MotorHead

I just put in a new Russel fuel gauge into the fuel rail on my Holley 750 and started the car and it showed about 5psi and thn slowly went down to 0psi but it was still running, what the heil is going on here.

I suspected some kind of fuel problem because when I hit the brakes a litle harder than normal it seems to want to stall, I checked the float levels and sure enough both priamary and secondary needed to be adjusted up. So at idle the float levels are OK but it still wants to stall when I hit the brakes.

A little history I put in a new cam and at that time I installed a new Carter high flow (110gph) fuel pump and all new braided hoses and a new Earls 6AN fuel filter. I had to rotate the base of the fuel pump a few times to get it in the right position, I wonder if I screwed something up there.

conway62

MoroHead,
I posted a similar problem a few months ago. Never got any response. I have the same condition using an Edelbrock carb. I even added a regulator to make sure pressure was set correctly. Still occurs. I have 6 psi at idol and when the car really warms up I look at then gauge and is says 0. I switched gauges to a liqued filled from Jegs. Same condition. I think we stumped the formum with this one. :hurray:

MotorHead

Wow that is amazing, i was looking for someone who had seen this only I thought there would be an explanation. I started the car again and it showed 6 psi and it was pulsing a bit, from the mechanical pump everyting looked fine, I watched tit for a minute and then I took it out for spin, got back 15 minutes later and it was reading 0 psi WTF is going on here, does Russell have a web site ?

conway62

Its not a problem with Russle. I actually have tried 3 different gauges. I happens with all of them. I am using an new stock fuel pump with a Holley fuel regulator and a Lequid filled gauge from Jegs and I have the exact problem you do. The funny thing is the car ran fine even on the freeway. Having a 454 I would think if the fuel pressure was actually 0, I would have had starvation problems. I have not idea whats going on.....Hopefully someone will chime in that has had this problem. :banghead:

Matt Gruber

first of all, i tape a vac/pressure gauge to the windshield for testing. once it passes at max rpm in 1st ad 2nd, i take it off.
i've never put one on the fuel rail as i can't see it driving.
What you guys seem to be seeing is a mechanical fuel pump at idle, losing its pressure because it is running so slow.

conway62

Hi Matt,
I have set the throttle at 3000 RPM and watched the gauge. Never moves from 0. Could a partically plugged return line possible cause this issue?

Matt Gruber

maybe if it is hooked to the return line!
Have u checked the gauges with air pressure? that is the easiest way to check them out.
they have a restrictor; it could have dirt in it. :cheers:

conway62

I have tried several gauges. All have the same problem. As soon as everything cools off. I restart the car and the gauge once again reads 6psi set by the regulator.

Fevre

Have the same thing going on with my liquid filled gauge, starts at about 6 and slowly sinks to 0. Never thought about the return line, how does it function? Don't have the gauge on the carb on it now but I wonder if you pinched the return line iif you would see a pressure increase, with the return line is has to be bleeding some pressure off. :confused:

Matt Gruber

:iagree: yes, that is it.
the return line will bleed off the flow at idle.
if it does not rise by 2000 rpm the return restrction is too large. use a 1/16" hole to restrict the return line

MotorHead

I bought it so the guy that does the chassis can have an assistant watch the gauge when it's on the dyno. I was going to tape it to the windshield but I don't see the point if it's not reading correctly :D

Matt Gruber

the gauges are fine
FIX THE PROBLEM :nopity

Matt Gruber

ways to restrict:(drill a 1/16" hole in any of these)
1. saw off a bolt
2. steel ball
3. metal fuel line bentover with vice grips
4. brass or copper fitting shoved in the return line
5. ball of JB weld
.
put it anywhere in the return line; watch pressure rise and power zoom :eek: :seeya

Twin_Turbo

or just do it the right way and get an external pressure regulator to put in the return line. that way your pressure will never bee too low or too high and the return line can be as large as you want.

Matt Gruber

how does it prevent vapor lock? :confused:

Twin_Turbo

who's talking about vapour lock? it prevents pressure bleeding off from a too large return, no messing w/ restrictor pills or anything, just dial in the pressure and be done with it. To prevent vapor lock with pressure you'd need a pressure much higher than most carbs will need (something above 6-8psi or so)


[Modified by Twin_Turbo, 6:01 PM 9/1/2003]

MotorHead

OK let me see if we are on the same page here, my return line is blocked off right now with a bolt in it. Do you want me to drill a 1/16 in. hole thru the bolt ?

Matt Gruber

1st check the fuel pressure.
If OK, then drill the hole(1/4" long would be long enough, you don't want to drill all night)
.
TT- the return line is there to prevent vapor lock.(that was discussed in auto shop the day you missed the school bus) :lol:

Twin_Turbo

yes, but you were not talking about the vapor lock. You were talking about a means to restrict the return line to prevent pressure leakage, the best way to do that is with a regulator. Messing with pills is just a PITA.

We don't have school buses here so there's nothing to miss... Maybe I missed the class in snide remarks, I see you did attend it :skep: :rolleyes:





[Modified by Twin_Turbo, 6:15 PM 9/1/2003]

Matt Gruber

:jester yes i was the class clown :jester
.
take apart a stock fuel pump(as i have) and you will see the 1/16 restriction is factory stock