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Fuel starvation on right turns, 96 Z

Old 10-19-2018, 09:49 AM
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Fuel starvation on right turns, 96 Z

Hello, all- virgin poster here. Thanks in advance for your help!

1996 Z28 convt, auto. The PO said it starved for gas on right-hand turns if it was low on gas. Actually, it does it regardless of fuel level, but it does seem worse at low levels.

If I turn gently, it is fine. If a make a moderate turn, it coughs and sputters exactly like its running out of gas. If I made a hard turn, it's worse, it never cuts off but gets close.

I can make hard lefts all day, no issue.

Only other fuel issue I have noted is a very faint gas smell every once in a while. Not sure that's related, but figured I'd mention it.

I searched the forum for this but couldn't find anything, hopefully someone can help. It's annoying!!

Thanks!
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Old 10-19-2018, 10:33 AM
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Re: Fuel starvation on right turns, 96 Z

The faint gas smell could be due to the carbon canister in the driver side rear fender well. You can check for carbon in the EVAP solenoid on the passenger side of the engine. Disconnect the vacuum lines and electrical connections then check for carbon in the solenoid (will be like course pepper).

Before any conjecture about fuel starvation, has anything been done with the fuel pump or tank?
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Old 10-19-2018, 10:45 AM
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Re: Fuel starvation on right turns, 96 Z

One problem with the 4th Gens is the shape of the fuel tank. When you have an indicated 1/4 tank on the gauge, you could have as little as 1 to 2 gallons left. Unfortunately that would not explain the starvation at greater tank levels. This is not a common problem on the 4th Gens, which explains why you couldn't find anything with a search.

The sock for the pump suction is way down at the very bottom of the tank. The pump also has a stock plastic bucket, that keeps the pump submerged in fuel, using the flow returned from the fuel pressure regulator. Perhaps someone replaced the pump and did not reuse the bucket. See writeup at the bottom of this page regarding the importance of the bucket:

RX-FLT1-FPKG-2

You can download a free copy of the 1996 factory service manual, here:

http://www.mediafire.com/?40mfgeoe4ctti

But there is not much in the way of troubleshooting included in Section 6C, which covers the fuel system.
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Old 10-20-2018, 09:12 AM
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Unhappy Re: Fuel starvation on right turns, 96 Z

Thanks for the suggestions! Dang, I was hoping this was a simple, common issue... It's very annoying not to be able to whip a quick right turn without a bunch of sputtering and coughing! It clears up quickly, a second or two.

The PO was a longtime F-body owner (4 of them) and fan, so I give him a bit more credit than your average Joe. He said he replaced the fuel pump, but who knows if he managed the sock and bucket arrangement properly. I would assume so, but there is no way to tell short of pulling it out, is there? How big of a PITA is that on this car?

The reaction is immediate to the turn, so I don't think it has anything to do with the tank venting. And a filter, line, or pump issue would seem to be independent of turns...

I usually seem to catch that faint whiff of gas when I'm getting out of the car, now that you mention it, and that would correlate with the carbon canister location, I'll check that out.
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Old 10-20-2018, 06:23 PM
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Re: Fuel starvation on right turns, 96 Z

Some people access the fuel pump by cutting a hatch in the package shelf, above the tank. There's a “how to” sticky post at the top of the “Fuel and Ignition” forum. Proceed at your own risk. Otherwise, drop the rear axle and exhaust and then drop the tank, wrestling with getting the fill pipe out of the fender.

Any way to contact the PO?

I would wait to see if you get any other suggestions. The fact the sputter is instantaneous seems odd. Have you checked the fuel pressure for excessive leakdown after the pump primes? Conceivably a leak in the flex hose that connects the pump to the pipes on the sending unit might allow air to be inducted under certain flow conditions. If that hose leaks, the pump should prime to about 40 PSI, and the pressure will leak down rapidly when the pump shuts off. A theoretical guess out of left field, but easy to check.
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Old 10-24-2018, 05:29 AM
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Re: Fuel starvation on right turns, 96 Z

Yes, I actually can contact the PO, I'll text him and see if he thinks he did it the sock and bucket reinstallation correctly.

I'm gonna say pulling the tank sounds like a fairly significant PITA... doable, but I hope it doesn't come to that. I don't think I'm gonna hack up the package tray- might not work as well on convertible anyway.

I don't have a way to test fuel pressure, maybe I can borrow something and check for leakdown. But that leak would be inside the tank too.

So far, I'm not hearing anything that doesn't involve pulling the tank. Bummer.
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Old 10-24-2018, 10:07 AM
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Re: Fuel starvation on right turns, 96 Z

You can get a fuel pressure testing kit from Harbor Freight for around $20.

The tank is a PITA because of the filling neck. Additionally, depending on the car's setup, the exhaust needs to move too. Really, everything but the filler neck is pretty easy, just time consuming. I would completely remove the rear end for extra room.
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