blaze2fury

I have a 84z 5.0ho and the car seems to idle fine but as soon as I start driving it and come to a stop and then want to go as soon as I press the pedal it wants to stall and die. I have to let the car creak forward and start to roll (automatic) and then give the gas a tap and THEN press the pedal if I don’t want it to stall. If I press the pedal without letting it roll it wants to die. I just got a brand new fuel tank, fuel pump and carburetor. I’ve read it could be the Timing, it could be the idle air sensor or the carb is getting too much air compared to fuel. Any ideas?

sofakingdom

iTrader: (1)

NOT "timing"

Accelerator pump (internal carb part) not working right

Time for a carb rebuild

naf

iTrader: (7)

well...first maybe make sure the linkage is connected correctly to the accelerator pump after the recent re-build.

with the engine not running you should be able to open the throttle completely and observe fuel being pumped into the primary bores from the accelerator pump.

blaze2fury

So I forgot to mention at idle it doesn’t have any issues when pedal pressed, also after I get going and full throttle it won’t have any issue. Just coming from a stop in gear is the issue.

sofakingdom

iTrader: (1)

Carb problem

Not enough fuel at a critical moment

Check fir proper accelerator pump function, if no bueno, time for a carb rebuild

blaze2fury

Well I checked to see if she was spraying when she was operating temp, and the carb is spraying right when I touch the throttle cable. No delay for the spray. I did notice my choke not working correctly, I can’t seem to get the choke to stay closed when car is cold, I even turned the choke thermo to see if it would close the choke. But I also advanced the timing and it seemed to get rid of the hesitation mostly but it’s still there some. How do I correctly adjust my choke? Thank you btw sofakingdom you have helped me a lot on several issues.

blaze2fury

Could the air/fuel mixture screws have something to do with it? I had to put the screws to about 8 each to keep it running until I fixed another problem. That problem is fixed so just for kicks I put the screws back to 4-4 1/2 where they were coming back from rebuild. Seemed to get better response, but still there some. Will put a vacuum gauge on it to dial it in but was curious if those could be the only culprit?

sofakingdom

iTrader: (1)

Not really; for several reasons. First of all, they have almost no "authority"; you can crank em 4 or 5 turns and tell almost no difference whatsoever. Second, because they don't just up and randomly move all on their own: if they were in the right place before, they're in the right place now. Unless of course somebody dinked with em, in which case, somebody needs to put em back where they were and figure out what's wrong with the car instead of dinking with other stuff that will just make it that much harder to deal with making the car back right again once whatever the thing that went bad is taken care of. Third, because they basically can't cause the symptom you're enjoying.

Kind of like "timing"... it doesn't just up and move all on its own; therefore, unless the bolt is REAL loose, or somebody has had their d***-skinners in it, it's not The Problem. Might be possible to make the car run better by changing it, but that doesn't mean it's The Problem. Best all-around when dealing with a car that's BROKEN, not to try "tuning" or "adjusting" or ANY of that; all that doing that will accomplish, is to create more work that has to be done (or more likely, UNdone) once the BROKEN thing is repaired.

If the choke thermostat has tension (i.e. if it's not BROKEN) then it should at least put tension on the choke flap as you crank it CCW. The flap won't close until the throttle is opened a bit, which is why the starting instructions for these cars (and about every other car with a carb and automatic choke, which covers around a half-century of them) calls for depressing the gas ONCE before turning the key. It's not supposed to "stay closed" when the car is cold, after it starts; once the car starts, there's a vacuum diaphragm that pulls it off partway, and the act of the air trying to get past it also tends to open it (the downward-moving part of the blades is MUCH larger than the upward-moving part). Best way to set it, once it's been disturbed, is to wait until the car is completely cold, with the outside air temp at around 70°F; then adjust the thermostat to where it JUST BARELY tends to hold the blades closed. That may or may not be "right", but it will at least be close enough that it won't create another BROKEN feature by way of dinking with it.

There's a theme here, in case I need to quit beating around the bush: DO NOT just stick your p****-pullers into everything and start messing with it!!! That just makes the car EVEN MORE BROKEN, and then when you finally do identify and repair the BROKEN thing that started all this in the first place, creates that much more stuff you have to go back and straighten out. Resist the temptation to just start dinking with stuff.

Now that we've got that behind us:

The "die" problem is NOT ENOUGH FUEL AT A CRITICAL MOMENT. Pure and simple. It is NOT "timing", NOT "mixture screws", NOT "choke", NOT NOT NOT NOT NOT NOT. It's NOT ENOUGH FUEL AT A CRITICAL MOMENT. All of your attention, mental exertion, effort, etc. etc. should be devoted to determining why there's not enough fuel being fed to the motor at that critical moment of when you tip-in the throttles. Forget all the rest of that stuff until you find and fix the lack-of-fuel problem. Note that I am NOT saying that your "timing" is perfect; NOT saying that your idle mixture screws are set exactly right; NOT saying that your choke is fine and can't be improved; NOT NOT NOT NOT NOT NOT. What I AM telling you is to LEAVE ALL THAT ALONE until after the car isn't BROKEN anymore, and then AND ONLY THEN it may be possible to optimize it. Trying to "tune" on a BROKEN car is guaranteed to be a failure, and to do nothing but just make a further mess. For the time being, FOCUS on fixing what's BROKE, and don't get distracted with merely dinking with whatever you come across.



Look for things that prevent adequate fuel delivery. First place I'd check is the fuel filter. It's in the big nut that the fuel line screws into at the front of the carb. Cryptically labelled "FILTER" with a big arrow pointing toward it. To get to it you must first undo the fuel line. To do that, use a 5/8" flare nut wrench (aka "crow's foot", aka "line wrench") something like this https://www.homedepot.com/p/Crescent...NWS0/303730626 on the small nut, and a 1" open-end on the big nut to hold it still. DO NOT attempt to remove the flare nut without holding the big nut still!!! If you do, you WILL destroy the fuel line, thereby creating a MUCH larger headache for yourself. Undo the line as described then undo the big nut. The filter is inside there. Replace it. Note that there's a little rubber thing in one end of the filter, and a spring against the back side of it, which is metal; make sure you put the new one back in in the same order and direction. (spring, then filter with the metal end first, then the big nut) Put the big nut back in FINGER TIGHT ONLY, until it's fully seated, and reinstall the fuel line, using the 1" open-end again to hold the big nut still as you tighten the line. DO NOT use a tool to put in the big nut!!! It has very fine threads that are tapped into the carb body, and you will DESTROY the carb if you strip or cross-thread them. FINGER TIGHT ONLY until fully seated! Then tighten it to maybe 6 - 8 ft-lbs with the 1", then thread the flare nut in BY HAND (no tools) until it also is FINGER TIGHT ONLY, then hold the big nut still with the 1" while you tighten the flare nut with a regular 5/8" open-end. NO TOOLS on ANYTHING until after it is well started BY HAND for a few threads.

While you have the line off, flush it out. Do this by sticking a 3 - 4' piece of rubber hose over the end, long enough to reach the ground, and let it dangle into a 3-lb coffee can or the like, or even <gasp!> an actual gas can </gasp!> while you have your assistant crank the motor for a few seconds. Be careful, gasoline is FLAMMABLE and if you're sloppy you WILL set your car on fire, which is ordinarily considered to be an adverse outcome. Fuel should come out in big gushes, like 3 - 4 ounces every time the engine turns over. If it does, then your fuel pump and all the rest of the system is probably OK; if not, you may have other problems further upstream.

blaze2fury

Well I just got the carb back from a rebuild so I didn’t think that was the culprit as in the accelerator pump. The only thing I haven’t changed that’s fuel related is the fuel pump on the passenger side block, should I change that? the old carb didn’t do that (had several other issues but hesitation wasn’t one of them). The tank/sender/carb all new. I just changed the filter and she is still hesitating under very light acceleration.

sofakingdom

iTrader: (1)

Uh-oh...

Not good. All bets are off as to what the problem could be then. Somebody has ALREADY had their d***-skinners in it, and now, NO TELLING what they did wrong, left undone, whatever.

My first guess would be that they left the fuel level in the bowl too low. Impossible to tell very much about that from outside the carb. Only thing you can do is to take the carb apart and bend the float a bit (that's the factory method) to raise the level a little.

Yes it could be the block-mounted fuel pump; BUTT, if the car didn't have this particular problem before the carb was "rebuilt", then it was OK then, and unless the FP broke while the carb was getting "rebuilt", then it's OK now. OK enough, anyway. I'd tend to discount that possibility for the time being.

Fuel bowl level first. You can change that without removing the carb, if you're careful to not drop anything down into it.





Here's an exploded view of the carb parts.

Once you get the air horn off, you'll be able to see the float (part # 237) through a large rectangular hole in the gasket. To see where it's adjusted to, hold part # 236 down with your finger, and see where the top of the float is. Regardless of the factory "spec", best adjustment is usually where the top of it is level and a little less than 1/8" from hitting the underside of the gasket. "Spec" is emissions-oriented (tries to make it so that if there's any error in the setup, it tends to be toward the lean side rather than rich) and tended to be too low even for a brand-new car. If it's below that, and/or if the top isn't level when you hold down # 236 and lift up on the end of the float, you'll have to pull it out to bend its arm, which has a place just specially made to be bent. Lift the gasket up and peel it back, then lift the float STRAIGHT out. The needle valve will be hanging from it by its little clip: don't drop it. Take it off and set it aside, then bend the float a bit. Repeat until the top of the float is level both front/rear and left/right. Then reassemble the carb and see what it's like.

blaze2fury

Well I put a vacuum gauge on and got about 20-21. That normal? I read it should be between 15-18.

sofakingdom

iTrader: (1)

Higher is better, in general. It depends on idle speed and various other things however: most often, high idle speed = high vacuum. Also, more ignition advance = higher vacuum.

Nothing to worry about in any case. Not material to the matter at hand, either.

blaze2fury

Just to rule it out, the ECM is the original one. Anyway that could affect anything? Like not giving the carb enough gas? If not I’ll replace the accelerator pump as see if it fixes it, and if that doesn’t I’ll move to the float as well.

naf

iTrader: (7)

please send it back to whoever rebuilt it

sofakingdom

iTrader: (1)

No it's not the ECM.

I'd agree with naf except for one thing... if whoever it was sticks his p****-pullers in it again, it's entirely likely it'll come back even worse. You're in a kind of sticky situation. This other entity obviously owes you making it right, but I'm doubtful that they're capable of it. IMO you're better off learning how to fix it yourself.

naf

iTrader: (7)

well, there's that....

take it off the car. take pics as you open it up and don't go too far.

blaze2fury

So I was messing with her and when she got up to temp I tried to ease the throttle and she tried killing herself, well right when she was in the middle of trying to die I closed the choke a little with my hand and she revved up. Then I tried again but this time with the choke where I was holding it with my hand and there was no hesitation. When the car is cold the choke is barley open like it should be, but when I go to drive the car it apparently is getting more air than fuel? Any ideas on this? Wouldn’t it still kill itself if it was the accelerator pump?

blaze2fury

Well I replaced the AP. Still doing the same thing. Not sure what to look for next. Might just have to take it to a shop.