carbs - runs like crap if car sits

[toddu]

I have PMO's on my car. If it sits longer than several weeks it seems I have to clean the jets out. Otherwise the car runs like it's on half the cylinders. Normal?

Had it flat bedded home today. Actually started up and ran great for about 15 minutes from home, then started sputtering and bucking and died. Would start for a second but not idle at all. Cleaned jets out and ran enough to move it back in the garage.

Todd

[Jack Stands]

Today's ethanol laced fuels don't last very long and it seems that carburetors suffer the most. Running the car often to keep the fuel from going stale will help, as will using Fuel stabilizers. My Webers were bad enough that we had to send them off to
Paul Abbot (Performance Oriented) to be rebuilt because of all the crud that had accumulated when I was unable to drive my 914-6 for over a year.

If you have recently started buying ethanol laced fuel in an area where it was not previously used may also be causing deposits that were in the fuel system to now be dissolved by the ethanol and are clogging up the fuel system. Old Motorhomes have these problems as well as they often sit for quite a while between uses.

[toddu]

I fortunate enough to be able to get 93 octane ethanol free gas in my area. It's probably a month or more old though. I need to start using stabil or the like as I'm not able to drive it very often.

Todd

[wayner]

how old are your rubber fuel lines?

[toddu]

Less than a year old. All new AN- lines and fittings. I probably need to check the "sock" in the tank.

Todd

[Gordo2]

Todd,

Bunch of questions you may want to look into to help you resolve - although you are thinking carbs, keep in mind your problem could also be ignition related.

What are you running for ignition (what kind of set up - stock / modified dizzy etc)? Are your plugs in good shape?

Is the condition new, or something you've fought with since you went to carbs (i.e. has something changed other than the atmospherics - slightly cooler weather).

After it's sat for a while, do you allow the fuel pump to run long enough to refill the fuel bowls before driving (mine tend to evaporate to low levels when it sits for ~ 2 weeks).

Hang in there, sorry you had to have it towed - that stinks...

Gordo

[toddu]

To be a little clearer, it not a constant problem if the car sits. The car sits quite a bit (unfortunately). I've probably had the rough running issue only 3 times, but those were after extended periods of sitting. If I run the car even once a week it seems to run fine. The last time this happened it ran like it was a cylinder or 2 down, hard to keep idled at lights, etc. Blew the jets out, sprayed a little carb cleaner down the passages and things were back to normal for months.

My normal procedure after more than a few days of sitting is to let the pump run for about 30 seconds or more before 5 or so pumps of the peddle and then start the car (might take 2 or 3 attempts).

Engine is rebuilt with about 1500 miles. JB racing twin dizzy, dual MSD boxes. Haven't pulled plugs in a little while, but looked ok then. Had been planning adjusting the valves, I'll check them them. So have a PMO regulator, about 3.5 psi. Inline gas filter, 30 micron I think.

Todd

[jpnovak]

These symptoms generally mean that the fuel system is dirty. Have you cleaned the tank, fuel sock, fuel lines, fuel filters and bottom of the float bowls? Carbs require very clean fuel or the jets get clogged.

You may also need to add additional filters. I run 4 total filters and almost never have issues with jets. A pre filter before the pump. A main fuel filter in the engine bay and small inline filters before each carb body. I have also pulled the tank, etched and sealed so the entire system is very clean.

Fuel evaporates from carbs and concentrates the dirt in the bottom of the float bowls. I would suggest to pull the carbs and make sure they are clean so you do not keep pulling in dirt that is already in the carb body.

[wayner]

Maybe try stabil in the tank as well. I make sure the treated gas runs through the carbs before storing. If float bowls evaporate the fuel can turn to Chrystal's of varnish and I find this helps

[toddu]

Yeah, I really need to keep stabil on-hand.

Curious as to why filters for EFI have a lower micron than carbs? Is it due to fuel pressure? I'd like to put a finer filter pre-regulator. Have 30 micron now, thinking 10. If it's before pressure regulator, that should be ok?

Todd

[jpnovak]

yes, you can run a smaller filter with the higher pressure to move fuel through the filter. Run a 30 and then put the 10 behind it.

However, clean your fuel system first. Then you don't have to worry as much about the size of the fuel filter capability.

[rbogh901]

Originally Posted by jpnovak

These symptoms generally mean that the fuel system is dirty. Have you cleaned the tank, fuel sock, fuel lines, fuel filters and bottom of the float bowls?

Jamie or anyone:

What are the methods for doing this? I have read plenty of threads regarding cleaning the tank.

Do you have to remove the tank to clean the sock?
Do you have to remove the carbs to clean the bowls?

[wdfifteen]

I had that problem with my Speedster (with Zenith 32 NDIX carbs) until Stabil came along. My first attempt at a solution was to use 100 LL avgas. Helped extend the fuel life to 3 months or so. Now I use ethanol-free 93 octane with Stabil. It sat for almost six months last winter and ran fine once I got it started. It has a mechanical fuel pump, so getting the carbs filled can be a battery-draining challenge. If I couldn't get ethanol-free 93 octane I'd go back to avgas and Stabil.

[jpnovak]

Originally Posted by rbogh901

Do you have to remove the tank to clean the sock?

No, the tank does not need to be removed. The sock can be removed from the tank on the back or underside depending on the year.

Originally Posted by rbogh901

Do you have to remove the carbs to clean the bowls?

It is best to remove the carbs so that they can be efficiently disassembled. I also soak the bodies and then blow out all the passages. To properly clean the float bowls the floats must be removed.

[toddu]

Ran across my own thread while looking for something else (still feel like the car is generally hard to start, but still need to adjust carbs) and thought I should close this out.

I ended up doing the following -
Remove tank screen, replace with new screen
Replace ~ 30 micron mesh fuel filter w/ Fuelab 6 micron filter
Remove, clean, "rebuild" carbs
Drain old gas replace with fresh gas and stabil

Car is running great now. Better than it ever did actually. I think part of that might have been that the engine wasn't started for probably 6-8 mos after I received it post rebuild/dyno run, so things were probably a bit gummed up from the get go. I even put the bigger idles back in (what it was dyno'd with) and don't get all the popping I had when I first put the engine back in the car.

I still need to go back through and do lean-best, etc. I did some adjustments when I first put the carbs on and it seems ok for a first pass, but warm idle is still a bit rough.

From now on I'll keep stabil in and I'm determined to drive it more often.

Todd

[wayner]

Thanks for coming back and closing the loop on this Todd.

I used to only put stabile in for winter storage but now with ethanol I am forced to use it for "weekly" storage sigh

Glad to hear that you are back on the road.

[Jdub]

Reading this I have to laugh since the topic could be on the Brit Bike list. If you have ever let a pair of
Amal carbs sit you know what this is like. Poking E strings into the orifices, blasting with pressurized air and Gumout - all applicable to this thread.

I would only say I use Av. gas when I store, with the Marine grade Stabil. But you have to run the motor regularly or you are lost.

[dfhtrhjn]

I have Zeniths on one of my 911s. Fuel begins to deteriorate after just a couple weeks.

Stabil fuel stabilizer helps keep the gas fresh.

I run a few tanks of gas mixed with the Red Line fuel cleaner to dissolve the deposits from sitting.

You can also get cleaning foam that you spray straight into the ITBs while running to dissolve and burn out some of that crap.

Once you're on top of the maintenance it's easy. It also helps if you drive it like you stole it when you finally get it out for a drive

[jpnovak]

Glad to hear positive results on the follow-up. Now go enjoy the car more often.

[obscene]

good read. I didn't realize you could use stabil year round