Carb Stalling Troubleshooting...Flooded ?

[Tynan918]

I have an '84 Monte Carlo SS with a 305 H.O. motor. I have an Edelbrock 1405 600 cfm carb and an Edelbrock single plane intake manifold attached to the motor. Bought the car about 2 months ago, and was told it sit in a field for a year or so.

The motor starts up and the car drives, but only for 8-10 miles before the motor bucks and stumbles and sometimes stalls. Sometimes meaning, when the bucking and stumbling starts, if I press the gas pedal it jumps and continues to attempt die out and if I repeatedly press the gas pedal it bucks and stumbles and dies...but if I coast it without continously pressing the gas pedal on a straight road or downhill at reasonable speeds, it corrects itself for another 5 miles or so before it starts bucking and stumbling again.

Once it dies, I'm able to start it right back up and drive another 8-10 miles and repeat the "coast fix" before ultimately stalling and restarting the engine. Only once have I experienced issues of it not immediately starting back up.

Was told in a MCSS forum that my carb is flooding, and after running a fuel pressure test, fuel pressure from the pump to the carb, at the carb read 7-7.5 psi... My carb MAX psi is 6.5, so it's too high...

(Key in "ON" position)

(Engine running)

Took a video of my jets with the engine warmed (choke fully open) and running, and at idle I don't see any gas in the carb, but when I rev it up, I can see spraying and dripping from the front jets, vents open, but nothing coming from the back jets, and the vents never open...Here is a link to the video :

My car idles too high, the factory RPM specs is 600@ idle and it currently runs at 1300-1500 RPM at idle, 1000-1200 RPM in gear with no load, and shifts every 3000-4000 RPM while driving. I have timing set correctly, adjusted the idle mixture screws, checked for vacuum leaks, adjusted the electric choke, played with the fast idle screw and idle screw...can't get the motor to idle below 1000 RPM without the engine running rough at idle and stalling when in gear and on load.

Could .5 over MAX pressure cause carb flooding and possibly be my cause of my issues ? Maybe even dirty or clogged from sitting a year or so ?

 

[Tynan918]

Definitely buying an inline fuel pressure regulator to bring down the fuel pressure for starters. I also seen and heard the glass inline fuel filters are better than the plastic clear filters, is this true ?

Also thinking maybe I need to open up the top end of carburetor and inspect and clean it...maybe just rebuild it altogether... EBay has some affordable carburetor rebuild and calibration kits available that I'm considering buying.

 

[ck80]

I understand you started a new thread likely to clean things up and get the updated info at the top. But. It's a bad way to use the forums as people can't see how the problem changed over time and what has been tried or discussed so far.

In the future just use the same thread until the problem is fixed. If it returns....Start using the same thread again too.

Now.

That said, checking fuel pressure at idle was a start, but, in a perfect world you get a fuel pressure gauge with a $30 dash cam pointed at it while driving around. Identify what's doing on when the problem occurs. That way you both show us and aren't distracted from the road by trying to watch gauges. I got a big dumb one at Walmart black Friday for $20, it's credit card sized but works without the expense of a go pro.

It's so hard to sort out someone else's abandoned project because you don't know where they started and failed, and what they gave the Bubba treatment to. Could be the car was parked because they "fixed" all kinds of things trying to address the problem you complain of and they gave up.

Have you pulled your spark plugs and read them for either black soot or white ash?

Your car is a big dumb animal. It wants fuel, air, and spark. It gets those in the right proportions it's a happy camper.

High idle issues make me want to also go through and hunt for a vacuum leak. The old carb cleaner trick is you spray around the gasket surfaces and places you can't visually confirm. If it sucks in and the idle blips faster you found a leak, either a break in a seal or a warped surface. Your rubber hoses and such you just need to check routing, and check condition. Anywhere its plugged off from factory you need to spray test for a leak to see if the plug they inserted is holding fast. If you see cracking on a hose it needs replacement. Flex the hoses. A hose can look OK at rest and when bent by hand show cracks.

As far as your inline visible filter bit, glass is more heat tolerant but can crack. Hopefully they make them of pyrex/gorilla glass and not fragile Chinese glass. Plastic dries out from heat and starts crazing cracking leaking. Many a car traced its engine fire to those things over the years. It's best as a diagnostic and not an everyday use IMO. Factory fuel filters are cheap, I just change them for 80 cents every other oil change. During the swapout is when I can see if I had a bad gas batch or some issue along the way.

Because you played with the screws on the carb so much you probably have another fight on the horizon. And, it's a reason so many ejunk carbs used to appear at swap meets used. You tried to tune to a problem, rather than have the problem fixed. So you're settings are all skewed a bunch of different directions from the start point, and, you'll need to slowly and frustratingly fight your way back.

Right now unless you wrote in a notebook every turn of each screw, how far you went, what direction, you can't precisely backtrack. But then again, even if YOU did. If the previously owner didn't, who knows if he mucked it up for you. And that's where so many of those edelbrocks got a bad rep for tuning and tossed at meets.

 

[MrSony]

i also think you have a big vacuum leak somewhere and your transfer slots are over exposed.
with the carb off back the idle speed screw off until the slots appear as a square, and then turn the two idle mixture screws by hand all the way in until they stop, and turn them each back out 1.5 turns. see if it will start up and idle normal then. if not the carb may need a kit, the throttle bores might be all wallowed out, who knows. do all the free stuff first.

also, those glass filters are fire hazards. quite literally. get the metal canister filters instead. its nice to see fuel flow, but not nice to see your car on fire on the side of the road.

 

[Tynan918]

That said, checking fuel pressure at idle was a start, but, in a perfect world you get a fuel pressure gauge with a $30 dash cam pointed at it while driving around. Identify what's doing on when the problem occurs. That way you both show us and aren't distracted from the road by trying to watch gauges. I got a big dumb one at Walmart black Friday for $20, it's credit card sized but works without the expense of a go pro.

I have a body cam I could wear and drive around recording with, just harder to upload and faster and easier to do from my phone.

 

[Tynan918]

Have you pulled your spark plugs and read them for either black soot or white ash?

Yea these were the first plugs I took out from the engine...AC DELCO

Then I replaced them on July 28th, 2021 with NGK UR4...

Checked the NGK plugs less than a month later (August 9th) and this is what they look like... I sprayed them off with brake cleaner and scrubbed them down with a wire brush, and put them back in but didnt make much of a difference.

 

[ck80]

Yea these were the first plugs I took out from the engine...AC DELCO View attachment 183883

Then I replaced them on July 28th, 2021 with NGK UR4... View attachment 183884

Checked the NGK plugs less than a month later (August 9th) and this is what they look like... I sprayed them off with brake cleaner and scrubbed them down with a wire brush, and put them back in but didnt make much of a difference. View attachment 183885

Soot like that indicates too rich of an a/f mixture, wrong heat range, or, ignition issues. So add that into your considerations of what you're tracing down.

Does it ever diesel when shutting off?

 

[DRIVEN]

Based on other posts and the underhood pics, I'm sure you have multiple issues. What is the base timing set at?

 

[Tynan918]

It's so hard to sort out someone else's abandoned project because you don't know where they started and failed, and what they gave the Bubba treatment to. Could be the car was parked because they "fixed" all kinds of things trying to address the problem you complain of and they gave up.

The car drove great, the only issue it had when I bought it was the alternator was bad. Here is a pic of the motor when I bought it...

Things got hairy when I replaced the distributor... I bought a new distributor and plug wires, spark plugs, a chrome engine dress up kit, and an oil change kit using Lucas 10w30 High Zinc HotRod motor oil

When I replaced the distributor, I had to time the engine again. Took me 3 trys to get it right, but I put the harmonic balancer on 0° TDC on compression stroke and used a screwdriver to adjust the oil pump shaft to position the rotor pointer facing cylinder number 1 with the distributor sitting flush on the manifold...

 

[Tynan918]

Soot like that indicates too rich of an a/f mixture, wrong heat range, or, ignition issues. So add that into your considerations of what you're tracing down.

Does it ever diesel when shutting off?

No i don't believe it does, shuts down when I turn it off... I'll run it after a while and shoot a video of it.