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SaxMan

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Tried to get Baby Blue back out on the road on an unusually warm 71 degree day, but failed. Replaced the fuel line and that seems to be working fine.

Using the Colortune, I found I had to get my rear carb to max rich to keep it from turning orange under acceleration. Front one was somewhere in the middle. When I tried to sync the carbs, the front carb was pulling down MUCH more vacuum, even at idle and the idle screw backed out full, it was pegging the synchronization tool. Meanwhile, the rear carb wouldn't even register. I also did the tube trick and you could hear a huge difference between the front and rear carbs at idle speed. Even when I'd sync the carbs at 2000 rpm and listen to the hiss using the tube, by the time I backed down to idle, they'd be out of whack again.

To top it off, the front float chamber now coughed up gas from the gasket. That's leading me to believe that there is something farther down the line blocking the gas and getting it to back up. I put a new jet in the front carb -- wondering if it is out of whack?

I'm also wondering if I just shouldn't do a full carb overhaul -- new needles, replace the rear jet, too, replace the damper springs...anything else? I'm trying to think if I'm missing something, but I've never had this much of a problem getting the carbs to sync in the past.
 
If your pulling them off opertunity is knocking I would.
before you do thou I would flow some propane or spray some starter fluid around the manifold and head and manifold and carbs and check for leaks.
 
David, are you sure your butterflies are opening EXACTLY the same and your float height is EXACTLY the same. Been my experience that those have to be right before any other adjustment can be made.

Kurt.
 
nomad said:
David, are you sure your butterflies are opening EXACTLY the same and your float height is EXACTLY the same. Been my experience that those have to be right before any other adjustment can be made.

Kurt.
Click to expand...

When I play with the throttle linkage by hand, they both appear to be in the proper place, but you can feel one carb engaging before the other. I'll check the floats. So, it is quite probable the butterflies aren't completely in sync.

The one thing I can't get past is why gas started spurting from the front float. It didn't happen immediately. It happened after two short test drives and probably 20 to 30 minutes of engine run time. I did try leaning out the front carb's mixture by 1 or 2 flats, but that should not have caused this issue.

I'm thinking I should replace the rear jet as a start, and probably replace both piston return springs to make sure the dampers are getting to their bottom position. And, if I'm replacing jets, probably the needles should be changed out too?
 
i would look closely at the springs make sure they are the same.
remove the pistons tape closed the holes on the pistons do a timed drop test thru the up make sure one is not hanging up mark them so they go in the same hole.maybe they did get swapped at some point?
you could have a bent jet that won't home all the way and and hangs in the seat.
what happens if you push them both up by hand?
probly not an issue with the SU's with the heat shield and phenolic spacers but on my 350 SbC the quadrajet would boil the crappy fuel we have now and after a hard run the boiled fuel would flood the Aux idle port causing a rich idle until the manifold cooled back down. A 3/4' phonic spacer cured that
 
Both dampers move smoothly when manipulated by hand. Thinking about it, the rear carb may be leaking at the heat shield -- I have the rear one bolted together from the heat shield: washer, fuel hose clip, nut, and I believe it should be, fuel hose clip-washer-nut, as I have on the front carb.

Flipping through the Haynes manual, it does seem to indicate that the jets require replacing periodically. I'm thinking if I replaced the front, probably should replace the rear, too?
 
You do have the floating needle's and they supposedly wear the jets. I think I would make sure everything else is up to snuff first though. Also I believe it is possible to get two different sizes of jet. Could be the replacement is at fault.

Kurt.
 
Some troubleshooting tonight. The fuel burp was a loose clamp on the fuel line from float to float. Butterfly valves seem very well coordinated. Front carb's damper rises faster than the rear carb. Both come down the same amount. Cranked down the rear carb -- some marginal improvement, but the front carb is really cranking down a lot more vacuum than the rear carb. The actual vacuum line is hooked up to the front carb -- could that be why?

The carbs were well adjusted before I put the car up for winter. When I troubleshoot audio problems in a P.A. system, the first thing I always try to figure out is "what has changed", assuming the P.A. was working fine before that. Obviously, the jet is the factor that has changed. I also know when trying to fix a problem, trying to make wholesale changes can sometimes make things worse, as you start fixing things that weren't a problem, so you isolate one factor at a time. Going back to the original jet is not an option due to the fuel leak. It seems the most reasonable course of action is to replace the rear jet before I start messing with other parts of the carb. I can always replace the other parts later. It may take more time to get the car running again, but I'm also not making more trouble for myself by bringing in factors that may or may not be contributing.
 
I would consider getting a kit to insure the jets match
mine started out with mismatched springs and needles
I got in touch with Joe and he got me the parts I needed.
 

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Got the new jet today. It definitely helped balance the two carbs. Now the vacuum is equal. I did do one stupid thing -- I was reading the Colortune backwards, so instead of going to max rich, I was at max lean. No wonder the motor was running like dog poop! The motor is definitely happier with a richer mixture. I'm still having idle fluctuations. At first the idle was jumping up and down as much as 500 rpm. I have the fluctuation down to about 200 rpm. The fluctuations are consistent, which I think is telling me the the carbs are not quite synched up properly. At least the car is now driveable, but still needs tweaking to drive well.
 
Maybe. One of the indicators of a vacuum leak is hunting idle. Maybe not 500rpms, but something to think about.
 
More tweaking today got things a bit closer. Still not 100%, but at least it's driveable.

Wondering if the coil is suspect. I remember the saying "most carb problems are electrical". The cap, rotor and wires are all relatively now -- I installed them last winter, and put less than 3,000 miles on the car. Plugs are brand new.
 
You didn't change the coil first?!?!?!
It's ALWAYS the coil!
No person driving a limey limo should ever leave the house without a minimum of three NEW coils in the boot!:devilgrin:
 
On the coil, there are three wire -- the red and black, which are pretty self explanatory, and then there is a third yellow wire. What does the yellow wire do? It looks like this wire may be damaged where it meets with the connector.
 
Could be a float level
time it at idle see if it's a consistent cycle
then partial open choke-just a tiny bit see it the fluctuations changes
if it just my money is on float.
 
Today's drive was more aimed at checking the brakes after rebleeding them. There was still some air in the lines that I didn't catch initially. Brakes are now fine. Car ran like crap. 43 degrees and dry. Very difficult to start. Once started, it ran okay, but once I took the car off choke, if I let out the clutch, the engine would die and wouldn't fire back up unless I used choke. The car was backfiring out the exhaust while coasting in 3rd gear. I know the carbs are set fairly rich, so that shouldn't be happening. My gut is telling me its the coil. Ordered a new one earlier this morning from Jegs. We'll see how it goes.
 
My car tends to run like cr*p every spring till I get a tank of fresh gas through her - even with Stabil - exactly the symptoms you describe
 
SaxMan said:
On the coil, there are three wire -- the red and black, which are pretty self explanatory, and then there is a third yellow wire. What does the yellow wire do? It looks like this wire may be damaged where it meets with the connector.
Click to expand...

Actually, those colors are not self explanatory. What year is this car and can you post a clear picture of the coil wiring?

For Negative ground cars, factory wiring for a 12V standard ignition would have a white wire from the ignition switch to coil (+)
Then there would be a white/black wire between coil (-) and the distributor.

You mentioned a yellow wire. That is usually present on cars with ballast ignition systems and it runs from a 4th terminal on the starter solenoid to coil (+). For ballast ignition systems, there is typically a white/pink resistor wire between the ignition switch and coil (+).

The only place I have seen red and black wires is on aftermarket electronic ignitions (like Pertronix) where the red wire goes to coil (+) and the black to coil (-). When that type of ignition system is fitted there MUST be a 3rd wire on the coil (as a minimum). Typically that 3rd wire is white and goes from the ignition switch to coil (+).

If an electronic voltage sensing tach is fitted (Smiths RVC or modern), that typically has a sense wire for the tach connected to coil (-). For older current impulse sensing tachs (Smiths RVI tachs or equivalent) the wiring is more complicated so I won't bring it up here unless necessary.

The important thing is that your car ran before you put it to sleep for the winter so you have to ask what happened in storage. Ignition parts don't typically fail while sitting. However, if you put the ar away for winter with any fuel in the float bowls, that can gum the float valves, jets and needles. Since you have new jets I assume you cleaned the needles while the carbs were apart. You did not mention if you cleaned or replaced the float valves at the same time. If not, they should certainly be looked at. They can also gum up from fuel while in storage. When only one float valve is stuck you can sometimes get the engine to run but it only has one sweet spot and will be terrible at speeds away from that RPM.
 
Even though the car was put to sleep, it never went more than 14 days without being started and run. Once the car gets up into the higher revs, roughly 2200 RPMs and up, she runs as smooth as a baby's butt. Once it drops below 2000, it gets balky, and below 1500, it starts stuttering. I will check the float bowls for any extraneous items.
 
Checked the float bowls and floats tonight. Everything looked in order. There was a small amount of sediment at the bottom of each float bowl -- not sure how that got past the fuel filter, but it may have been there prior to that. Cleaned everything up and put it back together. Did not try to start the car.

Also detailed the car. Wash, polish and wax. There was a lot less dirt, for lack of a better term, this year. Usually when I'm done with the polishing or waxing bonnets, you have a little bit of blue, but there was also some black that was lifted up. No black this year, just a smidge of blue on the bonnets. Baby Blue looks really good. It's supposed to be in the low 60s on Sunday -- hopefully I'll have a well running car by then!
 
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