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Discussion Starter · #1 ·
For the first time since I've owned it, my 65 Impala came home on a tow truck. It's been almost 20 years, so I suppose I've had a good run. Anyways, I was driving home from work, and it started to cough. First, a couple of stumbles. Within half a mile, it wouldn't accelerate. I idled it into a parking lot. It was idling ok, but when I opened the throttle, it would gasp like the carb was getting no gas. I decided to try and make it to my mother's driveway which was less than half a mile away. Big mistake, within 200 yards, it wouldn't even idle. The traffic jam I caused is a story for another day.

Thoughts?
- fuel pump
- clogged filter
- carb issue
- ignition/points/advance/coil

Haven't had time to check anything yet, I look forward to your opinions.
 

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Sounds like you might have some trash in your fuel bowl and possibly under your needle and seat that shuts off fuel when it gets too high. At idle the fuel pump isn't moving much gas in terms of volume, but pick up the RPM and it floods out. Going lean (running out of gas) yields popping and back fires, too much gas and it drowns the motor.

Big Dave
 

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Discussion Starter · #3 ·
It's not flooding for sure, it behaves the exact opposite, like it isn't getting any gas when the throttle is opened. I've had a stuck float before on other carbs, this isn't the same.
 

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Well if it is going lean it will back fire; so be sure to be wearing a safety face shield when you lean over the carb to see if you are getting gas out of the accelerator pump when you stab the throttle. You are looking for the squirt to cover the in rush of air so it will die either way: without gas or with too much gas (it is a very narrow ratio of fuel to air that makes for your Goldilocks combustion ratio).

It could be trash blocking a main jet; or obstructing the flow of gas to the accelerator pump well, if you are running lean. It could be trash caught under the needle and seat if you are running overly rich. With these old cars the tank and the mild steel tanks rust as the galvanized coating was only paper thin to start with (the car was designed to be used up in only seven years so no sense in wasting natural resources like Zinc on a car destined for the crusher). Combine that with gas stations that do not keep their tanks full in the hopes of gas prices falling more and you get a lot of condensate and sediments stirred up when they finally do fill up their storage tanks (which usually happens right after the yellow bags that say "out of order" are placed upon the gas pump nozzles).

If you have paper gas filters they could be what is clogging your carburetor as the paper disintegrates in water. You say you didn't put any water in your tank! But you did when you bought gasohol. It absorbs water right out of the air (not to mention the quart or two of water that got pumped out of the bottom of the under ground storage tank if you were among the first to refill your car after a drop of gas from the tanker truck). With gasohol you need a fiberglass fiber filled filter or one filled with stainless steel wool to avoid the effects of gasohol.

Big Dave
 

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I'm with you Jay, the symptoms sounded like lack of fuel to me.

Wouldn't hurt to check the fuel bowls for gas before doing anything, then I'm sure you know the usual steps. Filters are most suspect (to me anyway), and don't forget that you might have one built into the carb inlet.

Next for me, given that you've been driving it a long time, would be the fuel pump. (before I'd suspect any debris from the tank). I'll go ahead and put my money on the fuel pump and double-down. ;)
 

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Discussion Starter · #6 · (Edited)
I have at least one extra pump in the spares that I can try quickly.

I only use non-ethanol high test. Usually from the same place, 91 octane. However, I did put 3/4 of a tank from a different place of Ultra 94 in it (still no ethanol) right before this happened. Wonder if there's water in it...

<edit> Fuel is getting to the carb, the accelerator pump gives a nice shot. Car will start and idle. Still gasps and dies when the accelerator is opened. No cough, no backfire, does not run rough. Double checked all plug/cap connections. Pulled #1 plug, it looks great. The sintered bronze fuel filter looks great, no debris.

Decided to pull the pump. It's the original one. It looks like it's working, I can cycle the pump and gas comes out. Once I drained it, it will pull vacuum on the inlet when I cover it with my finger.

Both pumps I have are not correct for the 65. Had an NOS Carter in my spares, but wrong connections. Pulled the pump from my 71, and its outlet is bigger (and flare connection) than the 65.

Can't decide if I should throw a replacement pump on it, or put it back together and start looking at ignition.
 

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It could be the fuel pump or any of the other possibilities. They all need checked. I thought of another, The cam for the fuel pump on the camshaft. I would check the pump first. Pull the fuel line off the pump or the carb, run a line to a quart container and crank the motor over. You should get a good flow if pump is good. A helper is important here.
 

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There isn't much pressure on the cam shaft fuel pump lobe compared to valve springs. Maybe 20 to 25 pounds of pressure compared to 105 to 136 pounds of valve spring seat pressure (closed vs. going over the nose) for a hydraulic flat tappet cam. Because of this I doubt if the cam lobe failed for lack of ZDDP.

I have had cam drive lobes fail (along with the timing chain) where some bright spark sealed up the two big oil return holes in the front and back of the block with four brass Welch plugs. But that isn't a common problem.

Big Dave
 

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When you say it gas and dies when the accelerator pedal is opened was that in park or on a test drive?

Sent from my XT1254 using Tapatalk
 

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I've had a coil go out that behaved similarly. Would idle fine but bog out/spit and sputter with exceleration. Also ran slightly better when cold. Oh, and went rather suddenly.
 

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Discussion Starter · #12 ·
Thanks, I'll swap the coil over from my spares if the pump doesn't get it done!
 

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Discussion Starter · #14 ·
Back with an update. Couldn't find the adapters needed to use the later pump with the bigger outlet, so I decided to go with a new pump. Unfortunately, none were available in Canada. Found an AC Delco on Ebay, and had it sent to a family member in Detroit. Installed the pump today, and am happy to report that the 65 is running better than it has in a long time A nice bonus is the new pump is date coded correctly for my car!

Also realized that most of you have never seen my car. I don't post pics a lot because the thing is so reliable I don't work on it much! Lots of project threads for other vehicles of mine on other forums.

 

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Discussion Starter · #16 ·
Thanks. I scored those in the very early days of ebay. I wanted something "correct" that a buyer could have picked up at the dealer with the purchase of the car. They are in the 65 accessory brochure. I would never run SS caps on it, but these fit nicely.
 

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Discussion Starter · #18 ·
An unfortunate update today. Haven't driven the car since that (too) brief test drive as I was on vacation for a couple of weeks. Took the car out today to mail a parcel, about a 15 mile round trip. Within a couple of miles, it was stuttering at cruise speed. Soon, I couldn't keep it above 40. Had to let a couple cars by. Made it to the post office. After, car started right up. However, it was cutting out even at low speed, and stalling.

Has to be ignition. I went home, got an Accel coil and wire off my 71, and swapped it on. Same exact behaviour. Didn't mess around, had it towed home... again. I'll check the points, maybe swap the condensor. Last tune up I did plug, points, condensor, cap, rotor, fuel filter. All parts were fine, I kept them as spares. Idle speed is correct, dwell is too. The only anomaly I noticed when I was checking things after replacing the pump was that the timing seems too advanced. After cleaning off the tab, and finding the groove, it's almost 20 deg adv. I suppose that could be contributing to things. I'll recheck with my spare light when I go over everything tomorrow. Wonder if the advance weights are sticking? I checked that the hose is on the vacuum advance (it is).

I welcome your thoughts again...

 

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How many miles on your timing chain gear set? If it is the factory original "silent chain" (aka link belt) I would wager you have shed a few nylon gear teeth and are riding on the aluminum sprocket. If you have a double row true roller chain with steel or cast iron gears look elsewhere.

Of course if you bought an adjustable timing sprocket that can be accessed with a three piece timing chain cover while the motor is sitting on the dyno then maybe that has come loose changing the cam timing (which affects ignition timing as well).

Sounds like you are flooding out but that would be evident with black smoke pouring out the exhaust and black and sooty tail pipes.

BIG Dave
 

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Discussion Starter · #20 ·
I don't think the 60s small blocks had nylon coated timing gears.
 
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