Engine cutting out at speed

[MartyG]

I'm at a loss of what's causing this. Aldi driving along at around 40 45 miles an hour and ask her maybe 3 minutes of sustained speed the engine just sputters and stalls. I've immediately pulled over without adding any extra gas and I'm seeing there is fuel in the fuel filter. My carb is a new Holley.
Typically starts right up afterwards

 

[B RON CO]

Hi, it sounds like you are running out of gas. You have to check the float level ( see Holley website). And probably check the fuel pressure. Holleys like 6 PSI. Good luck

 

[DirtDonk]

Could be an old weakening fuel pump not able to keep up. Or could be the new carb's float height settings are off.
Or, it could be another fuel filter maybe? Is there any chance that your rig has a PO installed filter somewhere in line?
That's what happened to one of my trucks one time. Six months after I bought it I started coughing and sputtering on the highway when there was even the slightest incline. Then on flat road. Then at lower speeds. Eventually would hardly run.
That's when I found the two additional filters the original owner had installed under the truck.

With today's fuels too, it's hard for some pumps to get their full life expectancy. Being you're in CA though, the fuels are not as hard on stuff. But how old is the pump? They all die eventually?

Hopefully it's as simply as a fuel issue. It's still possible it's something to do with ignition, but my first buck is on fuel delivery.

Good luck.

Paul

 

[blubuckaroo]

First make sure your fuel tank vent works.
Next, I'd test the fuel pump's vacuum. Most vacuum gauges have a fuel pump scale on the gauge face.

 

[bronkenn]

Depending on what type of fuel/filter pickup you have in the tank, but it sounds like what happens when you have debris in the tank. Starts up, runs a while till it sucks the junk to the fuel line/filter then quits, let sit and the junk falls away from the fuel line/filter in tank and starts up again. Repeats this every time until you remove the junk out of the tank. Ken

 

[SHX669]

what type of fuel pump ? I had an electric pump that would get warm and intermittently quit working.

 

[edmedlin]

I had that problem and it was the fuel filter. It didn't look dirty at a glance, but the folds in the filter were almost completely clogged.

 

[MartyG]

Hey Thanks all. Fuel filter is new...so that ain't it. I haven't checked for additional one, I'll look but I don't think so. It might be an adjustment on the Holley.

 

[SHX669]

Keeping in mind that the experts say " 75% of all carb problems are something else " . You say " sputters and dies " that sounds like a fuel issue. If it was a bad coil ground , bad tach wire , bad distributor ground , bad magnetic pickup , bad MSD 6 al box, bad main fusible link then it would just immediately die no sputtering.
Do you have two tanks and using the factory switch over valve under the seat ? I've had those plug up . Do you have a rotary vane electric fuel pump? I've seen those have issues if not mounted below the fuel tank ; run dry then have to wait for fuel to refill fuel line . Typically if that issue then there is less problem when the fuel tank is full .
Just throwing out a few other things to check besides the carb .

 

[MartyG]

Keeping in mind that the experts say " 75% of all carb problems are something else " . You say " sputters and dies " that sounds like a fuel issue. If it was a bad coil ground , bad tach wire , bad distributor ground , bad magnetic pickup , bad MSD 6 al box, bad main fusible link then it would just immediately die no sputtering.
Do you have two tanks and using the factory switch over valve under the seat ? I've had those plug up . Do you have a rotary vane electric fuel pump? I've seen those have issues if not mounted below the fuel tank ; run dry then have to wait for fuel to refill fuel line . Typically if that issue then there is less problem when the fuel tank is full .
Just throwing out a few other things to check besides the carb .

Thanks for that info...
It's a stock fuel pump... Two tanks, with the factory switch, guess I can check that. Ah...the fun of a 40 year old vehicle.

 

[Broncobowsher]

The fuel filter full of fuel doesn't mean the fuel is actually flowing. There can be zero pressure and zero flow in the line and the filter will still have fuel. The times it goes empty is when you run out of gas and the fuel pump is pumping air through the lines.

Put a fuel pressure gauge after the filter and tape the face of the gauge to the windshield and go for a drive. See if you are loosing fuel pressure. If not, look at the ignition system. Coil or module may be overheating.

If you loose fuel pressure, check again before the filter. Still dropping? Tee gauge (reads vacuum as well, right?) into the fuel pump feed. What you are looking for this time is excessive vacuum where the pump is being starved for fuel. This could be a pinched line, collapsed rubber section, clogged in tank screen.

Vacuum doesn't really pickup at speed and the pressure drops off, the pump is probably dying.

 

[SHX669]

Good luck
ya Bronco owners need to be more mechanics than technicians - lol .
At least the float levels are easy to check

 

[Hotrodjohn]

Like everyone says, sounds like fuel issue. I recently had mine sputtering under a load, although it never died, and it turned out to be the coil going bad. I would've sworn it was losing fuel the way it was acting. New coil and no problems since. Does you 73 have original points or did you put electronic on it? Coils and modules can do things that mimic fuel issues.

 

[El Kabong]

First make sure your fuel tank vent works.
Next, I'd test the fuel pump's vacuum. Most vacuum gauges have a fuel pump scale on the gauge face.

x2 on checking for proper venting. If air can't get in the tank to replace fuel as it is pumped out, vacuum builds in the tank to the point where fuel cannot be pumped anymore. The quick test is to run it for awhile, then pop the gas cap open & listen for a rush of air.

 

[Broncobowsher]

It's not going to be pulling enough fuel out of the tank in 3 minutes to make venting an issue.

 

[MartyG]

Like everyone says, sounds like fuel issue. I recently had mine sputtering under a load, although it never died, and it turned out to be the coil going bad. I would've sworn it was losing fuel the way it was acting. New coil and no problems since. Does you 73 have original points or did you put electronic on it? Coils and modules can do things that mimic fuel issues.

I have an HEI Dist now.
Thanks

 

[MartyG]

x2 on checking for proper venting. If air can't get in the tank to replace fuel as it is pumped out, vacuum builds in the tank to the point where fuel cannot be pumped anymore. The quick test is to run it for awhile, then pop the gas cap open & listen for a rush of air.

Hey...never thought of that...I'll try it TY