could be pulsations pushing the diaphram over the edge. With my stock pump, teh pulsations would cause the fuel pressure regulator to make all sorts of weird noises as it ocillated.

 

OHHHH! I was under the impression the fuel ran the other way.

 

Take a good look at the return passage its insanely small and if you have a high volume pump it can't all get back to the return line. POP there goes the diaphram at higher pressures. drill it out some and you will be g2g.

 

Heres a pic of a return hole. its not centered and the return line fitting will hep close that up more I'm sure.

 

i have a 7.4L TB. i will assume the return hole in that unit larger? now i have an Aeromotive unit. when ripped was stock crossfire units with stock FPR.

 

That is a 454 TBI! I drilled out ther return and the incoming passage part of the way and knocked down the corners where they start and end at.

 

I thought the stockers were but my Holley wasn't... I was wrong. It's the same. It's for dampening the pressure pulses from the pump. The pump design for high flow is usually (not always) a vane style and that has pressure spikes. A screw type compressor or centerfugal (supercharger and water pumps) doesn't have as bad of a pulse. I think the stock TBI pumps might be a worm style, I don't know for sure but I wouldn't mind taking one apart to compare. Anybody got a stocker laying around theywouldn't mind hacking up?

 

I chopped mine up. It has dual vaned rotors in two stages that force the fuel to flow through the actual DC motor assembly and out the top of the pump to the rest of the fuel system. This keeps the DC motor from having a melt down. Its pretty neat that they actually did it like that. The commutator and arcing brushes are submurged in gasoline at all times. Wonder what would happen if the tank ran dry and fuel and air vapors made it into the pump?

Dont have any pics, though, tossed the pump.