Need some troubleshooting minds put together...

And before everyone jumps on timing, thats not what caused it to backfire. The excess fuel in the intake was preigniting. It ran perfect when it was idling.

 

I once had a carb float stick on a bike I was running without the airbox on.. Carbs when on fire. I pushed the bike on then center stand out of my shed and smothered it with a bike cover. My wife bought a fire extinguisher for my shed the next day. I understand your pain.

Strange that the electric fuel pump was fine for 2 years now it is over flowing the old and new carb. That part makes no sense. I would if thought 4-6 psi to be a bit much and 2-3 psi be more reasonable pressure.

 

Yeah, that's what gets me too! Don from Yokohama told me the carb is designed for 1.5 to 2 lbs. How did it run so well all this time?!

There is a solenoid on the end of the fuel inlet at the top of the carb, opposite end from where the fuel supply hose connects. It has one wire. Inside is a plunger that moves a round diaphragm in and out. This seals off overflow to the external canister. I don't understand what the function exactly is, but if it's not getting the right signal I'm wondering if it may be causing the overflow. I checked and have 12v at the plug, but couldn't get anything on the wire to the solenoid. It's a brand new unit, but it's doing the exact same thing as my old carb. What do both solenoids on the carb do? I can't get anyone to answer that for me...

There has to be something external to the carb causing my problem. Hopefully it is the fuel pump and I can replace it with a proper one, or go back to the mechanical pump if I can find one.

 

does it go to the charcoal caister?

 

Yes. What is that for? I assume it scavenges vapors from the fuel bowl? Can a stuck or non-working solenoid cause my overflow condition? Maybe it's not getting the proper voltage or signal? Something going out like a broken wire, blown fuse, or loose ground would help explain the sudden change overnight. Did I mention I absolutely hate engine electrical troubleshooting???

I didn't have a chance to try the gravity test today. I will get around to it this week. I have a feeling that's gonna be the issue though. But I'm still dumbfounded as to why all of a sudden...if that's the case.

 

The Charcoal Canister is directly connected to the vent at the fuel tank filler neck. The fumes from the fuel are stored in the charcoal. The solenoid opens during preset operating conditions and allows the fumes to be drawn out of the Charcoal Canister and introduced into the intake to be burned along with the normal combustion process. What I am stating is just from memory and you will have to do some research to find out the conditions mentioned for these vehicles. I am an old fleet mechanic and retired in 1990 so only am familiar with American made products and emissions back then. Each manufacturer(including foreign ones in order to sell their product in the US) had their own ideas as to how to control emissions to meet the govt mandated requirements and so there were many different ways it was handled, some a bit weird and some quite inventive. Why I say you will have to do some research on your particular vehicle, unless someone on here has already done this and can shed some light.

Fred

 

So would that create the overflow problem? Im looking for an external source causing both carbs to do the same thing. So far im leaning toward fuel pump overpressurization, as many have suggested. The only other external components are the solenoids. The other one not mentioned above is on top of the carb screwed in at an angle and has two wires.it has an internal plunger and appears to be a shut off of some sort. I initially thought it was the fuel shut off solenoid but from what I understand those only came on the speed limited US designated left hand drive trucks that had speed limiters. If thats not what it is can someone explain it?

 

go to the charcoal canister and follow the vent line that goes into the frame rail. pull it out of the and see if the end is full of dirt causing the engine to create a vaccuum in the carb thus sucking more fuel into the float bowl. its a long shot

 

The fitting is broken off the bottom of the canister where the hose would attach. I just noticed this but cant tell if its fresh. Would this be a problem? Can I bypass the entire system to eliminate that possibility?

 

Post pics.. And yes I would try running it with out the line from the carb to the canister

 

Hold on. I agree with your thought process but what about this... the overflow happens as soon as i turn the key on and the pump starts. The engine isnt turning over to create vacuum at that point? Im gonna try it anyway to eliminate the possibility.

I bought a lower volume fuel pump today. Gonna try the gravity feed and see if that or the new pump solves it. I may end up going back to a mechanical pump like Don said. A few more things to narrow down and im giving up.

I'm gonna have a grand in this repair if i keep going on. Good money to bad...but dammit it HAS to be something simple. The fuel pump still has my vote. Gonna be a real pisser if i spent all that and find out all I had to do was listen to people from the beginning.

 

This is kind of what I was referring to earlier about the different ways emissions were handled. As an example, solenoid may be activated to vent the charcoal canister only on certain conditions such as possibly when in 5th gear (transmission switch) and while coasting (closed throttle switch) such as when going downhill and creating high vacuum in the manifold. It may wind up to be something that at first glance does not seem to have anything to do with it. As I mentioned earlier there were some weird ways (some quite convoluted) different manufacturers went about trying to control the emissions emitted. Sorry I can't be of more help but to tell you to learn as much as possible and try to understand about the emissions setup of your vehicle. Things did get quite a bit less complicated when computers took over engine management but thats when I decided to hang it up.

Fred

 

It's ALIVE!!!! After going through every possible component from fuel to vacuum to electrical i finally got it!!

Problem 1 was the needle valve in the new carb had some debris in it which i found after finally pulling the float and checking it. No more overflow. And this is still with the old pump a lot of people said wouldn't work on these carbs! I do have the regulator in line now and have it turned down to 2 psi.

Problem 2 was I was losing spark. Changed the cap out with my old one i never threw away even though it is cracked up the side, and it fired right up! New cap on order.

Happy, happy, joy, joy!!!!!! Merry Christmas to me!!!

A big THANK YOU to everybody who has been following this and helping me! I cant believe how much of a headache these things can be. Especially when you are creating your own problems.

At least i tried to fix one thing at a time. So to wrap up i guess it started with a bad carb, and while i was waiting on a new one i did some minor maintenence, including scraping the carbon build up from the tabs of the dist cap. I didnt recognize they were half worn away. This created my spark issue. A new cap will fix that. The new carb reminded me to never assume just because its new that it wont have issues. It is running a little erratic but some fine tuning and a little sea foam will fix that.

Im done here. Thank you all for the patience with me. Merry Christmas!!!

 

Glad it's finally working for you. Sometimes its amazing how much we go through and it turns out to be something simple. Over the years as a fleet mechanic I've done that too and the only consolation is that its a lesson you will never forget, it is part of the scheduling at the school of hard knocks.

Fred