Classic Mini starting problems, part 2!

So, the little angry box roared back into life. I took it out today for a run, and it was happy.

For a while. Then it started to miss a bit under load, then a few backfires, then dead. I was able to fire it again a couple of times for a few seconds, but overall dead. 90 minutes later, AAA stopped by and loaded it up for the 5 mile trip home.

The plugs are dry. I've taken the SU apart and cleaned a bunch of sediment out of the bowl, cleaned up the inside of the dashpot and filled it with 20W-50 after discovering it was almost dry inside. All the various lines and bits were inspected and found good, and there was fuel in the bowl when I pulled it.

Now I can occasionally get it to fire and it'll run for 5 seconds, then just die. Pulling the piston damper out (to simulate the previous dry condition) seems to help, but I'm not sure. The plugs again seem to be dry. The fuel pump is delivering a considerable amount of fuel even when cranking. Everything that is supposed to move seems to move.

Umm, SUs aren't that complicated. When it was running, it was running strong. Ideas?

The failure felt like the mixture going leaner and leaner - I've had a very similar failure on a fuel injected car that had disintegrating foam in the fuel tank. When I pulled the plugs and found them dry, I assumed it was fuel. But maybe I have very high standards for "wet"

I checked spark, and got none. I went through a different coil and checked the performance of the Lumenition, then checked with a different plug. Spark. So I cleaned the carboned-up plugs, and now I have spark. And wet plugs. Quite wet.

Clamped off the fuel line, cranked with the throttle wide open and voila, it fired. So I've got an over-fueling problem again. I'll pull the carb off and see what's going on with the float. I may have missed something when reassembling. This thing is a bear to remove with the engine in the car, so I'm done for the night.

I'm not familiar with Luminition ignition, but if it's anything like Pertronix, it doesn't like being energized and not running. I had one let out the magic smoke, while trying to get static timing set.

I've also had a no-run incident, before going to pointless ignition. The plastic cam follower melted down, to the point that the points weren't breaking.

Ninja edit The Lumenition looks exactly like a Pertronix, and the official troubleshooting guide showed me what I needed to see.

Right now, I'm thinking I did indeed have a carb problem. I think the piston was sticking. But when I disassembled and cleaned everything, I may have messed up the float level or something like that. It's pretty telling that it runs happily with the fuel feed clamped off. For a little while, anyway...

Of course, this car specializes in making me wrong. So we'll see what we learn tomorrow.

That sounds like a dying coil to me or really, really, off carb float settings. Fuel in the bowl is not enough.

Aren't minis notorious coil eaters?

Easy way to tell if you have a fuel issue, put some gas in a spray bottle (DO NOT USE AS FLAMETHROWER) and see if it will run like that.

The vast majority of perceived fuel issues are electrical issues.

Is the distributor bolted down tight? I've had clamp bolts break and the timing is ummmm "variable" as you drive

Dizzy is on tight. I tried with a known good coil, no love. But clamping off the fuel line made it run quite happily until the bowl emptied, which did not have any effect on the electrical system.

You know the rule - go back to what you just did. I haven't touched the electrical system with all this work, but I have been screwing with the carb and fuel lines. Electrics don't mind a long sit, but carburetors do. That's why I started with the fuel.

I noticed a bit of fuel trapped in the float when I was messing with it, so I've got a new float on the way. Not a lot of fuel, but more than originally intended! I'm sure that's not helping.

I was gonna say if it runs with the fuel line clamped off but does not when the line is open and the plugs are wet, that sounds like a sunk or stuck float.

the combination of a float and the fuel bowl in a carb is a cool mechanical trick for making sure fuel pressure at the bottom of the fuel bowl is VERY constant and predictable. If the float sinks or sticks (or is not adjusted correctly) even a little bit the fuel pressure at the bottom of the bowl is unpredictable and that will give all sorts of issues.

I've had problems with sticky float bowl valves in the twin SU's on my Mini. Sometimes it idles really rough - as if it's only running on 2 cylinders - so I get out, tap the tops of the bowls with a wrench which seems to free them up and it runs sort of normally.

Keith Tanner wrote: I noticed a bit of fuel trapped in the float when I was messing with it, so I've got a new float on the way. Not a lot of fuel, but more than originally intended! I'm sure that's not helping.

Any fuel in the float is an automatic fail.

Kenny_McCormic wrote:

Keith Tanner wrote: I noticed a bit of fuel trapped in the float when I was messing with it, so I've got a new float on the way. Not a lot of fuel, but more than originally intended! I'm sure that's not helping.

Any fuel in the float is an automatic fail.

Good catch. Agree on root cause

The only time you dont throw a float with fuel in it straight in the trash is if its stranded you someplace where you can't get a new one, at which point you dry it out and coat it in Seal-All to get you home, hopefully the seal all holds up that long.

This is hopefully the final update.

I got me a new float and rebuilt the carb, setting float level carefully and all that good stuff. Now the garage doesn't smell so much like fuel.

But the problem persisted. The car would fire, idle for maybe 30 seconds, then die. Then it wouldn't run as long, maybe just a few seconds. Now it was dying instantly, not as if it was starving. Just...stopped. I dropped by Harbor Freight and picked up an inline spark tester so I could actually see what was going on.

Ignition. Or a lack of it. I finally figured the Lumenition was failing, and would work fine when it was cool. As soon as it got any sort of heat internally it would stop. I went through the troubleshooting guides from the manufacturer and everything looked good. Or it didn't look good, depending on how the ignitor felt. A dodgy unit wasn't in the book for some reason.

Of course, this thing has a hotrodded distributor. I contacted MiniMania and asked what Pertronix to use with my Alcon dizzy, and the tech didn't hesitate at all. Great product knowledge. So I ordered a coil/Pertronix/wire/cap/rotor set. When it arrived, I dropped in the Pertronix after reverse engineering what had been done to fit the Lumenition. I kept the existing coil, wires, cap and rotor because I was pretty sure they were good.

Happy car! Fires up better than it has in a long time, and ran well for my test drive that basically consisted of increasing diameter circles around my neighborhood in case I ended up walking home.

So, there you go. Two problems. One probably due to a long sit, and another that was probably getting ready to bite me in the ass and just chose to manifest itself at this time. I'd had trouble with the Lumenition once before (right before it went into hibernation) but I traced that to what appeared to be a bad connection at the time. Maybe it wasn't.

More exercise for the little guy this weekend coming up. Fingers crossed, and thanks for the help!

Awesome update glad you fixed the issues

happy time!