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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
I have a carter m6626 (40gph) and at WOT fuel pressure falls to 2-3 psi on just motor alone. NOS says no less than 4.5 psi when at WOT and nitrous is activated. So i got a edelbrock 1711 mechanical fuel pump (130 gph @10psi advertised) to keep up with the 150 shot of nitrous I plan to through at this engine. Since fuel pressure is so high with this pump I got a mr.gasket return style regulator. Part #2015.
My problem is that the mr.gasket instructions say the return line for this regulator needs to be the same as the Feed line. Im running the stock fuel lines on my 87 sport coupe which is 3/8 feed which should be fine but the return line on this car is only 1/4. I thought it was 5/16 which is questionable but 1/4 is really making me wonder. Will I have problems with this small return line size? Any personal experience with this sort of thing?
Im hoping I will be fine since Im running a 10psi mechanical pump and not a much higher psi electric pump that in my mind would need a bigger return line but I dont know.
Chances are...probably.
But here's my question. Is that regulator designed to work with a mechanical fuel pump? I couldn't find one.
I've gone through this scenario almost exactly except my Carter (same p/n) couldn't keep up on engine alone.
I eventually gave up on the mechanical pump (due to the regulator issue) and have since gone electric.
Did you determine if your regulator was designed to work with a mechanical pump? As I mentioned, mine said specifically in the instructions in bold letters not to.
If yours does, what's the make and part number?
Ill go out a buy one right now.
I can't find anything that says (not to use with a mechanical pump) on the instructions anywhere. Holleys website says (For use with a carbureted fuel pumps only.) whatever that means. It was only $35 so if it don't work I'm not out $100+ dollars that some of them cost. I'll post up results as soon as I get it all hooked up.
What regulator did you have that said not to. The one I got is a mr.gasket part# 2015. Just found out Holley bought out mr.gasket but part#'s haven't changed yet.
All of the by-pass style regulators I checked out specifically mention not for use with mechanical pumps. That said, I overlooked the Mr Gasket 2015 however, as you point out, Holley and Mr G are joined at the hip now. Holley's 1284 looks very similar to Mr G's 2015 and the 1284 is for electric pumps only.
------------------------------------------------------------------------------------------------------------------------------------ Holley 12-803BP. Presently installed but not yet tested with 3/8ths supply and 1/4" return. It didn't work in that configuration with either of my mechanical pumps.
------------------------------------------------------------------------------------------------------------------------------------ Perhaps this is Holley's version of the Mr Gasket 2015?
------------------------------------------------------------------------------------------------------------------------------------ Looks like Holley's 12-841 (without the anodizing).
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I have Holley's 12-803BP and it says not for use with mechanical pumps. I tried it with my Carter mechanical pump as well as my Edelbrock 110 GPH pump with no success in either application. I will say that I'm using the small 1/4" return line as my return although as far as applications go, the mechanical pumps and the electric pump I have (a Holley Blue) can all be dead-headed. Still, by not following the instructions as in the return line being the same size as the supply (3/8ths or -6 AN), I've brought the trouble onto myself.
And this was the original question in this thread.
I'm very interested in your results. Personally I can't stand the sound of the electric pump but after last years failures at the drag strip, (as in almost zero fuel pressure at the top end and close to that by half track with AFRs going dangerously lean), I've given in and re-installed (and rebuilt) the old Holley Blue).
If you succeed, then I'll revisit the mechanical pump installation.
I'd eventually like to go with a Aeromotive's Phantom in-tank pump setup. The mechanical fuel pump pushrod to camshaft lobe interface is a source of failure as I've experienced. I don't care to go through it again.
Since your user info says "Car: 87 camaro", let's go back a step:
Originally Posted by krisner89
I have a carter m6626 (40gph) and at WOT fuel pressure falls to 2-3 psi on just motor alone.
...
Im hoping I will be fine since Im running a 10psi mechanical pump and not a much higher psi electric pump that in my mind would need a bigger return line but I dont know.
I'm guessing your first problem is related to a weak in-tank electric pump. Since your car is set up with an in-tank electric pump, why are you messing with a mechanical pump at all? Put a good in-tank electric in there, use a return-style regulator, and get rid of the mechanical.
Since your user info says "Car: 87 camaro", let's go back a step:
I'm guessing your first problem is related to a weak in-tank electric pump. Since your car is set up with an in-tank electric pump, why are you messing with a mechanical pump at all? Put a good in-tank electric in there, use a return-style regulator, and get rid of the mechanical.
The in-tank pump on this car is just a low output helper pump. Airtex is the only replacement pump that I could find. 3-5 psi and 20-35 gph are the specs on it. I dont think its enough gph for my engine output.
I have seen high flow in-tank pumps but they are for fuel injected cars. My sending unit wont fit one of those because the electric motors are different sizes. Also all the fuel line connections were not designed to hold the high pressure of a fuel injection type fuel pump.
Hey z I was just wondering on what you said about no success with holleys 12-803bp regulator. What problems did that regulator give you exactly? I'm still waiting for all my an fittings to come in mail so I haven't tested my setup yet. Hopefully they come in by Tuesday.
I'll give you a little backstory first:
At one time, my Edelbrock mechanical pump worked well. I could maintain adequate fuel pressure (6 psi) for WOT. The only issue I had was what appeared to be vapour lock. If I sat in the staging lanes for any length of time, my next run would experience a dip in fuel pressure and then recover. I run an external gauge to monitor in real time.
That's when I started experimenting with a return style system. With the return system I could achieve a decent idle fuel pressure but the WOT would steadily fall away until there was nothing at about the 1/8th. This was with both mechanical pumps I had.
I experimented with the Carter pump, with the built in return "regulator" line but it wouldn't keep up. I tried it with both an external regulator and also just the 3rd line hooked up. Neither performed well with pressure dropping off as WOT time increased. My thoughts there are that the pump just doesn't have enough capacity to supply my engine.
I have tested with the Holley dual feed regulator (12-803) which is not a return style. Interestingly, I ran this with my Holley Blue pump with the 2nd carb outlet serving as a return line (through the 1/4" OEM vapour line to the tank). This worked well surprising in that it wasn't designed that way.
This setup didn't work with a mechanical pump.
My understanding of the situation is that the regulator can't do it's job when the fuel pressure is arriving in pulses rather than the steady state pressure you would achieve with a vane type pump.
I only tested the 803BP with the mechanical pumps. Neither worked.
I used the 803 with the electric pump (and it worked with the 2nd carb outlet serving as the return line).
You should try the Holley blue with the 803bp. Maybe it's a faulty regulator. That's very interesting you got it to work the way it is though. Have to remember that trick.
That's the plan. I've yet to rebuild the old Blue pump (I've got the parts) but I have the 803BP in place and I should be able (hope) to get it all together before the end of the racing season here.
My problem is that the mr.gasket instructions say the return line for this regulator needs to be the same as the Feed line. Im running the stock fuel lines on my 87 sport coupe which is 3/8 feed which should be fine but the return line on this car is only 1/4. I thought it was 5/16 which is questionable but 1/4 is really making me wonder. Will I have problems with this small return line size? Any personal experience with this sort of thing?
I do now.
Finally got the Blue pump rebuilt and tried a test with a 1/4" return line.
With the Holley 12-803BP regulator maxed out, it wasn't possible to get the fuel pressure below 15 PSI.
Disconnecting the majority of the return line and using a 3' length of 1/4" hose discharging into a pail (from the return port), pressure was down to 3-4 PSI (with the regulator maxed out).
The return line is now replaced with (about 15' of). -6 AN braided steel. The only restriction is the short length (2' ) of 5/16ths steel tubing that is the tanks original return.
Fuel pressure is now a consistent 7 PSI.
Well I finally got a chance away from work to button up this fuel system and go for a test drive today. I am extremely happy as it is running like a dream. I dialed in the regulator at just under 7 psi and went for a drive. If I'm cruising, coasting or wot fuel pressure never falls below 6 psi or goes above 7 psi. I was worried about the small 1/4" return line but it's not giving me any problems with this particular fuel pump. I also like how steady the gauge is with the regulator. It's not bouncing all over with a pulsing mechanical fuel pump. Now I think the fuel system is finally up to the task to handle some nitrous without running lean.
I do now.
Finally got the Blue pump rebuilt and tried a test with a 1/4" return line.
With the Holley 12-803BP regulator maxed out, it wasn't possible to get the fuel pressure below 15 PSI.
Disconnecting the majority of the return line and using a 3' length of 1/4" hose discharging into a pail (from the return port), pressure was down to 3-4 PSI (with the regulator maxed out).
The return line is now replaced with (about 15' of). -6 AN braided steel. The only restriction is the short length (2' ) of 5/16ths steel tubing that is the tanks original return.
Fuel pressure is now a consistent 7 PSI.
Glad to hear your fuel system is working. It kinda makes sense that you fixed it by replacing the 1/4" return line with some 6an size return line. Your Holley blue probably outflows my fuel pump which required a bigger return line for that extra fuel. I must be real close to needing a bigger return line because my eddy 1711 pump isn't far behind a Holley blue as far as flow goes I don't think
It's a mechanical pump? I had forgotten that. I'm surprised you needed a regulator at all. Then again you did say 10 psi advertised.
It's worth noting that your regulator works with a mechanical pump too. Something I'll keep in mind.
My Holley Blue electric cranks out more pressure than my gauge can read. It pegs at 15 psi and even with the regulator maxed out, it's still still 15 psi.
Glad to hear you have it sorted out. Good luck with your nitrous. If I wasn't afraid of destroying as piston, I'd give that a go myself.
08-20-2016, 09:14 AM
