440 Running rough, compression test results

[brywatz]

Hi all, I've been a member of fabo for a while because I have a '69 barracuda, but I just bought a '64 fury, so that brings me here too. I need help. My fury has a stock 1978 440 out of motor home, except for the Holley street avenger 670cfm carb. It ran great when I bought it, but of course after driving it once for 15mins, I parked it for 20mins, came out and it started running rough as if its missing. I changed plugs, converted to mopar electronic ignition, new coil, checked wires, changed fuel filter,and just did a compression test cause its no better. Compression results are as follows:drivers side 148, 144, 149, 141. Pass side 126, 138, 130, 130. Does that seem acceptable? I know it doesn't look good but do you think it's bad enough to cause it to run really rough? The last thing I just did was put the fuel Lin into a water bottle and crank the engine to see how much was coming out and after about a 10 sec count there was only 3/4 cup of gas at the most. Doesn't that seem too little? Thanks for any input, sorry for rambling, but I'm getting really frustrated........Bryan

 

[barnfind]

did you change out the fuel filter?

 

[brywatz]

did you change out the fuel filter?

Yep. Also, I forgot to mention, when I got home, I noticed that the car has an electric choke that wasn't wired up so I was driving around with a closed choke, and it ran well????wired it up and the choke works fine now but car still ran like crap.

 

[D575]

you probably fouled your plugs running with the choke on.

 

[barnfind]

you probably fouled your plugs running with the choke on.

x2

 

[brywatz]

i thought so too but i changed them and have the same condition.

 

[daredevil]

Sounds like a bad vacuum leak

 

[barnfind]

not sure if you posted it but did you go thru the carb yet?

 

[brywatz]

didnt really think vacuum leak since it happened out of the blue when i shut it off and then started it 20mins later, but ill have to check, thanks.
I'm not great with carbs, but unless something just clogged all of the sudden, i cant see any adjustments needing to be made since i was just running perfect a few minutes before.

 

[67 coronet]

easy to check for bad cyl.pull each one of you plug wires,individually,and restart the car each time.(dont do while running unless you dont mind the shock)if you find one that dont change how its running you have narrowed to that cyl.swap wires and restart to check that part.if it dont narrow down to one cyl,it will be fuel(carb or pump)or a vac leak more than likely.have you tried a leak down test to check the valves?

 

[brywatz]

thanks, ill check each wire individually, and check for vacuum leaks when i get home.

 

[19polara64]

You might run it at night to see if there is any plug wire arcing. Also check the fuel pump rod to see if it is worn down, making the pump hardly work.

 

[Meep-Meep]

Your compression numbers aren't stellar but they are enough to pop the cylinder. Vac leak as suggested is one thing to look for. You can also do a dynamic compression check to see how strong each cylinder is. Pull a plug wire from the cap one by one and note the RPM change. If no change then you found the affected cylinder/s. Before you start with the wires pull each one off with the engine not running to loosen them up.

 

[brywatz]

ok, last night I think I found the problem. I checked spark at the ends of all the wires-good. checked for vacuum leaks-none. Then went to the fuel pump. I disconnected the hose from the pump and ran it straight into a gas can in case there was a hole in the gas line somewhere, and it ran the same but I could see the pump wasn't pulling well. I hooked it back up to the tank and put a gauge at the carburetor and it hardly registered on the gauge at all. then I ran the line into a bottle at the carb again and cranked the engine for 20 seconds and got about an inch of fuel in a small Poland springs bottle. Now i'm pretty confidant it is the fuel pump. new pump comes tomorrow and ill let you guys know what happens. Thanks for all the help.

 

[dryheat]

Check your fuel pump rod length too ... seems to be a rash of instances where the rods are wearing prematurely.

 

[Garys1969RR]

Also a good idea to check the lines from tank to the pump for obstructions. Especially in an older car. Here is an easy way to do that. If the new pump still has a low output, check the fuel supply to the pump by hooking a hose to the INLET side of the pump and leading to a gas can. Crank over the engine and If fuel flow picks up, you have an obstructed fuel supply line between the tank and pump.

 

[brywatz]

I can't believe I replaced to fuel pump tonight and the car still runs exactly the same! I ran a hose to a gas can the other day and it made no difference. Tonight I climbed onto the front of the car so I could look into the carb while it was running and it seemed like the drivers side of the carb was not squirting as much fuel as the pass side, and not as consistent. I think I'm gonna throw a different carb on tomorrow. I don't know what else to do. As for fuel rod length, I'll have to look into how to check that

 

[Meep-Meep]

I don't think your problem is fuel related. How is the ignition? Odd why it was running fine one day then suddenly poor. Is the miss evenly spaced (rhythmic)? Or erratic?

 

[Budnicks]

Yep. Also, I forgot to mention, when I got home, I noticed that the car has an electric choke that wasn't wired up so I was driving around with a closed choke, and it ran well????wired it up and the choke works fine now but car still ran like crap.

maybe could be dead lean too, if it ran well/better with the choke shut... but didn't when it is open... sounds like it's an intermittent issue, not constant... among other tuning issues possibly, it could be bad coil acting up when hot, did you set the air gap in the dist. properly with a non-magnetic feeler gauge to 0.008", maybe the ignition/timing is retarded or possibly too far advanced {but would probably ping like hell if it was way too advanced}... vacuum leak maybe, bad hose bad gasket under carb or intake somewhere... maybe fuel supply issue, sending unit sock or line clogged, fuel pump &/or also carb issue from what you've described... did you check the fuel pump rod too ??, when you changed the pump

 

[bandit]

I just had a similiar issue. Car all of a sudden started running like crap, backfiring and missing. Was running fine up to that point. It ended up my plug to the voltage regulator had worked itself loose. Might want to test the regulator itself too. Cheap and easy to replace if you have to.