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Author Topic:   Mechanical fuel pump
GRTWallbanger
Dirt Maniac

Total posts: 196
posted April 27, 2005 03:53 PM  
I am still trying to get my fuel pressure right.I tried 4 different regulators today.From one with no jet(just a spring and diaphram)to a .140 jet.
I was told to get 3 to 4psi at idle and 10psi at wide open.
I can only get 3lbs difference.If i set the idle to 4 it only goes up to 7.If i set the idle at 7 it will go to 10psi.I took the regulator off all together and plugged the rear of fuel log to check pump psi.I had 14lbs so i think pump is good.Also tried 2 carbs.Is it possible to get what i want with a mechinacal pump??

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted April 27, 2005 04:19 PM  
I dont know whether you can do that with a mech pump. I would be most concerned with getting enough fuel at wide open and then let it idle wherever it does. I think thats why a lot of guys use the throttle bypass valve so they can tune it better. The main thing at idle is to make sure your not overpowering the needle and seat and flooding it.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted April 27, 2005 06:55 PM  
dirtbuster is absolutly correct! Your psi at idle just needs to be low enough to keep from pushing the needle out of the seat and flooding the fuel bowls. When I was running alky I used a Holley regulator and at idle I think I had around 3 or 4 and under full throttle it was 9. It worked. If you can't get it where you want it and you insist on running a mechanical pump (which is what I ran also) you will most likely need a bypass.

jdj9410
Dirt Full Roller

Total posts: 65
posted April 27, 2005 07:26 PM  
If you have access to another pump try it. The one you have may build up pressure but not enough volume to work through a regulator.

Dman
Dirt Freak

Total posts: 270
posted April 28, 2005 08:37 AM  
Yes it is possible. Not with a diaphram type regulator. The mech. pump for alcohol must use a barrel valve style bypass to do this properly.
C&S has one of these and so does Barry Grant but it is pricey. We tried to use a diaphram type(more than one)Even though the fuel system guys we talked to said it wouldn't work properly.We were stubborn but finally bought the Barry Grant unit.It works.We just need to dampen the pump pulsations at idle now.It will all come together eventually.

JT54
Dirt Maniac

Total posts: 170
posted April 28, 2005 10:18 AM  
bary grant ball valve.

A&M Motorsports
Dirt Maniac

Total posts: 117
posted April 28, 2005 10:44 AM  
Been there and done that. If you have to run a mechanical pump get a 15 psi pump and a mechanical ball valve bypass system with a return line to the tank. With the 15 psi pump you will have to put a regulator somewhere to limit w.o.t. pressure. I have seen some guys run a 9psi pump straight to the carb but that's not for me.

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Artie Perilloux
A & M Motorsports

JT54
Dirt Maniac

Total posts: 170
posted April 28, 2005 10:04 PM  
I just went through that 9 psi deal on a 408 ...it dont work .....the guy I bought the engine from had it set up this way and told me it worked great but that the engine floated the valves after 7000 rpm so he liked to keep it at about 6500 .....well ,I have always run the ball valve bypass with the 15 lb pump and never had a problem with it......last weekend I ran the new engine with the 9 lb set up and by the time I hit 5500 the float bowls were going dry and the engine was spitting and popping as if it had valve float....HMMMM.....this weekend I will see if my fuel system wakes this beast up ....It sure runs better in the driveway!!!!

GRTWallbanger
Dirt Maniac

Total posts: 196
posted April 29, 2005 09:39 AM  
When you say you tried that 9lbs deal?Do you mean 9lbs at wide open was not enough?

JT54
Dirt Maniac

Total posts: 170
posted April 29, 2005 10:56 AM  
It seemed like no matter what rpm I brought the engine up to the preasure never moved from 7 or 8 lb ....maybe I have a bad pump or something ,but I am going back to what I know works for me,....about 3 lb at idle and steady climb to 10 with rpm increase.

roushimca6
Dirt Roller

Total posts: 6
posted May 02, 2005 04:35 PM  
quote:
Originally posted by GRTWallbanger:
I am still trying to get my fuel pressure right.I tried 4 different regulators today.From one with no jet(just a spring and diaphram)to a .140 jet.
I was told to get 3 to 4psi at idle and 10psi at wide open.
I can only get 3lbs difference.If i set the idle to 4 it only goes up to 7.If i set the idle at 7 it will go to 10psi.I took the regulator off all together and plugged the rear of fuel log to check pump psi.I had 14lbs so i think pump is good.Also tried 2 carbs.Is it possible to get what i want with a mechinacal pump??

run A 15psi pump with BG throttle bypass.

A&M Motorsports
Dirt Maniac

Total posts: 117
posted May 03, 2005 05:27 AM  
quote:
Originally posted by JT54:
It seemed like no matter what rpm I brought the engine up to the preasure never moved from 7 or 8 lb ....maybe I have a bad pump or something ,but I am going back to what I know works for me,....about 3 lb at idle and steady climb to 10 with rpm increase.

It sounds like to me that you have a 7 psi pump. They all look the same. Very few pumps actually have the psi rating on them. Buy a new 15 psi pump, install the ball valve and regulator and you fuel problems will probably go away. Everyone on here including myself is giving recommendations from experience. If you're not going to run a belt drive this is the ONLY way to go.

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Artie Perilloux
A & M Motorsports

Kromulous
Dirt Forum Champ
Total posts: 796
posted May 03, 2005 07:30 AM  
A&M, you run a Ball valve like the BG throttle bypass, and then a regulator?

Were going thru the same drill, trying to set up a alchol system. Were planning on running a EB 15 psi super victor pump, and a BG throttle bypass.

Thanks, Krom.

A&M Motorsports
Dirt Maniac

Total posts: 117
posted May 03, 2005 09:19 AM  
quote:
Originally posted by Kromulous:
A&M, you run a Ball valve like the BG throttle bypass, and then a regulator?

Were going thru the same drill, trying to set up a alchol system. Were planning on running a EB 15 psi super victor pump, and a BG throttle bypass.

Thanks, Krom.


Krom , the way I had it set up is with a regulator between the pump and the carburetor so you can set your fuel presure at 4000 rpms to whatever you decide that you need. After that you adjust the linkages to the bypass ball valve to let it bypass at the idle pressure you want. The position of the ball in the valve determines how much fuel will be bypassed at idle. The shaft that the linkage is hooked to can also be adjusted with a screwdriver. If an ole coonass can figure it out anybody can get it right.

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Artie Perilloux
A & M Motorsports

Kromulous
Dirt Forum Champ
Total posts: 796
posted May 03, 2005 10:01 AM  
What regulator did you use?

Already have the BG bypass.

I never even thought about runing both, but now that you posted that, it makes perfect sense.

The regulator wont let more than X pressure (whatever u set it at) to the carb, then the Bypass blows off the excess at idle, brillant.

One question thou, should the regulator go on before or after the tee to the bypass?

Lets say you got the pump to the tee (bypass) then the reulgator, then the fuel log, or the other way, pump, regulator, tee, then fuel log.

A&M Motorsports
Dirt Maniac

Total posts: 117
posted May 03, 2005 10:27 AM  
quote:
Originally posted by Kromulous:
What regulator did you use?

Already have the BG bypass.

I never even thought about runing both, but now that you posted that, it makes perfect sense.

The regulator wont let more than X pressure (whatever u set it at) to the carb, then the Bypass blows off the excess at idle, brillant.

One question thou, should the regulator go on before or after the tee to the bypass?

Lets say you got the pump to the tee (bypass) then the reulgator, then the fuel log, or the other way, pump, regulator, tee, then fuel log.


I had mine just after the fuel pump in an area where it could be easily accessed. Once you get it set you'll virtually never have to fool with it again.

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Artie Perilloux
A & M Motorsports

James Birmingham
Dirt Full Roller

Total posts: 28
posted May 04, 2005 08:54 AM  
Man I tell ya what I never thought about the combination. But are ya'll taking about a regulator or a spring bypass. I have a barrel valve bypass and have it at 3 lbs idle and god who knows at full throttle. I do know this though, the car has a digital recording gauge. The fuel pressure has shown a max of 21 lbs. I'm not sure if thats correct but I would think those pulsations are a mighty force. A tee and both spring bypass and barrel valve might be an interesting combination.

Kromulous
Dirt Forum Champ
Total posts: 796
posted May 04, 2005 09:01 AM  
They way i understand it is a ball valve by pass, like the BG throttle bypass, and a regular type regulator with a adjustable pressure screw out the top of it.

Another good thing like you said is the regulator being on just after the fuel pump, it should cushion the pulses alittle better before it gets to the carb / log & bypass.

Like i said above, its a brilliant idea.

A&M Motorsports
Dirt Maniac

Total posts: 117
posted May 04, 2005 11:16 AM  
quote:
Originally posted by Kromulous:
They way i understand it is a ball valve by pass, like the BG throttle bypass, and a regular type regulator with a adjustable pressure screw out the top of it.

Another good thing like you said is the regulator being on just after the fuel pump, it should cushion the pulses alittle better before it gets to the carb / log & bypass.

Like i said above, its a brilliant idea.


Krom, don't claim to be brilliant, just coonass luck maybe but I have worked in refineries all of my life and plumbing a race car is easy compared to refineries.

Just think about it, all you need is a cheap pressure regulator suitable for alcohol service. With the ball valve bypass w/o the regulator before the bypass you will get full fuel pump pressure to your needle and seat at w.o.t. because the bypass is CLOSED. All the return line does is allow the bypassing fuel return to the tank at idle.
If you use a fuel pressure gauge make sure it is plumbed in downstream of the regulator.
Some people may have a concern about dead heading the fuel pump by reducing it's full output pressure capacity but I have never had any problems. I am glad to help my northen buddies out. This is a great place to learn, thanks Jammin.

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Artie Perilloux
A & M Motorsports

GRTWallbanger
Dirt Maniac

Total posts: 196
posted May 08, 2005 12:47 PM  
OK,
I tried again this weekend and fought it AGAIN.
I am going to buy a throttle by-pass tomorrow!!!
Can you draw a diagram of how you had the throttle by-pass and regulator plumbed.
Thanks for all the advise.
Maybe i will finally get thish thing to run.
"I think i get it, I run a regulator after the pump but before the 'T' for the by-pass.Then i set the psi. at 10psi at 4,000rpm ?
And keep keep the gauge at the back of the fuel log?Since the return line is no longer on the back of the fuel log?

[This message has been edited by GRTWallbanger (edited May 08, 2005).]

[This message has been edited by GRTWallbanger (edited May 08, 2005).]

Dman
Dirt Freak

Total posts: 270
posted May 09, 2005 07:00 AM  
Put a tee in the front of your fuel log. One of the legs of the tee screws into the log, one goes to the by pass and one goes down to the pump delivery side.In other words it is plumbed into the pressure side of the pump so it can by-pass the excess fuel back to the tank.By the way you should really run the by-pass line back to the tank.Some run it back into the supply line from the tank to the pump.This can cause aeration or flow disruption to your fuel supply.The return line doesn't have to be expensive line as there is no pressure build up on the return.
I really don't think you should run a pressure regulator on the supply side of a methanol system as they may restrict the larger fuel demand.A gasoline system is different due to the lower volume of fuel needed.On methanol you want to bleed off extra fuel not restrict it before it gets to the carb. Could be harmful to your pistons!

[This message has been edited by Dman (edited May 09, 2005).]

GRTWallbanger
Dirt Maniac

Total posts: 196
posted May 09, 2005 09:38 AM  
I just went to my local speed shop.They have a fuel log with a ball valve attached to it.Is this the same thing and will it work the same.It actually seems a little simpler to plumb.

samiller
Dirt Roller

Total posts: 14
posted May 09, 2005 08:07 PM  
sounds crazy,but a hose clamp on return line works also. tighten till 9 psi at high rpm.

Dman
Dirt Freak

Total posts: 270
posted May 10, 2005 12:24 PM  
The ball valve on the fuel log deal was something C&S carbs was doing a while back.
I know a couple of folks still use it.It works similar to a barrel valve set up.

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