1.4v at electric choke?

[flyboy1100]

good! for reference this is what i have have. highly debating just buying a rebuild kit too, so I can make sure everything else is good on the inside

 

[350runner]

No that's on the base of the carb. Manifold vacuum is what it should be.

 

[350runner]

This is the one I'm talking about. Your carb doesn't have one

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[chengny]

Some discussion on choke pull-offs and malfunctioning chokes in general:


Choke plate misaligned:
Results in: Poor cold-running characteristics, sticking choke, engine stalling when cold, engine not coming down off fast idle unless gas pedal is hit. Comments: If the choke plate is misaligned in the airhorn, the choke can stick and bind in a part-closed position. It cam also fail to close completely during initial cold-start. Check to make sure the plate fits squarely and tightly in the air horn. If not, crack the two screws loose and wiggle the plate around until it fits right.

Choke pull off seized or ruptured:
Results in: Poor cold-run characteristics, flooding when cold, stalling when cold, poor fast idle control, sag or hesitation going into the secondaries. Comments: This is one of the most common maladies on older Q-Jets. When the pull off fails, not only do you loose proper control over the choke, but you also loose opening rate control over the secondary airvalve. Always check the pulloff by attaching a long piece of vacuum hose to it and sucking on it. The pulloff should smoothly retract, and it should smoothly extend when the suction is released.

Choke pulloff incorrectly adjusted:
Results in: Poor cold-run characteristics, stalling when cold, flooding when cold, engine won’t stay running after
cold start-up.
Comments: The primary purpose of the choke pulloff is to crack the choke open just a tad upon initial cold-start. If
the choke is not cracked open, the engine will flood. If the choke is cracked open to far, the engine will lean out and
stall. When correctly adjusted, the choke pulloff will open the choke ¼” as measured from the forward lower edge
of the choke plate to the airhorn wall.


Choke linkage/intermediate shaft system incorrectly assembled or missing pieces:
Results in: Inoperable choke, engine not coming down off fast idle, sticky choke. Comments: The choke and fast idle linkage on a Q-Jet can be a mystery of odd parts once the carb is fully disassembled. It is easy to get some of the pieces incorrectly assembled or installed in a bind. When this happens, the choke system will not operate properly. Best to take a look at another carb and do a little comparison if you’re not intimately familiar with the linkage system.


Broken choke housing:
Results in: Poor choke performance, inoperable choke, vacuum leak. Comments: The 1975 and newer Q-Jets use a cast aluminum choke housing for either a hot air choke or for an electric choke. Many carb kits contain new choke hosing screws, and these screws are often too big for the intended application. Installation of the aftermarket screws will crack the choke housing, and can make it impossible to properly adjust the choke cover. The hot air chokes have a vacuum source from the inside of the choke cover to draw hot air through the choke system. If the housing is cracked from the oversized screws, and the choke cover is not tightly installed, the vacuum source will not pull the hot air through the system properly, and the choke will remain “on” too long. Broken housings can be welded.


Missing choke intermediate shaft seals:
Results in: Sticky choke operation due to dirt contamination. Comments: The 1975 and newer Q-Jets use two shaft seals on the choke intermediate shaft: One seal is installed inside the choke housing, and the other seal is installed in the carb float bowl where the shaft goes through the side of the bowl. Failure to install the seals can result in a sticky choke system.


Missing choke intermediate shaft bushing:
Results in: Sticky choke operation, fast idle won’t come down without romping on the gas pedal. Comments: On the 1975 and newer Q-Jets, the choke intermediate shaft (the shaft coming out of the choke housing and going into the carb body) is supported by a bushing in the side of the float bowl. This bushing also houses the shaft seal. The bushing is usually steel, but I’ve also seen plastic bushings on original carbs. On commercially rebuilt carbs, this bushing is frequently completely missing, leaving a ½” diameter hole in the side of the carb. This causes the choke intermediate shaft to be unsupported on its end where it enters the carb, and the shaft will stick and bind in the choke housing as a result. These bushings are not available, so you have to rob one out of a donor carb.


BTW - you have a computer controlled Q-jet. See the connection circled in yellow. That is the top of the MCS (mixture control solenoid). When not wired to an ECU - the MCS defaults to a (very) rich mixture.

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Try to find a two socket connector that fits in the cap. It might work - if you even have an ECM. Look under the dash above the glove box.

Otherwise, it might be time to find a new (non-ECM controlled) carb.

 

[flyboy1100]

My understanding is only the California emissions trucks had the computer controlled carb, and everyone else got one that looked similar but the electric connection was for a 2 stage accelerator pump. That is what I read this afternoon. My truck was federal emission. I would like to verify that, anyone know or have the resource to check it out? I can try to find the part number for it.

I do have the computer though, but almost every sensor is not hooked up and looks broken.

I was looking for a used carb today, but I really have no idea what to look for, eBay was full of them, but most didn't appear to be for Chevy or trucks, and I really don't want after market


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[chengny]

Yep, you have a dual capacity pump - not a MCS. They are mounted in the same place and the caps are identical. Except for the color. The MCS cap is blue and the DCP cap is kind of green? - I really don't know what color it is. I am severely color deficient. Blue and yellow I can see. But anything but those two colors (and silver/black/white) I am basically guessing.

But you are right, that cover is not blue.


How to ID a Q-jet with a dual capacity accelerator pump:

The dual capacity accelerator pump carbs can be ID'd by their solenoid plug mounted on the passenger side top front of the airhorn/carb top, along w/the LACK of a plug for the TPS (throttle position sensor) that's present on electronic feedback-type Q-jets used during the same years on vehicles using the "CCC" (Computer Command Control)emissions system.

These NON CCC/NON electronic dual capacity accelerator pump Q-jet carbs are found on 1985-'86 GM trucks and vans, and have desirable features- adjustable top-accessed APT, electric choke, correct linkage geometry for OD transmission TV cable, large 800 cfm casting, and generally less use/abuse/rebuilds on them than carbs from the '60s and '70s.

How to make it work: Basically nothing needs to be done to have the carb perform just like the earlier single capacity accelerator pump carbs. The plug and solenoid can be left intact, the default setting (with no external wiring or electrical source supplied to the plug) is such that the accelerator pump will deliver a normal pump shot. Or if desired the cavity under the solenoid can be filled with molten lead to prevent any chance of a leak.


Quadrajet M4ME

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Basic Q-jet - no electrical connections at all - other than the hot wire to the electric choke heater.

The choke pull -off may be either in front or in back (like yours) - some have two (front & back). I've and them all 3 ways and it made no difference. I am sure there is a good reason for the number and placement of these choke pulls, but I have never had to find out what the reason is.

If I get a good one I just keep it - and they last a long time.

http://www.ebay.com/itm/ROCHESTER-Q...ies&hash=item43cae25de0&vxp=mtr#ht_1010wt_916

 

[flyboy1100]

The plug is gray or very light tan colored, I can't remember right now. Pretty sure I have never seen a plug for tps.

When we were trying to tune it a few months ago the mixture controls didn't have much effect at all, my father in law was stumped. Maybe another good reason to rebuild it, in addition to the choke issue of course

Also brings up the question, I have a computer, but why?

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[flyboy1100]

99% sure the linkage wasn't hooked up internally, will see if I can figure it or tomorrow

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