350 W/QJet carb fuel question

[captmello]

I've had an ongoing issue with my boat since I bought it last year.

If it sits for a couple days the fuel is draining from the carb and the fuel line down to the pump. I've read a few posts in the past blaming the carb for having a part stuck open. I can't recall the part name.

I was having Idling issues as well last year and decided to have it rebuilt this spring. It Idles and runs great now but if it sits for a few days it is still losing the fuel from the fuel line.

I have faith in the mechanic that did the rebuild so I thought I'd ask here to see if it could be another issue before I pull the carb and bring it back to him. Could it be the fuel pump causing it to leak down?

Thanks.

 

[Don S]

Re: 350 W/QJet carb fuel question

You probably need to JB Weld the well plugs in the mid section of the carb.
Very common problem on Q Jets.

http://www.florida4x4.com/tech/quadrajet/www.toronado.org/wellplug.htm

The picture belows is also from the same site. The screwdriver is pointing at the well plugs I am referring too.

You will have fun here/
http://www.florida4x4.com/tech/quadrajet/index.php

 

[captmello]

Re: 350 W/QJet carb fuel question

Thanks very much for the link Don!!

Now I'm wondering if anyone knows if I can do this repair with the carb in the boat or if I need to pull it out completely, and, If I need to have replacement gaskets or parts for reassembly? Keep in mind it was taken apart less than two months ago.

 

[maxxman04]

Re: 350 W/QJet carb fuel question

carb does need to come off to seal the plugs. the lead they used eventually gets eaten away by the gas. and even the best forget, or don't realize, these plugs need to be resealed. pull the carb, and the only part you might have to remove after that is the throttle plate (base plate), usually a matter of 3 or 4 screws. then apply JB WELD over the plugs pictured in Don-s' post.

 

[captmello]

Re: 350 W/QJet carb fuel question

Thanks for the replies, I'm going to do it this coming week.


Since It was taken apart a couple months ago, I'm going to reuse the gasket. Let me know if that is a bad idea. I'll let you know how it goes.

 

[dan t.]

Re: 350 W/QJet carb fuel question

if the gasket doesnt tear re use it,also the base gasket. I also seal the 2 small plugs just forward of the indicated plugs ,these seal the primary main fuel wells.epoxy seems to work just fine ,I have never tried J B weld but cant see why it wouldnt work

 

[captmello]

Re: 350 W/QJet carb fuel question

Well I pulled the carb and removed the bottom plate and found the well plugs to be well sealed. At least they appear that way.

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Any other Ideas on what would allow the fuel to draining back to the tank?

I had it out over the weekend. At one point it sat for 2 days, when we returned, two pumps of the throttle and it popped off immediatly. Normally, after sitting for a full week, it takes 20-30 sec of cranking to start, doesn't help to pump the throttle at that time. I'm going to put a clear fuel filter in line from the pump to the carb and see how long it takes to drain down.

Thanks again for the input.

 

[parrisw]

Re: 350 W/QJet carb fuel question

I don't know if that carb does or not, but some have a check valve in the filter thats in the inlet of the carb. Pull the big nut off where the fuel line goes in and check if its that style.

 

[Ridemywideglide]

Re: 350 W/QJet carb fuel question

I'd smear some JB on the lower wells that don't have it while you have it apart..
Only way it could be draining back is if the needle valve is stuck open. Otherwise, unless your pumping the fuel out of the carb, there is no other way for it to get out. Needle being stuck open would cause running issues most likely tho.
Check your choke. Maybe it was just warmer the time it started easy. If your choke isn't closing, would make it hard to start when it sits.

 

[Greg Gessler]

Re: 350 W/QJet carb fuel question

Applying epoxy to the secondary wells is a short term fix, as they always seem to leak again.
Try these specially made o-ringed plugs to fix the problem.
Go to bottom of page to view : GHP-Q1742/Q1743

http://www.gesslerheadporting.com/members/gesslerheadporting/ghp.nsf/822dcaaaa26c6da985256dd80023623d/4f069c2b796f01e3852574fd005bbefc!OpenDocument

 

[Ridemywideglide]

Re: 350 W/QJet carb fuel question

I don't think you'll have to worry about the leak coming back with JB Weld.. Most epoxy on the shelves is not fuel proof, that's why you don't use it...

 

[captmello]

Re: 350 W/QJet carb fuel question

Well I put JB weld on the lower wells and put it back together. I also put a clear in line filter for testing. I found that after sitting for 3-4 days the fuel is draining out.

So I'm not sure of the next move.

If the needle valve was stuck as mentioed by one poster, what kind of running issues would go along with it? The boat runs, starts, and idles really good.

Any other suggestions?

 

[soaringhiggy]

Re: 350 W/QJet carb fuel question

this may be a problem in your fuel delivery system. How old is the fuel pump. If it is worn the fuel could be draining from the delivery side of the pump back to the suction side of the pump and back to the tank, or the diaphragm has a leak in it and the fuel slowly evaporates into the pump casting.

Other areas to look at are the fuel lines, if there are rubber lines they can cause this type of problem even though they look OK. I have had lines that break down internally and look fine from the outside. This allows fuel to travel up the braiding, or worse, allows air to leak into the hose and stops or decreases fuel flow to the pump.

I would spend some time really looking at the fuel deliver system.

 

[captmello]

Re: 350 W/QJet carb fuel question

this may be a problem in your fuel delivery system. How old is the fuel pump. If it is worn the fuel could be draining from the delivery side of the pump back to the suction side of the pump and back to the tank, or the diaphragm has a leak in it and the fuel slowly evaporates into the pump casting.

Other areas to look at are the fuel lines, if there are rubber lines they can cause this type of problem even though they look OK. I have had lines that break down internally and look fine from the outside. This allows fuel to travel up the braiding, or worse, allows air to leak into the hose and stops or decreases fuel flow to the pump.

I would spend some time really looking at the fuel deliver system.

You're the first person to bring up the fuel pump. I believe I have the original pump from 1988. I don't think i have a hose problem but I'll go back and check all the connections.

I'm wondering how I could test to see if it is in fact the pump? Any ideas?

 

[soaringhiggy]

Re: 350 W/QJet carb fuel question

pressure and flow tests, however, if yours in the kind that you can take apart a visual inspection would be best. Check the valves and the diaphragm for ware, warp, stickiness etc. If you can take yours apart there were be a bunch (8-10 if I remember correctly) small (#6 or #8) screws around the outside of the pump. If you remove the pump, make sure that the push rod does not get lost, and that you get the push rod to actuating lever back in properly.

If there has been a long period of non-use the one way valves can give some trouble.

Remember, hoses can look good and still be collapsed or cracked inside. Take a look at the hoses and make sure the are proper fuel type hose, many people have stuck the incorrect type of hose in a fuel system with out knowing and it can lead to frustration when trouble shooting a system like this.

 

[soaringhiggy]

Re: 350 W/QJet carb fuel question

fuel system problems can be so difficult. There is a very good description of testing in one of the stickies I think.

 

[captmello]

Re: 350 W/QJet carb fuel question

Thanks for your insight. All the fuel lines are new last year. I went and looked at it and it does have the ring of screws around the underside, but I don't know what I'd do if I took it apart. Do you think i can get a rebuild kit for it? I can get a new pump at napa for 79.99.

I hate throwing parts at the problem, however I believe the carb is good. If the pump is a possibility then I'll go ahead and either rebuild mine or buy a new one. I've never read anything about rebuilding fuel pumps on this site before.

 

[soaringhiggy]

Re: 350 W/QJet carb fuel question

they are very simple. There are two disk type valves, several springs and a diaphragm. The hardest part of the inspection would be putting it back on. The push rod from the cam always wants to slide out while you are trying to mount the pump again.

It would only take a bit of time to have a look at it. I think you can buy rebuild kits with all the parts still for them as well.

$25.00 could be cheaper at NAPA.