Help me help my neighbor: 1979 Quadraject issues

[Billccm]

Hope I don't get booted off the forum. Trying to help my neighbor this weekend with a really nice 1979 El Camino, slightly warmed 350 with Rochester Quadrajet. He brought it over this weekend with the complaint of stumble and frequent vapor lock symptoms.

The car idled fine. Vacuum measured between 10 and 11 inches. It has tamper proof idle mixture screws. I did not try to adjust. Visual inspection showed no vacuum leaks.

I went ahead and took the fuel filter out. The tin pan I caught the gas in had about half a teaspoon of rusty sand (picture attached). Quick trip to O'Rielly for a new fuel filter, seafoam, and some Stabil 360.

New fuel filter and went for a drive. The car drove fine, but one wide open throttle it stumbled and died. Car restarted immediately. Got home and let it heat soak 5 minutes as that was one of the symptoms that it would not restart hot unless gas was poured in the throttle opening. Car restarted fine.

The accelerator pump stream is good.

So, today I speak with my neighbor and he says the car is constantly stalling. Assume the seafoam is doing it's job and time for another fuel filter.

In the meantime, I have been googling around on quadrajets. I see that the fuel filter should have a spring to seal the rubber gasket to the line. I did not find a spring. So, do some quadrajets not have this spring, or is it missing?

My mechanic friend at work offered to rebuild the carb. We will get to that once we have the fuel system cleaned. I also know that this car might need a new gas tank, so that is in consideration.

Any tips, advice, or opinions are welcome. Thanks for helping!

 

[BeeKool]

What kind of fuel filter? If it's not an inline I may consider converting it. If it's one with the small filter on back of the carb.

I have a 350 with A q-jet that does not die but will lose its prime overnight and require dumping gas down the carb to restart if it sits more than 2 days. It needs rebuilt once every decade or so. If it was a vehicle that I used more often I would swap it over to an Eddy.

 

[Billccm]

It is a paper element filter that fits in the bowl; see picture of old filter.

 

[Billccm]

Filter.

 

[slimt]

drain the tank, take it out rince it out.. blow out the fuel line.. imagine that going through to the rings..

 

[69Bee]

For fuel leakdown, well plugs are known to leak on the Quadrajets because they come loose, and a common fix is to use epoxy to seal them up. As far as the filter goes, when I rebuilt mine for my 87 Dodge PU, I put a new filter with the rubber end in against the advice of my friend who has rebuilt quite a few carbs. I started to have starting and stalling issues, but when I removed the filter, it started right up, and ran fine. There is an inline filter before the fuel pump of course.

 

[wagonman]

Yup needs a spring. With that much trash you can bet the sock in the tank is plugged up also. As stated the well plugs a leaking also. I worked for GM as a tech for 25 plus years and rebuilt hundreds of Q-jets. Hopefully its not one of the feedback C-3 carbs as parts are hard to find, I still have all the Mickey Mouse tools to adjust them though. The non C-3 carbs are a good unit with the exception of the primary throttle shafts wearing out the base plate bores but can be re-bushed. Good luck and if you need advice on rebuilding it let me know. P.S dont buy a rebuilt one from the parts houses= junk.

 

[WileE]

Be sure the carb did not get clogged with charcoal debris from the evaporator canister.

 

[PurpleBeeper]

I had a Trans Am that did something similar. Take a close look. I think you're "rusty sand" might be the carbon out of the charcoal canister. They have replacement filters for the charcoal canister that look like a little white pancake about 4" diameter if I remember correctly. I rebuilt my Q-Jet 3 times before I figured it out. The carb kept sucking the charcoal into it.

Uhhh....sorry, see Wile-E's post above.

 

[slimt]

I forgot about the canister forget my earlier chime in.

 

[Billccm]

Well, there was a spring in the filter, but it is compressed somewhat (see pictures of new and old spring and filter).

Plan for this weekend it to try to get it to idle and run. I suspect the carb is in need of a rebuild, and I'm in discussion with my friend at work who is a Chevy 350 expert for the rebuild. Thanks again for the replies and information. I'll update what we find as we go.

 

[Billccm]

A few updates and the need for more advice/help.

We kept swapping fuel filters and driving the car. It started to run better by the third fuel filter. The car was starting up easy, idle was good, and driveability was much improved, but not perfect. Took the car for a long drive (as in 15 miles) and it started to backfire on occasion. Then one big backfire and the car was dead. No start. AAA towed home.

Have a nice accelerator pump stream. Car won't start and backfires on occasion. I know backfire is a lean condition, or timing. I'll see if I can TDC the motor Saturday and check distributor position, but any other advice?

My neighbor is a great guy and doesn't mind having a mechanic look at it, but it seems he has been 'taken' by a few mechanics who claim to fix things on this car and really do nothing. Thanks again for letting me get some bowtie advice on this MOPAR forum.

 

[oldbee]

Bill maybe the plastic teeth came off on cam sprocket? Saw a Poncho do that one time when trying to start after a tank fill up!