high fuel pressure at startup (should be moved to electrical

[rtm]

I am trying to set my fuel pressure by using the guage I installed at my carb inlet line.
it is installed after the bypass regulator I am utilizing.
the problem I am having is occuring when I start the engine cold, the guage is reading 10 or 12 PSI.
I adjust the pressure immediately at the regulator, (I have tried anywhere from 6 to 4.5 PSI ),then when the engine warms up, the pressure will drop to almost zero.
every time I start the car cold this occurs.
I have a mallory 140 gph pump mounted below my fuel cell.
all lines, including the return, are 1/2 inch diameter.

today I got my rebuilt carb to idle well,
but the engine only builds power to a certain point , then falls flat on its face (at launch ).
This is in the limited space of my driveway, as the car still remains unregistered, and has no glass or paint yet
I know there are a lot of variables I am leaving out here,but, anyone got any ideas ?

[firebird77clone]

Sounds to me like a defective regulator.

Re post your question on clubhotrod.com, and give more detail.

[cjbiagi]

I'd be curious to see what the pressure is doing before the regulator. The problem does sound like a bad regulator but not knowing if the pressure is varying before the regulator could give you a clue as to what the fuel pump is doing. I would also verify the voltage at the pump to make sure that is consistent.

[chevyart]

rick are you running a fuel pump safety type switch (works off oil pressure)(defective?) are you sure you have the right regulator for a return line. a 2 port one will probably just scoot the fuel right by the carb and back to cell. a correct 3 port on just bleeds the excess fuel back to cell. art

[rtm]

thanx guys ,
the regulator is a brand new mallory
the pump is another story.
do you think that the pump may be starting out strong, and slowing down as it gets warmer ?
just a thought.
BTW, to check the pump without running the car, can I jump the wires at the oil pressure sending unit ?

[rtm]

searched the site and referenced this thread;


viewtopic.php?f=44&t=30212


unplugged my oil pressure switch, and the pump ran with key on.
it should NOT run with that disconnected.
will let you know what i find

[rtm]

Should move this thread to electrical and wiring

my fuel pump runs continuosly (key in run position,no oil pressure, all three wires disconnected from oil pressure switch.
when I probe the blue wire with a test light, or the factory fuel pump fuse (glass one under dash ), the pump stops.
if I remove the test probe, it will start again,
do I have a missing ground wire ?
the pump is grounded, as is the summit fuel pump relay I installed.
the reason I thought I had a fuel problem is because the fuel pump was stopping while the car was running,
thus causing the pressure drop I described in my initial post.
funny thing is, the fuel pump did Not run when I initially would turn the car over,until it built oil pressure, then it would start.
SO maybe art is unto something with that defective O.P.S.
HOWEVER, I have cut the pigtail off of the wiring harness (it looked misshapen/burnt) SO, all three wires are now isolated from each other, as well as from the O.P.S. and the pump still runs continuosly with the key in run position, until I probe it with the test light @ the blue wire/fuse
??????????????????????
am also experiencing battery drawdown, unless I shut off my master disconnect

BTW, Brian (Stage 169) thanx for posting that diagram in colins thread about bypassing the O.P.S.

It saved me ALOT of head scratching

[chevyart]

rick is the fuel pump running off a relay. it always should be if you arent using one. just another thought. these guys on our site are real smart. someone will come up with the answer real soon. good luck art.... PS i tried calling you yesterday. no answer.

[spencerforhire]

Oh you absolutely have a wiring problem and it very well may be ground related. By probing the fuel pump line with a test light, you're essentially grounding it through the bulb in the handle of the tester. That bulb takes less power to light than the pump takes to run, so the voltage takes the path of least resistance. It could be the oil pressure switch only providing a partial connection. If you remember back last year I explained how the OEM oil pressure switch is wired; the blue wire to the pump rests connected to the purple start wire, and when the engine builds oil pressure it switches to the pink(ignition) wire. To diagnose what's going on, try a jumper from the pink to the blue with the switch unplugged; this would let the pump run as long as the key is on, and should now be unaffected bu the test light.

[rtm]

Oh you absolutely have a wiring problem and it very well may be ground related. By probing the fuel pump line with a test light, you're essentially grounding it through the bulb in the handle of the tester. That bulb takes less power to light than the pump takes to run, so the voltage takes the path of least resistance. It could be the oil pressure switch only providing a partial connection. If you remember back last year I explained how the OEM oil pressure switch is wired; the blue wire to the pump rests connected to the purple start wire, and when the engine builds oil pressure it switches to the pink(ignition) wire. To diagnose what's going on, try a jumper from the pink to the blue with the switch unplugged; this would let the pump run as long as the key is on, and should now be unaffected bu the test light.

I do have a relay system (summit universal ) in place and wired as per instructions that came with the relay.
right now I have all three wires (blue ,purple, pink ) disconnected and isolated from each other, and from the OPS,
with the key in the run position, the pump runs continuosly. (this is WITHOUT the engine running ZERO oil pressure)
when I ground out the blue wire the pump stops.
when i connect the pink and blue wires, the pump continues to run, BUT, I can hear a factory relay or switch click on
(located adjacent to the blower motor, I thought it was for blower speeds ? IDK
Will play with it some more 2day
BTW is that the factory relay?
or do i have some wires crossed?

[megavega]

Hey Rick, how about trying a digital voltmeter on your pump and see what the voltage drop is, I think spencer has it pinned down as thats exactly the same thing that came to my head. I bet when you check your voltage its a drop as the current is going "thru" another path of least resistance. Spence will fix ya up!

[spencerforhire]

Please explain how you have the relay wired; also the OEM fuel pump wiring doesn't have any relay of it's own. I don't know what relay you're hearing.

[rtm]

Please explain how you have the relay wired; also the OEM fuel pump wiring doesn't have any relay of it's own. I don't know what relay you're hearing.

relay wired as per these instructions:


http://static.summitracing.com/global/i ... 890023.pdf

spence, when I connect the blue /pink wires, the small switch (external ) on the side of my blower motor "clicks"
when I disconnect the pigtails from that unit and cross the blue /pink wires again, I can hear an audible "click inside the car, under the dashboard in the heater control/glovebox area.
long ago, when I purchased my car, I discovered the wiring harness @the firewall had melted.
now I'm thinking the damage may have migrated into the interior wiring as well.
I am in the process of removing the fuseblock from the interior firewall area (although I seem to remember inspecting it when i initially discovered the fire damage).
wish me luck

rtm

[rtm]

Please explain how you have the relay wired; also the OEM fuel pump wiring doesn't have any relay of it's own. I don't know what relay you're hearing.

relay wired as per these instructions:


http://static.summitracing.com/global/i ... 890023.pdf

spence, when I connect the blue /pink wires, the small switch (external ) on the side of my blower motor "clicks"
when I disconnect the pigtails from that unit and cross the blue /pink wires again, I can hear an audible "click inside the car, under the dashboard in the heater control/glovebox area.
long ago, when I purchased my car, I discovered the wiring harness @the firewall had melted.
now I'm thinking the damage may have migrated into the interior wiring as well.
I am in the process of removing the fuseblock from the interior firewall area (although I seem to remember inspecting it when i initially discovered the fire damage).
wish me luck

rtm

[rtm]

while taking a break I felt a brief synopsis was in order,
I started this thread because I was constantly adjusting the fuel pressure while running my car (to sort out idling /launching glitches) I didn't realize the fuel pump was running intermittently, because the car is so loud, I couldn't hear the fuel pump cutting out, (hence the loss of fuel pressure ) I would adjust the pressure @ the regulator, (meanwhile the pump would come back to life) and the pressure would spike
after removing the pigtail from the oil pressure switch, and turning on the key (to run position) I discovered the pump was running regardless of unplugging the (supposed) power source.
thinking the wires were somehow arcing/jumping at the pigtail, I snipped the end off, to no avail, the pump continues chugging along, but will randomly stop.
when it does so, a slight exitement, with the pink/ blue wires touching ,sets the pump off on its merry way.
in the interim, I hear the various clicking sounds (described earlier in the thread)
now, in retrospect, I remember that I have never had a working blower motor, (even though I replaced it ).
somewhere, (i believe ) there is interference between the blower motor/oil pressure switch circuits.
though I am frustrated with my dilemma, my typing skills are improving exponentially, as I am looking to the members of this forum to hold my hand through the sorting process.
thanx for looking.
and, of course, I'll keep you posted
rick the mason