jutta

Just bringing this post to the attention of anyone able to help and/or had similiar experience.

The carb rebuild specs and Mazda shop manual were double checked when the carb was rebuilt but when the float bowls were overfilling and flooding the carb. Adjusting the float numerous times did not help. Then the old needle valve was compared to the new needle valve and was discovered to be 2 mm shorter. The old needle valve (especially the rubber tip) was inspected under a microscope and determined to be fit to be restalled. The proper level in the bowls was able to be adjusted then. The car was run quite a few times on the highway but the gas tank levels caused some concern. The car stalled again with the carb overflowing in the driveway. This was now an intermittent problem. We were able to drive it to the garage last year for winter storage. This year we were unable to start the car and noticed again when the fuel pump was turned on that the carb was overflowing.There was noticable pressure in the gas tank when opening the cap.
We are thinking that the pressure could be the culprit and that the fuel pump delivers above the allowed pressure, overfilling the bowl.
After charging the battery, I will loosen the filler cap to release pressure, open the air cleaner on top of the carb, and start the fuel pump only by turning the key to "run". If the carb barrels and bowl overfills and the fuel level in the sight window is high, we believe the Check and Cut valve have to be looked at. We have the shop manual and presumably the description for the procedure and related parts and hoses. Missing is the proper description of what this valve actually does other than perhaps venting the gas tank through the evaporation system into a charcoal canister. In the shop manual it states this valve "Except for Canada" so we have not been able to determine if there is such a fuel Cut Valve. Regarding the Check Valve in the return fuel line frm the carb to the gas tank to take fuel back to to the tank once the carb bowl is at the proper level. This valve and fuel line was checked. The explanation of the function is not clear.
If I can get the car to the garage, we think we will ask to have the fuel fiter replaced, have the Check and Cut Valves looked at, and have a pressure test done. Also the tank drained and flushed, checking for leaks. The fuel gage unit needs testing because it seems to give false readings. The brakes need inspection because the right rear drum clunks after sitting for some time. We had hoped to find a low pressure gage to do some testing ie: fuel pump pressure.
Any technical insights from those who have gone through this are most welcome!

Rx-7Doctor

iTrader: (13)

The check and cut valve is a safety valve that is designed to shut off fuel in case the car over turns.

Normally the floats do not ever need adjustment on these carbs. The over flowing of fuel is generally caused by the needle/seat not closing properly. This can be caused by sediment from the tank getting thru the fuel filter.
I have seen in most cases after a rebuild though that the needle seat does not want to settle properly. Normally what I have done while you have the fuel pump on is either take a dead blow hammer or the rubber side of a screw driver and tap on top of the fuel inlet line at the carburetor.
Nice thread by the way. Very well thought out.

hanman

I agree with the doc above, but one more caveat; if you rebuilt the carb, make sure that the floats are not the problem. If you are not careful, when setting the floats and bending the tabs, you can bend them so they bind on the sides of the bowl. What I am attempting to say is, that the floats have to hang PERFECTLY, if they touch the sides of the bowls at all you can have a problem like you are describing. (don't ask me how I know this)

jutta

Ok, so just turned ignition to on with the gas cap loose after rapping the carb as suggested in previous reply post. Fuel pump is working but bowls are still overfilling. A pressure gauge was hooked up and reads 6.5 psi!!!. Shop manual says it should be 3.7-4.7 psi so does anyone know if the fuel pump pressure can be adjusted or do I need a new fuel pump. Maybe something else is causing the pressure to be so high. I need some suggestions from some members with tech experience. Help!!! Would like to drive the car again before fall. What happened?

kgray

fuel pump can't be adjusted, but you don't need a new one either. Go to a parts store and get a FPR (fuel pressure regulator) and regulate it back down to about 3.5 psi. I had the same symptoms when i first got my car and it turned out that the previous owner installed an after market carter 8psi pump.

jutta

The Check Valve was removed and guess what....The car ran but was not able to hold at idle. We're making some adjustments so we can drive it to a shop to have the tank FSU checked.

Kentetsu

Hmm, sounds pretty cut and dried to me:

1. Assuming that the fuel pressure gauge you used reads correctly (which is actually highly unlikely), then the simple solution would be to install a fuel pressure regulator. If you go this route, be careful what you get. Any of the dial type adjustables are crap, hold out for a Holley low pressure unit (like 1-4psi). You can order through Summit. In fact, check out this thread and it will give you all the info, including installation: https://www.rx7club.com//showthread.php?t=529605

2. If the pressure reading is suspect, then I'd say you still have an internal carb issue. I read the part about the issues with the needle fitment, and was thinking that maybe a better carb rebuild kit might be the solution. In fact, if the car ran fine before, and nothing was changed (like say the fuel pump), then the carb is where you should be spending your time. I'd probably even consider a junkyard carb with a rebuild kit. I suppose it would be way too convenient to have a buddy with a good carb you could swap in there, wouldn't it?

Nice post by the way, lots of good information...

Kentetsu

Where the hell is Utterson anyway?

jutta

Once we removed the check valve the car ran. we decided to remove it since we were told that the check valve was designed in case of rollovers. It does lead to a charcoal canister (fuel emmision control). The car will be towed to where we can better get the adjustments to the carb done or anything else that may come up. One thing at a time, I guess. The carb was rebuilt last year and everything ran great after the rebuild but then the fuel problem began. Check my threads. Trouble right now is keeping it running without keeping the foot on the gas. Mystery is who messed with the fuel linkage to the carb?...the bolts were loose. Security will improve after the tow.
Utterson is not far from Algonquin Park and Huntsville, Ontario, Canada.

blwfly

iTrader: (4)

i agree with the above to.

i have had needle seat problems as stated before from sticking and havin specs of crap on the rubber point.
are the floats spec to 2" and 5/8"?

i had fuel flowing out of my secondarys like a stream into my engine while it was bearly running got drowned.
have you takin the spark plugs out and disconected coils negative wires then turned the car over for a bit and see if like a mist comes from the spark plug holes if so the engine is flooded with gas.
the tips of the sparkplugs when you take them out may be wet with gas good indicator.
make sure the spark wires arnt fireing when doing so caue it could be bad.

Kentetsu

Is your fuel bowl vent solenoid hooked up and working?

jutta

the car has been towed to where it can be looked at by the person who did the rebuild. I'm waiting to hear what they are checking. I will try to post any progress.