Progr Carb T4 bus stalls when I hit the gas

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BellePlaine
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Location: Minnesota
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Progr Carb T4 bus stalls when I hit the gas

Post by BellePlaine » Wed Mar 18, 2009 9:17 am

My running parts bus...
76 Westy
Unknown displacement T4
Progressive carb - definitely needs a rebuild but it's going to be replaced with a set of Solex/Brosol PDSI's.
Electric fuel pump

My question...
She runs but when I give it gas at a normal rate, the engine stalls and wants to die. If I slowly give it gas it will take stay running. Does this sound like it's running lean? Could it be a fuel pump problem or fuel filter problem?
1975 Riviera we call "Spider-Man"

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Amskeptic
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Re: Engine stalls when I hit the gas

Post by Amskeptic » Wed Mar 18, 2009 9:39 am

BellePlaine wrote:She runs but when I give it gas at a normal rate, the engine stalls and wants to die. If I slowly give it gas it will take stay running. Does this sound like it's running lean? Could it be a fuel pump problem or fuel filter problem?
Let's start you on the IAC Learning Ramp.

If it will stay running if you slowly give it gas, it cannot be the fuel pump. There is greater demand at higher rpms, and that is where a fuel filter or pump symptom would show up.

If it stalls only during a transition, like your example, then we have to look at transitional devices, like accelerator pumps and their poorly aimed nozzles and horrible vacuum leaks that drop the engine right out. Put a little piece of clean wood over the top of the carb and carefully choke the engine's air supply just a bit, and see if you can rev it good. That would suggest accelerator pump, low fuel level, clogged as hell transition port (*my guess*), and aforementioned vacuum leak which you can track down with a can of WD-40 on a mildly warm engine.

Does it have a choke? If so, does it work? If so does the engine accept throttle inputs when cold better than when warm? Invest in blue chips yet?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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BellePlaine
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Re: Engine stalls when I hit the gas

Post by BellePlaine » Wed Mar 18, 2009 10:20 am

Amskeptic wrote:
Let's start you on the IAC Learning Ramp.
That's why I'm here!

It does have a choke, but I don't know if it's working not. I didn't think about low fuel as being a problem but it's likely a contributor. This also makes me think that the fuel I have in the tank is God-knows-how-old and can't be helping things either. I also didn't think about the accelerator pump but that makes sense too.

This carb is not long for this engine much longer but since I know I have a problem I wanted to think through what could be the cause for when I run into these symptoms again.

I'll see what happens when I rev using a block of wood over the carb.
1975 Riviera we call "Spider-Man"

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Amskeptic
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Re: Engine stalls when I hit the gas

Post by Amskeptic » Wed Mar 18, 2009 11:31 am

BellePlaine wrote: I'll see what happens when I rev using a block of wood over the carb.
Carefully. I use my hand so I can feel the vacuum I want, but if your engine backfires, it might make you lose bladder control, so I suggested the wood, carefully! to choke off the air just right, it is a subtle thing.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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