Starts then stalls. Stumped.

[Squirrely Brother]

The truck kept stalling last night and I ended up having it towed home. It will run for 20-30 seconds, then rough idle then stall. The truck has a 350, Edelbrock intake, Edelbrock 1406 carburetor, one vacuum t split for ac/350 trans solenoid, brake booster vacuum line, pcv vacuum line, hei distributor vacuum advance line and the fuel pump was replaced in August along with the timing chain and has maybe been driven 150 miles total since. The timing is at 10 and overall has been running strong until last night. I swapped out the hei module today, checked the fuel filter, checked battery volts and alternator is charging properly. Also cranked the engine with the fuel line disconnected into a cup to check for funk and the fuel was clean. It seems like a massive non-visible vacuum leak out nowhere or maybe the fuel pump is defective or even bad fuel (smells and looks good though). I’m completely stumped. I wanted to note the esc and emissions have all been removed years ago. Any and all help or suggestions would be appreciated. Thank you.

 

[Matt69olds]

Have you verified the choke is opening?

Get a can of starting fluid. Start the engine, when it begins to die give it a quick shot of starting fluid. If the engine recovers and idles normally for a few seconds, then begins to run rough, it’s time to look at the fuel system.

If starting fluid has no effect, after the engine dies check for spark. No spark, look at the ignition system.

 

[Squirrely Brother]

Thank you. I’ll pick up a can and try your suggestion. It seems starved, but when I looked in the cup after cranking for 5 or 6 seconds there was fuel. I’ll post an update hopefully within a couple of hours.

 

[SquareRoot]

If starting fluid Jason effect,

creepy...children of the corn kind of creepy.

 

[Squirrely Brother]

Have you verified the choke is opening?

Get a can of starting fluid. Start the engine, when it begins to die give it a quick shot of starting fluid. If the engine recovers and idles normally for a few seconds, then begins to run rough, it’s time to look at the fuel system.

If starting fluid Jason effect, after the engine dies check for spark. No spark, look at the ignition system.

I just started it. It ran for about 1 minutes fine until bluetooth from my phone connected to the stereo and shut it down instantly. I turned the radio off, restarted it and it went to die. I tried the starter fluid and it stalled the engine immediately. I tried it 3 times with the same results.

Could my battery an issues where an electrical drain is screwing with the spark? The headlights last night were on last night causing a draw, as well. Shooting in the dark here without nods.

 

[Grit dog]

Very frustrating.
Eliminate the battery issue? Recharge battery fully. Even if the battery is not great, it should run longer?
Other suggestion, cracked vacuum line or cracked fuel line sucking air?

Good luck diagnosing.

 

[Squirrely Brother]

I’ll trace the lines tomorrow to see if I missed something. Multimeter shows the battery’s at 13.62 volts. I had enough for the day, started to get frustrated and needed to walk away from it.

 

[Matt69olds]

creepy...children of the corn kind of creepy.

I HATE autocorrect sometimes!! I fixed my reply

You must be registered for see images attach

 

[M00SE]

If it "pops/spits" (backfires) out the carb then you have a fuel delivery issue. If it backfires out the tail than you have a vacuum or flooding issue. I had this issue and it was a bad gas tank and pick up in the tank. But notice when it starts to die or right when it dies, does it spit out the carb? If so, I would be clearing the little filter inside the carb, then replace the pump and so on.

moose

 

[Squirrely Brother]

There’s not any pre detonation, pinging or popping. The car just sounds like it’s taking in a big breath of air. The only thing I noticed was vaporized fuel cloud coming out the electric choke vent. I need to look more at the fuel pump and maybe the carburetor floats or maybe needle/seat. Excluding my current car, because of all the electronics, I haven’t had a mechanic work on any of my vehicles since somewhere around 1995, but I’m getting frustrated enough to think about giving in.

 

[OldBlueDually]

I assume yes to this but, have you pumped on the gas pedal when it starts dying on you?

I assume you have a mechanical fuel pump due to you turning it over and seeing fuel afterwards. Have you tried an auxiliary tank? I just use a 1 gallon gas can, and a short length of snowmobile fuel line to the pump in a situation like this to be sure it is not my pump. If it runs good then you may have a fuel line/tank issue like Moose stated.

I had a similar problem with an Olds 350 I built from the ground up, it would run a few seconds then die on me. Had the intake & carb off of it 2 different times trying to see what the hell I did wrong thinking I effed up a gasket somehow, turns out one of my emission block out plates was loose on the intake causing a massive vacuum leak...oops.

I remember one time my dad had this same kind of issue he was trying to find, I "believe" he used carb cleaner and sprayed it up & down each side of the intake while it was running...sure enough the thing ran good when he hit a certain spot and found that it was the intake gasket leaking.

Best of luck, I hope you can find it! These moments suck!

 

[Squirrely Brother]

Yes, I have pumped on the pedal and it still chokes out. It’s a gradual stall too. It just doesn’t stall instantly.

I need to try your suggestion of a stand alone tank. I can hear the diverter switching between tanks and the gas needle moving. Maybe something is going on between the switch and the pump or a faulty diaphragm on the mechanical pump.

I keep looking for a vacuum leak, because last night I thought the brake pedal felt different, but I disconnected the check valve on the brake booster and there was vacuum.

I have carb cleaner and starter fluid, so I’ll try your dad’s fix too. I’m just really puzzled.

I really appreciate all of your suggestions and taking time out to help me. Thank you and take care.

 

[OldBlueDually]

@Squirrely Brother I learned a LOT from my dad, and still do. He is a now retired GM mechanic of 35 years so he remembers many of these mid to late 70's trucks being on the GM dealer lot, and worked on many of them!!

In fact two years back coming home from camping in Northern MN using our 2001 Suburban 2500 I could smell this strange sweet kind of smell, not like a coolant though. Almost like a restaurant kind of sweet deep fried who the hell knows what smell. So I stopped to fill her up and looking under the hood, underneath and checking stuff expecting to see some kind of leak or who knows what.

I went to the innerweb surfing looking around...nothing! So I talked to my dad about it and he said "oh, that's common, it is your rear & front differential fluid you are smelling"....why the hell does it smell like that I asked! He said GM did that (if I remember right he said because the stench of regular fluid was horrible, so they made it smell differently. He remembers people complaining about the sweet smell too, so he would run new hoses and breathers on them to get them to dissipate that smell away while driving.

So, he crawls under our suburban with his ratchet, pulls off the fill plug and gives it to me and says "did it smell like this"....sure as heck it did, exactly like that! Who would have thought! Here I worried the whole time thinking I am breaking down soon...

 

[Squirrely Brother]

@OldBlueDually Your dad sounds like a really cool man and extremely knowledgeable. Sounds like y’all have a great relationship. And, him teaching you by showing instead of telling is the best way to learn.

I wonder if the differential used some sort of friction modifier like the T-5 and Tremecs back in the 1990’s. The stuff had a sweet rotten citrus sent to it or at least I thought it did. My daughter’s sure thought it smelled like death. Good memories working and teaching family members, so they don’t feel they have to go to a mechanic except for maybe an alignment or a some weird fluke where you keep stalling.

I got tied up with a client issue the entire afternoon and up until a little bit ago, so I didn’t get an opportunity to work on the truck. I’ll try your suggestions tomorrow late afternoon and hopefully find resolve. Thank you, again.

 

[OldBlueDually]

@Squirrely Brother You got that right, he is cool and has way more knowledge than I do!! I am not sure if it is a friction modifier added or the fluid itself that has that smell?? Most things I do, I do best when I have hands on....I don't like reading a book to learn something, I like books for simple advice & diagrams with quick instruction.

I sure hope you can figure out your truck, crap like that drives me nuts!!! Hate it when I get an epiphany in the middle of the night so I wake up and go work on stuff