I need some help with my blowthrough carb setup. I have my stock gsl-se fuel pump wired to the engine fuse, so it comes on w/ the ignition.

The problem comes in with the fuel pressure. The carb needs very little fuel pressure, the gsl=se one puts out a lot. So, i have put in a mallory 4307M rising rate pressure regulator.

It doesnt seem that it is regulating anything, as it keeps flooding my engine when i try to start the car. Regardless of what pressure setting we put on it, it seems to put through the same pressure.

Some things i'm thinking are the problem:

1) Bad Mallory unit
2) Clogged fuel return line, forcing all fuel through (unlikely, we blew the return line through, didnt seem to be any restrictions.)
3) too much resistance on the return line, need to run to a new location.

What do you guys think?

I thank you for your help in advance

~Geoff

 

Hows the project comming along? Im guessing you have the motor in>

Could it not be that the pump is overpowering the regulator? Do you have some gauge to see the fuel pressure?

 

well the reason why the regulator is in there is to prevent it from overpowering the carb....

it's been done many times before w/ this setup, and it works just fine.... so im' wondering if maybe my regulator is bad...

 

btw, it COULD be running this afternoon if i get this problem fixed.

 

you should have a pressure gauge to verify that it's working. Is it hooked up correctly?

 

yes its hooked up correctly.

pressure guage is pegged regardless of settings.

 

How is your regulator plumbed? Remember that the -8 line is the inlet from the pump and the 3/8 NPT goes to the carb. If you get that backwards, it would show the same symptoms as you're getting now. Also, if the return isn't plumbed, that would happen as well. You can't run the regulator dead-head like a domestic with a mechanical fuel pump, it just won't work.

BTW, I have a Mallory regulator in my Galant VR4, and it's a piece of ****. The diaphragm wore out in a year, and a rebuild kit is 35 bucks. Plus, they just arbitrarily decide to redesign the diaphragm, and make it impossible to use the high pressure spring (which I NEED in my application) in my "new" regulator, and don't offer the old style kit anymore.

Sorry... I'm done ranting now. Hit me up on MSN or something, I can take a look at your beast and see if I can help you bring it back to life.

 

Are you are using a fuel injection fuel pump? The regulators will not knock the fuel pressure down that much. I made that mistake when I put a carb on my sandrail. Most EFI fuel pumps run from 80 to 200 PSI. You only want about 20 with a turbo setup. The regulators are only good for around 50psi at the most.

-Mark

 

I had to re-plumb the return line on my blowthrough setup with 1/2inch return line from the regulator all the way into the gas tank. I knew the stock 1/4inch line would be very overwhelmed since with the carb base pressure, you WILL WILL WILL be bypassing almost all of the fuel right back to the tank except at maximum boost.

Remember with EFI setup, the fuel pressure is much higher, and less fuel is bypassed back to the tank requiring not that big of a return line.

I'm actually using a smaller feed line then return line, which is kinda funny, but it works just great. 3/8" feed and 1/2" return line.

 

I think you need the Mallory 4309, I don't know about the 4307 for carbs.

I am currently using the Malpassi RRFPR.

Oh, is your return line kinked?

 

ok lisen up. you can not use that fuel pump! you must use a pump for a carb not an fi one. they are very differant. high presure, high flow = fl (25 - 100 or so lbs). low presure high flow = carb (up to 15lbs) you need a low presure high flow rate pump. I have never seen the se pump used successfuly in your type of set up. you are over runing your frp. you may not even be able to get the frp for fi to hold your pressure that low. at the least I do not belive your flow rate will be high anuff at the presure you would need. what pressure and flow rate are you targeting?

 

actually, many cars are using this fuel pump on this setup. thats no tth eproblem.

The problem was i had the fuel send line screwed in too much, it was digging into the center bit that controls the valve.

Its hopefully fixed now, i'm out to try it.

 

he's been gone for a while... musta got it fixed?

Zachstylez

 

No, they will easily take the pressure down that much. I have a Porsche 911 Turbo fuel pump on mine, with the same regulaotr iotus is using, and it is working great.

 

People, stop giving advice when you DO NOT know what you are talking about.

You want a high pressure pump(at least 25psi) when running a blowthrough turbo setup. You need the base pressure for the carb, which is usually about 5 psi. Then, you need 1 more psi of fuel pressure for every 1psi of boost you run. You could get away with only a 15-20psi pump, but it would be borderline on flowing enough, which you do not want. The high pressure EFI pumps are a great way to go. That way you know you will always have enough fuel. The pressure regulator will easily take down the pressure to what you need, that's what it is there for. Yes, it will be flowing a lot through the return line, but as long as it is not clogged then it will be fine.

My car is running great, and I'm using a Porsche 911 Turbo fuel pump!!! Now are you still going to try to say that a GSL-SE pump is too much pressure or too much flow that it won't work?

 

Soooo Did ya figure it out..?

 

im pretty sure hes at work..... so either he got it done and drove his car to work.. or he didnt and walked

-greg

 

yeah coldy13 I still do not agree with you on this. and I do know. I may have over simplfied what I said for example. 5lbs base fuel pressure + 10 lbs boost presure does = 15lbs boosted fuel pressure on most carb setups but they do not all work like that. it depends on the carb. that is a good base formula though for figuring presure needs with out thinking about the pumps flow map. differant pumps flow differant amounts at differant pressures. just because a pump can make 80 or more lbs of pressure does not mean it flows the most at 80 lbs or more of pressure,it may fow best at 35-50lbs. it depends on the pump, one that makes 20 lbs may out flow it by a lot. I know there are low presure high flow pumps that pump up to 40 or so lbs and that is not low presure but most of them are in that 25and under lbs range. so please excuse me for useing less for an example. I can not say your pump set up does not work because your car is running. what I can say is, IMHO its not the best setup up you could have. its best to pick a pump that matches your needs, flow rate at desired pressure range. do you agree? and the same goes with the fuel pressure regulaters you need one that is designed to be use with your desired range( out side of the regs design range you lose flow rate ). his setup was not working corectly or he would not have ask. and I was saying he was most likly not getting anuff fuel with using the regulator to turn it down that much. you are not running 15lbs of boost are you on that 12a?

 

have you ever driven a blow through turbo car?

i have seen 18 psi on a stock ported 12a on 91 octane and no intercooler..............
and it had a 911 turbo pump on it.....


the best fix for boost creep is to turn up the BOOST

 

im using the stock SE fuel pump of my car in my blow thru setup and i never had problem of high pressure, or got flooded. the only time that my car flooded it was of old spark plugs and cap and rotor. the problem he can have is that his regulator is stuck close and if it is he have to take it apart and clean it.

 

680rwhp12a, yes, I have driven and owned both blow through and draw through setups. and I am aware of some people running high boost on 12a cars. some run even higher than the 18lbs you mention without an intercooler. but like you I sure would not plan on doing that very long. the cooler charge a intercooler gives the intake air has many bonuses. may be you can better explain the fuel pump map thing and presure regulator window for these guys. I do not know the 911 pump map so it may be fine do you?