Q-Jet frustration
 

In my 72 K20....I have sent the Q-Jet off to be rebuilt by the 'Best Guys In Town' .....three times now :( and it still isn't right. Maybe I am missing something really obvious here...let's see if you guys can find it ;)

It seems to run dry if it sets overnight...you have to crank it over a while and pump the gas before it decides that it has enough fuel to start.

Once you get it hot, you have to hold the pedal all the way to the floor to get it to start again.

When driving down the highway, it gives up at random times, but will restart after it sits for about 5 minutes.

It will die randomly when idling at a light.

The high idle will 'stick' at times, it just takes a tap of the pedal to get it back to normal.

I am about to jerk that dang gas burner out and stick a Cummins 5.9 in over that damn Q-jet.....I don't have the time or $$$ to do a Cummins swap right now and the motor is plenty strong.....any ideas what to do with the carb before I lose what's left of my sanity?


oh, and last time I took the whole truck to the carb shop....on the way home, it backfired (rapid fire- bang bang bang bang!) ...so badly a carload of bangers drove off of the highway into the grass....now, that was really dang funny, but it was freakin' irritating at the same... time

Re: Q-Jet frustration
 

first thing that comes to mind is the well plugs. Were they sealed properly?
(slide 24 of this site: http://www.gmcws.org/Tech/quadrajet/...iles/frame.htm

Also, the needle valve may not be seating properly and allowing fuel to drain. There's other possibilities but can't think of them right now.

Re: Q-Jet frustration
 

What does "best guys in town" mean? By the results it sounds like hack jobs. Many of these so called carb rebuilders don't understand q-jets. Did you get a warranty?
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Re: Q-Jet frustration
 

Yup, it has been back 3 times...still doesn't work for crap.....maybe 'best guys in town' is short for -> only people who work on these old cars anymore...I have lost faith in them (they have asked me to bring the truck back again, but I am not wasting another day waiting for them to get it right).

Re: Q-Jet frustration
 

Sounds like leaky plugs under the float bowl, not an uncommon problem on older Q-jets.
These carbs aren't that hard to work on. See the link in my Signature.
Get the book by Cliff Ruggles and rebuild it yourself.
Like my Dad always says, if you want to drive old cars, you'd better learn to work on them.;)

Re: Q-Jet frustration
 

THe high idle could be from the choke not being adjusted or assembled right. I am in that situation with mine right now (mine is an electric choke tho). I don't think I've assembled something right or cleaned it up good enough and the fast idle cam sticks. I've pretty much diasbled the choke until I have time to work on it again.

If you have the time and determination, try working on it yourself. There is an overload of information out there.

Re: Q-Jet frustration
 

It sounds to me like how mine was before the rebuild.

PM me and I will give you contact info of a guy here that does a fantastic job rebuilding them.

Believe me, I hated Q's until I had one built by someone who really knows what they are doing.

Steven

Re: Q-Jet frustration
 

^Good place to start^

Re: Q-Jet frustration
 

Pretty common to put the clip that holds the inlet needle to the float on wrong, that will cause the dying issues you are seeing and could cause fuel to drain back. It MUST be installed correctly.

Jeff

Re: Q-Jet frustration
 

That sounds like the problem to me too, kinda like a bad plunger.

Re: Q-Jet frustration
 

Send it to Sean Murphy.
http://www.smicarburetor.com/
s/t

Re: Q-Jet frustration
 

Yup yup, get the book and do it yourself. A q-jet was the first carb I ever rebuilt, with the book, I had it up and going the next day (over night cleaning), not a single problem - OTHER THAN - look at the picture posted by chipflyer. I once thought it didn't matter :D

But if nothing else, whoever did your carb slapped on a gasket kit and that was all I bet. I'm sure he's their 'go to' guy because he's the only one who knows SOMETHING about rebuilding carbs. There's hard parts (not found in your gasket kit) that should be replaced on a 30 year old truck, throttle shaft bushings and such.

Don't give up on that Q-jet. If you found someone to rebuild it who knew what they were doing, you'd love that carb forever.

Re: Q-Jet frustration
 

The quadrajet is a wonderful carb... IF its rebuilt correctly. The 'best' guys in town didnt know what they were doing. If the plugs are not sealed (which they obviously were not) and if the control shafts arent properly resized (which they probably were not),... then you will Never be able to get it adjusted correctly.. never.
Send it to "The Carb Shop" in California... they specialize in that carb. Or someone else who actually knows how to properly truly rebuild a quadrajet. cleaning and putting in a "kit" is Not a rebuild... trust me on this one.

Re: Q-Jet frustration
 

Thanks guys for all the help.

When I lived in Houston, I had a guy that was nearly 100 years old, and he could REALLY build any old carb up and do it right. He passed away a few years ago and his son gave up the business....I guess the hunt is on for someone who can drill and bush the body and make it run like a top....I just know that there is more to it than a simple clip out of place....if I had more free time, I would probably pull it apart and tinker with it, but I'm not 17 and unemployed anymore, so it needs to get done right the first time around.

Thanks again guys!

Re: Q-Jet frustration
 

The clip is there for a purpose, to keep the needle from sticking to the seat in prolonged non use. THe clip can be easily installed incorredtly. I've always used the clip, w/o problems. The clip CAN be left out, I've left it out on the last couple I've built, no big deal.

www.cliffshighperformance.com is the answer man, Sean Murphy is good also....don't give up

Re: Q-Jet frustration
 

And if they're backed up. try http://www.sparkyscarbs.com/ he's the man too. Think he mainly does muscle cars, but it shouldn't matter.

Re: Q-Jet frustration
 

I can tell you that Cliff IS backed up, WAY up. He's been only taking names for a waiting list (YES, he's THAT GOOD). He can sell you the parts and his book, and help over the phone, but sometines it takes a while for him to get back to you...

I've herd nothing but good things about Sean Murphy also, but am not as familiar w/ him...

Re: Q-Jet frustration
 

I support all positive statements about how good these carbs are if done right.

Also that Cliff Ruggles is "The Man".

Got his book, parts, and a primary shaft/bushing job from him, and did the rebuild myself. Couldn't be happier with the results.

I believe I left out the aformentioned clip as well.

I had never done a carb rebuild before. Just take your time, and don't rush it...it'll come out fine.

Re: Q-Jet frustration
 

make sure your ignition isnt contributing to your problems, kinda sounds like you may be loosing spark or something in the ignition. i love q jets but most dont understand them

Re: Q-Jet frustration
 

Chipflyer and Sport/truck know what they're talking about. I've sent my Q-jet to: smicarburetor.com, Sean Murphy Induction and have never looked back, very pleased. When you get the carb back from them, not only does it perform like new but it looks like NOS.:chevy:

Re: Q-Jet frustration
 

Well....I had a little free time to look things over....I took the air cleaner off and sure enough she was getting plenty of gas....so....off to the dark side of electrical I went.....no spark? hmmm, got out the digital multimeter and no juice at the dang coil....started looking and found a slightly melted plug at the rear of the ignition switch....Had the local parts pusher send me a new plug and harness....okay, now I have 12 volts at the coil with the wire loose and not so much once connected, but still no stinking spark...I'm thinking that the Mallory ignition module has bit the dust...I guess that I need to figger a way to test out that dang Mallory Coil too....

anyone want to hold the output stud and tell me how much juice it's giving off?

Maybe it's time to ditch the Mallory stuff and go back to GM HEI....I have had those little modules die unexpectedly, but a spare in the glove box has come to my rescue before.....what say the gurus?

I just hate a truck that doesn't start....and the new 68 fires every time and the 72 sits there in quiet shame....

Re: Q-Jet frustration
 

my edlebrock always "drained" gass back and would need a fair amount of pumping anytime it was left sitting. my 402 has an edlebrock Qjet and the little fuel filter has a check valve inside it. Maybe you need a new filter?

I would also vote for the HEI swap, but I'll admit my experience with points is slim to none. Good luck!

P.S. what kind of choke setup you got?

Re: Q-Jet frustration
 

The choke is factory, with the little metal spring in the intake manifold....the spring was 'supposed to be the cause of all of the issues' and was replaced by the carb shop.

Re: Q-Jet frustration
 

just make sure the choke can move freely and opens properly. or once warm wire it open and see if anything changes ( as far as drivability)

Re: Q-Jet frustration
 

Just got in from testing the Mallory parts...the optical ignition module is DOA...and they want $108 for a new one :eek:

I guess that I will be hunting up a good used GM HEI unit and ditch the Mallory crap...plus +++ NOBODY has one in stock here in town....sucks to be broke down and no parts :(

Re: Q-Jet frustration
 

Well, after a futile search on CL for a GM HEI, I broke down and got a replacement ignition module....$108 bucks, but she starts....I think that I have most of the carb issues found, but when she is hot, you have to floor it and then hold it down for a few seconds to get her to start....I know that this cannot be good for the engine (lacking oil pressure in the first moment of start up).....what am I missing now?

Re: Q-Jet frustration
 

Try putting on a phenolic spacer. It sounds to me like you are getting some vapor lock from the engine heat. The spacer will insulate the carb from the intake and stop the vapor lock.

Steven

Re: Q-Jet frustration
 

There is plenty of gas in the carb....I think that the choke is not opening enough when hot...if you floor it, the butterfly valves open up and she will start right up....it has the thicker cardboard gasket too....maybe I'm missing something somewhere?

The phenolic spacer would cause the choke rod to be too short and we would be back to no choke again...

Re: Q-Jet frustration
 

I second that!
He did a stage two for my 402 and I'll never go back to EFI!

I sent him all of my specs along with my slightly used E'brock 1904 and he sent me back a pot of gold!
It ran right out of the box. All I did was set the APT (using the aid of my WBO2 monitor) and all is well.!

Re: Q-Jet frustration
 

Was it a used part? What company won't replace a unit DOA? I wouldn't do business with them again!

Re: Q-Jet frustration
 

No refund on electrical parts :( They assume that you wired it incorrectly I guess....the instructions say that they are fragile and you cannot jump start your truck/car with a big battery charger that has 'start or boost' mode. I have been starting trucks with dead batteries for years with a big Napa battery charger that is made to do just that and never hurt anything before....

well, it runs, but is hard to start when hot...that's the current issue...I have been driving it to work since I got the module in on Tuesday...so far, only hot starting issues....

any ideas guys?

Re: Q-Jet frustration
 

what's the carb number?
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Re: Q-Jet frustration
 

I had hot starting issues a few months ago because my choke wasn't opening all the way. As soon as I shut off the truck and it cooled down just a few degrees, the choke would be fully closed again. I finally went to home depot, bought a metal rod the same thickness as the manifold mounted choke rod was, and made a longer choke arm.

I actually made several... some for winter when auto choke requirements are different, and some for summer. It only takes about 3 minutes to change one out for a different size.