Chasing rough idle and noticed full float bowls. Could it be related?
 

Hey guys, I'm new to the forum so let me know if you need any more info.

I recently bought an 85 GSL with a 12a and as far as I know, everything is stock or equivalent. Previous owner put a lower mile engine in it and never quite got it running right. When I got it, it wouldn't idle, and you had to have the choke pulled to keep it running, even then it didn't like to drop below 1500rpm. Most of this was fixed by redoing the rats nest and adjusting timing. Today I was working on tuning the carb and I was able to get it to idle below 1000rpm. The main issue was that it was still hunting around a bit, going between 700rpm and 1100rpm, and no adjustment of the mixture screw made it solid. I read that this hunting could be because of a lean condition, so I figured I'd check my float bows to make sure they had fuel in them. When I looked through the sight glasses, I noticed that there was fuel up to the top of the window. When the fuel pump is running but the car is off (i.e. the key is in the on position) there isn't any fuel coming out of the jets so it doesn't seem like the engine is flooding. Does this means I have to go in and adjust the float levels? Is it possible that something else could cause my float levels to be so high?

Is it possible that high float levels could be responsible for my hunting idle? I still have yet to check that the spark plugs are all firing ok, so it's possible it's an ignition issue too. I will check the spark plugs tomorrow, but I figured it would be good to get the float levels figured out first.

Thank you in advance!

I forgot to add that the old owner put in a new fuel pump, and it's wired to always be running. Is it possible this could be pumping at too high of a pressure?

First I’d put a gauge in the fuel line, should be 2-3 psi max. Verify that then go from there.

It ended up being about 6 psi. I got a Mr. Gasket fuel regulator and set it to 3 psi and that improved the idle. Now the float bowl levels are down to about 3/4's of the sight glass. It still hunts a little bit, so I'm thinking I'll still have to adjust the float bowl levels, but once I do I'll post back here with my results. Thank you for the help!

This seems to happen very often with these cars. People tend to want to throw the standard "Autozone/Generic" fuel pump options at them and this is usually the result. The Nikki carb can't tolerate these inlet pressures, and when you couple this with a small diameter return line (Factory 0.25" in some years), the carb will flood.

Regulator is a good starting point. Try to see what the fuel pump situation looks like and maybe make it proper. Put an OEM pump in and restore the fuel system back to stock and it will run another 40 years.

Yeah the current fuel pump is a Holley Red pump. Definitely considering getting an OEM one to help make everything easier.

I am running a Carter P4070 pump and a QFT 30-804QFT regulator. Works pretty well as far as I can tell, I set it at like 2.5 psi and the carb never drains or floods. The regulator has two outs so one goes directly to a fuel pressure gauge intended for under-hood use. Permanently installed. I can eye the pressure whenever.

The pump is a little noisy, but for the price of the whole package, I can't complain.