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Old 01-02-2019, 10:35 AM
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Quadrajets issues

As long as we are on carb issues I thought I’d ask this one.

I have three Quadrajet carbed motors. One in my elCamino streetrod and two in my big boat.

All of them are hard starting if they sit for a week or so. I have a good sized syringe that I use for priming them so I get fast starts that way but it’s pain to do this. It’s very common in the big boats. I hear them cranking forever to start. Starters are very expensive for boats as they need non sparking stuff on them and they are often pretty difficult to R&R.

It’s been ages since I’ve taken one apart. One of the boat carbs is brand new rebuild. As I recall there are two plugs that leak down that are often covered with epoxy as a fix. Only a dim memory for me.

None of the 3 have much of an insulating spacer under them. The boat motors run 160-170 deg all the time and have excellent ventilation. The el Camino runs 180-190 all the time.

The chokes all set nicely when cold.

Any help?

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Old 01-02-2019, 11:06 AM
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Assuming you are using the syringe to fill the float bowl? Have you verified that there is no fuel in the float bowl? If you pump the throttle does the accelerator pump give it a shot of fuel when you look down the throat of the carb? If not then the fuel in the float bowl is leaking out or evaporating. When I rebuild Q-jets I like to open my vise and set the middle section of the carb (float bowl) level on the vise and fill the float bowl with glass cleaner and let it sit over night. If the level is the same the next day then it is good to go. If it has leaked down it will be easy to see where the blue glass cleaner has leaked out. I've found everything from leaky plugs to hair line cracks in the castings.
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Old 01-02-2019, 11:06 AM
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Quote:
Originally Posted by bentwings View Post
As long as we are on carb issues I thought Iíd ask this one.

I have three Quadrajet carbed motors. One in my elCamino streetrod and two in my big boat.

All of them are hard starting if they sit for a week or so. I have a good sized syringe that I use for priming them so I get fast starts that way but itís pain to do this. Itís very common in the big boats. I hear them cranking forever to start. Starters are very expensive for boats as they need non sparking stuff on them and they are often pretty difficult to R&R.

Itís been ages since Iíve taken one apart. One of the boat carbs is brand new rebuild. As I recall there are two plugs that leak down that are often covered with epoxy as a fix. Only a dim memory for me.

None of the 3 have much of an insulating spacer under them. The boat motors run 160-170 deg all the time and have excellent ventilation. The el Camino runs 180-190 all the time.

The chokes all set nicely when cold.

Any help?
Yes, more than likely the welch plugs are allowing the float bowls to empty. Pull the tops off, clean the area and epoxy the plugs.
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Old 01-02-2019, 11:34 AM
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New epoxy on the well plugs is the most common fix recommended whenever someone has a Quadrajet that goes dry after sitting for a day or two. However, based on reading Cliff Ruggles' book and other references, leaking plugs was only common on 60's and some early 70's Quadrajets, and in later models they resolved the leaks (mostly). My point is that trying to re-epoxy the plugs may not fix your problem.

This link has a discussion and suggestions from Lars Grimsrud about other ways to solve the problem.
https://www.corvetteforum.com/forums...rain-back.html

Bruce
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Old 01-02-2019, 11:57 AM
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Yeah, Iíve checkrd the accelerator shot after sitting for a week. Itís bone dry...no shot on all three motors. I squirt enough in the bowl vents to give a accelerator shot then a small shot in the bores. Almost always I get an instant start.

The boat has flame arrestors for air cleaners. They have short hoses on the side to provide valve cover vents that would be normally used for valve cover breathers. It also works to just squirt a good shot through these hoses. Itís just a spray across the carb. This results in a quick strat then the motor stops. It then will restart easily. Itís not a good idea though as there is then raw gas outside of the carb. A little ďsneezeĒ then can set off a CO detector or one of the fume doctors. Big boats are required to have and use all kinds of saftey stuff that we never see on cars. There are 4 bilge fans that run during pre start and two run all the time under way. The boat is wrapped for the winter bit I want to be ready in the spring.

Over the winter Iíll get after the el Camino and check those plugs. Whatís the common epoxy to use? JB Weld?

The boat carbs are much easier to get at as far as stuff in the way, itís just that they are a foot below floor level. I now have a padded board that I can lay across the hatch opening but itís still more uncomfortable than a creeper.

The el Camino is a typical car....lots of stuff in the way.
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Old 01-02-2019, 12:42 PM
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The link is a great read. Nice to learn something the first active day of the year.

Now it got me further thinking. One carb is a fresh aftermarket marine rebuild. I’m sure it was costly. The other is a year old.

When I was purchasing the boat both fuel pumps had issues so they both were replaced with the marine version of the double diaphragm pumps. There is a vacuum line from the top of the pump to the carb. One thing I found in talking to other boat guys is that they all have hard starting after sitting for a week or so.
There are various devices that purposely drain the pump to carb line. In effect opposit what is talked about in the link. I would guess this is to prevent gas from being instantly available as in Holley. The other thing is I had forgotten about the needle and seat location. The overall effect is that it’s the way the entire system is designed to limit possibility of fires. Also the beginning as to why you don’t see Holley carbs on enclosed inboard motors.

The later EFI motors offer better starting for sure.

So maybe my issue is “ normal” for this carb situation and not safely fixed. Since both motors operate exactly the same with the same idle speeds and same WOT speeds I should not complain. It appears that a USCG inspection which is common here should go ok. as far as the engine room. All the fire saftey stuff is either new or freshly inspected.



My generater is another matter. Here there are check valves electrically operated that essentially lock the fuel in the fuel line on shut down. This is to prevent siphoning either way. I don’t understand the reasoning but that’s the way it is. There is a float but no accelerator pump. I suspect the fuel level is very low in the bowl too, even when running.

Last edited by bentwings; 01-02-2019 at 12:49 PM.
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Old 01-02-2019, 01:06 PM
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Here’s the best way to seal your bottom plugs.
https://cliffshighperformance.com/Qu...ottom-plug-kit
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