My car will idle (sort of) but dies with any throttle

[jimlj66]

Today we took the Mustang for a drive, all went great for about 20 miles. My wife wanted to stop at a store for a few minutes, and when we started the car it drove fine out of the parking lot, but died when we went to take off. My first thought was vapor lock, but I don't believe that to be the case now. I let the car cool off for several hours but it is still the same.

Now it will start and idle, but dies when it gets any throttle. It idles like it is starving for fuel, and will die after about 20 seconds.

I have checked the following...
Pulled and cleaned the distributor cap and rotor. (DSII, Motorcraft box)
Fuel filter is good
Choke is open.
Fuel pump is good.
I am getting a squirt of gas when the throttle is pressed.
I pulled the top of the carburetor (Autolite 1100) the bowl is about 1/2 full of clean fuel with the float out, I'd guess about 3/4 full with the top on. These are a guess, and I will pull the top again if I need better measurements.

Any input on what else to check would be greatly appreciated.

 

[xctasy]

Faulty coil. If there are no vac leaks, and the ignition advance checks out on an osillscope, then check the coil.

 

[bubba22349]

Check the condition or replace the fuel hoses at fuel pump and tank old hoses can be cracked and suck air not pull fuel up to the pump. Check the fuel cap to see if the venting is working correctly, check the fuel pickup in tank they have a sock on the end that can be deteriated, also check the tank for rust and crude this can be pulled out and clog the fuel pickup, good luck

 

[jimlj66]

xctasy, I will check for vac leaks. That was on my mind last night when I was laying in bed. Not sure how to check the advance with an oscilloscope, nor do I have one. I will snag a couple coils from the junk yard and give them a try. Are the V8 coils the same??...there seems to be a ton of them around.

bubba, Thanks for the input. I have not checked hose condition, but I will although I don't think that is the problem. I am getting plenty of fuel to the carburetor. I can fill a 1/2 liter water bottle in a few seconds, and when removing the fuel line from the carburetor I have back pressure like the float is doing it's job. I don't think the float is stuck as the bowl has fuel.

Thanks again for the input, keep the ideas coming

 

[bubba22349]

V8 coils are the same. Hows the battery condition? Needs to be full charge 13.5 - 13.8 volts to run good. Check that there is a ground from engine to the frame / body and that all your grounds are clean and tight. Is the Motorcraft control box new? Good luck

 

[jimlj66]

V8 coils are the same. Hows the battery condition? Needs to be full charge 13.5 - 13.8 volts to run good. Check that there is a ground from engine to the frame / body and that all your grounds are clean and tight. Is the Motorcraft control box new? Good luck

Battery condition/charge is great. I will check grounds and connections. No, the control box is not new. It came from my '82 Mercury Zephyr donor car. Is there any way to test it? Are the V8 boxes the same? I'd be glad to buy a new box and coil, but I hate to throw parts at it. If it turns out to be the coil or box I'll buy new and keep the junk yard parts for spare. I want to make this car as reliable as you can get a 46 year old car to be.

 

[bubba22349]

Control boxes are not always the same you ID and match them by the color of the strain relief IE Red, Blue, Brown, etc. Blue was a very commonly used one. I don't know of a way to test them but sometimes you can look at the bottom side and see the heat damage from a burnt transistor etc. On my service truck I always carried a "known good one" to test with. They can often work as you describe run good and than shut off, than after awhile of cooling off they will run again etc. until finally after a few times they won't start again. The last one on my 77 Maverick original box from new, it's a very low mile car too. It gave no warning at all it drove great parked it for the night and next morning it would not run until I replaced it. If you buy a new one stay away from the cheap or bargain parts house ones if you can. Personally I would only use the Motorcraft or a NAPA ones after opening up and looking at the circuit boards and parts in a few of them.

Other thoughs

Don’t know how your DSII is wired but maybe you have wrong voltage going to the control box if you still have your donor car check the power wire from ignition switch if it’s the resistance type.

Power to + coil terminal is the same way as an old point ignition. With the ignition switch in the "run" position, power comes from the key switch through a length of resistance wire (0.8 to 1.6 ohms). Old Fords mid 60’s up have a built in resistance wire in harness its a “Pink” wire really early cars 56 to 63 had a ballast resistor power out to the 2-pin connectors “Red” wire into the control box harness. The white wire in the 2-pin connector is connected to the "S" terminal on the starter relay. This is used as a cranking indicator to the module, to retard the timing slightly to ease the load on the starter motor.

Did you use the factory harness for the rest of the wires? The green wire runs from the module to the minus coil terminal you can hookup a regular tach there too. The orange and purple wire from the module runs to the pickup inside the distributor. The control module doesn't like heat so mount it away from heat sources. Good luck

Wiring diagram
http://i54.photobucket.com/albums/g108/ ... iagram.jpg

 

[69.5Mav]

it will start and idle, but dies when it gets any throttle

After it dies can you restart it right away.

Sounds like you have lost the main circuet in the carb, i.e. something is blocking the main jet. The car will start and idle with the idle circuet but when you open the throtle to increase power output the idle citcuet can't supply enough fuel and the engine leans out and dies.

 

[jimlj66]

69.5Mav, The car will start right up after it dies. If I work the throttle just right, I can get it to start to rev up, but that's it. It does act like it is starving for fuel. I bought a rebuild kit for the carburetor last fall that I never got around to installing, maybe it is time to do a rebuild.

Bubba, I'm working out of town until tomorrow evening so I can't check the wiring. When I wired the DSII I followed a wiring diagram I found on the net. The car has ran great since I installed it a year or so ago, but it still may not be right. Looking at your diagram I *think* that is how i did it. I'll check when I get home.

Thanks again for the input guys, it gives me something to look for.

 

[jimlj66]

Thanks again for all the input. Mav, you called it!

Last night I checked the wiring and vacuum lines. All looked good. I pulled the carburetor and disassembled it for cleaning. When I pulled the main jet, I found the problem. The tube (not sure what it is called) with the small holes in that should be pressed into the carburetor had fallen out. It allowed plenty of air but no fuel when the throttle was opened up. The rebuild kit don't show this "tube", so I knew it should not have came out when I pulled the jet. I cleaned the parts and used a bit of JB Weld to make sure it would stay in place. About that time my 4 year old grandson showed up to "help", so it had to wait till this morning to finish assembly. After I fixed a couple non related items, I finished the carburetor and the car starts and runs great.

One thing I did find while I had the carburetor apart was the float was set high by about 3/32". How would that have affected the way the car ran?

 

[69.5Mav]

Mav, you called it!

Every once in a while I get something right.

Glad you found it. Now enjoy.

 

[bubba22349]

One thing I did find while I had the carburetor apart was the float was set high by about 3/32". How would that have affected the way the car ran?

Having the float set too high can cause it to be richer and a lower float setting will be leaner. Glad you found the problem so it's running again.