Return style regulator with Mechanical Fuel Pump?

[drdano]

Is there a return style fuel pressure regulator that anyone has had success with a mechanical fuel pump? 

Has anyone tried the return style fuel logs from Moroso/Mallory and others?  Did they work as advertised? 

[afret]

I don't think the return type regulators work well with mechanical pumps.

http://www.robbmcperformance.com/products/regulator_bp.html

[drdano]

Yeap, I've read that on RobbMc site.  I'm pretty sure Jay was running a return style on one of his Drag Week cars a few years ago and it had a mechanical pump.  Care to chime in Mr. Brown on how well it worked long-term?

[afret]

I think Jay did run a return style regulator with a big mechanical pump.

Here's more info by RobbMc"

http://www.network54.com/Forum/74182/message/1299001452/Several+Issues+need+addressed

[jayb]

That's right, I used the Moroso log style regulator and a big mechanical pump on my 700HP FE in 2005.  Worked fine.

[drdano]

That's right, I used the Moroso log style regulator and a big mechanical pump on my 700HP FE in 2005.  Worked fine.

Did you have any fuel boiling issues after that, or was that also solved?

[jayb]

That setup solved the fuel boiling problem.

[My427stang]

I think its a good idea, get it as close to the carb as possible, everything on the supply side and discharge side will stay cooler as it cycles through. 

Then you only have the short leg(s) to the carb and the carb itself to manage.

A bone stock pump probably won't make enough pressure to trip the regulator, but anything aftermarket should assuming you don't set it too high.

[drdano]

A bone stock pump probably won't make enough pressure to trip the regulator, but anything aftermarket should assuming you don't set it too high.

The M6905 is rated at 5.5-6.5psi, but I'm not sure what it does at high RPM if that pressure climbs.  The bypass if not set lower than that 5.5-6.5psi wouldn't ever do anything, so that is something I should keep in mind.

I can see while the engine is running with a mechanical pump and a bypass solving a heat-soak / boil problem at low rpm cruise....but what about when you park and it heat soaks?  Wouldn't you have to crank the motor to get it to start if it's boiling without an electric pump to introduce cooler fuel prior to the startup?   

[afret]

I used to run a full sweep electric autometer fuel pressure gauge to monitor the pressure while driving.  When using the Carter pump, the pressure would really drop under acceleration.  IIRC, it would go below 2 PSI.  I don't know how much lower it would have gone with a return regulator in the system. 
With the big RobbMc pump and a dead head regulator set at 6 PSI, the pressure would only drop maybe 1-2 PSI under acceleration.

If it's a serious street/strip car, it might be better to just get an electric pump with a return regulator.  You don't need a huge pump.  Even the street/strip Aeromotive pump is more than adequate for a low 10 second car.

[cammerfe]

I said somewhere, recently, that I started using electric pumps many years ago, on flatheads. For those who might not know, the FP on a flathead sat back against the firewall on the back of the intake manifold. Stand within twenty feet of such a vehicle on a warm day and you could hear a voice coming out from under the hood saying, "Heatsoak me. Come on an'do it!!! The cure was to use an electric pump.

When we put the 427 TP in Brother Lon's '67 Mustang we put in a pair of the S-W 240-A pumps that were used on the Cobra. (NOS costs $1K each at present!) The 'clop-clop' sound of those pumps as we went out looking for unwary rat-powered chibbies up and down Telegraph will always be a pleasant memory!

KS

[babybolt]

One of my beefs is fuel pressure gauges, the only ones available for carbs are 0-15 psi, and we need them for 0-6 psi.

[RJP]

Dano, IMO it shouldn't make any difference between mechanical and electrial pumps as pressure is pressure regardless where it's sourced. I use a B/G pressure regulator as a bypass by reversing the in and out ports. Works just fine supplying a twin turboed draw thru engine so no boost reference needed.

[machoneman]

SW 240-A's! 

Hah, haven't heard that name in an age. Ran duals as well in a 10 second door slammer long ago and they were bullet proof.

[drdano]

I have an interesting update to my fuel delivery concerns on my wagon.  So, lets recap a tad...'62 LandBarge, warm 428, stock (5/16"?) fuel lines from tank to pump, Carter M6905 Pump, large canister style fuel filter on the front of the block, modified 800 Qjet.  I finally got an AEM 0-15psig sensor plumbed into my fuel line right in front of the fuel inlet to carb and took a short trip out on the road.  Previously I was trying to use a 30psia sensor and the granularity between pressures just was too wide for fuel on a carb...it was difficult to see where the pressure was and where the "noise" in the signal was.  Using my LM-2 I was able to drive this sensor and record the data coming back along with an analog pickup of the RPMs direct from the coil and the AFR of course from the wideband 02 in the exhaust.  What I had happening, particularly in warm weather was when on a quarter mile pass the motor would fall on it's face above 4000rpm in each gear fairly regularly.  Today it was maybe 35 degrees, quite cold and the carb was running consequently quite leaner than usual.  It was doubtful it would really fall on it's face as usual, but hit the record button on the LM-2 and made a pass through the first two gears and partially through the third.  I was more curious what the M6905 was doing at higher rpm, as I suspected it was losing pressure..and it turns out my suspicions were confirmed.

The graph attached shows a few different things.  In magenta is the AFR, which I'd not pay too much attention to, other than in second gear when the fuel pressure really dives the AFR is trending lean.  The rpms in black clearly show the shift points between 1-2, 2-3 and then 3-4 and a drop off the throttle. 

In red is the voltage coming back from the sensor.  I've not yet figured out how reprogram the graph for this with a formula to show psi, but the jist of this is that at idle/cruise the pump is generating about 6.5psi at the carb.  When I get on it, that drops to barely 2psi and I'm not doubting that given a warmer day this would probably go lower.

At this point I'm researching a better fuel system setup.  The factory hard line obviously will not be used, and I'm thinking of biting the bullet and just doing a full return style system with an electric pump, -8AN lines to and from the regulator and probably -6AN from regulator to the carb.  This should hopefully resolve the fuel boiling issue at the carb I had last summer at the same time.