Datsun Roadster Forum-311s.org

srfjay wrote: Sun Jul 10, 2022 12:09 pm Thanks guys for all the help. Also better when you have a different outlook on something.
So let's see . Fuel is fresh. Tank is clean.

Do the fuel flow test … May be just that simple

Questions:
1. Are you using a separate fuel pressure regulator at all?
2. Is that a second fuel filter by the fender?

Yeah will do flow test today.
No fuel pressure regulation. The pump is rated at 5 psi.
That black box is the fuel pump and the silver tube right before is a pre filter.

I'm not sure on the plug wires... I no longer have a distributor to compare to, however 1) it rotates counter-clockwise?; 2) #1 doesn't look like where I remember #1 being, so hopefully others can comment, and/or you put the engine at about 15-17 degrees (3rd mark from the left on the crank) and make sure the rotor is pointing at #1 (static time/not running the engine to your desired idle timing advance).

So, can you richen it to where it gives you a smooth idle ratio in the 13s? Are the carbs balanced? If you're not using a tool you're wasting your time beyond getting a rough estimate. A flow meter will also tell you if the carbs are drawing equally or if there may be an intake leak. Have you sprayed carb cleaner around the intake and carb gaskets? What do the plugs look like?

Yes I used a meter to balance carbs. They are synced idle is at roughly 13 .
I will have to test for vacuum leaks. That is next on my list.

Also, you can't run the fuel pump there... they are designed as pushers not pullers and must be closer to the tank... that could be your whole issue. Move it to below the fuel tank. Mine used to be mounted to the passenger side frame rail. You have to cut the metal line and run power. Alternatively, use a stock mechanical pump (might be easier).

Can you slowly increase rpms or does it immediately go lean? Can you confirm timing is advancing as expected (you need a timing light).

Gotta run to the store but will be back to see what's happened...

Yeah going to rebuild stock pump now and give that a shot. When I put my fuel psi gauge on the fuel line preasure is so low wont read. Any throttle will automatically lean and pop through carb and bog. Made a short video to help. Sorry about the quality. I am not a tech guy haha

I think that I see the problem. Do you have a restrictor in the return line? If not, that is where your fuel is going.

No restrictior. I think I have fitting that would cut out the return. Would that work also? I see some people don't use the return.

Ok so I blocked off return. That definitely helped. I could actually drive it. But any real throttle would bog and lean out. Now I am think it is the fuel pump. Like Greg's said it is meant to be by tank. I ordered a rebuild for the stock pump. Crossing my fingers I can drive this thing after 6 months of work. haha

You don't have to have the return line. Pre 68 cars did not have it. I would get an L fuel fitting to replace the T on the back, and put a cap on the return line.

Make dang sure your electrical fuel pump shuts off if the engine dies but ign still on ...like in a crash

redroadster wrote: Sun Jul 10, 2022 7:17 pm Make dang sure your electrical fuel pump shuts off if the engine dies but ign still on ...like in a crash

He's right, but I'm guilty of never having done so. You would need an inertia switch that reacts to the shock of an impact.

Yes, without fuel pressure or volume the carbs are simply running out of fuel. These type of carbs are very sensitive to fuel level as that effects the function of the emulsion tube/fuel/air jet system. I think you will solve the problem with the mechanical pump, and more safely.
Keep us posted!

I'm going to suggest it is not a fuel pressure / flow problem, here's why. When I park my car in the garage I turn off the fuel pump to run the carbs dry. If I do nothing the car will idle for about two minutes. What I do is run up the engine, watch the AFR meter and when it starts to go lean I apply choke until it wants to stall. Several pokes of the gas pedal to empty the accelerator squirter untill it has no effect. DRY!
What I notice in your video when you open the throttle the engine bogs. This suggests to me that the accelerator pump circuit is not working or like in my case wasn't enough. When I bought my Solexs from ebay, I didn't relize that they were the old 50mm racing carbs. so to get them to act well mannered until I hammered it I had to do a couple of mods. One was to enlarge the accelerator squirter jets, solved the bog / lean knock and the second was to add a tube between the 4 intake runners so at idle it was smother because they were balanced better. You can see it here, brass fittings and blue hose.

What's it do minus the air filter , cause " that's some weak sauce " Aquafina
foam filter ?
Ok I mistook your pic for his eng.pic