Trouble diagnosing problem

I'm having a bit of a problem with my 73 Duster. 360 engine. Stock carb.

I bought it last Saturday from a really nice guy who lives about 83 miles away from me. He said he filled the tank for me but on the way home I "ran out of gas" with about 24 miles to go

I put that in quotes because I seriously don't think I actually did run out of gas now. When it happened I took off the air filter and tried to squirt gas into the carb but nothing came out. It took about 2 1/2 hours to get to a gas station and fill up my little 2ga gas can and get back to the car. I poured 2 ga in squirted a bit in the carb and drove to the gas station. I expected to put quite a bit of gas in but it only took 8 gallons before overflowing.

This got me thinking maybe it only has a 10 gallon tank. But I texted the guy and he sent me the part number for the new tank he installed from custom industries. It's a 16 gallon tank. The tank looks brand new AND I can't find a single 10ga tank manufactured for the Duster ANYWHERE. They don't appear to exist. Additionally my tank matches the measurements of the model he says he bought.

So probably not a 10ga tank and probably didn't actually run out of gas. I start thinking bent or miscalibrated sending unit, maybe the wrong unit altogether.

I took a pic of the odometer when I filled it up. I then drove home and then drove my wife around a bit before we went home she wanted me to fill it up again fearing we would run out of gas

So I go to the gas station and it only takes 4.84 gallons before it overfills. I take another pic of the odometer and a little math tells me I had driven 88 miles on 4.84 gallons of gas. Not bad.

I drove the car again for two days just to and from work plus a little detour due to traffic. Then tonight the wife and I are stopped at a red light and the car "runs out of gas" again. Dies. Cranks but wont start.

Push it across the intersection to the gas station and it only takes 5 gallons of gas before overflowing.

Head home pull into driveway put it in park and it starts chugging then dies. Again strong crank no start. I wait 30 seconds or so frustrated then try it again and it fires right up. It has a mechanical pump so my thought is maybe vapor lock. Especially since it's been over 100 degrees Fahrenheit the last few days.

What are your guys thoughts? This is the same car with a non functioning gas gauge at the moment.

Will an electric fuel pump solve the vapor lock issue if that's what it is? What else might it be?

What kind of gas cap does it have? It sounds like either it has a non vented cap and should or it has a vented cap that's malfunctioned and doesn't vent anymore. Take the little gas can with you full. Drive it until it quits again. When it does, Remove the gas cap and see if it will restart. If it's pulling a vacuum on the tank from not being vented, it will stop the fuel flow and you will indeed "run out" of gas. Try that and report back. If it works, get a new vented gas cap.....and also look for the factory fuel tank vent. It could be stopped up.

That's a good point. It's a locking gas cap. The classic industries catalog that the guy says he ordered everything from doesn't say anything about it venting. In fact only the non locking caps specifically say they vent.

73 Duster 360 said:

When it happened I took off the air filter and tried to squirt gas into the carb but nothing came out. It took about 2 1/2 hours to get to a gas station

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You moved the throttle and nothing came out the accelerator pump shooters?
In that case, the next thing to check is if the carb bowl was empty or nearly empty of fuel.
Then the question is why. RRR suggestions are certainly possibilities.
Also check the fuel lines to and from the fuel pump.

You may have a problem with the venting, or with the pickup tube in the tank. There are several issues

A 73 car has the so called "evaporative emissions controls" Go to MyMopar and download the 73 factory service manual and read the fuel sections, and the emissions sections. THE TANK VENT which is part of the "carbon canister" in the enigne bay is a 1/4" tube from the tank to the engine bay. This MUST be in place and connected and OPEN in the engine bay (or properly connected to what belonged there from factory

Factory caps ARE NOT VENTED. They are what is called "pressure vacuum" which let air in or air out if pressure builds

Be SURE you have the right cap. Caps were different nearly every year from 70 onwards

Here is a famous photo someone posted on here showing the differences



The pickup tube might be damaged, the filter sock plugged, or it might be bent/ broken somehow so that it's only picking up from the top area of the tank

You will have to drain the tank and pull the sender to find out

Vapor lock? does it have headers? how far away is the fuel line from the exhaust? I could tell a story but will wait...

this really sounds like vapor lock. next time this happens open up the carb and see if there is any fuel in the bowls. if there is then possibly some debris in the carb. Make sure the fuel return line is actually hooked up. I have purchased cars in the past that has this capped off. Check to make sure the fuel lines are not hitting anything else that gets super heated. if the line is hooked up and no gas in the bowl, then its time to start opening up the lines and checking for a plug. You can shoot some air into the lines using an air compressor line to clear debris out of the lines.

Finally , I think you now know "why" the car was for sale. I would try to make the nice guy who sold you the car pay for anything that you need to do to get this right.

I sold a Duster to young ish mechanic buddy years ago. I drove it to work 60 mi one way every day before he bought it. No problem with me. The Duster did the same thing to him as the P here talks of, he replaced the gas tank 3 times (WHY!!!!) only to find a a dead bug in the long fuel line ( the front to rear one). The bug would get to a curve in the line and stop and plug it all up!!! Go figure!!

barbee6043 said:

I sold a Duster to young ish mechanic buddy years ago. I drove it to work 60 mi one way every day before he bought it. No problem with me. The Duster did the same thing to him as the P here talks of, he replaced the gas tank 3 times (WHY!!!!) only to find a a dead bug in the long fuel line ( the front to rear one). The bug would get to a curve in the line and stop and plug it all up!!! Go figure!!

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What would be a tough one to diagnose. I've had cars where someone removed the "sock" on the sender. Nothing to stop bugs and chunkies from going on through!

Ricks70Duster340 said:

What would be a tough one to diagnose. I've had cars where someone removed the "sock" on the sender. Nothing to stop bugs and chunkies from going on through!

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His problem was the sock was missing in every tank he used!!!! He had no idea or the $ to get a sock or where and how to order such!!! This was back about mid to late 90's/

barbee6043 said:

His problem was the sock was missing in every tank he used!!!! He had no idea or the $ to get a sock or where and how to order such!!! This was back about mid to late 90's/

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How funny! Not for him though....!

^^^ IF I had known of his problem. I would have ordered him a brand spanking new sock for it. This was before cell phones and I doubt he could have afforded one anyway! I still never carry one and usually just tell the wife to dial whatever!! LOL