Quadrajet problems after running for 20 mins

[Raystownboater]

Took the boat out last night for a quick test run after replacing the engine and putting on a rebuilt Quadrajet 4 barrel. One side note is the engine has an electric fuel pump. Once in the water, she ran great. I wasnt able to go to full throttle for very long because of the chop but I was more than happy with the performance, that is, until I was about 20 minutes into the test run. That's about the time i noticed a bit of a stumble at 3/4 throttle. It souded like the carb was choking. I went for a few more seconds at 3/4 throttle and the boat suddenly lost power and slowly died. I wasnt able to restart it immediately and when I looked into the carb, I could see fuel just laying in there. I put the throttle at full to dump the fuel and the boat started but would not idle. The only way to keep the engine running was 3/4 throttle or higher. The minute I dropped it to idle and tried to put it in gear, it died. This went on for a few minutes but thanfully I was out with Ezmobee and he pulled me back to the dock. THANKS JEREMY! Once on the trailer, I stopped at the marina and talked to one of the mercruiser mechanics and without looking at the engine, he is convinced the carb is not getting enough air. I havent been out, yet, this morning but wanted some input from the experts here. Any help is greatly appreciated

 

[CobiaXL]

Re: Quadrajet problems after running for 20 mins

If you seen raw fuel,chances are your needle and seat either crapped out or piece of dirt is lodged in seat.

 

[Raystownboater]

Re: Quadrajet problems after running for 20 mins

Carbs are not my strong suit here so can this be addressed without a tear down?

 

[RogersJetboat454]

Re: Quadrajet problems after running for 20 mins

If you seen raw fuel,chances are your needle and seat either crapped out or piece of dirt is lodged in seat.

I second that. Raw fuel dumping in sounds like a stuck float. Did you correctly set the float height when you rebuilt it? Is there a new needle and seat? Was all the fuel filters replaced?

Other than that, make sure your flame arrestor isn't gunked up too.

 

[CobiaXL]

Re: Quadrajet problems after running for 20 mins

Carbs are not my strong suit here so can this be addressed without a tear down?

Yes your gonna need to rebuild it...When you pull the top off carb most likely the gasket will tear.Your supply the kit and ill rebuild it for ya...3 beers a hr is going rate...

 

[Raystownboater]

Re: Quadrajet problems after running for 20 mins

I second that. Raw fuel dumping in sounds like a stuck float. Did you correctly set the float height when you rebuilt it? Is there a new needle and seat? Was all the fuel filters replaced?

Other than that, make sure your flame arrestor isn't gunked up too.

I bought it from the marina and installed it right out of the box. I was told it was set up correctly and it DID run great in the beginning

 

[RogersJetboat454]

Re: Quadrajet problems after running for 20 mins

Carbs are not my strong suit here so can this be addressed without a tear down?

You will need to do a partial tare-down. You can leave the carb mounted on the engine. You need to take the top of the carb off (air horn), and take a look at your float which is located between the primary venturis.

Check needle and seat. If they don't look new they should be replaced.
Check float height. Most carb kits come with a gauge for measuring float height.
Check to be sure the float isn't soaked through with fuel.

If carbs are not your strong point, you should consider getting a book.
I fully endorse this one, it will tell you EVERYTHING you need to know about the Q-jet.
http://www.amazon.com/Rochester-Car...3014/ref=sr_1_5?ie=UTF8&qid=1308148464&sr=8-5

 

[Raystownboater]

Re: Quadrajet problems after running for 20 mins

Yes your gonna need to rebuild it...When you pull the top off carb most likely the gasket will tear.Your supply the kit and ill rebuild it for ya...3 beers a hr is going rate...

If you are serious, I'd throw in some cash along with a case of your choice!

 

[CobiaXL]

Re: Quadrajet problems after running for 20 mins

If you are serious, I'd throw in some cash along with a case of your choice!

100% cereal...Ill pm ya my # and well get together..

 

[CobiaXL]

Re: Quadrajet problems after running for 20 mins

I bought it from the marina and installed it right out of the box. I was told it was set up correctly and it DID run great in the beginning

New,used or rebuilt out of the box?

 

[john3931]

Re: Quadrajet problems after running for 20 mins

If you just bought the rebuilt carb, I would go back to where you got it and see what you should do. Don't take it apart yourself and then not be able to get any warranty if there is any.

 

[john3931]

Re: Quadrajet problems after running for 20 mins

Also check to see if the choke is operating properly. May the choke linkage came disconnected after running for a while. It was working fine then started acting up. The little U shaped clip on the choke linkage may not have been crimped correctly and came off.

 

[Raystownboater]

Re: Quadrajet problems after running for 20 mins

New,used or rebuilt out of the box?

Sold as a Reman

 

[Raystownboater]

Re: Quadrajet problems after running for 20 mins

If you just bought the rebuilt carb, I would go back to where you got it and see what you should do. Don't take it apart yourself and then not be able to get any warranty if there is any.

No warranty, which is my fault. I purchased it last fall when the engine was installed and today I have no reciept. Live and Learn

 

[Raystownboater]

Re: Quadrajet problems after running for 20 mins

Also check to see if the choke is operating properly. May the choke linkage came disconnected after running for a while. It was working fine then started acting up. The little U shaped clip on the choke linkage may not have been crimped correctly and came off.

That was one of the first things I checked. Still connected and working

 

[john3931]

Re: Quadrajet problems after running for 20 mins

Find your problem yet??

 

[Raystownboater]

Re: Quadrajet problems after running for 20 mins

Find your problem yet??

Seems the electric fuel pump was the issue. I replaced it with a mechanical pump and now the carb just needs to be fine tuned. I spoke to one of the chevy guys at the speed shop who told me that certain electric fuel pumps have been known to push the needles off the seat, making the float useless and flooding the carbs. It made sense to me since the boat would only run at high rpms. Im gonna fine tune everything and try it on the water next week.

 

[RZR2007]

Re: Quadrajet problems after running for 20 mins

Quadrajets do not respond well to higher fuel pressure, the mechanical pump is the best way to go. Bet she'll run fine now as long as the float still works properly! You can adjust how fast the secondary butterflies come open, if too loose they open to quickly and will bog/hesitate when they open. Properly tuned they are an excellent carb.! Good luck.