Coughing and popping

When I wrapped up my 58 100/6 last winter in it's nice warm garage, with the de humidifier ticking away, it fired up on the choke, warmed up nice and ran like a dream
Since opening the door this spring it has struggled to start and when it does run makes loud sucking noises and is very hesitant to rev when given gas. When I do manage to get some revs into it after I have got it warmed up it is unresponsive and after blipping the accelarator a while it pops and bangs and struggles
I've had all the plugs out and cleaned them, they were new last autumn, I've had all the carbs apart, (twin HD-6 SU's ) cleaned a little gunge from the bottom of the bowls and put them back together, other than that they were nice and clean
What's my next step ?
Timing ? Cannot see that the distributor has moved at all, nice and tight, so why would the timing go out?
Compression test? Not something I've ever attempted, but it's almost as if it is only runing on 5 cylinders
Plug leads ? They were new last Autumn along with the points
Distributor cap ?
Coil?
Any help greatly appreciated
L

I am going to take a shot at this and say you should check the rotor. Had similar problem with the MG. Came back from Fl, car ran fine. Next morning had the same symptoms
you describe. Checked the usual suspect and found the locating tab on rotor was striped out. I could spin the rotor with my fingers. Car would gasp, bang and backfire.

Since you put it away running and it woke up ill, I would keep your attention on the fuel system.

You mentioned coughing and popping but you did not say if that was out of the carb or exhaust. If you haven't touched the ignition, carb popping and backfires are typically from a very lean (to the point of fuel starvation) condition.

You said you had the carbs apart. You did not mention how far you had disassembled them. My suggestion is to clean out all the fuel passages from the float bowls to the jets. Make sure you clean the center of the jet and carefully remove gum and varnish from the needle. When putting things back together, make sure the vacuum piston can rise and fall easily with the damper removed.

You could have a piston stuck partially open in one of the carbs that might explain the sucking and backfiring you describe as you would be too lean. If not while you are checking the rotor , if it looks ok , I'd replace the condenser and the points.

Old gas? My '58 T-bird used to run real rough if it sat for months. I just drove it to a gas station and added premium gas to it and it cleared itself up quickly.

Bad gas

Check if your fuel pump is acting normally: slow at idle, faster at speed. If the pump has points, the surface can oxidize if it isn't used for a period of time. If the pump isn't acting normally, clean its points.

Bad gas is certainly a possibility, but the gas should have been OK for several months. Did you use a fuel stabilizer? I've never had a problem with gas going bad, but I'm usually able to drive my Healeys at least a couple times in winter. If you didn't top up the tank you could have gotten some condensation in the tank; though a de-humidifier should have mitigated that.

dklawson said:

Since you put it away running and it woke up ill, I would keep your attention on the fuel system.

You mentioned coughing and popping but you did not say if that was out of the carb or exhaust. If you haven't touched the ignition, carb popping and backfires are typically from a very lean (to the point of fuel starvation) condition.

You said you had the carbs apart. You did not mention how far you had disassembled them. My suggestion is to clean out all the fuel passages from the float bowls to the jets. Make sure you clean the center of the jet and carefully remove gum and varnish from the needle. When putting things back together, make sure the vacuum piston can rise and fall easily with the damper removed.

Click to expand...

Coughing and popping is coming from the exhaust. I cleaned the bowls right through but did not clean the jets so could be there

Brinkerhoff said:

You could have a piston stuck partially open in one of the carbs that might explain the sucking and backfiring you describe as you would be too lean. If not while you are checking the rotor , if it looks ok , I'd replace the condenser and the points.

Click to expand...

I'll check them out again

Since you are reporting that the popping is out the exhaust it is less likely to be mixture related. Still... it won't hurt to clean the jets, needles, and fuel passages with some carb cleaner. Try not to disturb the jet setting to avoid upsetting the mixture.

Hi All,

Did you add any supplements to your fuel for storage? It is not out of possibility that prior to storage the fuel you added has excessive water that separated when standing for a long time. If you haven't added a fuel stabilizer for storage, I would suggest you add some Dry-Gas to your fuel...its inexpensive and won't heart.

Also, if you have points, any storage-developed corrosion will cause an ignition problem and cleaning will change the setting and result in timing changes as well. Again, cleaning and resetting the points and timing can't heart.

Since your car ran nicely prior to storage, rather then change ignition or any other components, I would focus on cleaning and resetting first. Only if that doesn't work or come across something that seems obviously malfunctioning would I consider replacements of any kind.

All the best,
Ray(64BJ8P1)

I have had a similar experience when I found that the nuts holding the exhaust manifold to the cylinder head needed to be tightened, but I doubt if this would answer your problem.



Bob

Hi Fellas
Update.....despite replacing the fuel bowl jets last year with nice originals from AH spares, one was getting jammed up and not allowing fuel in to the float chamber
I'm not sure the fuel treatment that a garage put into the tank was helpful as the one that was jammed up had a red residue around it.
I have upgraded the jets to the ball type and it now runs like a dream

"...the ball type..." a.k.a. Gross Jets. The following is a a bit of cautionary information.

Gross jets are kind of a hit or miss type device. To prevent corrosion while in storage, the maker applies a protective coating to the assembly and in particular to the steel balls. You need to wash that off with carb cleaner prior to putting the jets into service. Failure to clean them can result in brand new jets that stick open or stick closed. Unfortunately, the ball design is also prone to sticking later from fuel gum/varnish if the car is not driven regularly. They will work, just remember to wash them first, drive the car often, and keep an eye on them. Personally I gave up on Gross Jets when I had a couple of problems with them. I now use the Viton tipped float valves in my cars with SU carbs.