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What is this carburator part? (see pic)

C

ChuckC

New member
Hi all,

In the attached picture, the circled item is broken on my starboard side carb (the picture is of the "unbroken" port side carb). On the starboard side the plastic bracket on the part broke, so it's just hanging free. What is it and what does it do? 1985 Quadrajet on a Crusader 454 CID.

Background: All summer I've been dealing with a hard start issue, which I had planned to address in the off-season. After my boat has been sitting unused for more than a few days, the starboard side requires a manual shot of fuel down the carb in order to start. After that, it starts and runs fine all day long and for a couple of days afterwards. Give it a week of sitting though, and it needs the squirt of fuel again.

A few days ago however, I gave it the fuel squirt "trick" and it started and ran for about a minute, then died. I was never able to get it started again. I started poking around and noticed the broken part in the picture. Now I'm curious if this broken part was the cause of my summer starting woes all along, or if I have multiple issues going on. And, what changed now?

Other thoughts:
1. As an attempt at a quick fix on the day, I zip-tied the broken part back in place, but no luck starting the engine.
2. There is no fuel delivered by the accelerator pump. ​
3. Earlier in the summer, I did a full throttle run for approximately 2 minutes with no problems, so I think I can rule out a fuel pump issue?

Thoughts? Thanks all!​


Carb picture.jpg
 
That is the vacuum break though some call it a choke pull off....it has multiple functions, the most relevant is to open the choke a minimal amount after the engine starts.

Fuel pumps can fail fast so what you did a week ago may not reflect what exists now.

The "add fuel to start" process has become common with the reformulated gasoline ..... Some will tell you is the q-jet leaking out of the well plugs - I say that's a load (on the 170- part number); its the fuel evaporating in a few days, especially in a hot engine box.

No fuel from the accelerator pump discharge usually indicates a dry float bowl - you can verify by checking the bowl vents or using a good sniff.....a pressure check will tell you for sure.
 
Mark has nailed it.
Not only will this pull the choke plate open (during sufficient manifold pressure), it will let it return when manifold pressure diminishes, preventing a complete stall.


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Question.
It looks as though that linkage rod connects the diaphragm unit to the secondary air door shaft…...... is that correct?



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Last edited:
Thanks very much gents, the part in question has now been replaced. As it turns out, it wasn't the cause of my problem but obviously needed to be fixed anyway.
However, I think (and hope) that I MAY have solved my issue! I replaced the fuel pump (unnecessarily, as it turns out). After doing so, I noticed the fuel/water separator was still not being filled with fuel. I changed the fuel filter (the one mounted on the engine itself, that I didn't even know existed), and it started and ran fine! Hurrah! I'll find out if the fix "holds" tomorrow when I'll next be at the boat. Thanks again for your advice gents!

PS - Rick, yes, there is a linkage to the secondary, although it's able to "slide" in that small curved channel if that makes sense.
 
FWIW, I'd encourage you to eliminate the problem fuel filter as long as you have a good fuel/water separator....they are notorious for rusting and leaking....
 
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