Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Model 17082403 fuel leak only after shut down, Crusader 454 engine

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BarryK3:
Hi,

I am a new owner of an older boat with twin Crusader 454s, 1990 vintage. I exchanged the very dirty carbs for rebuilt Quadrajets of the same model (marine version). The accel. pump on the port engine was not working at all and it was very difficult to start; no choke system on these.

Both engines start and run fine now. The port engine has a mechanical fuel pump (Mark 4 Crusader) and the starboard has an electric fuel pump (Gen 5 Crusader).

The port engine has a minor fuel leak only after shutting the engine off. There is NO leak while running. The fuel leaks out of the base of the carb somewhere and accumulates on the top of the intake manifold (not inside manifold).

I thought that maybe I was getting heat soak. I have a laser temp sensor gun: carb was 104 deg and manifold was 144 deg after running for over an hour.

The float level is set to spec which is about 7mm I think.

The starboard engine with the electric pump does not leak at all.

Thanks,
Barry

Cliff Ruggles:
Where did the carbs come from?

Are they actually rebuilt Marine units or "remanufactured" automotive conversions?....

BarryK3:
I believe that both carbs are marine carbs based on the greenish color of the throttle plates and the angled vent tube. I've only owned the boat for a few months so I don't know the history. The carbs that were on it looked about 30 years old so I think they were factory originals.

The leaking carb is a rebuilt exchange for my original carb  (mechanical fuel pump). The one that is not leaking is a rebuilt original (using electric pump). Both were rebuilt at a local carb shop. The owner told me that the swap was identical to my original. The two look the same except that the swap does not have a vacuum port at the base under the fuel inlet.

Thanks,
Barry

Cliff Ruggles:
All of the "exchange" Marine carbs I've seen in recent years were automotive "conversions".

Do they have Marine part numbers on them?

Can you post pics of them?

Not surprising you are having issues.  The companies doing them use the wrong parts, poor quality parts, and if they were built from automotive cores they will be heavily "butchered" in a futile attempt to make Marine units out of them.

Even if they used genuine Marine units they will still be troubled and as you have found out they pumps they used don't last much longer than it took me to type this.  Below are pics of what this new fuel does to the "blue" pump seals other companies sell and are using in carburetors they build.

I just got the carb in last week with the pump in the 2nd pick.  The shop sent the carb out and the pump didn't last a month after they got it back and put it in service.......Cliff

BarryK3:
 I will get pictures of both carbs today.

Do the authentic marine carbs have vacuum ports at the base, under the fuel inlet? The swapped one doesn't have one. I was going to set idle mixture with a vacuum gauge but could not find a port to connect to.

Any idea what is causing the leak? This is obviously a fire risk on a boat, less of a concern on a car.

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