different q-jet problem

[DetroitDan]

had a friend freshen up my q-jet, choke wasnt working and secondaries didn't either. truck sat a couple years so I figured it was due. He said he only did the top, replaced the gaskets, cleaned it out and put a new accelerator pump in it, because it looks really new, it was a replacement carb at some point in recent years. And the reason the choke and secondaries werent working was probably the split vacuum line on the choke. I put it on and tried to start it, wont start. intakes covered with gas so I crank it while watching (shoulda done that in the first place) and the gas is coming up out of the accelerator pump!? I called him up and he says he has no idea has never seen one do that. Thinks maybe a seal or something in the pump may have gotten torn on install, but a stuck float should push it out the vent. I took it off and drained it, shaking it I cant hear the float move. It's going back to him Sunday if I cant get it fixed myself today. And no, the guys not a moron, he's been building squares for many years, and always rebuilds his own q-jets. Just never had this happen.

So, if anyone knows how gas is getting into the wrong part of the accelerator pump and coming up through the plunger rod, I'd like to hear it.

[85_C10_Sleeper]

is it a Q-jet w/ electronic metering rods and all that? because if so, your screwed and should probably start looking for a new carb!

[DetroitDan]

not sure about that, but it is fairly new, he said it's newer than all the q-jets he has which are probably from the 70s. so maybe. but it didn't have this problem before I took it off. believe me, I am considering a new carb, but I'd like to save this one if I can. I've already decided I want a q-jet. In the past I hated them and always took them off the minute I got a new truck home and replaced it with a 1406 Edelbrock 600. But those were smallblocks. I've read enough about the economy and performance of a properly functioning q-jet that I really want to run one on this truck.

[DarkReaper79]

If it does happen to be a newer electronic = crappy qjet, you can pick up a used rebuilt one fairly cheap. I was on the fence about getting a aftermarket carb or keeping the Q. but after i dug into one and read a bunch of stuff. I think they are they way to go. A balance between fuel economy and performance. I plan on pick up some more and keeping them on hand.

[DetroitDan]

so anyone ever seen this accelerator pump problem?

[DetroitDan]

I don't know about electronic, there aren't any electrical wires going to it. The front of the carb looks much different than his older ones do. It's on an 82 which had a GM crate motor done in 98. I don't know but I imagine that would have been just a long block, and the same carb would have been used. Or not. It's definitely a newer carb than 82.

[DarkReaper79]

i do know that when i rebuilt mine, the seal for the accelerator pump was too tight for the hole. I used the old one and it did leak out. Not as much as you are describing, but enough to wet the top of the carb. I got a new pump assembly off ebay and happen to luck out and fit right. I dont know if the different years of Q-Jets have slightly different accelerator pump bore sizes.

[DarkReaper79]

http://www.carbkitsource.com/carbs/t...jet-index.html might help to find your exact carb.

[85_C10_Sleeper]

yeah, worst thing you can do is attempt to rebuild an electronic q-jet. Everyone i know that has done has had nothing but problems afterwards.

I agree with everyone else, just pick up an older q-jet and get it rebuilt. or a holley or something very common.

[bmchevy1979]

Are you sure that the carb is not correct because there were three different Q jets for this body style of truck the 4mv (v for divorced style choke coil on intake, 73-77, Pic#1), m4mc/e (c for climatic choke tubes in manifold e for electric, 78-80, Pic#2), and the e4mc/e (c and e designations same as m4m style, 81-86, Pic#3)
wrote all this and remembered this http://www.cliffshighperformance.com...carb_ID_1.html
From the sound of things it almost sounds like he forgot to put the accelerator pump seal in at all but it is common that they leak in that area from years of use as you can see in second pic mine was leaking my grandpa used to say that it was a indicator of when the carb was in need of a rebuild

[C-10 simplex]

Originally Posted by DetroitDan

so anyone ever seen this accelerator pump problem?

Actually yes, but i can't remember why it happened. Will check previous posts of mine to find the answer.

Another interim solution would be to go with the holley 4175---it's a bolt in replacement for the q-jet at about $350ish brand new.


P.S. to further clarify i mean if you don't want to mess around rebuilding an older carb(i personally would continue rebuilding it because it's not that hard, is cheaper than buying a new carb, and the problem is probably a very simple thing) there is the option of buying a brand new carb, in this case the 4175 is a direct bolt-on. It is not nessesarily better than the q-jet, in fact it may be worse; For example i don't think the 4175 has the moveable metering rods.

[powerdriver 1958]

The float has sunk or something went south when he put the top back on

[DetroitDan]

popped the top off and took the accelerator pump out, the brand new little blue rubber seal thingy had a piece torn out of it. He said he inspected it when he took it out of the package and it was fine, so it had to have snagged somehow during install. He had another one, popped it right in and it's on the truck and running. Made sure to inspect the chamber for burrs or anything that could snag, didn't find anything. Maybe it had a tear and got caught and ripped going in. Changed the plugs and oil (and gas) and filter, fired up and runs and sounds better than ever. Secondaries are working now too, which is nice. Probably ought to turn the idle up a hair, it sounds like it's at about 500. But dual exhaust with glasspacks sounds pretty good at 500 rpm
Thanks for all the replies.