Old GM 350 engine suddenly quit

[Gryphon Rider]

My '81 GMC (350 4BBL) suddenly quit today.  The tank was getting close to empty, but not as low as I've had it many times before.  I was about 2-300 metres from the gas station and the engine quit.  I pulled over and parked.

Added a gallon of gas.  The fuel gauge went up a bit.  Cranked and cranked, fast.  No go.

Took off the air cleaner and held open the butterfly valves while my wife quickly floored the gas.  No fuel squirting into venturis, no fuel smell.

Pulled a plug and checked for spark.  Had spark.

The fuel pump is securely bolted to the engine.

This truck gets driven every day, and gets fueled regularly.  It was -20°C when I drove it to work.  It was -10°C when it broke down.

This seems to be a fuel problem.  What should I be looking at first?  Do fuel pumps fail instantly?  Does a fuel filter instantly plug?

[f6john]

Add more than a gallon???? Pour a little gas down the carb.

[baldo]

That's pretty cold, 14F...Could it just be frozen lines? Tank levels that low and that cold can be a bad combination....

[The emperor has no clothes]

The old diaphragm fuel pumps can fail instantly. I don't know if they were still using those in '81 though.

That's pretty cold, 14F...Could it just be frozen lines? Tank levels that low and that cold can be a bad combination....

Usually any water condensation doesn't freeze in the line while it's running. It's when it sits that usually happens.

[Beardo]

That's pretty cold, 14F...Could it just be frozen lines? Tank levels that low and that cold can be a bad combination....

Pffft...that's not cold. 

Maybe running your tank low...debris in the bottom of the tank plugged the fuel filter?

[Hooter]

What John said. If you have spark, it is like you suspected, a fuel problem.  Fuel pumps do take a dump but put some gas line antifreeze (Heet or the like) in it when you add more gas. To make sure dump the gas down the primaries, I would bet it will fire.

That's pretty cold so if there was any water in the tank it could have frozen up too. In a Holly carb there should be a stone filter behind the fuel line where the fuel line screws into the carb. That should be there unless someone put an in line in and took that out. You can also take the fuel line off at the carb and turn the motor over to see if the fuel pump is working. Use a coffee can to catch any gas. Takes 2 people.

[signart]

Put more fuel in, maybe add your favorite dryer and prime the carby. If your fuel pump is weak, it may have a hard time picking it up after running dry. I just put a pump on my '81 350 last weak, they're only 20 bucks. A Z pulled 3 wrong pumps before giving me the right one.

[baldo]

That's pretty cold, 14F...Could it just be frozen lines? Tank levels that low and that cold can be a bad combination....

Pffft...that's not cold. 

Maybe running your tank low...debris in the bottom of the tank plugged the fuel filter?

Pretty cold for here on the Banana Belt...lol...we're due for a two day freeze starting tomorrow. Low of 5 or so. Makes it a bit uncomfortable working outside at night.....

Then it's back to 40 and maybe 50. That's riding weather!

[Beardo]

Yeah, I know that sounds cold to someone from down south...but it's not, as far as fuel freezing. It's been -30 here for the last week, my truck has started fine, no gas line antifreeze in it.  Unless you had water in the tank, but water being heavier, that likely wouldn't be in the remaining of the tank, it would be long gone.

Try the fuel filter first. Easy to check, cheap to replace. Pump would be next.

[Gryphon Rider]

Thanks for the replies, guys.  After I tow it home (1/4 mile) I'll pull the fuel line off of the carb (Quadrajet, not Holley) and see if the pump is working.  If not, I guess I'll get a new one, along with a new filter.  If it works, the fuel filter is easy to replace, but it's odd to instantly plug up.

I think it odd to have frozen fuel.  The truck ran in colder weather, and I think the fuel they supply in winter is formulated to prevent freezing.

[The emperor has no clothes]

Thanks for the replies, guys.  After I tow it home (1/4 mile) I'll pull the fuel line off of the carb (Quadrajet, not Holley) and see if the pump is working.  If not, I guess I'll get a new one, along with a new filter.  If it works, the fuel filter is easy to replace, but it's odd to instantly plug up.

I think it odd to have frozen fuel.  The truck ran in colder weather, and I think the fuel they supply in winter is formulated to prevent freezing.

I don't think it was a freezing fuel problem. But as far as the fuel formulation, it really matters not much. With a half empty tank and cooling weather condensation forms in the tank. The emptier the tank, the more the problem.

[Beardo]

Thanks for the replies, guys.  After I tow it home (1/4 mile) I'll pull the fuel line off of the carb (Quadrajet, not Holley) and see if the pump is working.  If not, I guess I'll get a new one, along with a new filter.  If it works, the fuel filter is easy to replace, but it's odd to instantly plug up.

I think it odd to have frozen fuel.  The truck ran in colder weather, and I think the fuel they supply in winter is formulated to prevent freezing.

I don't think it was a freezing fuel problem. But as far as the fuel formulation, it really matters not much. With a half empty tank and cooling weather condensation forms in the tank. The emptier the tank, the more the problem.

True enough. 

Although if parked outside in the cold, condensation shouldn't be an issue. In and out of a heated garage, yes.

[The emperor has no clothes]

Thanks for the replies, guys.  After I tow it home (1/4 mile) I'll pull the fuel line off of the carb (Quadrajet, not Holley) and see if the pump is working.  If not, I guess I'll get a new one, along with a new filter.  If it works, the fuel filter is easy to replace, but it's odd to instantly plug up.

I think it odd to have frozen fuel.  The truck ran in colder weather, and I think the fuel they supply in winter is formulated to prevent freezing.

I don't think it was a freezing fuel problem. But as far as the fuel formulation, it really matters not much. With a half empty tank and cooling weather condensation forms in the tank. The emptier the tank, the more the problem.

True enough. 

Although if parked outside in the cold, condensation shouldn't be an issue. In and out of a heated garage, yes.

My first 4 wheel vehicle was a '59 Chevy truck with a 283. Great truck. We never had a garage growing up, and even if we did I would have not got a spot. But when we would get big fluctuations in weather from say 20* to -30* it would have condensation issues. Now this was in the early 70's and gas was probably not as consistent as nowadays. I learned it was best just to keep her filled up vs. having to pull the big heater out and thaw out the line. As I'm sure you are well aware of working on vehicles at -30* sucks big time.

[Beardo]

I hear you.

When I was a teenager, I had a '79 Mercury Capri...I had to carry gasline antifreeze with me, whenever I hit a snow drift, the snow would hit the engine, steam, then promptly freeze in the carb. Went through gallons of antifreeze with that car.

Gryphon is right though. They put additives and antifreeze in the gas up here, that should help with condensation vs back then. (One of the few things that have improved with respect to vehicles since back then   )

[Patrick]

Fairly simple. You either lost the fuel pump, fuel filter or if there is a bazillion miles on it it could be a timing gear/chain.

[Rams]

Fairly simple. You either lost the fuel pump, fuel filter or if there is a bazillion miles on it it could be a timing gear/chain.

Fuel Pump is my semi-educated guess.   While frozen condensation is always a possibility, I'm betting that fuel pump failed based on what you've told us.

[Firefighter]

Be careful pulling the fuel line and cranking the engine, if you squirt gas all over the engine you might build a fire! I would add more gas (several gallons) then crank the engine. I used to dribble gas down the carb vent and fill the float bowl, then it will run 20 seconds or so. Most likely a fuel pump if not just out of gas! Lots of luck!

[Jersey mike]

You said it's a Rochester Quadrajet....if you were empty and the carb ran dry, prime the carb with a little fuel in the primaries, add about 5 gal fresh fuel and pump the gas pedal.

Having a spray can of ether won't hurt either if she still won't fire.

Check the fuse for the electric fuel pump.

As other said too, you could have pull crap up and blocked the fuel line or the jets.

[old2soon]

With this 10% ethanol fuel you don't need the alcohol additives anymore I M H O. Not sure on an 81 but if the cam actuates the fuel pump the diaphragm might have taken a dump. Again-I M H O-git a New fuel pump or a rebuilt-winter comin on wouldn't mess with a used one. RIDE SAFE.

[Ramie]

I go with what F6John and Jersey Mike said, every time I've run out of gas with a quad carb I've had to prime the carb.

[Jess Tolbirt]

spray starting fluid into the carb and see if it will fire,, if not you lost the timing chain/gear...
the fuel pump is activated by the camshaft..

[..]

Am I correct in saying that a lot of older fuel pumps didn't like operating above the gas level in the tank cause the gas helped cool/lubricate the pump?

Consistently running the gas low in the tank causes problems.

[Gryphon Rider]

My fuel pump is a mechanical one, attached to the engine, like this one:

[The emperor has no clothes]

My fuel pump is a mechanical one, attached to the engine, like this one:

Looks identical to ones Chevy used going back to the 50's. I don't know if that is your problem, but I do know they can fail suddenly.

[f6john]

Am I correct in saying that a lot of older fuel pumps didn't like operating above the gas level in the tank cause the gas helped cool/lubricate the pump?

Consistently running the gas low in the tank causes problems.

   True of in tank electric pumps

[Cracker Jack]

There is a rod in the block that extends from the cam down to the fuel pump activation arm which will slide down when the old pump is removed and block installation of the new pump. The rod must be held up out of the way to allow the new pump to be installed. I use a heavy grease (wheel bearing) on the rod to create enough friction to hold the rod up.

[Challenger]

There is a rod in the block that extends from the cam down to the fuel pump activation arm which will slide down when the old pump is removed and block installation of the new pump. The rod must be held up out of the way to allow the new pump to be installed. I use a heavy grease (wheel bearing) on the rod to create enough friction to hold the rod up.

Or you could remove the bolt on the front of the block, install a longer one and gently lock the push rod into place, Remove old pump and install new one. remove bolt and reinstall the original plug bolt. On limited access engine bays, this is a lot easier than trying to get the rod pushed back up. 

[Paxton]

QUOTE:"spray starting fluid into the carb and see if it will fire..."  +10

I had my mechanic install an electric fuel pump out of junk yard Nissan. 
I imagine others would do the job. Now I have both(mechanical and electric. working in concert.

[Gryphon Rider]

It got up to 0°C today (but very windy), so I tried again and no fire. I disconnected the carb fuel line from the pump, and had my daughter turn over the engine. No gas came shooting (or even dripping) out. Removed the fuel pump and noticed not much movement to the arm. The new pump looked identical except the arm stuck out more and had movement. After a lot of verbal encouragement to the carb line nut, it finally aligned and tightened properly after loostening the fuel pump bolts. Ten seconds of cranking and it fired up and stayed running. Yay!

[The emperor has no clothes]

Awesome !

[Rams]

Excellent! 

Glad to learn it was a simple fix.   Just remember, if it's got tires, there's always gonna be something else. 

[Gryphon Rider]

Just remember, if it's got tires, there's always gonna be something else. 

Tell me about it.  This morning both headlights failed to light!

[john]

                I love a happy ending ...