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Hi everyone, I’m trying to diagnose a problem with my Volvo 740 B230K with Pierburg 2B5 carburetor.
The engine starts, runs for about 1–2 seconds, barely gains RPM, and then dies. Giving it a little throttle barely helps, it still dies. Interestingly, one pump of the accelerator before starting works better than continuously pumping or holding the throttle open.

What has been done:
New fuel filter
One faulty spark plug wire found and replaced
Carburetor recently rebuilt/resealed with new gaskets by a classic-car garage
Choke was initially incorrectly connected, but has now been corrected. When cold, the choke closes almost completely.

The accelerator pump does inject fuel when the throttle is opened quickly. It’s a thin stream with some droplets, but definitely fuel is coming out.
The most interesting test:
If I spray brake cleaner into/around the carburetor while the engine is running, it runs perfectly. As soon as I stop spraying, it dies.
The garage says the carburetor itself is faulty and needs replacing, but I’m not convinced.

Could this be an idle circuit/idle jet problem, incorrect fuel level, vacuum leak, or carb adjustment? What would you check first?
I also previously noticed a hissing/vacuum sound.

Any advice from people familiar with the Pierburg 2B5/B230K would be greatly appreciated!

Hi, I’ve been running into some carburator/fuel problems. For the last month, my ‘86 Volvo 740 Pierburg 2B5/7, has had a rough idle. Dropped in RPM’s, then stalled. Whenever I was driving in 4th or 5th gear and did a pull, it started stuttering as if it wasn’t getting enough air or fuel (no idea). I thought it was just a fuel issue (bcs I drove on e10 95 fuel for some time and the car had been sitting a few months before I bought it.) Changing the fuel filter, didn’t help. Usually I do everything myself, but I had no idea what the issue was.
Went to my local (classic car) mechanic, he told me that one of the compartiment in the carb wasn’t getting enough fuel, he took apart the carb, changed the gaskets etc. Turns out it didn’t help, issue remains the same.

Hi, I’ve been running into some carburator/fuel problems. For the last month, my ‘86 740 Pierburg 2B5/7, has had a rough idle. Dropped in RPM’s, then stalled. Whenever I was driving in 4th or 5th gear and did a pull, it started stuttering as if it wasn’t getting enough air or fuel (no idea). I thought it was just a fuel issue (bcs I drove on e10 95 fuel for some time and the car had been sitting a few months before I bought it.) Changing the fuel filter, didn’t help. Usually I do everything myself, but I had no idea what the issue was.
Went to my local (classic car) mechanic, he told me that one of the compartiment in the carb wasn’t getting enough fuel, he took apart the carb, changed the gaskets etc. Turns out it didn’t help, issue remains the same.

Hi, I’ve been running into some carburator/fuel problems. For the last month, my ‘86 740 Pierburg 2B5/7, has had a rough idle. Dropped in RPM’s, then stalled. Whenever I was driving in 4th or 5th gear and did a pull, it started stuttering as if it wasn’t getting enough air or fuel (no idea). I thought it was just a fuel issue (bcs I drove on e10 95 fuel for some time and the car had been sitting a few months before I bought it.) Changing the fuel filter, didn’t help. Usually I do everything myself, but I had no idea what the issue was.
Went to my local (classic car) mechanic, he told me that one of the compartiment in the carb wasn’t getting enough fuel, he took apart the carb, changed the gaskets etc. Turns out it didn’t help, issue remains the same.