1977 Olds 350 with Rochester 4bbl - car dies after first start...

[emarkay]

977 Regency 98, Olds 350, TH350.

Start car, let it idle a minute or so and pull out driveway... Then almost every time, on next accelleration after stop sign (one block) car bogs and dies, and won't restart. If I fully warm up car in driveway, all is OK.

Noticed no fuel when accellerator pumps at carb a few times after car dies, so last nite I tried to not "panic pump" the pedal when it died. There WAS some fuel in pump then. However the ONLY thing that will get it to run and continue as normal is to put some raw gas down the primary of the carb! It fires up immediately.

I know the Rochester floats can't be adjusted "on the car" and have Gumouted this thing inside and out, and still it seems to be a fuel starvation issue. I have not "dug" into it for it always dies on the road, but pouring a Testor's model paint bottle volume of gas ALWAYS works, and I can't get it to "die" again after that.

Maybe a vacuum problem that thermally corrects itself? I have NEVER had such a repeatable and bizarre problem in 25 years of working on cars....

Replaced fuel pump, fuel filter, plugs, wires, cap, rotor, adjusted choke, checked linkages, vacuum hoses, tightened up loose bolts at on carb, and blew out fuel lines, as well as all other "maintenance" items. Car is in VGC, and other than that it has no problems.

Any ideas????? Thanks!

MRK

[Oldsguy]

Did you check the carb-to-manifold bolts? There may be a vacumm leak that only shows itself upon acceleration and is most notable when the carb is still cold in the "choke" mode. If those are loose or you have a leaky gasket you may have a lean out situation that is starving the engine for fuel like you described. Good luck.

[emarkay]

Yea, they were loose, I got about a turn and a half on them - but that was something I did right away after seeing this in the owners manual - every 15K miles!!! I never heard of this before - they are snug as a bug in a - whatever... I also got about a 1/2 turn on the carb bowl screws...

This is wierd! - I have bumped up the idle, and messed with the choke - the wierd thing is that if you pour gas in, it works fine...

[Oldsguy]

I would agree with you that it sure seems like it is fuel starvation. I don't think it would be in the fuel delivery since you only have trouble during one circuit of the carburetor operation (choke). I would look closer at the carb again, has it been rebuilt? I have notoriously bad luck with carbs, have tried to rebuild both Rochesters and Holleys with limited results.....How about the throttle plate bushings, are they worn excessively? Just stabbing the dark now...

[emarkay]

I haven't "studied" the carb yet - I have a rebuild kit to eventually dig into it, (that was going to be a winter project), and since I pulled the original plugs of the car, and it still has the original GM fan belts I doubt the carb's ever been diddled with....

Any info/URL's/tips on checking the float level while carb is still "on car"??

I am leaning to maybe a thermal/vacuum issue - will disable all the 'smog' stuff and look at the intake manifold and it's bolts and see what happens...

[PetChemMan]

It sounds like a problem specific to warmup fuel delivery. One cause I've run into was a choke plate that was closed too tightly, and the engine wouldn't restart until I stuck a screwdriver into the primaries to open the choke plate a bit. Backing off on the choke thermostat setting solved the problem.

[yogi442]

I have the same problem with my 76 Buick Custom Wagon. Stock 350 with quad 680 cfm. It has been rebuilt and was the original from the factory and still has the same problem. Simply put, it is cold blooded. Though it has an electric choke and works perfectly the mechanics I know have all said the same thing and that is manifold heat seems to work the carb. When it is cold the engine idles in accordance to the choke but once I put the car in gear if I did not allow full warm up time than as soon as I put the pedal down the car stalls. I have just learned to feather the pedal lightly to keep it going. I grew up knowing this problem as simply "cold blooded" and always appeared to be more of a problem I had with my Chevy true small blocks.

[Oldsguy]

There is also a choke pull-of on most carbs that will pull the choke plate open just a little more on acceleration when the carb is still in the choke mode. The reason this is done is to allow a little extra airflow during acceleration which in turn keeps the fuel flowing which keeps the engine going. The pull-off is usually operated by manifold vaccum. You might check that out.

[emarkay]

Thanks - it was the carb.

I rebuilt it and the float was a bit low, but the wierd thing was the seat for the needle valve had no bypass holes - the fuel had to go all the way up and over the seat assembly and with a low float - no gas... I think it was rebuilt once before, for it was clean in there and there were nicks on the screws, but it runs excellent now - in fact I am heading to Indy for the P.R.I. show in it in about 5 minutes!

Now about those A/C compressors - no, I know they are expensive - it's shot, and burned out A/C clutch to prove it... Wil deal with this via my mechanic in the spring!

Thanks again!

MRK