Paulieboy72

So got a mazda fuel pump from atkins. When car is idling it runs rough close tonflooding out with the pump running 84 gsl, when I shut fuel pump off after about 30 seconds the idle evens right out then starts to die from lack of fuel, turn pump back on and it starts to flood out again but stays running just roughly again till I again turn the pump off. Fresh rebuild has 4 heat cycles and about 8 miles of driving. Any ideas or suggeations? Tried using a fuel regulator no change, also turned A/F screw all the way in no change, brought it back out to 2.5 turns floats arw set per the FSM and newish plugs.

KansasCityREPU

iTrader: (9)

I wonder if the fuel return is working?

Paulieboy72

Hm, how would I check that? I have a check valve on it. I did notice the check valve/cut valve near the tank is is not connected. How do I check the return? It just seems like the carb is pushing just a hair more fuel out than what the plugs can burn efficiently, until I lean it out by shutting off the fuel once I do that the car runs great for a minute or two then I have to turn the pump back on

KansasCityREPU

iTrader: (9)

My thought was that if the return isn't working, then fuel gets backed up and causes it to flood.

I'd try the flow test to see how much the pump is suppling.

Paulieboy72

I will do that again, 1.5 quarts per min right?
also I blew air through check valve seems to make bubbles in the tank so the air is going back ti tank as should the fuel

Paulieboy72

Does the shape of the fuel filter affect flow....I.e. in line vs T shaped filter?

Paulieboy72

So I found out the fuel pump from Atkins rotary bushes four to six PSI which is way too much for the stock Nicki

KansasCityREPU

iTrader: (9)

I've never heard of anyone doing this, but the return restrictor raises fuel pressure. I wonder what the outcome would be if you removed it. It would in theory decrease fuel pressure.

Paulieboy72

Can't hurt ill tey it and report back

Paulieboy72

KC, didn't change anything, however did notice a tiny bit of fuel comming out while car running when I put the xheck valve back in. Also my aftermarket gauges don't work all the time( cheap amazon ones) oil, temp. Beneficial to switch to mechanical? Thoughts?

KansasCityREPU

iTrader: (9)

I'm at a loss of the flooding.

The mechanical gauges will work. I have iEquus electrical gauges, but they do make a reasonable priced machinal set.

https://www.oreillyauto.com/detail/c...ufacturer=true

Paulieboy72

I really believe it is the fuel pump. I talked to dan at atkins rotary he said the stock pump for series 2 pushea 4 to 6 psi. This is too much for the stock nikki. I have a 1-2.5 psi pump on the way.
on the gauges, would better quality elwcteical gauges be better? Not sure I like the idea of hot oil in the passenger compartment. I have a stock oil sender hooked up to the gauges but no luck. I have ordered a oil sender block.

KansasCityREPU

iTrader: (9)

I like electrical gauges for the easy and, like you, don't want oil or water in the cabin. I doubt a stock sending unit would work with an after-market gauge.

Paulieboy72

The ones I ordered came with sending units however they didn't read, oil especially when it got hot. At cold and thick it would read good but then as the oil heated up it would show 0 same with the temp. Mabe not grounded well enough? Or just crappy gauges?

KansasCityREPU

iTrader: (9)

The threads make the ground as long as you don't use tape or sealant.

Paulieboy72

Got my sender block today for under the oil filter. Does this need to be grounded?

KansasCityREPU

iTrader: (9)

No, the ground is the body of the sending unit to the sender block. Do not use any form of sealant. To test to ensure the sender block is properly grounded to the iron, with an ohm meter put one lead on the sender block and the other on the rear iron. You should have zero ohms.

Paulieboy72

Ok will do. When I get my new fuel pump I will report back on the idle results

peejay

I think you have a carburetor problem, if it was excessive fuel pressure then it would run well for a couple minutes with no fuel pump. What it sounds like to me is that the carburetor is running extremely rich and it only runs well in the moments before it dies from lack of fuel.

4-6psi IS stock for a Nikki. I usually cap off the return line altogether, it's just a bleed to keep fuel flowing through the line so it doesn't vapor lock in the arch above the rear axle. That's not your issue.

Paulieboy72

It is a new rebuild with 2 miles on it. When I had the stock OE fuel pump(which died) it ran and idled great. It does idle good once I shut the fuel pump off. However I did notice that turning in the A/F screw didn't really do anything. I turned it in all the way no change then turned it back out to two turns. No change. I have done 4 heat cycles of 30 min. All this idleing issue started after the fuel pump died.

peejay

"New rebuild" means "untested and might have problems".

If the fuel pressure was too high, overpowering the floats and flooding the carburetor, you'd see fuel dripping from the boosters at idle from the excessive float level. Shut the fuel pump off, and as soon as the fuel level in the carb dropped below that point, it would run fine, and from experience there is about a minute or two worth of fuel at idle in the carburetor before it runs out of fuel.

That is not what I understood to be happening: it runs badly right up until just before it dies from lack of fuel. So when the carb bowls are not overfull, it is still running extremely rich. That isn't a pressure issue, it's a carburetor issue.

Paulieboy72

this is exactly what it does idles like its fouling with pump on, turn pump off and it idles smooth after 10 secs or so and continues to idle smooth until i turn the fuel pump back on then back to rough idle. my floats are adjusted according to the FSM and i have used the old seats and needles. it throttles ok just a little rough until i turn off the fuel pump, what do you mean by the boosters? what is this? also i do notice fuel in the secondaries often at idle

peejay

Okay, then I misunderstood you.

It's possible that the floats have sunk, or got stuck all the way down when the fuel pump died. Whack the carb with a hammer (lightly!) to shake things up when it's flooding.

It's also possible that whatever junk killed the fuel pump is keeping the needle and seat from sealing properly, and you may have to take the carb top off again to clean it.


The boosters are the bits inside the venturies. That is where fuel comes from the main fueling circuit. When the fuel level in the bowl is too high, they will dribble fuel at idle. When the floats are stuck down, fuel will pour out

Setting float hight is really tricky on these carbs and I always manage to get it too high if I mess with it. On my car, I have them 2-3mm down from what The Manual says, and I can make the car stumble at idle by rocking it, so it's still a little high.

Paulieboy72

Mine are set at 2". The needles close all the way I have done considerable testing with a fuel can and hose with the tophat off on the bench. They are good. I have used compressed air to clean out the bowl passages to ensure nothing is blocking them. That is what's leading me to believe there is too much pressure. I have read on this forum in multiple places that the nikki likes pressure no more than 2.75 as thisbis what the stock gsl pump was pushing. I think mine just died from old age. I will find out soon as I have a pump comming that pushes 1 to 2.75 psi

KansasCityREPU

iTrader: (9)

The factory service manual on page 4A-47 of the 12A fuel section list 2.84 ~ 3.55 PSI.

I know you removed the rat's nest. This might be playing into the issues.