sucking noise from carb and when engine fires, a flame shoots up then car dies. new 1405 eddelbrock carb put on yesterday. manual choke. someone suggested using a auxillary fuel supply (dont know what that is)? i think the sucking is a vacuum leak but it is coming from the top of the carb? any ideas?
put the air cleaner on it. Cars of this vintage would frequently backfire without the air cleaner on if the throttle was suddenly opened.
Make sure the firing order is right first and the distributor rotor is pointing at # 1 terminal on the distributor cap when the engine is at top dead center.
Timing chain.
Valve timing and ignition timing off? Timing chain.
Tester
have not looked at the timing yet, just figured it may have been the turkey baster full of gas i shot down the carb. do you know how to set up an auxillary fuel supply?
Suppose you give us a realistic history of the car. Have you EVER seen it run? How long have you had it? What other modifications have been done to it?
Aux fuel supply. Have you ever seen how they hang a bag of fluid in a hospital? Pretty much the same concept. Disconnect the current fuel line somewhere near the carb and connect another temporary fuel line that ends up feeding fuel to the carb. Place the fuel container (1/2 gal.) is plenty big higher than the engine so fuel can feed into the carb. If there is some clear tubing you can see fuel flow which will hopefully fill the carbs bowls. You might want to tap the carb in the bowl areas to aid the floats in case they are stuck from just sitting around empty for awhile.
A turkey baster full of fuel is way too much. If you put fuel down the carb throat you only need a spoonful or so. Get it to fire and if there is fuel in the carb floats after a couple of fires, it should catch and run.
If you hook the aux fuel line into the fuel pump you don’t have to raise the container above the motor, but you are relying on a questionable pump to move gas to the carb. Remember if you get the motor running and the fuel pump does work it will be pumping fuel somewhere so make sure you have a way to catch any fuel safely.
You do understand that the ‘auxiliary fuel supply’ is just to test it, correct?
Someone has likely crossed the plug wires or the distributor has been installed 180* out.
I think Tester is on the correct path…Check the timing with a strobe light at cranking speed and see where the mark is…If you can’t find it with the light, the timing chain has probably slipped . Another check…With the distributor cap off, turn the crankshaft back and forth (with a breaker bar on the crankshaft pulley nut) and see how much rotation is needed before the distributor rotor also changes direction. That will give some indication of how much slop is in the chain…The CHAIN seldom wears out…The problem is usually the plastic teeth on the cam sprocket fall apart and the chain starts jumping over the nubs on the sprocket…
Before you check any of this, be sure the spark-plug wires in the cap are in the correct position (firing order)
Most carburetors “Hiss” at idle, the intake air screaming around the almost closed throttle plate…That’s normal.
One more thing…Should the problem turn out to be the timing chain, you should pull the oil pan and remove all the plastic debris that broke off the cam sprocket…Otherwise it can plug up the oil pump pick-up screen…
I have a procedure that I use when working on a problem like this. First is to determine where the rotor is pointing when the engine is at TDC for the #1 cylinder. Remove the #1 plug, either put your thumb over the spark plug hole or screw in a compression gauge, then bump the engine over until the pressure begins to build in that cylinder.
cont.
Finish turning the engine to TDC by hand, use the timing marks for a reference. Now remove the distributor cap, check that the points are opening and mark on the side of the distributor where the rotor is pointing, put the distributor cap in place to see if it is pointing directly at a post and which one. If it is not pointing directly at a post, then there is a problem either with the timing chain or the distributor is off a tooth.
cont.
Next determine that the wire of that post goes to the #1 cylinder and check the rest of the firing order from there. Looses the distributor hold down clamp and turn the distributor so that the rubbing block on the points is at the top of the lobe, check the gap and adjust as needed. Turn the engine backwards until the specified timing mark for idle is lined up.
cont.
Turn on the ignition to run, turn the distributor back until the points just close, then turn to open until you see a faint spark jump the gap as the points just begin to open. Lock down the distributor. Put her all back together and try to start. If there is still a problem, look at the fuel system next.
I think I told you to set up an Aux fuel supply when you were suspecting a different issue…a fueling issue… I THINK…or maybe that was someone else? Doesn’t sound like an Aux fuel supply has anything to do with what you are seeing now…The guys mention timing and with good reason…sounds like its too advanced to me… THAT would do this
There is a chance someone has mixed up your plug wires and you’re cross firing. The correct firing order for the 390 is 15426378. It’s written somewhere on the manifold. Never try to start this engine withour an air cleaner or you’ll possible cause an uncontrollable engine fire. That carb holds a lot of fuel. Good luck, LEE
Yup surely Tbird…I think we ALL want him to look into the timing and firing order…surely couldn’t hurt here…and its quick and EZ to do
BB
Me too. The ign timing or the valve timing (timing chain).