Starfox07

I'm pretty sure that pulsing was an electrical problem. My battery was in really bad shape. I haven't had any issues with the fuel pump/regulator since I bought a new battery.

Just retested my vacuum and it sits around 15-18 inHG at idle, which I think is about normal, right? When the car started doing it's brap brap thing the gauge bounced around all over the place.

Could it be as simple as needing to replace the little o-rings on the jets? I never did that when I rebuilt the carb, I just assumed they were ok.

wankel=awesome

Well I just saw in one of your pictures that your adjuster nut was totally removed from the reg, and I thought you may have done that on purpose, but I was wondering why.

Let me see If I got this right..

The car idles fine, responds to idle mixture changes, and runs fine free revving the engine?


Your problems occur when load is on the carb, at dip in?

My engines also have bouncing vacuum at idle, but it only bounces a few inches. Its a steady, yet rapid pulse from 15 hg-18 hg.

The "brap brap" thing is exactly what any one of my engines do when they are over choked, IE far too rich. Itll run fine for a sec, but the total mixture overpowers the ignition quickly, and it starts to miss and then die all on its own. It happens pretty quickly too, like youll hear it start to miss, and then in a matter of seconds she dies. Same thing happens when the carb floods.

My theory is your fuel supply is overpowering your needle and seat. Do me a favor, run your fuel pump into a gas can and let the engine start and run with just the supply of fuel it has in its fuel bowl. See how long it runs that way. If its the same as what youre experiencing now, it is a carb calibration thing. If it just runs until its out of gas, your fuel supply or needle and seat are defective.

Starfox07

It idles ok (sort of brap brap, but steady and doesn't die) and only subtlely responds to mixture changes. If I poke the accelerator too hard the engine makes a weird kind of growling noise and the rev's don't increase, like it's getting way too much air and not enough fuel to mix it with. Probably accelerator pump adjustment issue, no?

Mostly I just want to know why it isn't running properly at idle and low rpm conditions.

rwatson5651

iTrader: (5)

I may be wrong but I think you should try this to insure your fuel system is not overpowering your needle.

This may have been suggested already, but a wideband o2 sensor would make childsplay of all of this.

Starfox07

My gauge right before the carb only says 2psi.

rwatson5651

iTrader: (5)

There are a lot of inaccurate guages out there. Maybe try turning the pressure down further to see if there is any improvement.

Youve got a gremlin somewhere, could be a bad guage.

wankel=awesome

Correct, but 1 psi fuel pressure could overpower a bad needle and seat, or a float that isnt rising properly to close off incoming fuel!

Please try to run it without the fuel pump feeding the carb to let the carb run on its fuel supply. Its just a troubleshooting step, not permanent.

rwatson5651

iTrader: (5)

What he said.

wankel=awesome

Also, regulating the GSLSE fuel pump alllll the way down to 2 psi should be hell for your return line, and FPR.

Starfox07

Ok I will run it with the fuel line disconnected, see if that helps. I suppose letting the fuel from the regulator run into a jar at 2psi is not a big deal.

edit: Ran that test. When I took the line off the carb, it drained fuel (key off, pump not running) for about 2-3 minutes and it filled 1.5 large coffee containers. Is that indicative of too high a pressure?

When I started the car it seemed to run pretty much the same, maybe slightly better, but it ran out of fuel before I really had a chance to find out and adjust things. Really wish somebody around here could help me

j_tso

iTrader: (2)

I just realized my last post was a repeat from last year.

What size chokes/venturis do you have installed?
I searched this thread, but couldn't find one listed.

rwatson5651

iTrader: (5)

Dont give up, usually it ends up being something simple.

Try it again except this time warm the car up first and have it situated so that it is demonstrating the problem (running poorly under no load at modest throttle). Then disable the fuel pump somehow, maybe pull the fuse, and you will have about 5 minutes worth of running time to see if the problem improves or goes away, if it does you will know it is a needle or pressure problem.

I'm not sure why so much fuel came out w/o the pump running unless your gas tank is not venting and is building up pressure somehow??? dunno.

Starfox07

This is a elemental question, but how do I remove the choke/venturi to see? And thanks, I will try that!

wankel=awesome

1.5 large coffee cans that fast?

...

What float/needle+seat are you running?

Starfox07

There has been a new development. I don't think the brap brap idle and low-mid rpm problem is due to the fuel mixture. I think I'm only running on 1 rotor constantly and intermittently on the other.

This last time I tried to start the car, it started, but I could tell it was only running on 1 rotor. However, it was running smoothly on that single rotor. Sounded like a weedwacker, but it was holding 1,000, 2,000, and 3,000rpm just perfect. When I raised the RPM I could hear/feel the second rotor coming in intermittently, and when it was chiming in, it sounded exactly like it did before. A few weeks ago I was driving the car and out of nowhere one of the rotors cut out for about 10 seconds, then came back online like nothing had happened. This never once happened when it was EFI, so I'm inclined to believe it's fuel related.

Now, is this a carb problem or an ignition problem? This is so weird!

Edit: Let's try to eliminate any and all possible reasons the carb could be causing this problem.

Starfox07

I took a few videos for you guys, they are uploading now. HD resolution so it might take a little while. Should give you a better idea on the symptoms.

Starfox07

Also took a few photos of the plugs.

Front trailing - Front Leading - Rear Trailing - Rear Leading




(they all look pretty much the same, rich, which shoots down my one rotor fuel issue theory)

I'm still enjoying this journey into the world of carburetors. Maybe it's because I don't need the car to depend on, maybe it's because I'm patient. Mostly I just like old things.

reo

iTrader: (4)

stumbled op this thread looking for answers. Have the exact same problem, it is a 13b with a weber 48 side draft. was running ok for a weber, recent changes; opened up exhaust to 4" and real loud, and left key on and ran battery down overnight. Have switched idles and idle setting of the idle screw changes as it should, flushed out carb passages with FI cleaner spray, fattened up the main slightly with no change, then frustration set in; changed plugs, igniters, coils, same same-- smooth while picking up under load on road, then bucks and snorts when lightly loaded, smooths out when throttle is opened, Really likes to pull a grade. also get the feeling that it is wanting to heat up sooner especially the oil. when setting and you rev up it acts like a plug that is trying to fire and gets worse the higher you rev it. Am going to do a compression tent next on the off chance that I might have damaged the engine. will keep you all posted on progress.

rwatson5651

iTrader: (5)

One barrel of the carb supplies fuel and air to one rotor and the other barrel supplies fuel and air to the other. I had a buddy that had a similiar problem on his weber where one rotor quit. Investigation led us to the stud that holds the main venturie in had fallen out. This created a bad leak in the main circuit. His would idle but not run at wot. You may have a similar but different problem where one barrell has an obstruction in the idle progression circuit and the rotor for that barrell is only running right when the main circuit comes alive. I would pull the carb, clean it well, locate the idle circuits for both barrells and blow air through all the passeges to make sure there is no obstruction and make sure the circuit has no leaks, like a bad o-rng. Check where the idle circuits open into the throat of the carb, there should be several holes, if one of these is blocked then the progression from idle to wot will be shitty.

j_tso

iTrader: (2)

You take off the air horn and aux venturi, then the main venturi is behind that. On Dellortos, there's a nut over a screw that keeps it in place.

When I was tinkering with my DCO single set up, I found that 42 mm venturis would let the car idle, but was really weak and would stall out unless I gave it a lot of gas. I had no low end. The car ran very well on 38mm.

wankel=awesome

The one rotor thing comes from one rotors plugs being wet, and the others firing through it by chance. Youll notice when this happens if you give it gas to higher RPM's they both start to fire, and then it will maintain an idle. Your engine is pig rich, the brapping its doing is it fouling the plugs in a few moments.

Starfox07

First video
This is with power to the fuel pump


Second video
This is after disconnecting power to the fuel pump and running it until it runs out of fuel
You can hear it initially running on just 1 rotor, then the second rotor coming on a few seconds later.


Third video
This is after reconnecting power to the fuel pump and giving it some revs as well

Whatever the real problem is, I think the previous owner of the carb drastically adjusted things to try to workaround the problem instead of fixing it. That would explain the crazy out of wack accelerator pump setting and the way, way too lean idle jet. Both of these things would likely conceal the problem somewhat, at least under no load. I am improving it though, so at least I have that to say!

wankel=awesome

Its pig rich.

Starfox07

I'm going to check the Venturis/Chokes tomorrow. If those are ok, I'm just going to pull the carb and give it a thorough cleaning/rebuilding. Any other potential reasons for it to be this rich?

wankel=awesome

Not familiar with that carb, but Id check the restrictions that allow air to the emulsion tubes.