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77 jimmy- puzzle of the day

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rixrock

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Greetings, I have been restoring a 77 Jimmy. Been running great till about 2 months ago. Started sputtering and stalling after driving down the road for about 30 minutes. seemed like it wasn't getting any gas. After it died it would take a couple of minutes till it would start up again. I assumed it was the fuel pump going out, so replaced that. Still had problem. assumed that there must be some gunk in the tank or fuel line. removed tank and flushed. it was in great shape, little to no gunk.

Next step assume (you know what they say about assume) that it must be the carburetor. So off the carb comes for a rebuild. once again looked to be in great shape. STILL not the problem! To cut this tragic tale short, new air filters, PCV valve, pcv filter, new vacuum lines, timing checked, new distributor about 6 months ago. checked gas cap to back sure venting was ok. new spark plugs and wires. HELP!!

this has already cost me three planned camping trips and we are on the heels of hunting season.
 
yes. the one in the carb as well as an after market filter before the carb, that didn't work so I pulled the aftermarket one to see if that was a problem. also pulled fuel line from carb and did the run for 15 seconds test to see the volume, the min they say is 1/2 pint. I had a full pint.
 
rixrock said:
yes. the one in the carb as well as an after market filter before the carb, that didn't work so I pulled the aftermarket one to see if that was a problem. also pulled fuel line from carb and did the run for 15 seconds test to see the volume, the min they say is 1/2 pint. I had a full pint.
Click to expand...
fuel pump to carb metal or rubber hose. It could be vapor locking.
 
"New" distributor,or used one new to your truck?...some aftermarket ones have crap ignition modules and pick up coils...I'd stick with AC Delco ones...

Sounds like you need to determine what goes away after 30 minutes,the spark,or fuel delivery...next time it dies,pull a plug wire off and put a spark plug in it and ground it,and crank it over--see if it has spark..

If it is spark that your losing,it could be the ignition coil,pick up coil,ignition module,or even a bad ignition power wire that has a pinched spot with only a few strands barely making contact that heat up and fail to conduct,then work again once it cools off some..
 
metal from pump up to top of water pump then rubber to carb, bout 8 inches.

As far as the coil. Was new after market. Leaving for local napa in about 10 min to get a new coil. Will check spark first.
 
Sometimes throwing parts at a problem is the easiest and cheapest way to go. If you have old plug wires and get a misfire, just replace the wires instead of doing an ohms check or spraying with water.
But you soon reach the point of diminishing returns.

Sounds like you have reached and gone past this one.

First thing I would do, is try running it with the gas cap off. I know you said you checked, but it sure sounds like its sucking a vacuum on the tank.

Next, when it quits, you are going to have to get busy. Since is carbed, be ready, and when it quits immediately pop the hood, pull the air cleaner and look for gas squirting when you work the throttle.
The idea here is to isolate the problem.

Since its super unusual to suddenly lose compression and then get it back, odds are its going to be ignition or fuel.
If you see fuel, and it won't run, then you have eliminated the entire fuel system.

If its ignition, and you have not changed the coil, then I would throw one more part at it.
Otherwise, you are going to have to find out why the spark is going away.

Of course, if you see no fuel, then you have to consider vapor lock, or one of the parts you replaced being bad.

See if you can figure out which system is killing it, and post back.
 
I gotta start typing faster. By the time I finished my typing, you other guys had already posted the same ideas.........
 
Watch the tail pipe next time it starts quiting. Black smoke means loading up, no smoke is lack of fuel or ingnition.

Had this issue on a friends car. Cooking the fuel in the carburetor.
 
Had a similar problem on an old Ford some years ago, bought it from a frustrated owner who had replaced the carb, fuel pump, coil, distributor etc in vain trying to fix the truck. It would run great for sometimes as long as twenty minutes then die. Could not be re-started for a few minutes then it would catch and off you go till it died again. It ended up being a flake of rust caught in the fuel line from the tank. It was caught in such a way that it would hinge like a flap and restrict fuel flow almost entirely. When suction diminished it would open again. Sounds crazy but there it was. Maybe you can run a temporary line from tank to fuel pump to test?
 
Had the same thing with a rag in the tank one time. It even survived being pulled out and flushed.
Finally found it when we pulled the tank a second time and this time took the sending unit out.
Rag was wrapped around the sock, and stayed there when we flushed the tank through the filler hole the first time.
 
You guys are amazing!! I replaced the coil and module, as well as checked all grounding wires. Something worked. Happy trails again!!
 
Fordum said:
Had the same thing with a rag in the tank one time. It even survived being pulled out and flushed.
Finally found it when we pulled the tank a second time and this time took the sending unit out.
Rag was wrapped around the sock, and stayed there when we flushed the tank through the filler hole the first time.
Click to expand...

Many moons ago a friend bought a mint '62 Plymouth Valliant from an elderly neighbor,with the indestructable slant 6...it ran perfect...for about a week..

Then it would stall after running long enough to warm up fully--anywhere from 10 minutes to an hour--sometimes it would start right up again,sometimes it would crank and crank and refuse to fire again..

We suspected fuel filter clogging up,since it sat a lot and was never driven very far...it looked like new and you could blow thru it easily--we replaced it anyway..

No change...stalled 10 minutes later,refused to start..waited a half hour,it fired right up and we drove it home..died as we entered the driveway!..

My friends dad was a good mechanic--he said "it might need a fuel pump--it looks original"...so my friend buys one,we install it--same thing..died again 3 miles up the road...

This went on for several weeks--every payday my friend bought another new part--ended up replacing the coil,points,condensor,ballast resistor,plug wires,plugs,rebuilt the carb too,with his dad's help...it was finally determined not to be a lack of spark problem,they tried blowing out the fuel lines with 125 psi air pressure and it did seem to delay the stalling awhile,but it still did it--they also drilled a small hole in the gas cap,thinking maybe it was not allowing any air in...didn't change a thing..they were completely baffled..

Finally,my friend had enough--he loved the car when it ran,but it was risking his job,he was almost fired for either being late too often,or missing work entirely...he sold it to another guy we knew for 150 bucks,which was about how much he had spent on parts...(he paid 300 for the car,but it was worth a grand,it was that nice!)..

The new owner drove it one day,and it stalled,just as he was told it would...

He pulled the gas tank out and took the sending unit out,and went to dump out the old gas,and he expected to see tons of rust come out--but it was clean as new inside...then about a dozen ping pong balls came out,and landed in the drain bucket...:eek1:...:doah:

Turned out the guy who bought the car really liked it--but didn't like my friend!..he admitted a few years later after several beers,he had dumped the ping pong balls in the gas tank,knowing it would drive him nuts,and want to sell it cheap soon afterwards...:thinking:...

He heard about that trick from an old timer--he said the ping pong balls float for awhile,then end up sinking,and getting sucked against the "sock" filter on the sending units fuel feed pipe...after the suction dies off after sitting a while,they float back up again..:rolleyes:
 
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