I have a Holley blue pump and recently installed a bypass regulator. With the deadhead regulator the fuel pressure was pretty consistant at 5lbs. I plumbed a line to a Marshall liquid filled gauge to the cowl. First I couldn't get the pressure off 6lbs. Then when I took it down the road, and under acceleration, it drops to 3lbs. or less. I'm really puzzled. Any ideas? Thanks in advance, Rod
fuel pressure inconsistant
- Thread starter raj4851
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http://garage.grumpysperformance.com/index.php?threads/c3-corvette-not-getting-fuel-to-carb.11668/
I can think of several potential reasons, but from what I,ve seen over the last 20 plus years ,the first thing that comes to mind is that you might have the feed fuel line and out put ports to the carb and return line in the wrong place, its almost mandatory guys seem to do that, I know my brother-in-law did the first time
do fuel lines yours look like this,
THEY SHOULD match this config.!
this is hardly exact, but its giving you some idea of port lay out
for some reason no one reads instructions and thinks the fuel return lines, supposed to be located at the bottom of the regulator and fuel should flow strait thru the regulator from side to side...WRONG! the fuel feeds up from the bottom center, and for some reason i always seem to get more consistent results with the lines hooked up as posted in the picture
viewtopic.php?f=55&t=635
viewtopic.php?f=55&t=211
http://garage.grumpysperformance.com/index.php?threads/c3-corvette-not-getting-fuel-to-carb.11668/
I can think of several potential reasons, but from what I,ve seen over the last 20 plus years ,the first thing that comes to mind is that you might have the feed fuel line and out put ports to the carb and return line in the wrong place, its almost mandatory guys seem to do that, I know my brother-in-law did the first time
do fuel lines yours look like this,
THEY SHOULD match this config.!
this is hardly exact, but its giving you some idea of port lay out
for some reason no one reads instructions and thinks the fuel return lines, supposed to be located at the bottom of the regulator and fuel should flow strait thru the regulator from side to side...WRONG! the fuel feeds up from the bottom center, and for some reason i always seem to get more consistent results with the lines hooked up as posted in the picture
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let me know how the change in port routing works out and what your results are.
WELL?? did the re-routing of the fuel and return lines in the fuel pressure regulator, to the correct ports as shown cure your inconsistent fuel delivery/pressure issues??
Hey Grumpy, I did the re-routing on the regulator yesterday and thought it was okay but when I took it for a drive today it began to do the same thing. Under acceleration it dropped to almost zero. Sitting in the driveway, when I use the prime switch, the pump goes to 3lbs., then drops back to almost zero. I've changed the pressure several times but that seems to be where it sits. Also, the pump doesn't sound good at all at times. I think I'm losing another Holley blue pump. I have a Carter P4070 I'm getting ready to install. Hopefully I'm on the right track, Rod
Hi Grumpy, I took a Fram inline fuel filter out of the line before the pressure regulator and installed a tee and another fuel pressure gauge. It registered 7 lbs. at all times. The gauge on the cowl said 5lbs. I thought I was good. Under acceleration, same thing, dropping to zero. I can't seem to get the regulator adjusted so I guess it's down to taking it off and taking it apart to see what's happening. I also picked up another pressure gauge to double check the unit on the cowl. I hope I'm going in the right direction. Any words of wisdom about checking out these regulators? Thanks, Rod
I have seen those regulators be defective in the past but most of the time its simply a case of the lines being connected in the wrong ports, if you have the feed in the lower center port show consistent 7 -12 psi like it should from the pump, the adjustment screw in the center should have little problem keeping the port feeding the carb at a consistent 4-5 psi , the other port directly across feeds the return line and its not important what it reads, as its go near zero back pressure so it will fluctuate, in that range but you won,t see it , I don,t generally put a gauge on the return line.
If you see a consistent 7-12 psi feed and that never varies and the feed exit port can,t maintain a consistent 4-5 psi to the carb feed the regulator diaphragm is probably leaking or some other internal flaw, has occurred.
If you see a consistent 7-12 psi feed and that never varies and the feed exit port can,t maintain a consistent 4-5 psi to the carb feed the regulator diaphragm is probably leaking or some other internal flaw, has occurred.
Hi Grumpy, I did hook the regulator up as you instructed, feed to the bottom, outlet to carbs on our right as pictured, and return to the left. Yes, the line from the pump to the bottom of the regulator reads 7lbs. while the gauge I have plumbed up to the cowl reads very incosistantly. Tomorrow I'll take the regulator off and check it out. Thanks, Rod
NOT A TA
reliable source of info
I've been watching this thread to see if grumps line routing for the regulator cured your problem. As he noted that's the most common problem.
In a couple cases this year I found that the 1/8" NPT ports in new T fittings and dual carb feeds sold by Summit and Jegs were threaded a bit too much so that when a gauge or line is screwed into the fitting or carb feed it blocks the fuel flow enough to cause a pressure drop under partial/full throttle conditions. The gauge would read fine as long as enough fuel could pass to keep the carb full, once the float dropped in the carb by revving the engine the pressure would drop.
In a couple cases this year I found that the 1/8" NPT ports in new T fittings and dual carb feeds sold by Summit and Jegs were threaded a bit too much so that when a gauge or line is screwed into the fitting or carb feed it blocks the fuel flow enough to cause a pressure drop under partial/full throttle conditions. The gauge would read fine as long as enough fuel could pass to keep the carb full, once the float dropped in the carb by revving the engine the pressure would drop.
Okay, Grumpy, here's the latest. The Holley blue pump was putting out 7lbs. Since they're supposed to put out 15 or so I figured it was toast and a Holley guy confirmed it. I had a Carter P4070 so I put it on. Still no pressure. I took the regulator off and put a piece of line in. Pressure. Driving down the road, under acceleration, the pressure still dipped. I took off a Marshall liquid filled gauge which I had mounted on the cowl and replaced it with a Mr. Gasket cheapie. The pressure is much more consistant but it still is up past 7. I really want to run at 5 or 5.5 for my Edelbrocks. Can you suggest a regulator, or do I need to get an other pump setup? By the way, the guy at Holley, today, said that I need a much higher pressure pump than the P4070 to be able to run a return style regulator. Anyway, it's good to have pressure but I still need to refine things a little. Thanks in advance, Rod
the problem with all decent quality fuel line supply component parts is they cost more money, than the cheap low quality parts and generally take up more room and take a bit more time and thought to install correctly, but you tend to get what you pay for in car part quality, and carefully matched parts will significantly increase flow volume, and stabilize the pressure.
you NEED a high quality ,return line style, fuel pressure regulator
http://www.summitracing.com/parts/hly-12-841/overview/
http://www.amazon.com/Moeller-Separatin ... d_sbs_sg_1
http://www.summitracing.com/parts/edl-1792/overview/
CARB PUMP BELOW
EFI PUMP BELOW
http://www.highflowfuel.com/i-10388...rainers.html?gclid=COabwduFgs0CFZKGaQodbGQCOw
450 LPH EFI FUEL PUMP
READ THIS
http://autolabscopediagnostics.com/fuelpump.htm
you NEED a high quality ,return line style, fuel pressure regulator
http://www.summitracing.com/parts/hly-12-841/overview/
http://www.amazon.com/Moeller-Separatin ... d_sbs_sg_1
http://www.summitracing.com/parts/edl-1792/overview/
CARB PUMP BELOW
EFI PUMP BELOW
http://www.highflowfuel.com/i-10388...rainers.html?gclid=COabwduFgs0CFZKGaQodbGQCOw
450 LPH EFI FUEL PUMP
READ THIS
http://autolabscopediagnostics.com/fuelpump.htm
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8
87vette81big
Guest
I have used Holley Blue pumps & had nothing but problems after 1-2 years.
There is an internal bypass valve that sticks in the Electric pump housing as it wears.
Gives erratic fuel volume &pressure to the regulator.
A Mallory Comp 110, Comp 140, Comp 250 , Comp 250 EFI & Comp 500 Daul pump is 1000 times better than any cheapie Blue Pump.
I use Comp 110, Comp 140 on 2 of my cars.
Have a Mallory Comp 250 EFI Also on hand. Its a big monster pump.
There is an internal bypass valve that sticks in the Electric pump housing as it wears.
Gives erratic fuel volume &pressure to the regulator.
A Mallory Comp 110, Comp 140, Comp 250 , Comp 250 EFI & Comp 500 Daul pump is 1000 times better than any cheapie Blue Pump.
I use Comp 110, Comp 140 on 2 of my cars.
Have a Mallory Comp 250 EFI Also on hand. Its a big monster pump.
Thanks for your replies, Grumpy & 87vette81big. I have some homework to do. It's just a choice about who I spend my money with. Good point, Grumpy, proper fuel systems cost money. I'll be upgrading very soon. 87vette, those Mallorys look pretty nice. Thanks for the info. I'll be deciding soon.
8
87vette81big
Guest
The Very Best & Ultimate reliable external ekectric fuel pumps are Weldon.
Also used in aircrafts.
But the price is beyond reach of nearly all.
Professional drag race quality.
Also used in aircrafts.
But the price is beyond reach of nearly all.
Professional drag race quality.