stalling at stops and turns - fuel pump? fuel tank debris?

i have an A20A1, 87 DX that's running pretty well all things considered, but this stalling problem has me scratching my head.

if the gas tank is full, and the car has sat for a little while (overnight, say) it runs fine, idles well at stops, no problems at all.

if it gets below half a tank, it usually starts getting just a little bit jerky, and then stalling every time i take my foot off the gas. meaning at stop signs/lights, and even if i'm taking a low speed turn. it will start right up immediately when it stalls.

once i let it sit, if it's got a full-ish tank it usually kind of "resets" by the next time i drive it.

notably, today i flogged it pretty hard up through the mountains with no problems. then, driving home it got under half a tank and started stalling again.

i'm thinking this is a fuel pump issue, or maybe something in my fuel tank clogging things up? like when it hits the fuel pump's filter it just stays there from suction or something?

suggestions?

(i've recently replaced both fuel filters, so i doubt it's that)

How many miles on that fuel pump? The fuel pump nice enough to give me warning before it went out acted like that.

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Originally Posted by rebuild

How many miles on that fuel pump? The fuel pump nice enough to give me warning before it went out acted like that.

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good lord, i have no idea. 236k miles on the car, saw lots of deferred maintenance and hacky fixes while rebuilding it.

i have a spare fuel pump (from a jy, but obviously a relatively recent replacement) but until today it's not given me enough trouble to bother swapping it.... i just want to make sure i'm fixing the problem.

cripes.

so i swapped out the fuel pump (old one looks original) and had the same damn problem.

i'll check/swap the fuel pump cutoff relay next, and i guess if it's not that then it's not getting spark? i would be thinking coil, igniter, or rotor/points at that point. am i missing anything?

Sounds to me like fuel pressure is dropping off as the tank level declines. I would be looking inside the fuel tank at the pump assembly. I don't know what it looks like but if the pickup is damaged/has a hole/not seated correctly/etc., it could cause problems like you're experiencing. Alternatively, if the entire assembly is bent at a different angle than OE, it could do the same. It wouldn't be a bad idea to test fuel pressure under various conditions either. That should tell you a lot. It's also possible that your gauge is registering inaccurately and showing that you have a half tank, when in fact you're running out.

yeah, i've focused on fuel because it seems like if it were spark-related, it wouldnt be possible to prevent stalling by maintain rpms in neutral with light pressure on the gas pedal.

the other day though i was babying it with a full tank of gas and it still did this. first time it's done that that i can recall before getting below half a tank, but still.....

i'm wondering if the slow mixture cutoff solenoid could be intermittently malfunctioning? it bench tested fine on more than one occasion, but it is one of the relatively few parts i carried over from the previous carb to this one.

Did you solve the problem? I've been experiencing this, too.

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Originally Posted by KillahKitt

Did you solve the problem? I've been experiencing this, too.

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nope. i mean yeah, it's "solved" in that i can shift into neutral when i need to go slow around a corner or come to a stop, and gas it a little.

i think this weekend i'm going to check the FAQs and do some vac line removal and see where that gets me.

I wonder if the baffles in your gas tank are not working properly.

did you try a different coil?

I had a similar problem just weeks ago. Ran two full tanks with seafoam treatment and now my stalling at low rpms is gone. Worth a shot.