She Cuts Out Above 2500 RPM - ???

Hey all, I have a problem with the '75 MIdget. When I get to 2500 RPM while on the road, the engine starts cutting out! She'll idle in neutral all the way up to 4500 RPM, but when there's a load on her (driving) she starts to cough!

I've checked the timing (10 degrees before top dead center), the valve clearance is correct, compression is good (110, 110, 110, 105), fuel is in the filter, and she idles pretty good at 800 RPM.

I have noticed the distributer is a little loose. You can rock it back and forth a very little bit - maybe an eighth of an inch or so.

I'm thinking it's the carb. I really don't know my way around it. I've just added a little oil and adjusted the idle speed screw.

What guidance can you guys provide? I really, really want to get this car on the road and have some fun, but I don't trust her when she's bucking back and forth at 2500 RPM and above.

Thanks!

Point bounce? My vote is to replace the points & the condenser first.

I've replaced the spark plugs, rotor, distributor cap, spark plug wires, installed new fuel filter, all new hoses, etc.

I had a the same problem and for me I checked the fuel pressure and only had 1 to 1.5 pounds of pressure and I had the same symtoms you are having so I put new fuel pump in. It has 3.5 pounds of pressure and I have had no more problems.

Larry, I have the mechanical fuel pump.

Did you replace yours or did you add an electrical pump?

I have a mechanical fuel pump also and that is what I replaced

Mine did the same thing found that the rubber fuel line at the tank was soft and the vacuum from the fuel pump colapsed the line.That and all the rust in the tank from the last 30 years did not help in much.

We had a similar problem with an early '90's (dare I say it) Miata at around 30,000 miles.

It would run fine and rev like crazy in neutral, but under load it wouldnt climb a slight grade. Rather than trade it for an MGB (we already owned one), we found it had a common Miata malady...

The coil pack was going bad, and it wouldn't provide sufficient spark under load.

Now we all know the MGB is no Miata (and vice versa, thank goodness), but before I tore into the carbs, I would...

Try a different IGNITION COIL that you know to be in good shape.

As Dick O'Kane once famously wrote in R&T,

"Carburetor is a French word meaning 'Leave It Alone'!!!"

A few things come to mind for me. Bad condenser, or bad rotor (yes they can be bad when new out o the box!!!)
Weak fuel supply.

If it stutters when you hit higher rpms under load, I'd suspect fuel. If it basically shuts off or acts like its trying to run on one cylinder, I'd look at the ignition first.

I second the coil being bad. Just solved a similar problem on my '63 SAAB. Wouldn't run over 5g's under load ( it's a two stroke) . Swapped the coil. Done.
Bill

Okay, I received a new mechanical fuel pump and put it on. Unfortunately, the car still stutters when under load and at about 2500 RPM! She actually died about half-way up a hill!

I looked to see if fuel was getting to the engine and the fuel filter just before the pump does have fuel, but it's never full or even half full. Should it be full?

Also, I've put on a new exhaust system and think it may be choking the engine. It's the MOSS exhaust (new pipe and new muffler) specified for the 1500 Midget. Would this be causing the problem?

Or.... should I now focus on the coil? The car takes a moment to start after turning the key. I thought it was the starter, but perhaps it's not.

Once again guys (gals??) any guidance is appreciated!!

Thanks
Mike

I don't think the exhaust is the problem. Try the coil, they aren't that exprnsive.

Bought a new coil (upgraded version at NAPA) and gave it a test run. Unfortunately, she's still stuttering and stopping.

I live on a hill and she couldn't make it up the hill!! I had to tow her 200 feet to get her home!

I'm starting to think it's a fuel issue. I never really see the fuel filter fill with fuel (say that 3 times!). I have all new rubber fuel hoses and I've cleaned out the fuel tank. Perhaps something is caught in the steel line somewhere.

Any ideas??

Thanks!

The fuel filters usually don't fill up, and often appear empty.

Take the fuel line off at the carb and run it into a can, cup, or jar. There is a formula for how much it should pump in a given time. Can't recall what that is. Maybe google it, check the library on here. Hopefully, someone here will remember it.

I had some similar problems this earlier year. My issue was air getting into the fuel lines from a boogered up pickup line in the tank. Replace some of the rubber lines under the hood with clear ones from the hardware store temporarily, drive the car until it sputters,and lift the hood and check to see if you are sucking air when you rev the engine. Good luck.

CJ,

How'd you fix the problem? Did u have to purchase a new fuel tank?

I was watching the fuel go into the filter and it looked like it was being spat in there. so I attached a hand pump to suck fuel into the filter and it looked the same. it wasn't a steady stream of fuel, it was just like someone was spitting fuel in there from time to time

thx!

Yup, new tank solved my problem. The clear line method helped me trace the problem to the tank. Since I have an electric pump in the back, I had less line to check than you would. Your issue could be anywhere upstream from the pump. I hope this helps you out.

Michael,

Did you ever figure out what the problem was?

Sure sounds like a stuck mechanical advance in the dizzy to me.

Wow, thanks for the follow up!

My new gas tank just arrived. I'm going to brave the cold (28 degrees here in Atlanta) and install it this afternoon. I tried to suck some fuel in thru the filter and couldn't get very much, so I'm guessing the the 39 year old tank is full of rust and debris even though I tried to clean it out.

I'll keep you posted!

What's a dizzy?? The rotor?? I have the electronic ignition my dad had installed years ago.

Thanks!

It's the distributor. Even the electronic ones have mechanical advance weights found below the baseplate inside. The weights can get rusted, stuck, or the springs can break. Your symptoms are consistant with stuck weights.