Acroyer

I had to get a tow home the other day, which always puts me in a bad mood...

Anyway, '86 Trans Am with the carb and mechanical fuel pump.. The car will sit and idle just fine when it's cool. It also seems to drive fine when cool. When it hits operating temperature, it stutters and eventually stalls out. May or may not be temperature sensitive, and I might be imagining it, but i thought I would throw it in there.

If I pour some gas in the carb, I can get it to start, go a few feet, and it stalls again. When manually working the throttle, I couldn't hear the squirters, so figure it was a fuel problem. I changed the fuel pump, with some minor swearing and cursing. Someone at the factory called upon the strength of Castle Grayskull and all of the Masters of the Universe when putting the fuel fitting into the old pump. I had to put it in a vice and whack the old pump with a mallet to get it loose. Anyway, got the pump on, fired it up, let it sit and idle for about 5 minutes. Took it for a test drive, and it died on me about 300 yards from my house. Wife brought the fuel can, and I limped it home. I noticed that when I dumped some gas in the carb, some of it ran out the side of the carb onto the manifold where the secondary lockout stuff is. Great, bad carb? It was a reman....

So, this morning I put an extra carb I had lying around on the car. Let the car idle for about 10 minutes to get up to operating temp, shut it off, poured in some fuel: no leaking. Yay! Took it out for a drive, and in about 100 yards it stalled. Pouring some fuel in the carb to get it restarted every 25 feet or so, I finally got it back to my driveway.

This just started out of the blue the other day while I was cruising on the highway. It acts like it's out of gas, aside from idling just fine when I first start it up. I filled it up less than 100 miles ago, so I know the tank has plenty of fuel.

The car is all stock, all of the computer stuff still hooked up.

Any ideas? Computer killing the timing for some reason, or maybe gremlins? I would be pulling my hair out if I had any left.

Thanks,
Tony

sofakingdom

iTrader: (1)

Not "timing". Not sure why that's every n00b's go-to "guess"; but, no.

If 2 different carbs & fuel pumps had the same symptom, then it's likely not caused by either.

Fuel filter is in the carb, so changing the carb also changes that. Again, not likely.

More likely, the pump is sucking air, due to a deteriorated rubber hose at the gas tank; or, the "sock" on the fuel pickup inside the tank, is clogged.

Acroyer

N00b's go-to guess? Really? Next you're going to ruin my day and tell me that it isn't gremlins, either...

Actually, what I was thinking is maybe I hit a bump on the highway, and this car that has been sitting for so long had something shift or drop, and the fuel line is somehow close to the exhaust, and the fuel is vaporizing before it gets to the carb. But I thought that sounded a little outlandish. It would explain why it starts to act up after reaching operating temperature.

I was just seeing if someone would say "oh, that's the such and such. You need to do this and that" before I throw more time and money at it. Like what happened with my catalytic converter in another thread.

I'm used to 60's and 70's cars, not so much this computer-controlled stuff, which is why I'm asking.

Komet

Oh, that's the busted old third gen. You should check fuel pressure and volume going to the carb, and inspect the entirety of the fuel lines from tank to carb.

sofakingdom

iTrader: (1)

Yup, "timing" seems to be every n00b's go-to guess "explanation" for every driveability problem, even when the symptom at hand has nothing whatsoever to do with the relationship of the point in the engine cycle when spark occurs, to the motion of the pistons. Gets hilarious at times.

"Computer-controlled stuff" isn't at issue here. Highly unlikely that it has any bearing on the matter at all. It's fuel delivery. Which is the same in one of these cars as in any other carbed car from the 50s onward. About the only thing that might be different is, an extra electric "helper" fuel pump was added to a few of these cars inside the tank at the dealership to cure certain complaints back when these cars were new, and it's not impossible that if your car has one, it's gone bad. Other than that, if you are an expert on 60s cars, there's nothing different about this problem in this car than the same problem in one of those.

Personally I'm not expecting that it's caused by "gremlins" either, whatever those are.

dlinger

iTrader: (4)

I know changing carb should eliminate the fuel filter issue, but sounds like my car when gas tank was rusting out plugging fuel filer. It would run fine for a while then die. One day it died when my daughter was driving home from school. After work we went back it started fine and drove it the rest of way home.

Acroyer

I did order a new OEM ignition control module. Long ago I remember those burning out due to under-hood heat and causing similar problems. Might as well change it anyway, since I have plugs, wire, cap and rotor sitting around collecting dust. It won't be here till Monday, though.

So, while I wait, I'll check the fuel lines for anything weird. I'll also replace the bolt on the negative cable going into the battery. Previous owner really chewed it up and the cable is not tight; easily moves by hand. Not going to fix my issue, but definitely needs corrected.

Thanks, guys.

sofakingdom

iTrader: (1)

An ignition module isn't affected by pouring gas into the carb, any more than "timing" is.

Your problem is fuel delivery. Don't mess with the ignition, it will just give you more things to UNdo whenever you find the REAL problem, preventing fuel from being delivered to the carb, while delaying you from focusing your attention where it belongs.

Not that I am NOT saying "your ignition module is fine", NOT saying "your timing is spot-on", NOT NOT NOT NOT NOT NOT NOT. Only, that those things DO NOT account for the actual observed behavior of the vehicle. Get the fuel delivery issue sorted out, then maybe dink with ignition parts, if they seem to need it.

See my signature for a little bit of head-clearing logic. Give special thought to the part about "fits all the facts". Emphasis on ALL.

Aaron R.

Lot of back and forth here. A few good ideas, maybe a few that are stupid.

I am interested in whether it will continue to idle without stalling. All your posts indicate it only stalls while driving and not while idling. Can you confirm if it will stall out at all at idle?

Running fine at idle but quickly stalling while driving is not a guarantee to be fuel problem. I'm leaning toward fuel supply issue but am not ready to throw out ignition ideas.

Acroyer

I'll start it up tonight and let it run a little, maybe 20 minute or so. last time I tried to drive it, I idled for about 5-10 minutes and drove about 100 yards when it choked and died.

OrangeBird

iTrader: (1)

This, coupled with the fact that the OP states the car will start and run for a bit (25 feet at a time, in fact) after it stalls out, with fuel poured into the carb, leads me to believe it's not ignition related.

Remember Sofa's "It's gotta fit ALL of the symptoms" mantra regarding diagnosis, here the ignition system does not correlate with the above two established facts

sofakingdom

iTrader: (1)

Pouring gas into the carb fixes it (somewhat).

Pouring gas into the carb does not fix ignition systems. Ever. At all.

Fuel delivery.

Just for the halibut, pour gas into the vent on top of the carb, and fill up the fuel bowl all the way like that, just like you'd do for a 60ss or 70s carbed car that's acting up. See how long that makes it run for, and if it runs at least somewhat normal for a brief interval. This would be irrefutable proof (to the extent that proof can be irrefutable, by any logic other than merely refusing to "believe") that it's a fuel delivery problem.

Focus. Focus. Focus. Focus. Focus. Focus. Focus.

Acroyer

I let it idle while I mowed the lawn. I came back at around the 22 minutes mark and it had died. I hopped in, got it to start for about 2 seconds, then again for 1 second, and now it just cranks with no start.

I did notice that the carb is super hot. Pouring gas into it, it percolates, steams and hisses.

This all started out of the blue, though, while I was about 20 miles from home and cruising just fine at 70mph on the highway.

sofakingdom

iTrader: (1)

https://www.thirdgen.org/forums/carb...ard-start.html

See post #4.

Check for fuel things touching exhaust and stuff like that. This falls under the general category of "fuel delivery". NOT ONLY does the fuel system have to "deliver fuel", BUT ALSO, the fuel has to be in usable condition upon delivery.

Although usually, with that condition, it'll be EXTREMELY hard to start, but then once it gets started, will gradually smooth out and become normal, as cool fuel flows up etc.

And of course, pouring fuel into the carb won't fix that particular problem; it'll just make it worse.

Aaron R.

Good test. This seems to indicate extremely unlikely to be ignition related. I have seen ignition coils malfunction very strangely and cause your type of problems, but I think this test shows that to be unlikely.

Next step I recommend is attach fuel pickup hose into a 5 gallon gas can and see if it will idle continuously. This will tell you whether problem is in the fuel lines/tank before fuel pump, or if it is from the fuel pump on.

There are some idiots on these forums with very little experience actually fixing things. These are the types who spend most of their day surfing the internet from their sofa offering repair advice. I recommend you avoid those. They just want to tell everyone how much (i.e. little) they really know. What you want is advice from an actual mechanic who spends his day repairing cars and occasionally surfing the forums.

Acroyer

Well, I was checking underneath to see if anything was hanging weird or otherwise out of place, and saw nothing obvious. Starts with a dribble of gas in the carb, but not at all otherwise, now, even cold. I pulled the line off of the carb inlet and cranked for about 3 seconds. Nothing. Dry as a bone. No fuel getting pumped. I'll run out and get a couple more jack stands so I can get all 4 wheels off the ground. Then, I guess I'll crawl under and follow the fuel line to see if there is a break.

Yes, I should have done that in the first place! I know

Anyone have a handy diagram showing the path of the fuel line from pump to tank?

Komet

The fuel line should be fairly visible all the way back once you get underneath the car.

Since you've got no output to the carb, I'd follow Aaron R.'s advice and try drawing fuel from a gas can. You might want to pour a little fuel backwards into the feed hose as well to prime the pump.

Of course, if you follow ALL of his advice, you shouldn't listen to me at all, because I'm not a professional parts replacer.

Acroyer

Hooked up a gas can to the pump and after a few seconds the engine fired right up. So, we know the pump to the carb is working. Next step is to crawl under, which I'll do when I get off work tomorrow.

Thanks, guys.

Acroyer

Well, this is embarrassing. Yep, car runs just fine hooked up to a 2.5 gallon fuel can. I crawled under the car to look for breaks or bulges in the lines, and saw nothing weird.

So, I dumped about 2 gallons of gas into the tank, and drove down to the gas station, no problem. I put in just over 14 gallons of gas (over $66 worth). Turns out the car was acting like it's out of gas because, and get ready for this; IT WAS OUT OF GAS!

I feel like a horse's ***! Either I grossly miss-judged the amount of mileage I drove since the last fill-up, or someone helped themselves to my gas last time I had it out in a parking lot. Unbelievable.

Thanks for all of the input, guys. Turns out I should have tried the simplest thing first, and not just assumed. At least there's a new fuel pump on there now! Plus I found I had a bad radiator cap, so not a total loss.

Aaron R.

Thanks for posting an update to final fix, even at the expense of your pride. It's nice to see outcomes posted and helps people later when they are searching posts. We all do boneheaded things at least occasionally. Anyone who says otherwise is a liar.

89fast5oh

lol

sofakingdom

iTrader: (1)

That'll generate a fuel delivery malfunction, for sure. Maybe the best way to create one.

Thanks for letting us know what it was, even though it's something a bit humiliating to have to admit.

OrangeBird

iTrader: (1)

With the price of gas these days this could be a plausible explanation. Things get much worse the world's most dangerous job will be being the tailgunner on a Sunoco gas tanker truck......

erik69&85

iTrader: (1)

Did the same on my 92 when I bought it... Car died... Had to get towed home... Later figured out it had no gas... Gage read half full... Replaced a bent sending unit... Live and learn