as before 53 f-100 460 engine. a/c... elec fans on radiator

truck starts fine. volt meter on dash reads over 12vdc at idle and right at 14 after 2000 rpm. brand new otima battery
drove today 5 miles surface road 35-45 without a/c then 10 miles on freeway 60-70 with a/c
entered chic-fil-a drive thru line (which was around the building so approx 10 minutes at idle with a/c and elec fan on

just as i start to pull away from window it stumbles and stalls... helpful chic guys/gals helped me push it to park space

tried to start..would turn over but not fire off... voltmeter reading less than 12 volts drops lower with starter engaged
let it set a few minutes tried again... it would try and start but stumble and die.. giving it gas did not rev engine

few minutes later tried again and started but running rough... till I could feather the gas pedal and get rpms up to 2000 it was rough running
finally smoothed out when alternator kicked in..

I looked in carb when it wouldn't start and opening throttle shows gas squirting as normal...so it ain't starving for gas...it's electrical.

I thought the new battery had fixed it but... evidently not. The battery is new . Alternator new. All the wiring is new and gauge is larger then
spec'd. all connections clean and tight. My head is sore from hitting the same wall...

more ideas please!!!

john

 

What kind of alternator is it? Is it a 1-wire?

 

yes it's a cvf racing one wire

 

Maybe you should try a smaller-diameter pulley on it. It should be producing 13+ at idle.

 

Sounds like a little hot soak/idle voltage draw. Even the GM based alternators used a load sense wire for high loads at point of draw and ignition activation from GM. 1 wire originally designed for low load agricultural type applications. If you don't have one sorry for the misdiagnosis and 1 wire rant. Carbs get a little unhappy when hot idling. Ford had throttle kicker for AC use and temp sensor would kick in around 210 and switch vacuum advance from ported to intake bring idle up a few hundred rpm. Just out of curiosity what type of ignition system are you using and what type of starter?

 

ignition is performance distributors DUI alternator is a cvf racing one wire 100 amp

 

I am not a fan of 1 wire ALT's but I dont see that as a issue if it turns over but will not fire.
The battery supplies power to the starter to crank and it was cranking from what I just read.
The ALT only puts power back in the battery when running so not the ALT.

You did the first thing I would have checked, gas at the carb when throttle was moved and that was good.
So we have gas and air from cranking did we have spark?
You need to check for spark when this happens.

What are you running for IGN system?
Start from the key / wiring out to the dist., wires & plugs.
If you are running a DSII system I would say the IGN box is going bad.
If you get any replacement parts ask for the top of the line parts.
They are a little more money but if you dont ask for them they give you the cheap parts and they dont last.

As a side note you do have a thick gasket or a insulating plate under the carb right?
Dave ----

 

I would check the dizzy coil for a good ground connection, some of the Davis Unified Ignitions have bad coil to ground connection.

 

So it is a HEI set up

Yes I remember something about paint on the outer steel of the coil so it did not make a good ground.
Why they painted them who knows as GM never did.
Dave ----

 

A lot of electronic ignitions just shut down when voltage gets below a certain point. It sounds to me like your alternator just isn't keeping up. I have a GM 1-wire and it charges from 500 RPM -on. I don't need to rev it to get it to kick-in.

 

I'm leaning towards vapor lock/fuel starvation due to heat. I went through this exact same thing you're experiencing on my 33 Hot Rod. Chased it for months, very frustrating. You may not be running hot enough to "boil" the fuel the point of total evaporation in the line but it may be to the point of vaporizing the fuel and causing an air lock to the carb.

I too had fuel squirting into carb when the 33 stalled so I too was looking at electrical because I thought it's getting plenty of fuel.

Had a buddy explain to me that once vapor forms in the line it causes an airlock in the line which chokes off the vehicle due to starvation. Once the vehicle stalls the fuel pressure in the line refills the float bowl due to pressure so when you go to check the carb, gas will squirt as normal. I thought he was full of s**t, but turns out he was right.

I solved my vapor lock issue by doing the following:
1) Added a 1/2" fiber spacer for between the carb & Intake to insulate the carb from direct intake heat
2) Added 15 feet of DEI thermal tape for insulating the fuel lines by the engine, anything close to the heads, exhaust and I also insulated the electric fuel pump
3) Added a WIX 33040 vapor separator fuel filter with a return line (also insulated this filter with the thermal tape)
4) installed 25 ft of 1/4 vapor line so I could run the vapor line from the 1/4" fuel return nipple on WIX filter back to the 1/4" port I installed on my fuel tank.

What the WIX 33040 does is it provide an outlet for any vaporizing fuel and forces that back to the tank via the 1/4" vapor line verses causing an air lock and cutting off the fuel so the fuel can continue into the carb via the 3/8" nipple on the filter.

After installing all this I can run my 33 all day long on 100 degree weather sitting at idle or cruising without issues verses before I could go about 3 miles.

I also only now run 91 in all my classics because 87 or 89 with ethanol has a lower vapor point than higher octane fuel.

I also did the exact same thing to my 55 as preventative maintenance

Link to the filter I got on amazon -->
Jim

 

Jim you did almost what Ford did on the 80's 460 trucks with the hot fuel bypass.
They used a Tee in the supply after the pump but before the carb with different orifice sizes depending how hot where you were.
This kept the fuel moving so it could not get hot.

AMC also used that filter on some of its cars (Gremlins & Hornets) and Jeeps.
It is not vapor but fuel that is moving in that line.

Now I got a question?
If the carb refilled because of pressure in the line pushing the fuel in, the motor should then restart no?
Why is it not restarting if you have gas squirting?
Dave ----

 

My guess is that may be contributed to heat soak on the coil but without being there in front of the engine to see the set up I'm just guessing. I have this on one of my classics, the car run great when cruising around but if we stop for ice cream and the car sits for a bit it takes a while to restart.

Jim

 

moe, I think you mentioned that problem earlier in this saga and I corrected and yes, coil core was painted black...cleaned both terminals and tightened it all back up
thought that cured it but Murphy was only jerking me around...

I only have that standard 1/8" spacer under carb...will remedy that tomorrow and today I ordered an undersized alternator pully... gonna try that before ordering a 140 amp unit
that is 200 bucks.

j

 

That dose sound like heat soak but not of the coil but the carb.
On v8 motors the carb sits right in the center of all that heat and heat rises and heats the carb.
This heat then boils the fuel in the bowl(s) and because the fuel is heavier than air goes to the floor of the intake manifold.
Now when you go and start it it just cranks till it clears out the fuel vapor just like if the motor was flooded.
I know when this will happen as I can smell gas fumes.

Some times this is worst with the brand gas you get and like most we get it from the same station.
Next time try a different brand of gas. If you normally use xxx brand next time get it from zzz brand to see what happens.
It has also been said to add a little diesel to the gas at fill up but I have not tried this as I dont really have this issue with my 300 six as the carb sits out to the side of the motor not over heat but I do get a little heat soak and I just hold the throttle wide open till it fires up.

The not charging is 1 BIG reason I would never go 1 wire ALT as I have heard to many times of batteries not charging even that the ALT was putting out at the out put stud.

The 1 wire senses out put at the out put stud and sees it is charging and kicks back the volts needed to charge the battery.
If you look how the ALT wiring was from the factory the sense wire was tied in to the main feed wire into the cab.
This was far enough away from the battery that the ALT would not charge with out over charging.

If you could run that sense wire even back to the battery post would be better than at the out put post on the ALT.
A higher out put 1 wire ALT is not the answer.
Dave ----

ps I dont know why some have issues and others do not?
Guess some get lucky