oldsbucket

so i had a shop clean and rebuild a jy carb 7042250 for the 350 after a few days of chasing vacuum lines it does everything fine except for an off idle stumble. Noticed that the accelerator pump linkage has a gap between the plunger rod and arm about 3/16" didn't notice this before the rebuild but never looked that close. i think the fulcrum arm should sit on the plunger. yes or no ??

Just put the motor in but was missing a carb so i had a spare built for it. i still need to determine if the vacuum advance is working with the thermostatically controlled port working or not, 71/72 variety, i like to try and keep it as oem as possible but first off that plunger just doesn't look right. thanks for any help

pcard

The lever must have positive contact with the pump. Can you post some photos to help us diagnose this issue?

joe_padavano

I'd say that is a pretty obvious source of the problem. Your next question should be, if the shop screwed up that adjustment (which is clearly specified for each model of Qjet), what else did they do wrong?

Yet another example of why I do all my own work...

1970-W30

Could the pivot arm possibly have been installed upside down? If so, it would be a very easy fix......

BILL DEMMER

wow! some people shouldn't be allowed near screwdrivers. sounds like a mess.
it's nearly impossible to install the accelerator pump lever upside down. now, knowing they screwed-up the primary accelerator pump spec. what else did they botch?


bill

oldsbucket

no it's not upside dn today after a 60 mile drive i still have the hesitation but the pump rod is now tight to the pivot must have just been hung up i didn't think to pull up on it . tonight i by passed the thermo port and running the advance from the carb didn't have time for a test drive but i will in the am.

This hesitation really gets tricky with a automatic and trying to pull away from a stop on a steep hill i don't know if it was going to lurch forward or die and roll back into the car behind before i could get the brake on

brown7373

I the rod in the inner hole? Also, what kind of a kit did the shop use to rebuild it? Many kits do NOT contain rubber parts that are impervious to the ethanol and other additives in today's gas. The rubber pump cup swells and sticks in the bore, or in some cases pulls right off the pump shaft. When it sticks in the bore, guess what? It doesn't let the spring return it to contact the rod and there is a space. It is not working now and will only get worse. I only buy kits from www.cliffshighperformance.com and they never fail. You can also buy just the pumps. They cost more than store brands, but the kits contain more and the parts are the best.

oldsbucket

good point on the rubber parts i don't know about the kit installed but its only been in there a few days . This morning i advanced the timing a few degrees and routed the advance direct to the carb, this has helped but its only disguised the issue as its still there. on this carb can the primary metering rods lift point be adjusted ? saw something about this on utube but i didn't catch what the carb model was

joe_padavano

Sorry to repeat this, but you really need to be sure the carb is adjusted properly BEFORE you go changing anything. Otherwise you'll just be chasing your tail. Simply changing things without knowing where you are starting from or what the effect will be is exactly why people badmouth the Qjet. Also, and sorry for saying this again, given their screw up on the pump adjustment, I wouldn't trust anything your shop did to that carb.

As for the pump adjustment, the spec and procedure are shown on page 6M-35 of the 1972 CSM. The correct way to do this is with the carb off the car. You need to ensure that the fast idle cam is completely disengaged (ie, choke fully open). Next you need to adjust the idle speed screw so that the primary throttle blades have a 0.030" clearance to the bores (using a pin gauge or drill bit). Be sure the pump linkage rod is in the inner hole on the pump arm (closest to the pivot point on the pump arm). Finally, adjust the pump arm by bending the tip to get exactly 3/8" as measured from the top of the choke plate wall to the top of the pump tip. This is hard to describe but easy to see in the drawing in the CSM. The pump arm should compress the pump slightly. It sounds like yours isn't there yet. DON'T go changing anything else until this setting is correct. While you are at it, I'd verify that things like the float setting are correct, too.

oldsbucket

thanks Joe
this is why i wanted to have someone else mess with it I'm comfortable with holleys and just about every other carb from su to briggs but from the first time i took one apart and found all the rods hanging after i got the top off without removing the pump pin i knew i didn't like em and thought they were a mistake in 66 because i liked the way the Rochester secondaries would kick in as on a 65 442 and prior cars couple that with a down shift and the butt dyno really jumped i couldn't see the need to change but i digress .

when i first removed the carb we found that the primary throttle plates have a small (1/16) hole drilled in each is this normal ? i do have other carbs that i could use for parts but left it as it was on the chance that it was suppose to be there but now everything is suspect .
i don't have a csm yet and you lost me on the points to measure the 3/8" i had one but it was a reproduction that i could not read with pages missing i might have tossed it ,wasn't worth the paper it was on so if i get another it will have to be an original.
the shop said he would stand behind his work so i will have to give it a shot i think the pump rod hang up was not a real issue as it freed up on it's own and is giving full stroke now. i'll post results, the wagon will be down for a few as the steering needs $$ picking up a jeep box for it mon.

pcard

Mike: I believe the holes in the primaries are normal for the 7042250.
I would recommend Cliff Ruggles book and also Doug Roes book, on Rochester carbs, available on Amazon.
As for the pump, if it stuck once it could stick again. It may have just been dry, but it could have been because the cup assembly got hung up on the rod (happens with the new parts MIC). I would buy a new one from cliffs high performance and slip it in there while you have the thing apart. Also, check the sides of the pump reservoir to make sure there are no scratches or burrs.

oldsbucket

Yes i drove back to the shop to get his opinion also, after a few checks he said it wasn't responding well to the pump so a new one is the next step, cleaning the bore is something i will mention if i let the shop do it . while there we talked about the petronix ignition and whether i need a full 12v or was ok running with the resistor harness off the coil he then said it was only the points that needed reduced voltage i disagree and think its both the coil and the points that need reduced voltage. if just the points then you can just run 12v direct for both the petronix and coil but i think the coil will be fried unless it is an internal resistor type yes??

joe_padavano

It is only the points that need the reduced voltage. The reduced voltage reduces arcing when the points open, increasing their life. The coil doesn't care and would rather have full voltage.

As for the Pertronix, you need to do what the instructions say. Some aftermarket electronic ignition conversions are designed to accept the lower voltage, some are not. A Pertronix is not a GM HEI.

oldsbucket

Well that's what i needed a second opinion so what is an internally resisted coil doing just protecting the points ? the ignition was in the $200 motor when i bought it so i don't know the model but it seems to be working the harness had equal length terminals that fit the coil but i have no way of knowing the supplied voltage i'll have to look for part numbers on the petronix unit.

after another drive the accelerator pump seams to be seating itself better maybe just my imagination i'll have to try a hill take off again to be sure

oldsbucket

car is driving normal today i set the timing back to correct marks but left the vacuum advance direct to the carb . i can't complain about the off idle in traffic evidentaly the accelerator pump bore was not honed for the new pump to work properly untill it had a few miles

mpowell

I know this is an old thread, but the information was valuable to me. I just rebuilt the Quadrajet on my 67 442 and I had the same condition with the accelerator pump gap to the pump lever. I manually extended the pump arm a few times and worked it in and now it’s fine. hindsight, I should have lubricated the accelerator pump through its full stroke before I put the top on. Great thread, though, thanks.