So I started up the project car this weekend. Well just about....

The car is an 87. It had a 4cyl in it originally. It now has a SBC. I used a holley fuel pressure regulator. I have a pressure gauge plumbed into the regulator and a clear fule filter mounted close to the regulator so I can see all that's going on. The carb is an new edelbrock (don't know the part # right now) 4bbl.

I gave power to the fuel pump and watched the fuel filter fill up with fuel (this actually took 2-3 times of turning the key on and off). I them heard the carb bowl fill with fuel as well and the fuel pump stopped. No pressure was read on the gauge at this point. Upon further reading I discovered that the fuel pump does not come on until there is oil pressure detected.

Started cranking the engine and saw that there was about 4psi reading on the fuel pressure gauge while cranking. Once the engine stopped cranking the pressure reading would jump up to 6-8psi for a few seconds and then drop to 0psi.

Started cranking the engine again until it fired. It caused a slight flash fire under one of the headers... no damage done.. it went out in a couple of seconds. We then cranked it over again and noticed that the carb was FLOODING. The carbwas literally overflowing out the top of the carb and had filled some of hte cylinder with fuel.

Disconnected power to the fuel pump and ignition and cranked the engine over to remove most of the fuel that I could.

I don't know a whole lot bout carbs and am looking for any info I can get.

1. I know I'm going to have to remove the fuel line and isolate the fuel regulator to see what it's doing in a deadhead situation.
2. I'm not quite sure why the carb flooded. I don't know enough about carb operation to fully troubleshoot the problem.
3. I hope I didn't damage anything on the carb.

As far as I know the fuel flows into a bowl which is controlled by a float. Once the bowl is full the float shuts the fuel flow off. I'm assuming that the inlet shut off can only handle a few psi (thus the need for a regulator). I'm just wondering that if I overpressured the carb if I did damage to that shut off mechanism.

If I find out I did NOT overpressure the car then then next questions is WHY is the carb flooding if the pressures are correct. Is there any other function of the carb that would allow the thing just to overflow like that? Honestly, it appeared that the fuel pump was just pumping into the carb with no restriction or stopping. Something obviously wan't working right.

Any insight would be appreciated

I'm no carb expert, but if your bowls are overflowing, then there is likely some debris/dirt in the needle valves (based on personal experience). If there is, they won't shut when the bowls float up and try to shut them. They need to be cleaned out. I had this same problem when I did my carbed 3.4 swap. I figure it was small bits of rubber in the fuel lines left over from when I cut/fit them.

It was easy to do with my carb (holley 390 4bbl). I just removed the top screw on each bowl (ones used for adjusting fuel level). I then stuck in the hose from a can of carb cleaner and gave each side a few short bursts. This flushed them well. If you do have debris you will likely have to do this a few more times (ie, it will act up again about every other day) until everything is out. I have a smaller fuel filter between the carb and the pressure regulator now.

Don't know about your fuel pump. It could be defective or the circuitry could be. My new NAPA pump died in about 1000 miles. I switched to an AC Delco and it's fine now. I wired my fuel pump directly to a 12v ignition source so it would run once the key is turned. I didn't want any of the old wiring harness or computer in my car.

Dave

[This message has been edited by ditch (edited 04-16-2006).]

Fuel overflowing out of the carb is typically 1 of 2 things.

1. Trash in the needle & seat preventing it from sealing

2. Fuel pressure too high, forcing the needle off the seat.

If your fuel pressure is about 4-5psi, it should be ok. My bet is dirt in the needle & seat. If you pull the needle valve, blow everything out good, because sometimes the debris can be so small you can't see it, but it can still keep the valve from sealing.

Also, how'd you wire your fuel pump to only come on with oil pressure? Fieros aren't wired that way from the factory. The fuel pump comes on for about 2 seconds when you turn the key to start, then it stays on once the ECM reports the engine is running. There is an oil pressure switch on the fuel pump, but that's a backup relay. It brings the pump on when oil pressure comes up, but since it's wired in parallel, it does not cut the pump off if pressure falls.

Well, I don't know what signals the fuel pump to come on. I did some reading yesterday here on the site when I was troubleshooting the fuel pump for not running. The information I read said the pump only comes on when it senses oil pressure. That information could be wrong.

I know that it comes on for a few seconds when you turn the key on and that it doesn't build pressure/come on until it's been cranking for a short period. I imagine there's an event where the computer senses that it's ok to turn the fuel pump on.

the next question is..... Where's the needle and seat? I can rip and tear apart the carb, but if I need a seal kit I'm screwed until I can get another one. I'll have to see if there's info in the manual that came with the carb.

Thank you for the info. Much appreciated

quote Originally posted by Soelasca: Well, I don't know what signals the fuel pump to come on. I did some reading yesterday here on the site when I was troubleshooting the fuel pump for not running. The information I read said the pump only comes on when it senses oil pressure. That information could be wrong. I

A lot of misinformation floating around various car forums on this subject. The oil pressure switch is a backup that will turn on the fuel pump in the event that the relay fails.

The ECM doesn't need to see any oil pressure to activate the fuel pump beyond the 2 second prime....it needs to see distributor pulses.

If your oil pressure falls off to 0 psi while it's running, the switch will NOT shut off the fuel pump....your engine will disintegrate.

In all likelihood, your needle and seat are dirty.

I had the same problem with my demon carb. I called summit racing and they said the regulator was not rated for that much presure. I had to use a three port regulator with a return line. It did not damage my carb.

quote Originally posted by Frizlefrak: If your oil pressure falls off to 0 psi while it's running, the switch will NOT shut off the fuel pump....your engine will disintegrate.

No that is wrong. The ECM does not require distributor pulses to run the fuel pump when a carb'd engine is being used.
The harness from the distributor to the ECM is not used.

The oil pressure switch is what is used to run the fuel pump carb'd engine.
So yes he needs oil pressure to run the fuel pump and if oil pressure drops, The engine will run on whats in the fuel bowl of the carb then stop running.

The "safety" feature is only for if the car is in an accident.
On the stock EFI system, If the car is hit and the engine dies, There are no pulses to the ECM AND no oil pressure so the fuel pump shuts off. This is to make sure that in an accident, If the fuel line is cut or broken the fuel pump will shut off.

With a carb'd car it is just the oil pressure being less than 4psi that will turn off the fuel pump.

As for the topic,
As mentioned your fuel pressure is either too high or the float is stuck.
The ALDL connector by the cig lighter has a fuel pump line (Pin "G" ) If you apply +12V to this pin the fuel pump will run all the time.
First crank down the fuel pressure at the regulator. (close it)
Jumper +12V to the fuel pump line inside the car.
Start opening the regulator until you have about 6 - 6.5 psi on the gauge.
If fuel is flowing out the top of the carb before you get to any pressure built up, then the float bowl is stuck open and needs to be cleaned/checked.
If it doesn't then remove the +12V jumper and start the engine.
The fuel pressure should be between 4 - 6 psi while the engine is running. 5 psi is the "ideal" pressure while the engine is running.
Edelbrock and Holley carbs have the float needle set for about 7.5 - 8 psi.
Anything higher and the fuel bowls will overflow.

------------------

Happiness isn't around the corner...
Happiness IS the corner.
ZZ4 Powered !!

[This message has been edited by Oreif (edited 04-16-2006).]

Had the same problem. My pressure was too high and I had junk in the valves. Took off the float bowls and blew out the valves then lowered my fuel pressure. I noticed that my pressure would climb if I ran the fuel pump without starting the car, if I set it at 4.5 PSI at idle it would jump to almost 7 PSI with just the fuel pump running. I have a new regulator with a return line built into it, that should help keep the pressure where it needs to be.

quote Originally posted by Soelasca: the next question is..... Where's the needle and seat? I can rip and tear apart the carb, but if I need a seal kit I'm screwed until I can get another one. I'll have to see if there's info in the manual that came with the carb. Thank you for the info. Much appreciated

i'm assuming you have a carter AFB style carb (even though it has an edelbrock plate on it)
all 4 holes look about the same size.
the floats, needle and seats are attached to the "air horn" (the top 1/3 of the carb)
you can take the "air horn" off since the gasket line is above the fuel level.
if you tear it dont sweat it too bad, it's not the end of the world, but you should replace it.
1472 is the part number for a gasket kit and should cost $10~$15.

I'm no expert either,but my experience with my v-8 is this. If the car has been sitting for weeks, I turn the key and the pump runns for the 2 seconds, maybe some pressure at the gauge maybe not. Turn the key again and pressure begins to build. Might take a third time to hit the 6 lb setting I have it set at.Then it will hold this amount of pressure for maybe 20 minutes or more before it leaks back down. I would be interested in the model number of your FPR and how you have it pumped. I also use no return line and it has worked for 3 years now. Hope you get this worked out.
Thanks Gary

I don't have the model number on the FPR right now. I'll have to check the box. (yes, I save EVERYTHING). I believe it's a Holley product. It has one inlet and two outlets. The documentation that comes with the FPR says the two outlet ports are for a dual carb setup. The parts guy at the speed shop said I can just plug one port off. I ended up plugging it with a pressure gauge so I could see what's going on right at the regulator.

Downstream of the regulator (about 2") is an inline fuel filter. After that the hose connects directly to the carb. I took a look at the book for the carb today. It looks like I'll have to split the body as buddycraigg stated. Probably won't be for a couple of weeks until I can get to it again.

Thank you so much for the information guys. Especially the part# you gave me for the gasket. I'll see if I can't pick one up before I pull it apart. Hopefully, one day, we'll get the rumours sorted out on how exactly that fuel pump triggers .

Off topic...
It's 10pm here and I just got home from purchasing my first 1988 GT (Fiero #4). It's in pretty darn good shape with 250 000 km on it.

quote Originally posted by Soelasca: I don't have the model number on the FPR right now. I'll have to check the box. (yes, I save EVERYTHING). I believe it's a Holley product. It has one inlet and two outlets. The documentation that comes with the FPR says the two outlet ports are for a dual carb setup. The parts guy at the speed shop said I can just plug one port off. I ended up plugging it with a pressure gauge so I could see what's going on right at the regulator. Downstream of the regulator (about 2") is an inline fuel filter. After that the hose connects directly to the carb. I took a look at the book for the carb today. It looks like I'll have to split the body as buddycraigg stated. Probably won't be for a couple of weeks until I can get to it again.

The fuel pressure gauge needs to be as close to the carb as possible. Mounting the gauge on the second output port of the regulator will not give you a accurate reading of the fuel pressure.
Now knowing where your pressure gauge is hooked up at, I bet you have too much pressure going to the carb.

FYI the Holley pressure regulator with the bypass is #12-803BP I use it on my V8 and it helps especially when the tank is very low on gas. The return keeps the the fuel pump cool vs hot when dead headed.

ok just finally read thru this thread;
did you ever ADJUST the float level on this carb? I am assuming that it is new since you have the box, and thus the needle and seat shouldn't be worn. If you got it second hand somehow, just replace them. Also on the same vein, take the float and just make sure if DOES float. It is likely a very thin hollow bronze/brass affair. It COULD have a pinhole in it; it is one of the checklist things to do when you are having probs. Immerse it for a while; look for air bubbles, shake it for noise etc etc. Be sure it isn't compromised.

All the above (and thread items too) being covered, I would say the NEXT thing is to become familiar with how to adjust it. It could be WAY out right from the factory. This is where the time comes in. Since you're at the upper end of the range fuel pressure you will need a 'tight' adjustment. A lot of the old mech'l style fuel pumps only put out 7psi max so you are pushing it a bit with 6 to 8 next to the carb.
The needle is spring loaded so it will take a good "push" (from the fuel level, raising the float) to actually seat the needle. You likely need to start it seating a bit on the low side. All in all it is a trial and error situation so don't feel unique here; just be patient, .... and fireproof (from leaking fuel on a hot engine repeatedly.....) and be very diligent with your 'graduated tweaking' of the float level. It might be (I haven't worked on a Carter before, sorry) simply a matter of bending a tab (yup, might be that unscientific) bit by bit to get the float height you need. Or if it is like a Holley you have to open a 'sighting port' in the float bowl and adjust the float with a wrench and screwdriver till the fuel just seeps out. Different strokes........

There are lots of other things but I am guessing it is new so things are not worn out for now.

However having the float improperly adjusted will GUARANTEED give you severe flooding. Without exception, every time. So this is what you will have to do, dirt or no dirt. (Yes, check for it too; it is a common prob.)

Anyway
maybe search the net a bit for info on your particular model, realize that this IS a bit of a process and just bite the bullet.

good luck.
gp

Ok, I actually got around to looking at the carb today.

IT'S ALIVE!!!!

Yes the carb is new. Everything is new on this car. Which reminds me of my personal quote. "The difference between new and used is new has warranty".

Took a good look at the construction of the carb and the drawings in the manual. Pulled the top off the carb and inspected it. Yes 308.... the construction is as you said. two metal floats that looked like they're brazed. They can probably be adjusted but I made sure NOT to screw with them....yet

Pulled the needles out and inspected them. No visual indication of dirt. Sprayed out the whole fuel passage with brake clean then aired it out with compressed air. Put the needles and floats back in and reassembled the carb. I noticed 2 really skinny long rods in the top of the carb which line up with two holes in the bottom part of the carb. perhaps this is part of the jets??? D'know. I just knew they had to go back in the holes an couldn't be bent.

Then I deadheaded the regulator and removed the adjustment screw. Put the screw back in 2 threads and had my wife turn on the key. The pressure gauge read 3psi. I then had her turn over the car. the pressure came up to 4psi and stayed there. When she shut it off the pressure climbed to 6psi and held. I screwed in the the adjuster all the way and the pressure IMMEDIATELY jumped to 9psi the second the key was turned on again. So I verified which direction was up and down on the adjustment.

I returned the adjustment to the 2 threads in and had my wife fire up the car. She fired up on the first hit no problem. It sounds SUPER mean with only the shorty headers.

I let it run for a few seconds and then shut it off. Fired it up a couple times more and reved it up a bit here and there. It sounds pretty good but it seems to be running rich. I guess I'll have to figure out how to adjust the fuel mixture.

It held 3psi at the gauge and is still holding. No flooding. Looks like I got that issue resolved.

Thanks for the tip on the pressure gauge orief. I'll try to mount it close the carb and see what the reading is there.
308 thanks once again for your insight. Sounds to me like you should be here to help with the carb.