Quadrajet loading up at idle

[RHUBBARD422]

I am having issues with my quadrajet wanting to load up and die at idle speed. It it doesn't always do it. One minute it will idle perfectly and then after cruising around for a bit then hit a no wake zone it will slowly lose RPMs and die when i kick it down to idle speed. I have not touched the mixture screws yet as i do not have a tool to reach the one on the left side of the carb. Also after a cold start i always end up with black soot on the side of my boat from the exhaust and i will get a little bit of white smoke but only after the initial start. It doesn't do it any more throughout the day. The engine is brand new but the carb was not rebuilt. I would also like to mention that after a cold start last weekend the carb loaded up so much i noticed gas on the intake manifold when i inspected the carb to see what was going on. Scared the heck out of me. I've got to get this taken care of. The boat runs so strong above idle speed but that hit and miss smooth idle is just driving me crazy.

 

[alldodge]

Sounds to me like its time to rebuild the carb. I would also check the fuel pressure (3-7 psi) and also check the fuel pump diaphragm over flow line

 

[RHUBBARD422]

As to checking the fuel pressure and overflow line; could this be done by me or should i have an experienced mechanic do it? This is all new to me.

 

[alldodge]

As to checking the fuel pressure and overflow line; could this be done by me or should i have an experienced mechanic do it? This is all new to me.

The over flow line is clear tubing and goes from the fuel pump to the top of carb or flame arrestor. While the engine is running, there should be no fuel dripping from the tubing. If you see fuel dripping then the fuel pump has gone bad.

Don't think you have a fuel pressure issue but it's good to check during carb work. A tee is fitted in the fuel line and attached to the gauge. Its pretty easy but if you don't feel comfortable with it then yes get someone to help.
http://www.summitracing.com/parts/anm-cp7803?seid=srese1&gclid=CMvst5Lmj8cCFVGAaQodqnsNPw

I believe your probably having carb problems, but would like to check some other things before carb is removed.

Have you replaced the fuel filter?

 

[RHUBBARD422]

Yeah i replaced the fuel filter last week. The old one was full of debris. Still having the idle issue after changing. I will inspect the over flow line. I dont recall seeing a clear tubing anywhere near the carb though.

 

[alldodge]

You never mentioned what size, year or type the motor is so I just found a Q-jet on a 350, note item 2, there is a filter in the carb
http://www.mercruiserparts.com/Show...br=140&bdesc=CARBURETOR(ROCHESTER+-+4+BARREL)

 

[RHUBBARD422]

It is a 5.7 ltr 350 mercruiser. The boat is a 92 but a new motor was installed last year. I replaced the fuel filter on the carb. Is there another in a different location?

 

[NHGuy]

Does the choke open fully and stay open?
It also wouldn't hurt to go over the bolts on the carb, just hand snug them-no gorilla stuff.
Take off the throttle linkage and set the idle to 725 with linkage off, and engine fully warm. Also make sure it returns to idle dependably. Just give it a couple of revs with the lnkage off. It's ok to spray a little carb clean on the links.
The throttle cable should push the throttle link closed at idle.

 

[alldodge]

It is a 5.7 ltr 350 mercruiser. The boat is a 92 but a new motor was installed last year. I replaced the fuel filter on the carb. Is there another in a different location?

Yes there should be a canister type filter (item 14)
http://www.mercruiserparts.com/Show_...ND+FUEL+FILTER

I would say since you found the crud if the carb filter your other filter is toast or not there. This also says that you need the carb taken apart and cleaned.

Edit: also note item 19 is the clear tubing which should go to the top of the carb or flame arrestor

 

[biggjimm]

Besides a carb rebuild, it might be a good idea to clean or replace the fuel lines & fittings/anti-syphon valve & inspect/clean the tank & the fuel pump. Sounds like they might be crudded up too if you had a lot of crud in the filters. Good luck. Jim.

 

[RHUBBARD422]

Going to have the carb rebuilt. Need some direction as to where to get the kit. It's a Rochester quadrajet 4 barrel 17080561. 5.7Ltr 350. Thanks for the help. You all are great.

 

[alldodge]

Going to have the carb rebuilt. Need some direction as to where to get the kit. It's a Rochester quadrajet 4 barrel 17080561. 5.7Ltr 350. Thanks for the help. You all are great.

You need kit 823426A1 and can be found by google using "mercruiser 823426A1
Also crosses to this Mallory kit number http://www.iboats.com/Mallory-Carb-K...view_id.365342

In the link it states to not use the flange gasket that comes with the kit to use 27-52457 2 , this to can also be googled
http://www.mercruiserparts.com/Show_...2D+4+BARREL%29

 

[RHUBBARD422]

Any idea why it would call for a different gasket? I purchased a kit from a different company and I'm still having the same issues. Loading up occasionally and when cold fuel is leaking from around the accelerator pump and somewhere along the sides of the carb.

 

[alldodge]

Any idea why it would call for a different gasket?

Unable to say for sure but in most cases the gasket either interferes with the throttle plates or does not seal well.

I purchased a kit from a different company and I'm still having the same issues. Loading up occasionally and when cold fuel is leaking from around the accelerator pump and somewhere along the sides of the carb.

Need to readjust your float or your float is sinking, or weights to much. Need to been the tang to adjust the float level

 

[RHUBBARD422]

My mechanic just informed me that the fuel pressure is 6.5 psi and is pushing the float open. Should I go with a different fuel pump or fuel pressure regulator?

 

[flipbro]

That's not your problem. 6.5 is fine. Listen to what Alldodge is telling you and check that the flot is set properly...

 

[Bondo]

That's not your problem. 6.5 is fine. Listen to what Alldodge is telling you and check that the float is set properly...

Ayuh,..... Agreed,....

 

[Grub54891]

I'd just replace the float, and set it properly.Only had 2 go bad in my many crab rebuilds, but hey... ya have it apart twice, why not?

 

[alldodge]

If float is set correctly then only other thing is needle and seat

 

[keith2k455]

I'm sorry, one thing is still sticking in my mind. ...problems are at idle and you still haven't adjusted the idle circuit with a vacuum gage attached. Get the tool you need to reach the idle adjust screws and adjust that first. Then adjust floats. Then check timing then verify idle adjustment once again. Idle adjustment is easy, you want the smoothest idle at the highest rpm and highest reading on the vacuum gage. After you achieve this, use the idle set screw to bring the idle down to the recommended rpm.