Bosko

As I've been rebuilding the suspension and brakes on my 1971 Mach 1, I would occasionally start and run the engine for 10 minutes or so just to keep the oil circulating and hopefully keep condensation to a minimum. The engine always ran great and idled fine.

Now that I am getting ready to test drive the new brakes and suspension, the car will not idle at all. It starts fine, but then the RPMs drop quickly. If I stay on the throttle a bit (1000-1500 rpm), it will keep running but rough. As soon as I let off the throttle, it dies.

I pulled the fuel filter, and it was full of gunk. I opened the top of the carb to peek into the fuel bowl, it was full of gunk too. I pulled the carb and cleaned it out with carb cleaner, put it back together, adjusted the float level, but still have the same problem.

I'm guessing that the fuel sitting so long caused tarnish to build up, and plugged some of the passages. And there's no telling what the contents of the fuel tank look like. My next course of action is to drain the fuel tank and clean it out as best I can, and rebuild the carb.

Any other thoughts as to why the car would suddenly not idle? 351C-2V.

Coupe

Well, I dont know how you could consider it "Suddenly" with varnish, that stuff takes a while.
I think all you can do is rebuild the carb and clean the fuel system, provided you have eliminated everything else. Maybe try some WD40 in the distributor to check for condensation?

Bosko

Thanks for the thought. I have not opened my distributor yet to see what's in there. I have not upgraded the ignition yet, so this may be a problem with the points.

I agree, varnish should not sneak up on you. The last time I started and ran the engine was on 12 April. It ran great then. I went on vacation for a week, came back and tried to start it on 19 April, and it wouldn't idle. So, yeah, it seems kinda sudden to me.

Bosko

I just siphoned about 5 gallons of gas out of my tank. I see no water, but it is dark and has black particulates in it. Definitely contaminated. I don't want to take the tank out yet, so I'm going to put in some fresh fuel and see what happens.

JC316

You might want to look around on the car for an inline filter. Someone had installed one on my 70 cougar near the back of the tank. Sucker was completely clogged up, as was the one on the carb. Mine was the opposite though, I could get to idle fair, but going down the road it would die.

jp1967stang

I would at least take the sending unit off and clean the screen that might also be plugged. Or you can just blow air into the tank with an air compressor to clean out the screen.

Bosko

In the spirit of going to the source, I drained my tank today and took out the sending unit to inspect. It is so corroded and plugged up that I will not be putting it back in. The screen is gone, and I cannot blow through the tube. A new sending unit was ordered from Mustang Unlimited. Sometime soon I will end up replacing the tank, or at least giving it a good cleaning, but for now I just need it to run enough to test out the new suspension, brakes, wheels, and tires.

If I can figure out how to post a picture I will.

jp1967stang

If you have the sending unit out and the tank mostly drained i would just clean the tank out now for the extra hour at the most it would take to remove clean and reinstal i would do it now. Its no fun draining buckets of gas twice, just rinse it out and let it dry out good.

Bosko

JP is right, I'm most of the way there so finish the job!

I just pulled the tank, not too hard to do. It took about 25 minutes to get it out of the car. To my surprise, it is in really good shape. Sometime in its past someone put a liner in it, which is still holding strong. There was surprisingly very little gunk or rust in the tank. Since it is lined, I took a garden hose to it and flushed out the little gass and gunk remaining. I shook out as much water as I could, it is now outside sitting in the Texas sun drying out. I will probably reinstall it tomorrow evening.

The only thing I can figure is someone dropped the tank, cleaned it and lined it, then put it back together with the same old fouled sending unit. Why someone would do that is beyond me, but the crap plugging my sending unit and fuel lines apparently did not come from this tank.

New sending unit from Mustangs Unlimited arrived today. I'll follow up here once I have it all back together and running.

Thanks for your help guys!