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Discussion Starter · #1 ·
My 70 judge started just out of the blue dying at low RPM, No pattern just anytime. Could pump the gas pedal and it would restart. would run fine for a while or die again in a short while. Don't run it much so my thinking is fuel pump, replaced that and now it's even worse, fuel doesn't seem to be getting to carb at all. Can dump little gas down carb and it will start right up. So before I slam my head in the car door, any thoughts on what the problem could be. THANKS. Gary
 

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Look for a disconnected or leaking vacuum line. If it's an automatic, don't forget to check the connection at the transmission vacuum modulator.
To find out if a component is leaking vacuum, disconnect and cap off all of the vacuum connections at the carb and intake manifold. If that clears it up, reconnect them one at a time until you find the guilty dog.

Bear
 

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A fuel line could be collapsed internally. But actually sounds like vapor lock, since you said the problem was at low RPM’s and the new fuel pump “made it worse”….

a new fuel pump gives better suction and vapor lock stalls the car because the suction on the feed line between the pump and the tank creates a drop in vacumn and thereby a rise in temperature of the fuel. That makes the fuel “Vaporize” in the line, and vapor will not pump so you stall.

You then add fuel at the carb and it starts up. It would likely also start up when cold, as vapor lock is pressure and temperature related. Today’s gas has a very low volatility rating especially now with winter blend gas.

The best fix for vapor lock is a return line to the tank from near the carb or from the fuel pump. This keeps fuel constantly moving so the fuel pump never “dead heads” and creates too much suction. Anything you can do to remove heat from the fuel feed line may help, especially if it is near a header or exhaust pipe. You wrap the fuel line there with DEI wrap. It comes in Velcro so just wrap around the lines near any heat source.
 

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Discussion Starter · #6 ·
Well it's pretty cold outside, it's not running to be hot and at this point no fuel seems to be getting to the carb, so doesn't look to be a vapor lock problem. The return line from the pump is connected as before. Is there any other vents in the fuel lines that could be malfunctioning or clogged? or would trying to blow out that return line be worth a try?
Look for a disconnected or leaking vacuum line. If it's an automatic, don't forget to check the connection at the transmission vacuum modulator.
To find out if a component is leaking vacuum, disconnect and cap off all of the vacuum connections at the carb and intake manifold. If that clears it up, reconnect them one at a time until you find the guilty dog.

Bear
It's a 4 speed
 

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How are the rubber lines at the tank? And at the pump? The rear ones sometimes get soft it not replaced in years and could collapse internally.
 

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Discussion Starter · #9 ·
I will check those, that makes sense, has to be something between the pump and tank. Don't know if the lines have ever been replaced. Not familiar fuel sock, where is that? It is an original car and I don't drive it much for that reason. THANKS for your responses.
 

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Welcome !!
if it were mine .........
it sounds like a fuel issue possibly ,,, this is what would go thru my mind if it did it a few times
how many pumps and long did I have to crank it before it starts again
2 pumps and fires right up or pump pump crank crank crank pump zoom ...........
after it did it a couple times
after it stalls I would pull the air cleaner and look down the carb and pump the gas pedal medium fast
to 1/3 throttle ,,,,,is the gas streaming or spitting ? this would kinda let me know if the carb had fuel in it
if it didnt have a nice squirt I would pump it twice a little farther..
if it has a good squirt ,,,, I would lean towards spark ...
poor squirt ,,, would be either accelerator pump parts or poor fuel pressure
does it stumble before dying,,,,can you feather the gas to keep it running ? or does it just shut off??
 

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Welcome !!
if it were mine .........
it sounds like a fuel issue possibly ,,, this is what would go thru my mind if it did it a few times
how many pumps and long did I have to crank it before it starts again
2 pumps and fires right up or pump pump crank crank crank pump zoom ...........
after it did it a couple times
after it stalls I would pull the air cleaner and look down the carb and pump the gas pedal medium fast
to 1/3 throttle ,,,,,is the gas streaming or spitting ? this would kinda let me know if the carb had fuel in it
if it didnt have a nice squirt I would pump it twice a little farther..
if it has a good squirt ,,,, I would lean towards spark ...
poor squirt ,,, would be either accelerator pump parts or poor fuel pressure
does it stumble before dying,,,,can you feather the gas to keep it running ? or does it just shut off??
 

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Inside the gas tank is the fuel sending unit, it has a sock like fuel filter on it and all the fuel goes thru that first and into the feed line. You have to take the sender out to get it, drop the fuel tank and remove it.
 

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A fuel pressure test and a fuel volume test would be the normal procedure now. To see if both are adequate. But if you are not set up for that stuff be careful you don’t want gas everywhere.

it stalls, then you add gas and it starts, so fuel starvation somewhere. You replaced the pump with a new one. So you need to look at the lines and the tank.

something is collapsing, blocking, choking or starving the fuel.
 

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My 66 had same issue, after I went through changing alot of things that weren’t the problem I started at the gas tank, the sock on the sending unit was deteriorated, but the real problem was the small rubber gas hose that goes from the sending unit to the first steel fuel line, where it bends right after the sending unit was cracked and split behind against the tank where you couldn’t see it. So it would start, then sputter and stall unless you feathered the pedal, if you tried to rev it the air would get in and bog out. All new rubber gas lines back to front will fix a multitude of problems, the newer gas eats the old 55 year old lines up.
 

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Discussion Starter · #15 ·
A fuel pressure test and a fuel volume test would be the normal procedure now. To see if both are adequate. But if you are not set up for that stuff be careful you don’t want gas everywhere.

it stalls, then you add gas and it starts, so fuel starvation somewhere. You replaced the pump with a new one. So you need to look at the lines and the tank.

something is collapsing, blocking, choking or starving the fuel.
That's my thinking I'll start with the lines, there is some cracking, not bad, 8-10 inches back from the pump but who knows further back. Not set up for much detailed testing so I'll go back to old school with the lines and then to the tank. Thanks !!!!!
 

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Discussion Starter · #16 ·
Welcome !!
if it were mine .........
it sounds like a fuel issue possibly ,,, this is what would go thru my mind if it did it a few times
how many pumps and long did I have to crank it before it starts again
2 pumps and fires right up or pump pump crank crank crank pump zoom ...........
after it did it a couple times
after it stalls I would pull the air cleaner and look down the carb and pump the gas pedal medium fast
to 1/3 throttle ,,,,,is the gas streaming or spitting ? this would kinda let me know if the carb had fuel in it
if it didnt have a nice squirt I would pump it twice a little farther..
if it has a good squirt ,,,, I would lean towards spark ...
poor squirt ,,, would be either accelerator pump parts or poor fuel pressure
does it stumble before dying,,,,can you feather the gas to keep it running ? or does it just shut off??
That's my thinking I'll start with the lines, there is some cracking, not bad, 8-10 inches back from the pump but who knows further back. Not set up for much detailed testing so I'll go back to old school with the lines and then to the tank. Thanks !!!!!
My 66 had same issue, after I went through changing alot of things that weren’t the problem I started at the gas tank, the sock on the sending unit was deteriorated, but the real problem was the small rubber gas hose that goes from the sending unit to the first steel fuel line, where it bends right after the sending unit was cracked and split behind against the tank where you couldn’t see it. So it would start, then sputter and stall unless you feathered the pedal, if you tried to rev it the air would get in and bog out. All new rubber gas lines back to front will fix a multitude of problems, the newer gas eats the old 55 year old lines up.
My 66 had same issue, after I went through changing alot of things that weren’t the problem I started at the gas tank, the sock on the sending unit was deteriorated, but the real problem was the small rubber gas hose that goes from the sending unit to the first steel fuel line, where it bends right after the sending unit was cracked and split behind against the tank where you couldn’t see it. So it would start, then sputter and stall unless you feathered the pedal, if you tried to rev it the air would get in and bog out. All new rubber gas lines back to front will fix a multitude of problems, the newer gas eats the old 55 year old lines up.
Went through some fuel problems with my 65 a while back turned out to be just crap inside the lines breaking loose and after a few filter changes it cleared up and never had another problem. I'll start with the lines, It's only had maybe 1000 miles on it in the last 25 years so they are probable overdue. It just excites me so much the thought of dropping the tank. Thanks
 

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If you are gonna drop the tank replace the sending unit, comes with new sock filter and upgrade your rubber lines to be able to handle the 10% ethanol gas. You may find a lot of crud floating in there. I just put in a new tank, hey 50 years of service I figured was enough!
 

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Well it's pretty cold outside, it's not running to be hot and at this point no fuel seems to be getting to the carb, so doesn't look to be a vapor lock problem. The return line from the pump is connected as before. Is there any other vents in the fuel lines that could be malfunctioning or clogged? or would trying to blow out that return line be worth a try?

It's a 4 speed
Power brakes? Could be there. It might not be a vacuum line problem but that's super easy to check and eliminate. Disconnect "everything" and cap off the fittings at the source.
I'm a big fan of checking/eliminating all the 'easy' things first before moving on to the harder to check stuff.

A vacuum leak can cause the behavior you're seeing. It doesn't take much of a leak at idle to let in enough air to make the mixture go very lean - lean enough to where it wants to run really rough and die - yet it'll seem to run mostly ok at RPM. Fuel starvation is going to get worse as RPM goes up. Since you said it happened "out of the blue" I took that to mean that the onset was sudden - like it was fine, then started happening at the next stop light.

Bear
 

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Went through some fuel problems with my 65 a while back turned out to be just crap inside the lines breaking loose and after a few filter changes it cleared up and never had another problem. I'll start with the lines, It's only had maybe 1000 miles on it in the last 25 years so they are probable overdue. It just excites me so much the thought of dropping the tank. Thanks
I dropped the gas tank in my 66 and it really wasn’t very hard to do, and I didn’t really even need to do it but wanted to look inside and surprisingly it was clean as new really, not sure how 65 is but 66 can pull/replace the sending unit without dropping the gas tank as its on the front of the tank.
 
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