What's wrong with my truck? Fuel? Dies on road

New project, 65 GMC driver. Was a parts runner, kept in good shape, ran great for past 900 miles (two weeks)

Truck has: 327 2bbl, th350, HEI.

Last week I filled up, pulled out on the highway, and around 50 mph/3000 rpm in gasped for air. As soon as I slowed down, it was fine. Put it in 1st, spun it to 6k, then 2nd, 6k again, no problem. High gear, it fell on it's face and slowed to 50. Let off gas, runs fine at 45. a minute later it goes away

Fast forward to today. Driving home from work, hit 50 on the highway, same thing. Now it is getting worse, slowing down to under 40. Pull over, poke the carb, curse at it, smack her around a bit, get back in. Again, up to 40, and it starts gasping. Milk her home 2 mre miles. By the time I get to my street, she won't do 20, and dies at stop signs.

At home, I notice the fuel line is against the radiator hose. I jump in the Lincoln, get steel fuel line, a new filter, a new air cleaner, and put it all on. Line is now far from heat.

Go to the store, runs great, take an off-ramp, and around 30 mph, she gasps again. Dies at the light. Spins over like she jumped time, finally starts. On the way home, I have to keep her at 3k to stay running. Dies as soon as I let off the gas.

Any thoughts? I plan to try swapping the carb tomorrow. Can't do it tonight, need a 4bbl adapter.

 

I would adjust the valves first. I have experienced tight valves on a sbc, acts like that.
Next, internal carb vacuum leak?
3. hei has two circuits in the module, high and low rpm, it could have a bad ground. not likely, but could be a bad pickup
i hate trying to fix drive-ability issues. if its got 0 spark, i can fix it. if it gets 0 fuel, i can fix it. a strange miss that jumps around, shit, i don't know.

 

Same with me. I need someone to drive the bitch with me under the hood.

 

Hey, try checking for a rusty filter, rust in the carb bowl or tank ... maybe you have a cheap thin fuel line somewhere when you put the pedal to the metal the hose flattens out and pinches together causing fuel reduction all of these have happened to me...

Laterrrrrrrrr.......

 

checked that. Truck has all new lines, new tank, and I just changed the filter.

 

I'd check to make sure your fuel pump is pumping and make sure there is no crud in your lines. Sounds like your getting some fuel, just not enough.

 

Sounds a lot like fuel. Check filters and lines as suggested BUT there are often hidden filters in the carb - usually where the fuel line goes in. I had a problem that plagued me for months and then found a tiny little filter inside the floiat chamber of the carb (not evne referred to in the manual) that was chock full 'o crap - see picture below.

 

make sure the coil has the ground strap under it and theres a wire going to it, also check for vacuum leaks, lastly you might want to open the lid of the carb...you might have a jet plugged with something.

 

I have had problems similar to what you describe. First thing i would do is just makes shure the carb is tight on the manifold. Next get it running and start spraying stuff with starting fluid to check for vacuum leaks. If its not that next thing i would think of is dirt on the float bowl.
Also have you checked for strong spark?

 

sure sounds like a vacuum leak to me. if not are you running a mech., or elec. fuel pump? i've had electrics start to wear out, and they slow down. they won't deliver enough fuel for high rpms, acts just like that... then DEAD ON THE ROAD!!

 

new tank....hummmm is the tank or cap vented?

 

Fuel pump............

 

Agreed...

And just because the lines are new... doesn't mean that the tank was 100% clean when you put them on. Check the fuel filters. I had the same problem with my 51.

Mike

 

Could it be the ignition condenser ? ...
Klaz

 

You didn't say what kind of carb you have but if it's a q-jet there is a filter in it where the fuel line connects to the carb. It's not your valves leave them alone. If they do anything they'll get looser not tighter. Inspect those rubber lines good and make sure you aren't leaking any air. If you could disconnect the line at the pump and blow back through the line into the tank with the cap off, and then try it and see how it runs. there is another thing that I had happen to me one time, The fuel pump push rod in the engine was worn off to one side where the pump arm works on it and it would quit pumping. I like to have never found that. I'm betting on trash in the fuel system or the pump playing out on ya. One other thing although I doubt this is it, Is your coil getting too hot to touch? good Luck Stafford

 

Sounds like you have already eliminated dirt/crud, but the flow could be restricted with an object, lint-ball/rag in the tank, pinched line, etc. or sucking air. I had a seep (rust through) in the line along the frame. It stained the area, evaporated, didn't drip on the ground, but was letting air in and the result was kind of like vapor lock, but would go away, just like you describe.

Jack the rear of the car up. Disconnect the line going to the fuel pump, with big bucket under it. The gas should flow real fast. If it starts fast, then slows down.........you got your finger on it.

If not restriction, could be related to the pump, or worn lobe on the cam. In the pump, there's a return spring. If it's not returning the action completely after each stroke, at high consumption, it wouldn't be keeping up with the demand.

 

Really does sound like filter--remember, there's another in the tank on the pickup line, as well as the one in the carb inlet, AND a new filter can clog in half a mile if you got a load of rust and gravel from the bottom of the tank at your last fill up.

 

We have covered problems running before, and there is always an answer. However, it is soooooooooooo frustrating getting to that answer, that often, we just want to toss a quarter in the damed thing and leave it on the side of the road.

So, lets start with the easy things, and work our way to the more difficult problems.

1. Check the distributor cap. Is it on tightly? Pull it off. Inspect really really close for hair-line cracks. This will drive you crazy if there is a crack and there is any humidity outside. Youll really be suprised at the crazy problems this wil create, and randomly too.

2. Rotor, is it there? Is it clean or corroded? Is the contact worn out on it? (its only $2).

3. Coil, this usually works or doesnt work. Not applicable to your problem, but the next easiest thing to check. Points too. If you got points and are unsure, they are cheap and can be bad when brand new. Check the ground, if it losing ground, youll get intermittiant spark. Check on electronic iginition parts if applicable.

4. Spark Plugs. Are they gapped correctly? Too close a gap=Bad, Too much a gap=bad.

5. Spark plug wires. They good? They old? If old replace them, you need to anyway.

6. Vacuum lines to Distributor and carb. They good? Pull them off and blow through them. How about vacuum canister? If its cracked (the plastic ones) replace it.

On to the Fuel System.

7. Fuel filter. Pull it off, blow it out. There might be more than one. Find them all, replace if old. Pull the one on the Carb also. If you have a fuel injected engine or are using a newer tank from such vehicle, it'll have a filter on the fuel pick-up and one on the in-tank pump. (this is the most common problem and possibly shoud be moved to 1st on the list).

8. Fuel quality. Sometimes, youll get bad fuel. It happens if the gas station has tank problems. Drain it, replace. Did you put some of the newer fuel in that is made from Corn? Itll clean out the crud and send it straight into the carb to clog shit up.

9. Fuel lines. these are easy to remove. Pull them off and use compressed air to blow them out. Blow from engine side to the tank side, that way if something is lodged in there, itll blow out, instead of lodging itself in even harder. Are they ran away from heat sources. Vapor loc is a bitch to figure out. Are the rubber parts of them good, or are they collapsing?

10. Pull the tank. If you have crud in the tank, itll start fine when standing still, but will slosh the crud around when moving and suck shit up. The tank isnt that hard to pull, but more difficult than just looking at distributor cap. Thus this step is down here.

11. Check the carb, is the choke set-up properly? Pull a bowl off (if a Holley type) and check the needle and seat and for curd in the bowl. These are very sensitive and a peice of dust will screw up the needle and seat.

12. O2 sensor if fuel injected. Check the wires to it. Replace if necessary.

13. Computerized car? Hook it up the the machine, let it tell you what it wants.

14. Check electrical stuff. If you are using newer technology stuff, then I have seen the 3-4 shift solenoid go out and create havoc on the entire ignition system.

12. If all this fails, get a buddy. Show him EVERYTHING you already did and explain what you did in great detail. Perhaps he can help.

This wont fix your problem, but if you start with the easiest stuff 1st, itll possibly save you money and time.

 

I'll go through all the tips when I get home from work.

It seems to be related to heat. It only happens after the truck warms up fully. Actually, yesterday, it got worse the more I drove it. Last night it was fine until after 20 minutes of running.

This is what made me think vapor lock, but I think I've eliminated that.

Carb is an older rochey 2bbl. Fuel tank is a plastic unit, about 1 year old. All lines from front to back replaced with 3/8th line.

I removed the fuel filter from the carb and put a new inline filter.

I do wonder if some shithead stuck something in my tank. It first happened after a fill-up two weeks ago. I filled up Sunday, drove a few miles, and it happened yesterday. Again, full tank. I tried running without the gas cap, but I get the same thing.

 

I had a similar problem on my ton truck a few years back. The ignition module finally went out and the problem went away. A shop rag in the tank seems like a possibility.

 

Do you have a sock over the pick-up inside the tank?
Since you replaced everything else, I'll assume you also replaced the fuel pick-up, and didn't re-install an old one. Some guys don't replace that because it still reads accurate, but I've seen them plugged with lacquer.

If you don't have a sock/filter over the end of the pick-up tube, you could hae something plugging it off.

I had that problem on my '54--one of EVERY kind of fuel-related problem. Literally, I had every fuel related problem you can have on that stupid car.
One thing I did that was dumb on my part was to use silicone to seal the new sending unit to the top of the tank, and to seal the screw holes. The silicone softened and dripped down into the tank, and would get sucked into the pick-up tube in little chunks. The car would sputter, the draw would stop, the goop would drop off the end of the pick-up tube, and it'd go again.

Might help.
-Brad

 

I had the same problem last may in my '62, it did the exact thing you're describing. It was the fuel pump.
David

 

I once got ahold of an old barn found 40 coupe at the Pomona Swap Meet. It had origional running gear and rat turds in the door jams. Drove it home no problem. Buzzed around the neighborhood in the old beater for weeks, no problem. Then suddenly one day it started cutting out after 5 minutes of running fine, kinda like it was out of gas. Pulled over, cussed and kicked it a few times, she started and ran great for another 5 then the same story. Went through the whole process - checked fuel pump, lines, filter, carb, etc. After much frustration - there was a dead Bee in the fuel tank that would slowly float towards the pick up when the pump was pumping and then drift back home to the rear of the tank when she was off. Impossible to find under normal thinking.

 

A dead bee? This thread is getting out of control

I didn't do the tank job. Previous owner did it. Truck was a daily driven parts chaser.

I'm heading home to check the fuel system front to back. I'll stick a blow gun in the lines and shoot the sock off. Hopefully it's a line that rubbed a pimhole or the pump. I'd rather not drop the [full] tank.

 

Five bucks says it's the fuel pump.

 

Looks like alot of work towards the fuel which more than likely it is related, a plugged muffler will send out those symtoms, have you heard of the banana up the tail pipe or potatoe

 

WE AINT GONNA FALL FOR NO BANANA UP THE TAIL PIPE!!!!!!!!

 

I don't know it worked in Beverly Hills cop with that Eddie guy

 

Gas cap

 

HEY REPOMAN JUST HIT 666 POSTS , DO YOU THINK THAT HAS ANYTHING TO DO WITH IT!?!?!?!?!?!