Weber carb hesitation under load...

[2ndGenGuy]

I've had a pressure gauge on it for a while. I just couldn't see it while driving. I saw the same 1psi on the dyno while the car was under load. However, the air fuel ratio never leaned out like I would suspect if the carb was running out of fuel. I'm still not sure that dropping to 1PSI is enough drop to cause what's happening. Especially since there should be a steady flow of fuel through the carb...

Also sometimes the pressure comes back up to 3psi after I let off the gas, and I still get hesitation. I really have to ease off the throttle for a while for it to come back and be able to slowly work the car back up to speed.

The big thing that is concerning me is the 28Volts AC I'm seeing at the battery when the car is running. DC voltage seems normal. I'm still suspecting that it's causing problems with the coil or something...

[2oodoor]

What would cause you to measure for ac at the battery? That could be just slight "ripple" fromvthe charging circuit, bled thru diodes in the sys.
A fail col could producecthese symptoms. Im curious of tbe wiring changes right there at the coil circuit with mj, guess ill have to find the thread me thinks you showed the schematic diagram there?

[2ndGenGuy]

I measured for AC because at the same time that this hesitation started, my headlights began pulsing over 1000RPM. I read online that a good test is to check for AC current at your battery. From what I can tell, you shouldn't have much more than a half a volt of AC being picked up. But I didnt really have a reliable source for that...

I got rid of the MegaJolt and went back to a distributor. I thought maybe that was part of my problem, but the stock ignition system changed nothing in the way the car is running.

The problem is so hard to be specific with. I gave it a run up the freeway tonight. I was able to get up to 70mph no problem. Then I turned around and came back, and it started running like shit again, and I could barely keep it at 55mph. Even light throttle was causing stumble. Down hills was better. Had hesitation even at 2.5PSI, while earlier I had it floored and was having hardly any symptoms... it's killing me.

[2ndGenGuy]

Just want to say that I appreciate you guys chiming in here in this thread. I know that its super confusing all the stuff that's going on and all the things that I have tried. I'm happy to start from scratch and explain again exactly what is going on to clarify if it helps... I'm just at a total loss right now...

[Dr_Snooz]

Sorry if this is a repeat suggestion, but 1 PSI seems low to me. I'm not an expert of course, but it's not unheard of for a carb to want 6-8 PSI and 2.5 PSI is about the bottom of the acceptable range in most cases. Have you tested flow? As in how many liters in one minute?

I thought the dyno guys had taken care of this for you?

[2ndGenGuy]

The manual for the car says 2-3 psi is the nominal range for the fuel pump when there's only a gauge hooked up. I thought it might be kinda low too for the Weber. However, if that's what my old pump was putting out, and it worked fine for me for like 4 years, I'm not totally sure that's a problem (though I can't verify the old pump's output, I'm guessing it was probably in the factory spec).

I guess I can check flow rate, accurately, but it seems to just dump fuel out and an amazing rate.

The other thing is too, I've had it hesitate at full pressure (near 3psi) when on the freeway. So fuel pressure doesn't 100% coincide with when it hesitates. But that doesn't mean it's not part of the problem I guess. My only real option to get more fuel is to get an aftermarket pump.

[Rendon LX-i]

i would swap the pump an go from there john. wish i had that car for a day i would test a bunch of crap. i love diagnosis i get alot of shops that push there cars to us cause we figure out the mess. most of the time people tend to over look and dont go to the basics.

you have spark nows its a fuel pressure deal. adding a relay to your fuel pump prolly help if anything.

[2ndGenGuy]

Allright. I'll grab my Holley red and regulator off of my other Honda and see what happens. Can't get to it for a few days though... I hate waiting.

[KillahKitt]

What was the outcome?!? I'm going crazy with this same exact thing!!! Have to maintain exactly 4k rpm. If it drops, power is gone. If I tap the gas just a smidge, power is gone. Wtf, Car?!?


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[2oodoor]

What was the outcome?!? I'm going crazy with this same exact thing!!! Have to maintain exactly 4k rpm. If it drops, power is gone. If I tap the gas just a smidge, power is gone. Wtf, Car?!?


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Weber carb?

[KillahKitt]

No. :/


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[KillahKitt]

Ok. But here's something different about mine. It does the power loss only after I increase my elevation 3000ft.


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[PDXAccord79]

I just got my car working and it was jets/blowby. When I first built the engine nothing was set and the car required big jets to get any kind of power out of it. My first oil change also smelled like gas. Over time the gas smell went away in the oil and I noticed the car really started to hate the big jets so I started dialing it down. My guess is the rings needed time to seat and as they became more seated there was less blowby resulting in less gas needed to get a boom.

I took it through DEQ recently and it blew 300 (!!!) on CO which failed me. I replaced my air cleaner and brought everything back down to stock jet sizes and the car runs like a dream. It also also now passes DEQ with a score of 120 on CO which is 70 points lower than what the car did on stock jets right after the engine was rebuilt.

Everyone told me it was too much gas but I didn't believe them. It did end up being too much gas and by lowering jets everything now works fine. You might want to try to stagger your jets so the secondary is 5 lower than primary. The Webber is 140/140 by default so try 140/135 or maybe even 135/130. Your dyno shows that this is only happening when both primary and secondary barrels are receiving gas since it's over 3000. You could try lowering the secondary idle as well but that seems to affect the 2000-2700 range more than anything.

I also still think that OEM Honda fuel pump can't keep up. I don't get the surging uphill or at 65+ anymore but the float still needs to be way higher than I feel it should be to keep everything running right. Redline makes a low psi, high flow fuel pump that I'm going to try now that my car is working. It still requires a regulator but it allows you to fully remove the return line.

Have you done a compression check? I'm thinking your rings could be bad.

[2ndGenGuy]

UPDATE:

Did a compression test. Got 180psi, which I'm pretty impressed with. Did a leakdown test and the worst cylinder (#2) was 15% (this being a cylinder that I keep fouling a plug on).

So I got a borescope, and thought maybe if the plug is fouling over and over, that the pre-chambers are clogged with crap too. Sure enough:

https://www.youtube.com/watch?v=zUcrLEUrpkQ

Gonna check and see what the other cylinders look like. Not sure why this one is misfiring so bad and getting clogged. Gonna dive into the manual and see about pulling that chamber and cleaning it out. Maybe a crack in the intake manifold is letting in coolant? More investigation to come.

[Rendon LX-i]

Well that would do it eh. glad progress was made john. Update us on whats going on.

[2ndGenGuy]

Well the update is that IT IS NOW RUNNING LIKE A CHAMPION!

The carbon buildup in the pre-chambers was the problem. You can see in the attached pics, the one looking down inside has a black ring, that's ALL carbon. There was only enough room in the chamber for the valve to move!

Also in the other two pics, you can see how when I shine a light through the clean pre-chamber, vs when you shine a light through the dirty one. The spark has to ignite the fuel that's inside the chamber, then the flame comes through those holes into the combustion chamber to ignite the main mixutre...

It required pulling the head off, and modifying some tools to pull the pre-chambers apart. But I wound up getting them all apart, replacing the gaskets, and cleaned out all the carbon buildup. Slapped the engine back together and it ran so well!

[Rendon LX-i]

holly cow. well that explains it. Looking good. Now ripper vids please lol

[2ndGenGuy]

Test Bump.

[tof]

Bump confirmed.

Thanks for posting final solution for posterity. Seriously. Too many threads like this just end with no conclusion. Glad your 1G is back in action.