Two fuel issues

[DirtyDYT]

Howdy again!

My C10 (454 swap) is dribbling fuel from the carb when shut off. Damn near hydrolocks whichever cylinder’s intake is open every time. The throttle blades close all the way and my throttle return is tight. It also wicks just enough gas through the throttle shaft to appear wet on the shaft about 1/4” outboard of the carb but it never puddles or drips. Other than that it pulls like a champ. Sounds like it’s time to rebuild the carb?

Secondarily, once it dribbles all the fuel out I end up with vapor lock if the engine is still warm. I know part of this is a ridiculous fuel line routing I employed to “make it run and worry about it later.”

Now that I’m using the truck to do some landscaping for my family I need it to start and go without a 30-60 minute rest in between. My questions begin here:

Can anyone recommend their favorite Qjet rebuild kit?

Does the throttle shaft weep mean I should think about replacing it?

Does anyone have a part number or diagram for the solid metal fuel line that goes from mechanical pump to carb on a Gen IV 454?

Thanks in advance.

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[climb-101]

if it were me i would just get a holley carb for it. never have liked the quadra jets.

it does sound like its time for a rebuild if it’s leaking by the shafts

 

[DirtyDYT]

if it were me i would just get a holley carb for it. never have liked the quadra jets.

it does sound like its time for a rebuild if it’s leaking by the shafts

Yeah, it also idles a little high because of the dribble.

Despite the issues outlined above I am really happy with how these quadrajets perform, especially under mid throttle conditions. I’m probably going to stick to the same for now.

I’ve rebuilt many smaller carbs (VW, motorcycle, welders, powered implements) so it shouldn’t be out of my wheelhouse but I’m leaning towards replacing it to save time.

Is there any good vendors of remanufactured/rebuilt carbs?

 

[Crispy]

I havent done it myself but everything I've been reading about Qjets is that they are pretty straight forward to rebuild. I would try a $20-30 rebuild kit before spending money on a new one.

Gonna be pulling the qjet on my Trans Am soon for a rebuild and I hope I'm not forced to eat my words.

 

[Blue Ox]

Carburetors are not my forte but I've rebuilt a couple of Q-Jets and they are fairly straightforward. My guess is your problem is leaking well plugs or faulty float or needle and seat.

If you really want to be informed "Rochester Carburetors" by Doug Roe is a good book on them and a lot of people here have recommended Cliff Ruggles book and or rebuilt carbs. No firsthand experience with him though. I'm sure you can Google him.

And don't worry about the haters, Q-Jets are great carbs.

The only fuel pipe I had to replace I did by buying tubing and using my brake line bender and flaring tool to copy the original.

 

[1987 GMC Jimmy]

Cottage rebuilders will put bushings in the primary throttle shaft to stop them from leaking vacuum. I suppose they can leak fuel, but as mentioned above, I’d be more worried about the well plugs. I say rebuild it.

 

[DoubleDingo]

Yes, contact Cliff Ruggles or @Quadrajet Power or other reputable supplier of parts/rebuilder. I've dealt with Cliff and he is informative and will get you the correct kit for your application. Quadrajet power has a website with rebuilt carbs ready for purchase, and also will rebuild yours if you send it in. They're not hard to rebuild, but with the stuff going on with yours, it may be best to have someone with knowledge of the quadrajet to tackle it, or get one already built so it's just a remove and replace. Cliff has a roughly 12 month turnaround. Not sure about quadrajet power. I'd stick with the quadrajet, they are great carburetors.

 

[1987 GMC Jimmy]

Or Mountain Man in Hackett, AR. They did mine, still going great. One week turnaround there, give or take, and $200 plus shipping.

 

[Craig 85]

Does anyone have a part number or diagram for the solid metal fuel line that goes from mechanical pump to carb on a Gen IV 454?

I used Inline Tube #CTC8101 (79-87 pump to carb, page 13). $20
http://online.flipbuilder.com/wmmk/wlho/mobile/index.html

 

[DirtyDYT]

I havent done it myself but everything I've been reading about Qjets is that they are pretty straight forward to rebuild. I would try a $20-30 rebuild kit before spending money on a new one.

Gonna be pulling the qjet on my Trans Am soon for a rebuild and I hope I'm not forced to eat my words.

I’d like to rebuild it myself but I have a whole bunch of other things eating up my time and I just need this truck to work correctly as soon as possible. It may work out that I buy a new one and rebuild this later.

Yes, contact Cliff Ruggles or @Quadrajet Power or other reputable supplier of parts/rebuilder. I've dealt with Cliff and he is informative and will get you the correct kit for your application. Quadrajet power has a website with rebuilt carbs ready for purchase, and also will rebuild yours if you send it in. They're not hard to rebuild, but with the stuff going on with yours, it may be best to have someone with knowledge of the quadrajet to tackle it, or get one already built so it's just a remove and replace. Cliff has a roughly 12 month turnaround. Not sure about quadrajet power. I'd stick with the quadrajet, they are great carburetors.

I’m in a need by Sunday (ASAP) kind of situation. I’m also realistic enough to know I won’t be able to get the parts here that quickly, let alone get it rebuilt.

Or Mountain Man in Hackett, AR. They did mine, still going great. One week turnaround there, give or take, and $200 plus shipping.

That sounds hopeful but a week without a truck might not be doable.

I used Inline Tube #CTC8101 (79-87 pump to carb, page 13). $20
http://online.flipbuilder.com/wmmk/wlho/mobile/index.html

That is exactly what I need, thank you!!


Thanks for the input everyone. At this point I’m leaning towards just buying a new quadrajet to get this thing back to functional fast.

 

[1987 GMC Jimmy]

Maybe see if they have a core exchange thing you can do. It might cost you more, and you won’t have your original carb, but you’ll get it however quick it takes to ship so a few days. Unfortunately, it’s the weekend now so you’d have to get on it bright and early Monday.

 

[75gmck25]

I have both the Ruggles and the Roe books, and I find the Ruggles book easier to read and use because of the color pictures. However, Ruggles spends a lot of time discussing different versions of the Quadrajet and how you can improve performance, and sometimes its a challenge to figure out what applies to your carburetor. Various features and orifices came and went over the years as they tweaked the Quadrajet, so the way to modify them also changed. YMMV

I bought the Ruggles rebuild kit, along with throttle shaft bushings and the electric choke conversion, and it worked well on my stock 350 truck. How after I upgraded to aluminum heads and more cam I had to go back to Cliff to get new rods and jets so that it would work well with the new combination. Its still a work in progress.

Bruce

 

[Matt69olds]

I’m wondering how a Q-Jet could leak enough fuel to hydro lock the engine? The float bowl isn’t that big. Does the fuel pump have the small 3rd hose nippe? One nipple is fuel supply from the tank, the threaded fitting is obviously the fuel feed to the carb, and some fuel pumps will have a third nipple that is a fuel return to the tank. Those are used on engines with air conditioning. The 3rd fitting has a small orifice, it’s designed to circulated a small amount of fuel back to the tank to keep the pump cool. It also bleeds off fuel pressure when you shut off the engine. Under high under hood temps (like working the engine hard, or running the a/c) the fuel can boil in the lines, creating enough pressure to push the needle off the seat, overfilling the float bowl and flossing the engine. If your pump has the fuel return, make sure the fitting isn’t blocked, and the line to the tank is clear and connected to the tank

 

[DirtyDYT]

I’m wondering how a Q-Jet could leak enough fuel to hydro lock the engine? The float bowl isn’t that big. Does the fuel pump have the small 3rd hose nippe? One nipple is fuel supply from the tank, the threaded fitting is obviously the fuel feed to the carb, and some fuel pumps will have a third nipple that is a fuel return to the tank. Those are used on engines with air conditioning. The 3rd fitting has a small orifice, it’s designed to circulated a small amount of fuel back to the tank to keep the pump cool. It also bleeds off fuel pressure when you shut off the engine. Under high under hood temps (like working the engine hard, or running the a/c) the fuel can boil in the lines, creating enough pressure to push the needle off the seat, overfilling the float bowl and flossing the engine. If your pump has the fuel return, make sure the fitting isn’t blocked, and the line to the tank is clear and connected to the tank

To reiterate, my truck seems to flood quickly at shutoff and idles a bit high. Symptoms have occurred and seem worse when it's hot and but have even occurred when it's cold after a 3/4 mile drive to Autozone. I can't think of any direct cause for these symptoms besides having dirt between the needle and the seat or maybe float issues. In my experience with smaller engines, it's usually a needle/seat issue. Since my truck idles high and seems to continue to leak fuel when shutoff, I don't have any other guesses.

The fuel return line is connected. I would not doubt that fuel in the line to carb boils post-shutoff with the way the line hugs the block. It's a rubber line routed in a funky way around the pulleys such that it is longer than the standard metal line (CTC8101) mentioned in posts above and holds more volume. If my needle and seat are not sealing correctly, this would allow the extra fuel in the carb and lines to heat up, percolate through, and leak into the engine because it would never see that back pressure allowing the fuel to pass through to the return.

Just my .02. I'm putting a carb on it today or tomorrow.





Update: Sticking by my float, needle, and/or seat diagnosis after spending more time with the truck this morning. I’ve also clarified a few things below.

On cold restarts: it empties the bowl and floods but does not try to lock up.

On hot restarts: it empties the bowl and the lines, vapor locks, and sometimes totally fills the cylinder.

Idle symptoms: The idle creeps upward from around 7-800 as the engine heats up. I left it running while I unloaded mulch today and my ears tell me it got up to almost 1500 rpm once fully warmed.

After running: the engine bay smells strongly of fuel, especially once warmed up. You can also smell raw fuel from the exhaust after a cold (flooded) restart.



Further update:

I have a fresh carb and the fuel line arrived in record time with only $5 shipping. I’m currently waiting on some insulating spacers to arrive before I slap it all together.

 

[DirtyDYT]

I put on the carb, line, and spacers. It runs better than ever, my idle is under control, and it restarts when hot. Massive score! Seems like my fuel system is finally just about dialed in...

Then I lost power brakes pulling out of my driveway for the first test drive. It never ends, does it?