Nikki floods within 15 min of shutdown
06-07-11, 12:17 PM
#1
Nikki floods within 15 min of shutdown
Like the title says after I shut off my car, the secondary barrels fill up with fuel and the car is a bear to start. I pulled the carb and checked to make sure the floats are set paralell to the body as well as not sticking or hanging up in any way. I also checked my fuel pressure with a gauge after the regulator. I run a holley red pump with reg set at 2lbs. I know the stock specs require a little higher pressure than this, but this is what made the car happy and ran and drove well at 2lbs. I did have a leaking diaphram at the accelerator pump which I just replaced, and I cleaned a bunch of crap out of the bowels. I just want to cover my bases before I try to use this carb again with the same problem. Is there anything else I am missing? Thanks in advance for any help.
06-07-11, 02:15 PM
#2
My searching is turning up a lot of bowel vent solenoid threads. I am pretty sure this is not hooked up on my carb. Anyone have a pic or can tell me where it is on the carb?
Could it be this
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or this
Could it be this
Uploaded with ImageShack.us
or this
06-15-11, 02:22 PM
#7
Ok so a little update with this...I have the same flooding problem. Turns out if I pinch the fuel supply line after I shut the cat off, there is no flooding. I think I have a couple of things going on that may be contributing to this problem. Let me know your ideas...
1. My fuel pump is mounted in my engine bay and it sits above my carb on the firewall. I know ideally the pump should be below the carb and near the fuel tank, but this is not an option for me currently. Is this a contributing factor???
2. Is it possible something is wrong with the pump? I was always under the impression that there was some kind of check valve that kept fuel in the pump when the car was turned off. Is this not the case???
3. Is there a way around this (tempoary at least) instead of pinching the hose every time I turn off the car?
Thanks for any help as always
1. My fuel pump is mounted in my engine bay and it sits above my carb on the firewall. I know ideally the pump should be below the carb and near the fuel tank, but this is not an option for me currently. Is this a contributing factor???
2. Is it possible something is wrong with the pump? I was always under the impression that there was some kind of check valve that kept fuel in the pump when the car was turned off. Is this not the case???
3. Is there a way around this (tempoary at least) instead of pinching the hose every time I turn off the car?
Thanks for any help as always
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06-15-11, 04:07 PM
#10
Lol.... I couldn't even remember who I sold that carb to. Glad to see it's seeing some use. I think you hit the nail on the head. Having the fuel pump mounted higher than the carb is likely causing a siphoning effect when the pump is shut off. It stops eventually because the siphoning force is not strong enough to pull the fuel up from underneath the car.
There isn't a check valve in the pump to stop this. This is also the reason why the pump should be mounted below the tank so that gravity can help feed the pump and make life a little easier on it. Since you already said that moving the pump isn't an option, then you might need to look into a bypass regulator. It may or may not solve the problem. At the very least you need to lower the pump to be below the carb to prevent the siphoning.
There isn't a check valve in the pump to stop this. This is also the reason why the pump should be mounted below the tank so that gravity can help feed the pump and make life a little easier on it. Since you already said that moving the pump isn't an option, then you might need to look into a bypass regulator. It may or may not solve the problem. At the very least you need to lower the pump to be below the carb to prevent the siphoning.
06-15-11, 09:23 PM
#13
"Life's been in the way" Divin you said a mouthful...lol...this is the primary reason currently that I will not relocate the pump at this time. With two kids, a wife and a mother in law in my little *** apartment, there is always somewhere to go and something to do that keeps me from "playing cars" As long as I can get around the situation in the meantime, I'll be fine with putting off this repair until winter storage and teardown. I would really like to do over the whole fuel system with a fuel cell and relocating the fuel lines to the other side of the car. To put the car down during the nice summer months would just make me cranky lol...I spent the winter building it and it really is a ton of fun to bring it out this time of year to a meet or show or two or just a quick blast around the neighborhood to blow off some steam after work.
06-15-11, 09:27 PM
#14
If you want to rule out tank venting, simply unscrew the gas cap after you shut the car off. If you hear a whoosh sound, your tank is building backpressure.
I really think it's your fuel pump draining into the carb, though. Put it back there where it belongs.
I really think it's your fuel pump draining into the carb, though. Put it back there where it belongs.
06-16-11, 11:03 AM
#16
Lives on the Forum
These are the items that I know of that will cause this issue:
1. Float bowl solenoid missing, disconnected, or inoperative.
2. Small "bullet" restrictor in return line missing.
3. I've read about a small orifice in the carbon cannister system that can become clogged.
Good luck...
1. Float bowl solenoid missing, disconnected, or inoperative.
2. Small "bullet" restrictor in return line missing.
3. I've read about a small orifice in the carbon cannister system that can become clogged.
Good luck...
06-16-11, 09:46 PM
#17
Thanks Kentetsu...
Float bowel solenoid is hooked up and working
Return line device is installed
Not running a cannister, just a regular vent hose that vents out in the open (if that makes sense)
It does make sense about the siphoning effect that 81WideMariah mentions. Thanks again for all suggestions. I'll keep posting until it is resolved.
Float bowel solenoid is hooked up and working
Return line device is installed
Not running a cannister, just a regular vent hose that vents out in the open (if that makes sense)
It does make sense about the siphoning effect that 81WideMariah mentions. Thanks again for all suggestions. I'll keep posting until it is resolved.
05-09-12, 02:32 PM
#18
Well I am back at it again with this issue. Here is what I am able to determine...To determine if the supply side was providing fuel, I ran the car, shut it off and disconnected the supply line to the carb...still flooded. This led me to feel that the return was malfunctioning in some way. This time I ran the car, shut it off and disconnected both the supply and the return...STILL FLOODED! WTH! OK...has to be a carb issue right? Switched nikki's and tried all the same tests....still flooded...I'm really thinking of taking a friends advice and turning the Nikki into a door stop.
I would like to get to the bottom of this as it is embarassing to have your car restart with a huge cloud of fuel smoke and revving to burn off the extra fuel anytime I go somewhere with it. What am I missing??? I'm sure it is something simple.
I would like to get to the bottom of this as it is embarassing to have your car restart with a huge cloud of fuel smoke and revving to burn off the extra fuel anytime I go somewhere with it. What am I missing??? I'm sure it is something simple.
05-09-12, 05:05 PM
#21
Still fighting this, too... and I think it contributed to my early oil ring failure, due to fuel washout/dilution of the oil film. I thought I had it licked at one time, but it came back on me.
I'm going to try replacing the vapor separator valve on top the fuel tank (connects the vent line from the engine) this weekend, as well as all my tank-connection soft lines since they need it in any case.
I've also done a fresh carb rebuild with brand new floats, special emphasis on sealing of the base-to main body gasket, and have verified again the function of the vent control valve on the ratsnest.
Symptom was always the same; the rear bowl level would slowly rise (over 15-20 minutes) after shutting down until it passed the top of the sight glass, then it would fall, draining into the intake. Front bowl seemed pretty much unaffected.
It seems like it siphons down via the richer circuit once the upper richer orifice in the rear bowl is covered with fuel, but that's still not certain.
The only places above float-level in the carb that contain gas even with the fuel hoses disconnected are the fuel rails themselves, which should be closed off by the needles, and the fuel circuits that lead to the main jets, the accel pump, and the richer circuit.
Assuming that the jet seat or needle are not leaking (because if they were they'd leak worse under pump pressure and flood during operation), that leaves only the fuel in the carb, and for the most part it should stay were it is absent a pressure gradient to move it. And if the vent is working, there should be no pressure gradient.
It's a serious mystery.
I'm going to try replacing the vapor separator valve on top the fuel tank (connects the vent line from the engine) this weekend, as well as all my tank-connection soft lines since they need it in any case.
I've also done a fresh carb rebuild with brand new floats, special emphasis on sealing of the base-to main body gasket, and have verified again the function of the vent control valve on the ratsnest.
Symptom was always the same; the rear bowl level would slowly rise (over 15-20 minutes) after shutting down until it passed the top of the sight glass, then it would fall, draining into the intake. Front bowl seemed pretty much unaffected.
It seems like it siphons down via the richer circuit once the upper richer orifice in the rear bowl is covered with fuel, but that's still not certain.
The only places above float-level in the carb that contain gas even with the fuel hoses disconnected are the fuel rails themselves, which should be closed off by the needles, and the fuel circuits that lead to the main jets, the accel pump, and the richer circuit.
Assuming that the jet seat or needle are not leaking (because if they were they'd leak worse under pump pressure and flood during operation), that leaves only the fuel in the carb, and for the most part it should stay were it is absent a pressure gradient to move it. And if the vent is working, there should be no pressure gradient.
It's a serious mystery.
05-09-12, 06:41 PM
#22
Glen...your rebuild is what has me so paranoid about this now. I totally forgot all that fuel has to go somewhere...down the intake and in the motor...washing away the oil. I have not put many miles on the car, maybe a grand or so and have recently changed the oil and filter again. End of this month all other projects get put on hold so this can get dealt with. This is a sweet 12a and I would hate to ruin it because of this problem. The only way to keep it from flooding currently is to pull the fuel pump relay and let the engine run until it dies...no fuel in the carb=no flooding. Hardly a practical solution. Lol
05-09-12, 11:55 PM
#23
Originally Posted by cfamilyfix
4070? Thats the one I was thinking about. Can I leave all the relay and circuit breaker in the engine bay?
I ran a 10 gauge wire to the back and hooked up a 30A relay to the battery. Maybe overkill. I also installed a 3/8" hardline and a 16 gallon fuel cell.
05-10-12, 07:26 AM
#24
wow 16 gallon? I think the stock tank is 9 gallon max. Currently I have a holley red pump, with one of those Summit Racing elctric fuel pump relay and circuit breaker kits. I'm hoping to just be able to extent the wiring to the rear of the vehicle where the pump will be mounted. The kit came with a **** ton of wire that I shortened quite a bit so it shouldn't be a problem to extend it again. I ordered the Carter pump last night 4070 72gph...91 bucks after shipping...not horrible. My holley I believe is rated at 105 gph I believe and that might be contributing to my problem as well....now for a decent regulator...maybe mallory or holley...suggestions?
