Carb Issues

[awesomesteven]

This seems neverending, but I'm getting close!

I put in a new carb kit since the float to the fuel bowl was sticking and now I'm getting a few issues with the carb.

On the first try, I got the engine to turn on but I had to have the throttle open all the way - once it did turn on, I pulled back on the throttle (about 3/4 the way back to idle) then it sounded like it was about to die, I gave it more throttle - the carb popped twice then it died out. It did this about 3 times.

Next, I turned the choke counterclockwise one knotch and got the same thing. So I turned it ccw 1 more and no more pop but now it runs really rough - and it still died after about 30 seconds and still can't bring it down to idle.

I am having someone take a look at it this weekend but I wanted to see if you guys had any thoughts on what it could be or anything I could do that might be an easy fix?


Here are how I have some of the parts set:
Idle fuel/air mixture screws: 1.5 turns
Choke setting: 2 knotches ccw
Accelerator pump linkage: I can slip in a 0.015" feeler gauge in between the spring bolt and the accelerator pump arm with the arm held fully down

[Salty87]

i'm no carb expert. are you sure everything else is set correctly?....plugs wired right, good gas, timing

what's the history so far? have you gotten her running good at any point?

[wotan2525]

Does it have good gas? Sounds like just a hard cold start at this point...

Have you tried a shot of starting fluid?

Electric or mechanical fuel pump?

When "cold" the electric choke should be all the way closed. If you leave the key "on" without the engine running, the coil in the electric choke will heat up and open the choke. Can you visually check and make sure it's staying closed?

[awesomesteven]

Gas - I just put a fresh 5 gallons of 91 octane gas
Plugs - I got new plugs few weeks ago. Hooked them up the the firing order accordging the tag on the engine.
Timing - It did run for about 10 minutes before the carb rebuild...sounded nice, but then died out - the floats were sticking. I think it's set at 10 degrees since there is a mark at that spot. But since I it was running nice (until it died) I don't think that's the issue.
Fuel pump - mechanical (new)

I haven't tried starting fluid since I can get it to start. And I actually did check the choke last night (I had to change the screws that hold the choke plate since they were stripped) and it was closed when the enigne was cool.

[awesomesteven]

I went back home during lunch to mess around some more.

I turned the choke back to normal - factory setting - and it started running a lot more smoothly. It didn't pop this time when I gave it more throttle. What would be the difference - why pop and then not pop with the same setting? Odd - but not complaining.

It still cut off on me when I was trying to get it back to idle speeds. Never got there. Was probably at about 2000 RPMs when it cut out. What do you think I need to do to fix this?

[wotan2525]

Honestly, this sounds like a timing issue to me. Dieing @ 2000rpms means either fuel starvation or timing. You need a timing light to check and see where you are at.... When was the last time you replaced the cap/rotor? Does this still have points or has it been converted to an electronic setup?

[awesomesteven]

I relpaced the cap, rotor and points about 3 weeks ago.

I've done the timing before with the timing light, but only at idle. Could this also be a flooding issue since it ran for a bit then died?

How would I go about checking the timing if it's reving at high RPMs?



Thanks for everyone's help by the way. I'm fairly new to most of this stuff and everything has been extremely helpful - and has probably saved me a few hundred bucks as opposed to having someone come and check it everytime something doesn't work. I've learned a TON and have nothing but respect for everyone on this forum. It's exciting getting the engine to this point since it was in pretty bad shape when I got it and hopefully I'll have it in the water soon. Just wanted to express my gratitued.

[Salty87]

you put a fresh 5 gal of gas in, was the tank empty? do you have a water separator filter? running for 10 mins previously and then just dying is odd.

crossed plugs or timing being way off would do what you're now describing. crappy gas too.

you just had her at 2k rpms and it stalled?...ran smooth at 2k? or rough?

[awesomesteven]

you put a fresh 5 gal of gas in, was the tank empty? do you have a water separator filter? running for 10 mins previously and then just dying is odd.
It had gas in the tank previously but I think it had been sitting for a while so I drained it and added fresh fuel. Yes to the filter


crossed plugs or timing being way off would do what you're now describing. crappy gas too
you just had her at 2k rpms and it stalled?...ran smooth at 2k? or rough?

at 2k it was running pretty smooth. Not quite where I want it, but pretty smooth.

[wotan2525]

You can check the timing at any RPM and it will give you some indication if you are super far off. I'd just play with it and see if it makes it better or worse.

Make a chalk mark that goes between the distributor and intake manifold so that you have a reference point. Then, loosen the hold-down bolt on the dizzy and rotate the whole assembly a few degrees in one direction. You can then try to start it and see if it sounds better or worse. Try it in the other direction... better or worse? Once you get it running you can adjust it back and forth a few degrees to find the "sweet spot."

That's the first thing that I'd try. Report back and let us know how it goes.

[awesomesteven]

Thanks for the info wotan. I'll give it a shot tonight.

[CornRickey]

If I read it right your saying than it won't idle but will run wih throttle and when you give it a burst of throttle it bogs. Also the secondarys are dripping. If your able to get it somewhere near 10 degrees when below 1000rpm and it still does what yoh describe I would bet the issue is isolated to the carb.

What it sounds like is that your idle circuit is clogged and it will only run on the main jets, which are also constricted which makes it only run with a little choke. The bogging down sounds like a accelerator pump problem. When you give it throttle the carb needs the added shot of fuel to compensate for the added airflow til the primary jets can catch up. Take a looke down the throat of the primaries and hit the throttle ans see if fuel shoots into them on both sides. For the other stuff tou need to do a complete tear down dip and rebuild. Your floats were stuck for a reason and the same reason probably fauled up the jets.

[rideevol]

Other things to check when the intermediate circuit works and the idle circuit doesn't - Too much gas going in. When the engine dies, turn off ignition and look down primary and secondary throttle throat. Wide open throttle to move plates out of the way (engine not running) and flashlight to see intake manifold surface. The cast inner surfaces of the intake manifold should appear nearly dry. If the are very wet you are dumping too much gas into the engine, hence the high RPM run and the idle flood out.
To check if it is Primary or secondary related you can set the secondary float so that no fuel goes into the secondary float at all. Yes, an engine will start and even idle with only Primary fuel, in fact it will even run some RPM into the range before the secondaries are called in at about 2.5 inches of manifold vacuum.

[awesomesteven]

OK...so I took the easy way out. I'm having a guy make all the adjustments to the carb so it runs smooth. Carburetors are one of those things that I just can't figure out. Anyways, I came across another problem to work on...NEW THREAD! haha

[jtomasik]

Any idea how to identify the carb for kits/replacement? I know mine's a Holley, but there's no Holley tag (there's one with Motorcraft info). I sent an email to Supra, hoping they can help.

[wotan2525]

You probably won't get much help. Motorcraft should be able to cross reference the carb number. I'd check with summit racing and see what they say.... There's only a handful of holley kits that fit everything they've ever made.