300 Will Not Idle

[Straight6]

I have an 83 Bronco with a 300 cid newly rebuilt motor. When I start the engine it will not stay running unless I hold the accelarator down a bit, and if does die and I get it restarted the engine takes a few seconds to build RPM while black smoke is coming from the exhuast. The engine ran fine after we put it back in the truck this is new problem also the carb is a rebuilt but I don't know how old it is. Any ideas?

 

[Seabronc]

Does it work OK once at normal operating temp?

I'd say you probably need to do the carb idle adjustments, not the idle mixture, atleast not yet. The blacksmoke is too much fuel, but it might be loading up because of the problems. The slow windup is also indicative of getting to much fuel at that point.

The proceedure is on the emission sticker.

Basicly, run engine till it gets to normal operating temp, disconnect distributor vacuum and plug, check timing is set according to the sticker, replace vacuum on distributor, set choke on high step, adjust cold idle ***** to whatever it says on sticker, probably some where between 1900 and 2100 RPM. Put in run and hold brake and check curb idle, set approx 550 to 650 RPM

Good luck,

>-

 

[BigNasty]

Newly rebuilt carb... bought or did you rebuild it?

I gave myself an overly rich condition like that by messing up the float adjustment on one... also, could be the rebuild itself, if you did it, did you follow the instructions well and make sure to replace everything that the kit gave for that model of carb?

Oh yeah, had a similar prob on a 289 once.

The carb to manifold gasket that came in the kit was cut wrong and gave the entire back side of the carb a vacuum leak due to not even being in contact with either the carb or the intake surface. Had to hold it full throttle to start and run all while spewing smoke out of the tail pipes.

Just food for thought /emoticons/[email protected] 2x" width="20" height="20" />

Edited for - Just caught the part of not knowing how old the carb is.

Could be all gummed up and even a jet clogged up with dried fuel if it was rebuilt a long time ago as well as gaskets dried out and cracked or the butterfly rods having worn out their journals and allowing a vacuum leak there..

Seems that all the probs started with the old/new carb /emoticons/[email protected] 2x" width="20" height="20" />

Still have the other carb, if there was one?

 

[Straight6]

No I don't have the other carb this one came with the Bronco and this problem just started. Also this Bronco set for more than a year and was not run. Is it possible that a pice of buildup broke loose inside of the carb and cloged-up something when I put new fuel into it?

 

[Seabronc]

That is a key piece of information.

I'd say that is a good possibility. Did it set with old gas in the float tank? Most likely! New gas will loosen up a lot of varnish created by gas setting around. if it had old gas in it, you might have smelled something like terpentine near the carborator. If the gas dried out the inside of the bowl almost inevitable had a coating of varnish.

You might want to get a rebuild gasket set and take it apart clean it up real good and make sure the passages in it are not clogged. If you get a complete kit, it will have instructions with it. It is not a difficult thing to do.

I personally have given up on rebuilding carbs. You can get a new one for not much more than it costs you in time and the cost of the kit. Also, a kit doesn't address vacuum leaks caused by worn bushings. So some times you end up with a good running carb and sometimes you end up with one that works a little bettter but is flakey.

So what am I suggesting here:

1. lowest level of attack, carb cleaner it to death

2. Level 2, pull the float bowl off and clean out the gunk that is most likely in it.

3. Level 3, do a rebuild.

4. Best, throw it in the garbage and put a new one on it.

Good luck,

>-

 

[BigNasty]

The truck also sat for a year?

Sounds like mine /emoticons/[email protected] 2x" width="20" height="20" />

I yanked out the entire fuel system, including the tank, to give it a thorough going through shortly after I got it.

There was quite a lot of rust including half a tank of bad gas in the tank that kept clogging things up from the get-go on it.

The problem in letting vehicles sit for a long time, is that most people don't fill their tanks before parking them, or draining the bowls on the carbs..

The fuel in the carbs will become sticky varnish over time and the fuel tank will rust easily due to condensation of humidity due to repeated heat ups and cool downs from season to season.

I would yank the carb, clean it up and replace its gaskets, drain the tank and possibly pull it to clean it well or at least put a good filter inline so you can see how much, if any rust and other deposits are being passed.

I put a plastic, nearly see through filter on mine, just before the carb just so I can tell at a glance how bad it is.

 

[Straight6]

When I started it this morning I had to keep my foot on the floor just to get it to run at 2500 RPM. I took the tank out some time back and cleaned it out and it had six gallons of bad gas in it but the tank has a plastic coating in it and it looked good not loose. Where can I get a new or rebuilt carb it is a one barrel?

 

[BigNasty]

Parts places MIGHT have some on the shelf (factory replacement type) and would most likely need your old one as a core.

Same with online sources, some of the bronco salvages might have them and need a core etc..

If it were me, I would rebuild it myself, it isn't too hard and for me, always on a budget, it's cheaper to rebuild.

Got any part #s cast on the carb body anywhere?

Put them up here and someone may just have what ya need lying around or be close enough to rebuild it for you.

Always a good idea to learn to rebuild anyways, it makes future repairs and trouble shooting a lot easier /emoticons/[email protected] 2x" width="20" height="20" />

 

[Straight6]

Today I took off the air breather and smelled a bad gas oder, so I smelled of the inside of the bbl and it smelled like bad gas I than removed the fuel filter just north of the gas tank and it smelled like fresh gas. So is this smell from the varnish mentioned before and is a total rebuild in my near future?

 

[BigNasty]

You can purge the lines easy to get rid of any more bad fuel.

But yes, a rebuild may be due for the carb.

The way I purge the line is to-

Get a two liter coke bottle and a friend.

Remove the coil wire so the engine can't throw a spark out, you may want to remove the hot wire off the coil also, just to be sure no spark escapes the coil itself (high voltage coils do this easy)

Remove the fuel line as close to the carb as possible (may need a short length of fuel hose to go on the end of the hard line)

Put the line in the bottle to catch the fuel and simply turn the engine over with the starter to activate the fuel pump, being careful to prevent spraying or splashing the fuel out.

You can also drain the bowl/s on the carb easy, just take the carb off the engine and pump the accelerator linkage till no more fuel comes out of the carb.

SAFETY NOTE****

Have a fire extinguisher handy in the event a fire does start.

Wear eye protection.

 

[Streetgang44]

Its just a shot in the dark.....but have you checked for codes????