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

[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.

[Cliff Ruggles]

Leaking after shut down could be many things. 

Miss-matched parts will cause that problem IF the upper idle airbleeds aren't in place to "vent" the flow from the idle tubes to the discharge ports.

A leak under the fuel inlet seat will also cause this as an residual fuel pressure in the line will continue to fill the carb till it overflows from the boosters.

Bad needle/seat assembly is another cause.

Very few Marine carburetors had PCV or any other vacuum ports for vacuum advance and such as most didn't use either.

Pics of the carbs will help me identify them......

[BarryK3]

Cliff,

You are completely correct. I was mistaken. The leaking "exchange" carb is NOT an original marine model. I thought it was the same as the other one. The model number is 17000580. It has a straight vent, not an angled one.

I returned it to the carb shop today. He is rebuilding my original one (the "core" that I gave him) and it will be ready tomorrow. I hope that it is a marine model. I believe that it is.

The first picture is a poor picture of the model number on the leaking carb, hard to read. It is painted black.

The last 2 pictures are of the working carb that he recently rebuilt, model 17082403.

The local guy runs a very clean professional shop and does good work. I just don't think he is familiar with marine parts. He deals almost exclusively with automotive.

Assuming that I get back a 2nd working marine carb, what should I do next? Should I replace the accel. pump skirts on both with the ones that you sell?


Thanks so much,
Barry

[Cliff Ruggles]

You are extremely fortunate to still have access to the original Marine units.  Marine carburetors are NOT the same as automotive units and it's not just the calibrations.  They are specifically built and designed to power engines that are heavily loaded most of their life, so they have specific parts, features and take different rebuild parts than their automotive cousins.  Failure to use the correct parts is why I get so many in here that don't work well or at all.

I haven't had a "rebuilt" Marine unit come in here in at least 10 years with the correct parts in it.  I get them in here all the time "freshly" rebuilt and not working.

All of the kits being supplied in the aftermarket have the wrong parts in them, but I'm not going into great detail to help out the folks supplying them.

They do not come with a good pump seal either.  NONE of the blue seals that show up in over the counter and on-line kits will hold up in this new fuel. 

You just found that out if one of the carbs placed in service didn't have any pump shot.  I test the seals being supplied in kits and on occasion I have to grab one locally if I'm out of stock on a gasket or two.  I submerge the pump in fresh fuel and usually within an hour or so the "blue" seal is swollen to nearly two times it's original size.

I preach using good parts all the time, and a lot of "builders" are getting my parts, but sadly many still build carbs using "kits" obtained locally or what is being supplied by the vendors who still sell parts for these carburetors......FWIW......Cliff

[BarryK3]

I brought back the "exchange" carb today and got my original one back, cleaned up and looking good. Thank you so much! I got it before someone else did. So now I have 2 original marine units, identical. I installed and ran the one I picked up today and NO LEAKS of course!

You were a huge help Cliff! I will be purchasing 2 of your rebuild kits soon. Do you have rebuild instructions on this site or can you recommend where to get them?

Thanks again,
Barry

[Cliff Ruggles]

Good news.  There is a link in the package with the kits to basic instructions, plus I put a list of Marine kits by carburetor number in with them so you know the float levels and basic settings.

In the kits you'll find the correct high flow Marine Viton N/S assemblies, correct HP Marine pump with a stainless steel return spring, chrome vanadium duration spring, and lifetime warranty pump cup w/garter spring.

The main body to airhorn gasket is also made from a better material and .015" thicker for improved sealing.

I ship the same day if ordered before apprx 11am...tks...Cliff

[BarryK3]

Thank you!

[BarryK3]

Sorry, one more question: are these carbs susceptible to well plug leakage?

[Cliff Ruggles]

Pretty rare to find a Marine carb leaking at the bottom plugs post about 1978.  They are very well made and the plugs are swaged in place better than most other units.

Marine castings are typically in better shape as well as they see much less use and not nearly the heating/cooling cycles automotive carbs get.   The big enemy to Marine units is rust and corrosion as they live in a wet cold environment often tucked under an engine cover or in a closed engine compartment.....

[BarryK3]

Thank you!

[tayto]

I helped a buddy with a 1988 era mercruiser original Qjet, both well plugs leaked. Infact the last 3 Qjets I've done had at least 1 well plugs that leaked (primary and/or secondary). I just do them as a standard repair now.