78 running problems

[bko4x4er]

well my 78 will start and idle fine. and will stay idling. but when i go to give it gas it will start to bogg out . it wont die or anything. it will just bog out and sputter and things. until i give it more gas then it will run in the right motion. but thats almos to the floor

 

[Little Giant]

well my 78 will start and idle fine. and will stay idling. but when i go to give it gas it will start to bogg out . it wont die or anything. it will just bog out and sputter and things. until i give it more gas then it will run in the right motion. but thats almos to the floor

Have you tried putting carb cleaner down the carb it might be the carb sticking.

 

[79fordblake]

Mine is doing the same thing. I am going to check at Advance Auto Parts and buy some good cleaner that is ok to put in the tank and drive it like crazy until maybe the trash will finally pass. Sometimes it will run good then it will act up again, I have me a good clear inline fuel filter on mine now. It wont leave you stranded or quit on you, but it is annoying as heck when it starts doin that crap.

 

[bko4x4er]

well i sprayd a little bit of carb and choke cleaner in there, and i also sea foamed it just a little bit and its still acting up. i need to put new spark plugs in and stuff like that though.

 

[Little Giant]

Have you tried STP fuel injection/carb cleaner. What I used to do is just set under the hood rev up the engine and just keep pooring the cleaner down it. That and make sure that the fuel filters are good.

 

[bko4x4er]

Have you tried STP fuel injection/carb cleaner. What I used to do is just set under the hood rev up the engine and just keep pooring the cleaner down it. That and make sure that the fuel filters are good.

ya i just replaced the fuel filter with one of those from autozone. those chrome ones...do yo think it could be too small or something? not letting enough fuel through?

 

[BroncoJoe19]

One thing about thsoe older engines is that a good percentage of the time changing out the points, condensor, cap and rotor, will take care of a bunch of problems. While doing that make sure the baking plate for the points is nice and clean, (so that a spark doesn't jump around in there.) Also make sure that the vacuum advance is working. Just give it the gas and watch the vacuum actuator move the plate.

Check for vacuum leaks.

Check that the accellerator pump inside the carb is working... just look down the barrel, and see if it squirts fuel when one depresses the throttle. The engine needent be running.

 

[HardMaple]

Unless he's modified it, the '78 has electronic ignition, no points or condenser.

Its hard diagnosing carbureted engines over the Internet, but I would stay with it being a fuel problem. Have you messed with the float lately? Since it smooths out when you open it way up, I would not be surprised if its giving too much fuel. It may be the new fuel filter is less restricting than the old one (or too restricting). I don't know what model Holley you have, but if it has an external adjustment try to adjust the Needle and Seat (on top near the fuel inlet, not the idle adjustments at the bottom).

Its been many years since I've adjusted one, so visit Holley's website for detailed instructions. But basically put it on absolutely level ground, unscrew the sight plug (if its the old non-clear plugs, or just look through the plug if its the new clear style), and adjust the float level with the ***** on top until the gas is at the bottom of the sight plug [hole]. If you have too much flow like I suspect, it may pour out of the sight plug so have a spare rag at hand. And keep it away from the distributor. If it overflows like that, shut the engine off and adjust the float down before restarting it.

And BE SAFE. Fire hurts her more than it hurts you.

 

[BroncoJoe19]

Unless he's modified it, the '78 has electronic ignition, no points or condenser.
Its hard diagnosing carbureted engines over the Internet, but I would stay with it being a fuel problem. <snip>

I usually don't know when they made changes from one ignition system to another, so I am guessing that it is an early duraspark system with a vacuum advance. Bad vacuum and lack of vacuum advance would cause it to bogg until until the RPMs catch up to where one wants it to be.

Great post! I didn't know that there is a site hole and that one could adjust a carb like that! All the one's I ever opened up, required one to flip it over and measure the float height, and bend a tang.

HardMaple's suggestion that it is a bad float adjustment makes sense.

I'm going on a trip, be back in a couple of weeks. I hope you get it fixed by then.

joe

 

[HardMaple]

I usually don't know when they made changes from one ignition system to another, so I am guessing that it is an early duraspark system with a vacuum advance. Bad vacuum and lack of vacuum advance would cause it to bogg until until the RPMs catch up to where one wants it to be.
Great post! I didn't know that there is a site hole and that one could adjust a carb like that! All the one's I ever opened up, required one to flip it over and measure the float height, and bend a tang.

HardMaple's suggestion that it is a bad float adjustment makes sense.

I'm going on a trip, be back in a couple of weeks. I hope you get it fixed by then.

joe

Its a Holley thing (I have never seen this done on a Rochester, and I've rebuilt a couple of dozen of them too). But not all Holleys have this adjustment. The Traditional Street and the Emissions Replacement don't, you have to take the float bowl off and adjust it the old fashioned way. But this isn't too bad because Holley's bowls are easily removed and installed (clamp off the fuel pump and run the carb as far down as it will go first, and have a rag underneath to catch the remaining fuel when you open it).

But any model with a center-hung float is adjustable from the outside. Not the photo below. Sorry, the sight plug is on the other side and not visible in the pic. I ran a red circle around the adjustment nut.

 

[bko4x4er]

One thing about thsoe older engines is that a good percentage of the time changing out the points, condensor, cap and rotor, will take care of a bunch of problems. While doing that make sure the baking plate for the points is nice and clean, (so that a spark doesn't jump around in there.) Also make sure that the vacuum advance is working. Just give it the gas and watch the vacuum actuator move the plate.
Check for vacuum leaks.

Check that the accellerator pump inside the carb is working... just look down the barrel, and see if it squirts fuel when one depresses the throttle. The engine needent be running.

yes it does squirt fuel bcuz sometimes it squirts on the hood wen the filter is off

 

[BroncoJoe19]

Just got back... did you get this fixed? IF so, what was the problem?

 

[bko4x4er]

no it will still run and idle fine but when i go to give gas it will sputter. i messed with alot of the screws on the sides so......haha i dont know what i did

 

[Yardape]

It definately shouldnt be spraying gas on your hood. Ive had terrible luck with carbs in the past. I have rebuilt them but they never seemed to run like I knew they should. Unless you know what your doing I would suggest bringing the carb in for a rebuild. Setting up the choke is a real chore and will give symptoms like what you are experiencing.

 

[Johnny Reb]

It definately shouldnt be spraying gas on your hood. Ive had terrible luck with carbs in the past. I have rebuilt them but they never seemed to run like I knew they should. Unless you know what your doing I would suggest bringing the carb in for a rebuild. Setting up the choke is a real chore and will give symptoms like what you are experiencing.

If it is a 2 barrel motorcraft---take the top off the carb and look for dirt or water in the bottom of the feul(carb bowl) . If you see any,take a paper towel and get it out. Also, try and rember if it acted up-before you put gas in it and where you got gas. I have had the same sound and problem and -that is what I found.You might also want to see that the jets are open and cleaned out.(the adjustments where the fuel and air comes in.) Good luck. Also STP gas treatment works good .