67 200 CID will not idle

[oldtown]

My 67 Mustang with a 200 CID six, will not idle when it is warm. The story started when I backed it out of the garage, and noticed clear liquid on the garage floor. It was gas. I looked underneath the car , and gas was dripping from the fuel pump.

I replaced the fuel pump with a Airtex brand from the local auto parts store. That is when it started not idling when the engine is warm, and the choke is fully open, It starts great when it is cold, and the choke is closed. It goes to fast idle and runs smooth. I did some research, and some people have had problems with Airtex fuel pumps. I ordered a fuel pump made by Carter. People seem to have had good luck with this pump. The new fuel pump did not change anything.

The engine ran great before the fuel pump was changed. I replaced the fuel filter, that did not do anything, I cannot find a vacuum leak.

It has a Autolite 1100 carb that has been rebuilt by Pony Carbs 2 years ago. It has not had any problems before this. I have to adjust the idle screw to max just to keep the engine running. It surges rpm's up and down. The mixture screw has little effect. If you put it in drive, it dies.

If I manually move the choke toward the closed position, the engine rpm increases. It is 76 degrees outside, and the engine is warm. Shouldn't the choke be fully open? The temp gage shows about 1/4 in the warm area. Should I adjust the choke? It ran great all summer, and fall.
Any ideas?

 

[JackFish]

Have you got a spare good coil you could swap in?

 

[bubba22349]

You may want to pull the carbs top off there is chance that a chunk of crud has lodged in between the needle and seat when fuel pump started leaking. Choke should be fully open when it's fully warmed up and with the linkage is pulled off the fast idle cam (at lowest point). Also is the chokes hot the air tube hooked up?

 

[Frankenstang]

I have to adjust the idle screw to max just to keep the engine running....
If I manually move the choke toward the closed position, the engine rpm increases.

That would suggest to me it's starving out. Check the fuel delivery by FIRST disconnecting the coil wire then take the fuel line loose at the carb and run it into a small (preferably see through) container while cranking the starter over. Should get a steady pulsing delivery of fuel. If not trace the line back from there. If okay, I'd suspect the carb as bubba suggested. FSM state min. fuel delivery should be 1 pint in 30secs. Good luck

 

[powerband]

You may want to pull the carbs top off there is chance that a chunk of crud has lodged in between the needle and seat when fuel pump started leaking. Choke should be fully open when it's fully warmed up and with the linkage is pulled off the fast idle cam (at lowest point). Also is the chokes hot the air tube hooked up?

> Opinions and @%#&**, we all 'got one....

I'm with Bubba ( ), Sounds like the FP replacement stirred up some latent crud and now it's reaching or inhabiting the carb. A thorough carb cleaning and a cheap clear filter before the carb is my suggestion.

Have Fun

 

[Frankenstang]

> Opinions and @%#&**, we all 'got one....

uh ....translation: Welcome to the Ford Six Forum! :mrgreen:

 

[oldtown]

More info.

It is not the fuel pump, tried several. I put a tach on the engine, and started it while cold. The rpm's were about 1800. The choke slowly opened , and I watched the rpm's slowly fall, at about 10 minutes, the rpm's slowly fell until it got about 800, and it dies. It runs smooth while cold at fast idle, but begans to run rough as the rpm's fall.

This all started from a leaking fuel filter. There is a inline fuel filter at the carb, I can't see how trash could have gotten into the carb.

I am out of ideas.

 

[Frankenstang]

The rpm's were about 1800. The choke slowly opened , and I watched the rpm's slowly fall, at about 10 minutes, the rpm's slowly fell until it got about 800, and it dies. It runs smooth while cold at fast idle, but begans to run rough as the rpm's fall.

When choked the engine is receiving less air than when the engine is warm and unchoked. This makes for a much richer running condition (as needed when cold) and allows you to get under way while the engine warms up. As the engine warms and the choke opens and the amount of air pulled into the engine at idle increases making for a more lean running condition as needed once the engine is warm.

In your case once the engine is warm and your choke is fully open, it still appears to be leaning (starving) out of fuel...insufficient fuel. Just as bubba described junk can be stirred in the fuel bowl of the carb during the changing of a fuel pump (or even filter) and clog the needle valve opening, idle passage etc. It could also be junk stirred or picked up from the fuel tank. Verifying the correct and consistent min fuel flow rate eliminates the 3/4 of the entire fuel system as problem, isolating it to the carb...and takes very little time to do. For example eliminates the possibility of...old rubber fuel lines have been know to collapse internally under the pressure of a new fuel pump.

You have insufficient fuel delivery (restriction) somewhere. Normally you would increase the mixture screw to alter the lean/rich mix at idle, but you've said that has no affect (and would not at 1800rpm as you are out of the idle circuit...throttle plate too far open for idle circuit to receive vacuum source for fuel delivery).

The inline fuel filter of an 1100 that attaches to the carb body is notoriously porous and known for letting too big of particles get past...which is why PB suggests running a paper element fuel filter (Fram G2 or preferabley napa equivalent) ahead of that. You're able to see the rpms jump when you manually close the choke butterfly because then the engine is receiving less air (manually richening...to a more proper ratio) and is no longer starving out.

EDIT: Conclusion...If fuel delivery is verified sufficient and consistent...rebuld the carb as suggested.

 

[oldtown]

I have been able to get the engine to idle 3 times. Each time I drove it many miles, and everything is great, I turn it off, and immediately it will not idle. The fuel filter is screwed into the gas inlet of the carb. I have put Techron in the tank several times. I put a bottle in when this started.

Today I watched the tape Pony Carbs sent with the carb. The tape has a section on tuning a Autolite 1100 carb with the 200cid six. The speaker says get a vacuum gage, attach it to the vacuum manifold. Adjust the idle mixture until the is max vacuum, about 20 inches. I did that. You can see small changes on the gage, that you cannot tell by listening to the RPM's. I did that.

He also recommends not using a timing light to sent timing. He says adjust the distributor until the rpm is maximum. I did that. If it pings, slightly turn it back. I drove the car 20 miles, up to 70 mph. Ran great, never had any idle problems. Ran around town and stopped at lots of red lights. Ran better that it ever has. I brought it back home, and turned it off. I restarted it in a couple of minutes, won't idle. Would not idle 2 hours later. Pushed it into the garage.

I pulled the top off the carb to see if anything is inside. It was clean. Sprayed it with carb cleaner anyway.

Doesn't seem to be vapor lock, but maybe.

I only run 93 octane gas, that is what Pony Carbs recommends.

Confusing. I'll call Pony Carbs in the morning and see if they have any ideas. I really don't want to sent the carb back, and they find nothing wrong.

 

[Frankenstang]

How many turns out is your idle 'mixture' setting?
When you are able to get it to idle, what is curb speed idle rpm?
When it does idle, is it always at a fast idle setting (ie above 700 rpm)?
Do you know what the timing is currently set at, actual degrees? (over advanced timing can make for hard starting)
What method do you employ to get it to start and idle when you've been successful? (foot to the floor, pump once, twice, etc)
Have you adjusted the choke?

BTW did you ever check the fuel delivery rate?

 

[JackFish]

I only run 93 octane gas, that is what Pony Carbs recommends.

This is stupid advice unless you have a high compression engine.

Because the issue seems to be heat-related it could be electrical.

 

[Frankenstang]

Because the issue seems to be heat-related it could be electrical.

+1 Ignition should definitely not be ignored. As for Jon at Pony, because these older one piece style pulley-balancers have been known to slip, he's decided 'none' are reliable. A bit of a leap, eh? However, some prefer headlong, fell swoop decisions to systematic or logical diagnosis :roll:

 

[oldtown]

I know what is wrong. I replaced the fuel filter with a inline Fram G2 clear filter. The car started right up, the container was about 80% full. The vacuum was at 20 inches.I watched it until it got up to temperture, Slowly the fuel flow slowled, the vacuum slowly fell, and the RPM's slowly decrease. Finally the flow slowed to a small trickle at about 600 RPM's, and it died.

Why? I have tried a Airtex pump from Autozone, and it now has a Carter pump. Hard to believe they both are bad. Why does the flow slow with a mechanical pump, as the engine comes to full temp?

What kind of pumps have you guys used?

 

[ludwig]

The problem might be even farther back in the fuel system. Check the fuel intake in the gas tank. It may be slowly crusting over with debris that has sunk to the bottom. This happens slowly. Often it happens at highway speed. The car dies from fuel starvation, sits for a while and then starts back up when the contaminating parts fall away from the screen at the fuel inlet.

The tape from Pony is absolutely helpful on first startup. From that point on, you are allowed to use a timing light and dwell tach. Just don't tell Jon. Oh, and don't go and call them for information on mods you may have done over and above the Pertronix. They build: stock or reengineered stock and nothing else. Period. Don't ask. No! Got it? I can live with that. He was very helpful to me. Just don't ask about a non-standard application. No. Don't. NO!

You might want to mark TDC with a white pen on the top and sides of your own timing ring. It may or may not have slipped. Once you have TDC, then you can proceed to the timing light and such. It actually does help you make fine adjustments once everything is going well.

However, if it is an electrical problem, the parts you need are not particularly expensive. My thought is that it could be the coil, being as it is anchored right on the block and heats up.

 

[69.5Mav]

Sounds to me like your engine can run if you keep the RPMs up above idle. If youve got enough fuel flow to run the engine above idle youve got enough fuel flow to idle.

I believe your idle circuet is plugged. Rust in the tank can get past the carb fuel filter and plug the idle circuet, ask me how I know. With today alcohol fuel blends lots of varnish that trapped sediment in the tanks is getting dissolved allowing the sediment to get picked up and transported to the carb.

As a preventative add an inline paper filter to the gas line, I see you have already done that, if it gets plugged frequently think about having the tank boiled out and sealed. I did this to my 72 Maverick tank and it made a world of difference. When I removed the tank it had over a gallon of varnish chunks from 3/8 to 1/2 inch thick. It would have taken forever to filter that lot by replacing fuel filters as they clogged.

 

[oldtown]

I called Pony Carbs. I talked to a tech, he agrees that the idle circuit has trash in it. He said it is difficult to clean without special tools. He advised to send the carb to them for eval.

I took the air horn off twice, and cleaned all I could, but it did nothing. I pulled the carb and shipped it to Pony Carbs on Friday.

 

[Astrowing]

I have found that you have to dissassemble the carb and soak it in cleaner followed by blowing it out with compressed air. The spray cleaners don't do the job with the small idle passages. The carb on my 352 had an idle passage clogged on one side so it was only idling on every over cylinder since the intake manifold on that engine is a dual plane. I was also starting with a professionally rebuilt carb that I assumed was in good shape. It runs beautifully now with a thorough cleaning.