pmr2000

Have had my stock 75 coupe L48 with qjet carb for about a year. Up to 81k miles, did all maint. last year except the fuel filter -could not get fitting off. Did plugs, wires, air filter, PCV, coil, rotor, cap. Seemed to run a little stronger after this work.

Always been hard to start when cold takes a few attempts of 5-10 seconds now, used to fire up on one 5-10 second attempt. I pump the gas a few times, I have tried pumping more but can smell floodling. Car usually sits 2 or 3 weeks between use.

Once warm the car restarts immediately in a second or two. Idles fine, no hesitation.

Any suggestions on where to start troubleshooting links etc. Could it just be the choke stuck open? Have not had a car with a carb in 20 years so did not know where to start if it is the carb.

Thanks.

SwampeastMike

After the engine is fully warm, let it sit overnight or until stone cold.

Take off the top of the air cleaner. Pull back the throttle slightly. The choke plate over the two front (smaller) barrels should immediately snap shut (well a small slit away from fully shut). If it doesn't close it's very likely that the linkage is just dirty. Spray carb/choke cleaner works well. If that doesn't work the choke operator (on the passenger side) may be misadjusted, the spring inside it may be broken or the linkage may be bent/disconnected/missing.

You MUST use two wrenches to remove the fuel filter. One goes on the body side on the adapter fitting, the other goes on the fuel line side. It is FAR best to use a "flare wrench" on the fuel line side as they grip 4 of the 5 sides of the flare nut. Standard (even worse adjustable) wrenches are notorious for rounding off flare nuts.

Alan 71

Hi per,
After you pump several times, are you releasing the accelerator ?
You should be.
Swamp is right... having the choke set properly when you depress the accelerator is one of the keys to starting a cold engine.
Regards,
Alan



Choke set.

pmr2000

Got it a little more closed after line and adjust. Spring cover slit has a crack...can I get new spring and rod? Definitely not as closed as it should be after cold pump. See pic.

lvmyvt76

yes they are for sale, most parts stores can get them, or a junk yard might have them.

lvmyvt76

loosen the 3 screws around the choke diaphragm, adjust the black plastic round part to where the butterfly looks like Allan's 2nd picture. make sure it is not completely closed. tighten screws back, try staring car. if too rich, adjust again when engine has cooled completely down. yours is still too far open for a good choke. make sure it goes open after warming up. if it does not open up, car will run real rich, and may flood out. then you have an other problem. Maybe Lars will chime in here and explain more, he is the expert on these. Read his papers on carb repair & rebuilding!!!

pmr2000

I turned all the way and it does not close the choke completely. Better than before but not near being closed as should in the pic. Can feel the spring tension, tried bending the rod a little but don't get enough travel to close it completely and then back off. Should I try new choke thermo looks like about $30 part?

bmotojoe

Here are some good numbers for a replacement choke.
GM #17051918
Standard #CV156
Carter #170-1400
Borg/Warner #TH156
Tomco #9093

This is the method I use if I have to bend the choke linkage

pmr2000

Thanks I will try bending the choke rod a little more first and also try to reorient the choke rod bracket to down. Mine seems to be angle up so perhaps that is close up the choke more.

Should have done this a year ago!

Thanks so much guys.

bmotojoe

Here is the next step once you get the choke rod set, This setting is from my 77 rebuild. There should be a small cut/grove in the plastic choke cover, align it with the second notch in the aluminum housing as shown in the illustration. If your choke spring is good it is a very good starting point.

pmr2000

How does the choke rod attach to the thremo spring? Just accidentally unhooked trying to bend. Any tricks to hook it back up does the hook face forward?

bmotojoe

Are you asking about items #57 58 59 deep inside? The end of the hook faces towards the choke housing. It is a little tricky the first few times.

pmr2000

Thanks yes bottom of 58 will give it another try! I am printing this all out great to have.

pmr2000

Any tips on getting this hooked on the bottom end in the carb slot? Is there a slot or hole the bottom 90 degree bent end of hook grabs. I am told the bottom end of hook tip faces back of thermo spring housing.

SwampeastMike

Don't forget that the engine must be stone cold before the choke closes fully.

bmotojoe

Remove choke from the hot air housing so you're not working against spring pressure . Rotate the intermediate shaft so the lever is as high as it can be in that little cavity. Tip the lever end towards the choke housing. You should now have enough room to insert the rod like your holding it, while turning, align it with the lever hole, connect rod to upper choke plate lever and shaft. Like I said before its tricky.

lvmyvt76

you need a picture of a complete carb showing where the ends go, Alan , pictures please

pmr2000

Is the hot air housing what I am pointing to? If so I should unscrew from carb?

bmotojoe

NO, the round black plastic piece with the little white round sticker on it. 3 screws.

pmr2000

Ok thanks will retry with the thermo housing off. Just replaced it....