jordanZ

I have a 1965 Ford Mustang with the 3.3L 6 Cylinder. The engine only has 40K on it. Recently, it has been stalling out on me once it reaches 50mph. Anything under runs fine, but when it hits 50mph it feels like it hesitates and then shuts out. The fuel pump and fuel filter are brand new, and when I took the stock carb apart everything looked clean and the linkages operate fine. The distributor is a new Mallory 4700 series, and the spark plugs/wires are also new, so I don't think it is an electrical problem. In idle, it can rev as high as I want it to as often as I want it to without hesitation or stalling. There is no vacuum leak that I can notice either. It'll start back up almost immediately after it stalls. Anybody have an idea as to why it kicks out at 50mph?

Carlos Pineiro

The 3.3L is a v6. Stock was an inline 6. Is your motor an inline 6 (200) or a v6?

If it cuts out right at 50 every time, it could be a carb issue, but if it stalls as you accelerate it might be the fuel pump. Which motor and carb?

Good luck.

CP

JMD

You might have some chit in the tank accumulating on the pickup screen once the flow of, and the demand for fuel is high.

It sounds like a fuel starvation issue to me, being that the fuel filter and the pump is new, I would check pickup. I think that the p/u will come out with the fuel sender if you remove the cam lock.

I HAVE to mention that the tank should be empty if you pull the sender...

tx65coupe

I think 200 CID equates to 3.3L.

I agree with whats been said so far. I would guess that it is a fuel problem.

JMD

Number of liters X 61 is ballpark.....

And, after all these years, I still prefer good old CID... and probably will for life.

After all CID is my "native tongue", all displacement expressed in liters gets converted in my mind before I actually use the info.

To me a 5.0 will ALWAYS be a 302, a 5.8 will ALWAYS be a 351, a 5.7 will always be a 350... just the way it is....

Strangely enough, a 2.3 L is a Pinto engine.... I think that is the only exception for me though, I still find myself converting Modulars and LS engines to CID....

jordanZ

The 3.3L Inline 6 is the 200CID. In response to JMD, I replaced the old fuel tank and sensor about a week ago with a brand new one and had no issues afterwards, so I don't believe the problem lies there. The carb is the stock one barrel Autolite 1100. It can't be the fuel pump because I literally put a new one in two days ago, thinking that the old one was bad. Since that swap, it does in fact run better than before, but the stalling remained. I considered the accelerator pump in the carb, but neither of the diaphragms are torn and the linkages are smooth.

tx65coupe

Before my 65 became a V8 car, it had a 200 with the 1 bbl autolite. By the way, the 1 bbl Holley is worse. Back then it was my daily driver in high school and we went through rebuilding the carb ourselves 2 times and then about 4 rebuilt ones before we could get the car to run half way decent. We ended up getting a brand new carb from a place in NY. After that it ran perfect and felt like it gained 20 hp. You can get new carbs from pony carbs I think its called. That may be what will clear up your issue.

Stepman

How old are the rubber lines on the suction side of the pump? Some lines aren't good with today's gas and will get soft and collapse, cutting off fuel under high demand.

bmaytum

My 72-302 4bbl stock fuel pump-showed a similar pattern. Engine stall at 50+ Pull over, restart right away after stopping. In my case the problem was dirt in the tank clogging the intake filter. I removed the intake filter and installed an extra disposable filter disposable filter upstream of the whole system. When those filters got dirty, the first symptom was having the engine quit (stall) above 50mph. It would start up immediately after.

Both behaviors were a result of partial blockage of in the fuel system.

Trouble shooting suggestions:
1)Eliminate the fuel system as a variable entirely. Bypass the tank/fuel feed system by using a gas can and a long piece of fuel line hooked up to the fuel pump. Now the only possibilities are the fuel pump, carb and connection between the two.

2)A fuel pressure gauge on the outlet side of the fuel pump. Ideally visible while driving. Pattern of pressure drop, if any can indicate type of problem. Can separate between carb and fuel pump problems.

2)install two transparent fuel filters, one ahead of fuel pump, one after. These will help indicate flow volume through the system.When the engine stalls, the one on the carb side will be empty. Whether the other filter is full will speak volumes about the fuel flow through your system. Check it at other times to see what is going on.
3)Your new fuel pump may not be working to full capacity.
4)The fuel line along the length of the car may be clogged or restricted.
5)The connections to the fuel line may be restricted, If you have any rubber lines in the system, they may be partially blocked.
6)Blow out fuel lines. Don't blow into the tank as you can blow off the intake filter on the pickup. Hmmm...How do I know that???
7) If your fuel line won't pass sufficient volume, replace it.

The car will be a lot more fun when you can just hop in and go!!

Good luck

jordanZ

Cleaned the carb more extensively this time, as well as checked the fuel lines. One of the two solved the problem. Car runs great now. Thanks for the advice everyone.