Well, in the never ending battle to get my car to stop smoking, blue, black, whatever the hell it feels like, I am now trying to figure out my pig rich problem. the car runs rich all the time, idle, cruise, WOT. I did have a horrible vaccum leak due to a bad intake which was fixed via Air Gap RPM and it doesn't seem to be smoking blue anymore, but it lays out a cloud of black smoke that makes some turbo diseils look like 2 cycles, ok it's not quite that bad but had to use the comparison.

The problem I want to fix first is my fuel pressure, When I try to adjust the fuel pressure, sometimes it doesn't move, after I do get it set around 4-5 PSI, it moves around. For example, when i start the car, it sometimes has 8psi, then it wonders down to 1-2, then to 5, or whever it wants. I am using a stock TBI intake pump, and the mallory 3 port regulator. It's been like this since I put the car together, I have 6an feed line from the tank to the regulator, then 6an to the carb, and use the factory steel return line. I know for a fact with the fuel pressure moving around it's impossible to keep the float bowls right, actually when i turn the key on sometimes, when the fuel pressure is 8psi or more, I can hear float bouncing in the carb from the needle and seat being blown apart. I have had two different gauges on it, it's a mechancal gauge that screws into a AN fitting right before the carb. I have heard before that the TBI pumps won't flow enough to keep the PSI constant. Should I switch intake pumps? If so what to? If I knew at the time My car was going to run this good, i would have ran 8an, but I figure if I can get a good pump, it should be able to keep up with the carb.

Any help? I am completely lost on this one.

 

This may not seem right at first but this fixes a lot of pressure regulation problems throughout the sport: Make sure the return line is larger then the feed line.

 

All factory return lines i have ever seen are smaller than the feed line.

 

They usually are...I think he means to install a larger return line and do away with the factory one.I run a 6AN feed and 8AN return on my Z.Rock solid 6psi.Did you bleed the air out of the fuel system like described in the Mallory directions?That helped mine stay set at 6psi..otherwise I had the symptoms you describe.Get rid of that TBI pump with your combo...asking for trouble.Upgrade to a good electric in line.

 

I am using a TBI pump in my 'ROC. I have the mallory 3 port and the stock feed and return lines 3/8 feed, 5/16 return, and I have NO spikes in pressure or any problems. My gauge sometimes fluctuates a little but I know it's the gauge cause when I tap the gauge the needle move right and it is a cheap checkers gauge,LOL. I know I should get a good one.

 

I used to run a stock TPI pump with a Mallory regulator and had the same problem you do. My fuel pressure would NEVER sit still, it would constantly bounce back and forth from 2-8PSI (really fast most the time). My float levels were always fine and the motor never had any problems so I never cared too much about it.

What do your float bowls look like with the car running? Your fuel pressure may not be the problem.

 

There has to be a reason it jumps back and forth, regardless if thats causing my problem or not, it shouldn't do it. especially when it bounces the float off the seat. Do guys that use a holley blue pump have problems like this?

 

Nope I'm running a holley blue right now with the factory lines and the same regulator... Fuel pressure is steady.

 

I run the black pump..and no fluctuations..it's dead set at 6psi.Has been for the last 4 years now.

 

ttt

 

I think the only way to fix your problem is like said above... Put a HUGE return line on the car. Making that high fuel pressure go down to carb-friendly levels is a hard task especially since it works by returning un-needed the fuel If you notice most aftermarket pumps (especially BG) always say a bigger return line is required for it to operate properly ..due to the same reason.

 

That pump runs at a higher pressure than a stock TBI pump doesn't it?

 

Holley Blue I believe pushes out like 14psi

 

Then why do you think I need to put a bigger return line on it when your pump puts out more pressure than th eTBI pump, and you are running stock lines? I am not trying to be a smartass, I am just asking.

Thanks
Jason

 

I thought the TBI pump put out something like 20-25psi? Have you tried experimenting with different springs inside the regulator? (regardless of what they're rated at). Another thing is that you could have the regulator mounted too far from the carb? How do you have the fuel pump wired up? That COULD be the problem if its "hot wired" rather than run through a relay. Might cause the pump to operate funny.

 

A TBI pump runs between 9-13 psi, a TPI pump runs around 45 psi. the regulator is mounted on the driver side strut tower, It's probably 1.5 feet. The pump uses the factory wiring with the factory relay. Maybe I got a bad pump I thought about putting a new one in, but wanted to check here first.

Jason

 

Where have you guys mounted your Holley electric pumps?

 

Thats the TBI pump man, it's starting to fail. They always seem to fail early when run at any different pressure than they were designed for. You don't need any larger lines anywhere.

 

Get your self a fuel pump that is meant to be used with a carb. Get one that has enough volume to feed your hungry motor at max rpm/power.
That TBI pump is never going to keep up. Sounds like it's on it's way out too.

 

Thanks F-bird and Jester, those are the first two real answers I've had. I will look into getting a blue pump.

 

I am going to run a 1/4" return line like factory. Does this seem too small? The tank sending unit has a 5/16" line but the factory return line in the engine bay is 1/4". Pick a size GM! GM is so weird sometimes.

 

If you're running new line anyway you may as well go larger, even if it is overkill. 3/8" or even 1/2" line isn't much more expensive than 1/4"

 

werd, bigger is ALWAYS better when it comes to fuel lines.

 

i am thinking about doing a tpi to carb swap. the mallory 3 port is going to have problems?

 

Wouldn't the TPI pump be a lot better than the TBI pump? The reason I am asking is I wouldn't have to run new stuff for a blue pump if a TPI pump would work.

 

Uhm, NO. I dropped the motor in, hooked up the fuel lines and turned the key. Vroooooooooom.

My return line is much bigger then the supply line btw.

I still have the TPI pump in the tank. No problem with it at all.

Primes, pumps, no pressure spikes or drops at all.

 

I ran the stock TPI pump with a mallory regulator on a daily basis for over a year. 0 problems.

 

thank you guys

 

I just fired up my carbureted 350 engine last night in the 92 RS. It was previously a TBI 305. I used the afore-mentioned Mallory 3-port regulator. I am still using the stock TBI pump, factory lines (3/8" feed and 5/16" return), still run by the factory computer, wiring and fuel pump relay system. No pressure fluctuations during engine break-in to report. I guestimated the adjustement on the regulator and got it pretty close. 4 turns up from fully seated with the factory-installed spring in the unit. 5 PSI reading on the gague throughout engine break-in at varying RPMs. It will spike to 5.5 PSI when the pump first turns on, but it immediately settles in to 5 PSI and stays there as long as the engine/pump is running.

So, no, I don't think there's anything wrong with the Mallory regulator or stock lines. At least not from my 30 minute experience with this setup so far.

I never bled the fuel lines. Hooked em' up and turned the key.

I don't see how the regulator itself could ever cause a "wandering" fuel pressure reading. It's a very simple device. The only thing I can think of that might cause problems is if the plunger/diaphragm that operates the bypass valve got "sticky" or bound up somehow, causing the bypass valve not to open gradually and proportionately.

If your return line was too small/constricted in some way the fuel pressure would be consistently high at idle (when fuel demand from the engine is nil) and then drop off the more throttle/RPMs you gave it (when the engine is "eating" more of the fuel and bypassing less back to the tank).

I think I'm with Jester and F-bird on this one. Fuel pump failing or not getting constant voltage for some reason.

 

I have used the Mallory 3 port on my former TPI car for over 2 years now. I have a solid 7psi at the carb. I am also using the factory feed and return lines.

 

I'll chime in, too. Stock lines, TBI pump, Mallory 4309, no problems. Slight fluctuations of less than .5 PSI, I attribute that to the gauge.

 

I had pressure flucuation with the mallory 3 port regulator w/TBI pump. What ultimately fixed it was mounting regulator with return line up. Apparently when pump came on with return at bottom, it was trapping some air that made pressure move around. It is a little more difficult to change setting, but I have not seen and change in months now.

 

I'll chime in. My Mallory 3 Port would not drop less than 9PSI with my Holley "Blue" pump and a 5/16" return line. Had to return Regulator.

 

that tbi pump ismore than enough to feed my 430horse 350... at 6500 it only pulls 32gph... stock pump puts out twice that doesnt it?

anyways, im running the same setup, 4port mallory regulator, and sucker is dead set on 6lbs no matter what... the guage will flicker at idle sometime becuase of the ruff idel... just cuz its a cheap guage....

 

Had the same problem..but with the Holley Black pro series pump on my Z.It wasn't the regulator for me though..I swapped stock fuel lines for a 6AN feed and 8AN return as suggested in the Mallory directions.There is a section that helps you determine what size return line to run determined by the length of the return line..fuel flow and such.Set it up...set it to 6 pounds and never touched it again.That was going on 5 years ago now.Just fired the car up the other day to get her ready for some summer beatings..still at 6psi.Either way get rid of the TBI pump..

 

How did you plumb a -8 into the stock tank and where did you mount your pump?

 

Welded a steel 8AN fitting to the tank..pump is behind rear driver side seat.

 

Same place I put my pump. You have to mount that turkey like 1/2" from the tank to get it away from the rear end. I had to mount mine twice to avoid the brake lines. When I mounted it I took out the coil springs and lifted the car with the rear on the bump stops to make sure on large bumps there was no way the pump could hit.

 

Im kinda curious about this subject. I just got my mallory 4309 in tonight and was thinking about how to plumb it all together. I dont have my carb ready yet, so I was just going to hook up the feed/return lines to and from the regulator. Heres an idea I had....

if I remember correctly, on my friends S10 blazer, we replaced his fuel pump. I also seem to remember that the feed and return lines on the tank went from the plastic fittings on the pump, to rubber hose, finally to the hard lines. Is that the case with, at least, LO3 fuel pumps/tanks? If so, coudlnt you just swap the rubber hoses over so that the return line would then be bigger than the feed? It might be more labor-intensive, but it might also be cheaper than buying all that hose. Just an idea I had, feel free to bash it