Need some guidance.
History - I performed a GSL-SE fuel system swap on a 12a 82' RX7 about a year ago on Ron's car.
Put in the GSL-SE tank, fuel pump/filter and lines. Also installed a 48mm Dellorto sidedraft.
We installed a Mallory 4309 FPR w/return.
We had it started on the first try, dialed it in and it works great.

Current - I did the same swap with above fuel system on my 82' GSL stock port 12a w/Yawpower modded Nikki.
Lot's of flooding, unable to stop the carb from dribbling fuel with the car shutoff.
Found a small leak in the diaphram on Mallory 4309 FPR, ordered a new diaphram. Swapped out the Mallory for Holley -804 FPR and dialed it in for 2 lbs, it runs rich and will not idle, after shutting the ignition off, fuel is still dribbling into the carb, had to disconnect the fuel pump and run the carb dry to keep it from flooding again.
The GSL-SE fuel pump generates 49.8 - 71.1 PSI per the tech data sheet.
Is this overwhelming the carb floats even with the FPR's dialed down to 2psi??

Need some help.
Thanks!

 

I think that what is happening is, due to the extremely high pressure of the fuel injection type fuel pump, you are overpowering the spring in the fpr. You might have to either find a specialty fpr that can tame those types of pressures, or swap the pump out for a more reasonable one.

Good luck.




.

 

Are you sure the problem is not with the carb itself? Does it work okay on the stock 12A pump?

When the FPR is set to 2lb, are you measuring this with an accurate gauge or are you just assuming it is at 2lb because the regulator setting says so? If the FPR is good and set correctly and the carb is good, I would look at the return line. If the actual pressure is not getting down to where it should be, the return line may be too small (assuming it is not the GSL-SE return) or may have a partial blockage. For the FPR to work correctly, it needs to send the excess back down the return. If it can't send enough back, the pressure at the carb will be higher than what the FPR is set to.

 

This regulator is not a return type regulator I don't think. I bet its just
overwhelmed by the 50 to 2 reduction in pressure.

 

This is the FPR I'm using http://www.malloryperformance.com/Pr...minselection=4
The Yaw carb still has the return fuel line and I have it "Tee'd" to the FPR bypass (Mallory), the Holley FPR has no bypass so I just used the return line on the carb by itself.
The fuel lines are GSL-SE (large 5/16" supply and return)
I am going to try a spare carb for my next step. I do have a new Carter pump but wanted to get the stock GSL-SE dialed in if I can.
The Yaw worked fine with the stock 12a pump.
Going to do some testing tomorrow after I get some more gas in the tank.

 

woah Lloyd, i don't know why it doesnt work..you did make it work on my car...interesting...oh by the way, i sent you a pm a long time ago...

 

possible that the floats or needle valve are sticking? Maybe during the swap a little debris got in? What is the volume rating on the FI pump vs. the stock one?

 

I use a barry grant fpr and it has a guage on it. It is a return style regulator so my carb only see regulated pressure. Have has no issues for over 5 years now and it is the factory gslse fuel pump and system.

 

Stock 12a pump 2.88 - 3.11 psi
GSL-SE pump 49.8 - 71.1 PSI

Using a RED fuel pressure guage, 1-15psi


Sorry Ron, forgot to respond buddy, it was good to hear from you.

 

If I remember my Dad's lectures on hydraulics, the psi can be right and the flow still be to high. Pressure and flow are not the same. Is the gpm rating significantly different on the FI pump? May not be the cause anyway as long as the psi is correct. I do remember having a similar problem with a holley fpr once. When the gauge was mounted at the fpr it read one thing, but when I moved the gauge to being inline on the feed right before my fuel union, it read much higher. I replaced my fpr and problem went away. Not sure that helps, but thought I'd toss it out there.

 

Right. Flow and psi are not the same, but it does not matter in this case as long as the return is big enough (return style regulator).

I would plumb it like this:

feed-->FPR-->gauge-->carb
..............|---->return

Cap the return on the carb. The FPR will allow fuel to go back to the tank as needed in order to regulate the pressure. If the carb asks for more fuel, the pressure drops slightly and the FPR lets more fuel go to the carb (and less to the return) to compensate.

You will need to use a return style regulator to bring the pressure down. The non-return style regulator won't be able to do the job in bringing it down from 60psi to 2-3psi.

In terms of flow:

12A pump: 1400+ cc/min
GSL-SE pump: 1700+ cc/min

Again, it doesn't matter, though. The pump is feeding the same all of the time. Obviously, the amount of fuel going into the engine at idle is much less than at WOT. Whatever is not used is returned back to the tank. So at idle, almost all of the fuel is sent back down the return. Return style regulators adjust outlet pressure by changing how much fuel goes back to the tank. If the return was too small or partially clogged, the minimum pressure at the FPR may be too high for a carb (the FPR wouldn't be able to dial down the way it is supposed to).

 

Good advice.
I got my replacement diaphram for the 4309 FPR w/return from Summit yesterday and will try plumbing it as you suggested.
Thanks again guys for the input!

Lloyd

 

I too have a GSL-SE tank and some of the lines in my '81 for an EFI swap in a little while with a Walbro 255lph (sold the GSL-SE pump many years ago... oh well). But for right now I'm running a Carter fuel pump which typically outputs around 6 psi. Also a Holley FPR into an Edelbrock performer series carb (dead-headed; no return at this time) and a Camden 7".

Works perfectly.

Since your carbed setup is just temporary at this point, why not swap to a temporary carb fuel pump? Skip the headaches. It's just a 12A, man.

 

The input/output on the GSL-SE tank and lines are too big for the stock 12a pump. This setup should work, done it before, just not with the return as what I did with Ron's Dellorto carb setup. Going to try it that way and see what happens.

thanks Jeff!

 

My Carter already had 1/2" nipples which perfectly match the GSL-SE tank's output. Then on the output side of the fuel pump, I had to use a couple of brass fittings to adapt down to 5/16 to work with the stock lines. My carbed setup is just temporary so it was ok to do.

 

Check the tank vents as well, I just fixed a local car that wouldn't idle correctly, and was dribbling fuel after shutdown. It turned out to be plugged vents.

Isaac

 

The problem is you can't tee the returns together. What happens is the excess pressure that was meant to return to the tank is now forcing itself into the carb through the carbs fuel return. Use the mallory, cap off the carb fuel return, only use the FPR fuel return. Enjoy! Should've just called me Lloyd.

 

Adrian,
I thought of that, I was using the stock return line check valve and even used a 2nd one on the Mallory return line as well.
I will be trying the capped off carb senario once I finish with the Camary that's in my shop right now, new cam shaft, crank seals, water pump and timing belt replacement.....I hate pistons.

I will call you buddy, don't you worry!

 

What the heck is a camshaft? LOL!
The stock check valves are designed to deal with 2-5 PSI. No way they'll be able to stop 40 PSI of bleed off fuel from going where it wants to. Don't use them at all. The less restrictions in the line the better; let the Mallory FPR do the work.

 

hey Lloyd, did you get this figured out? im still wondering why the return isnt working, you were able to install the gslse tank lines and everything to the mallory fpr and everything worked fine...i mean i know my car is your first for a few things..but if you installed everything exactly like you did to mine i dont understand what could have gone wrong...maybe the fact that we didnt disconnect anything..we installed it all as one unit, lines, tank and pump..also i think we did leave my 12a hard lines lying around..hopefully you didnt use those...

 

Couple of things

as mentioned above you can't tee the carby return line into the mallory return line, you need to either dead head the carb by blocking it's return line, or plumb an extra return line into the tank

also the Mallory has a lowest base setting of 3psi, a dead headed Nikki according to sterling wants around 2psi or possibly less, any higher than this will flood as you have described

if you continue to have troubles get a rebuild kit and put new needles and seats in there, these could well be worn down and not sealing as well as fresh ones.