280 ZX Fuel Damper: The Mystery Leak - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 12 (permalink) Old 08-03-2014, 05:27 PM Thread Starter
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280 ZX Fuel Damper: The Mystery Leak

With a title like that, it's bound to show up in someone's search. This might help the rare Z driver who experiences similar symptoms. You're welcome.

Recently, my 81 280 ZXT started missing intermittently. Then, one morning after starting, I noted a small pool of fuel below the fuel pump area on the garage floor. Assuming another old fuel hose gave way, I drove to my mechanic's, only to find everything dry. No leak at all. Next morning, I started the cold car, and checked underneath. Fuel was pouring out again. I slid under and noted the gas was emanating from the fuel damper (new fuel hoses going to and from the unit with tight clamps). By the time I got it back to the mechanic's, the car was warm and the leak had disappeared again.

On this forum, I have only come across one other guy in my searches who posted re: a similar problem. This was on 7/9/14, about 3 weeks ago. I can't explain why it leaks cold and dries up warm, but there it is. Replacement part is on its way and I presume it will fix both the occasional miss and the occasional leak.

It's a new one on me, and maybe on a great many others.
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post #2 of 12 (permalink) Old 08-04-2014, 11:52 PM
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Prob a design by the guys who thought up the SR-71. At start up the fuel lines were loose and leaked so at altitude they would streatch tighter and seal.

Don't understand it but that's what I caought on a History Channel bio on it.

Ed and Jeanne's ZXelda 1981 280ZXT ZXita 1987 300ZX 2+2 ZXena 1990 300ZX 1941 Buick Special Sedanette (Betty) 1956 Dodge Royal (Dorothy) 1971 Buick Riviera (Rita) 1984 Ford F-150XLT (Freya) 1987 Pontiac Firebird TA Convt (?)
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post #3 of 12 (permalink) Old 08-04-2014, 11:57 PM
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I wonder if there's not a long period of "where's that gas smell coming from" seepage before the visible leakage.

Thanks for sharing, I'll be looking for signs of seepage/leakage next time I'm under my car.
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post #4 of 12 (permalink) Old 08-05-2014, 05:36 AM
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The search feature sucks...it's in there before 2014. You don't "need" the pulsation damper so much if you are running a high volume aftermarket fuel rail, and there is an aftermarket accumulator/damper which works much better than the stock unit....especially when batch-firing 720cc injectors!

JeffP's website has details.

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post #5 of 12 (permalink) Old 08-06-2014, 01:06 AM Thread Starter
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Fuel Damper Update

Replacement Fuel Damper(s) arrived today (thanks again, Jamal, for shipping quickly). Swapped it out in mere minutes, fired the Z up...no leaks or misses.

Car was still warm (though the FD was cold), so I indulged in a few beers while waiting for the engine to cool down. After what seemed an appropriate time, fired it up again...no leaks, no misses.

The final evaluation will come upon start-up tomorrow morning but confidence is high as it is raining at the moment in Northern California in August which is a good omen.

You will find your FSM will not say much re: the Fuel Damper, other than its primary function. Maybe they did not envision so many would still be on the road after 30+ years.

Last edited by TheBob; 08-06-2014 at 01:10 AM.
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post #6 of 12 (permalink) Old 08-06-2014, 01:32 AM
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I am glad that you figure it out.
Jamal

70 240Z #6920, 73 C110 Kenmeri Coupe #851, 82 280ZXT 2+2 Auto
Phoenix AZ....KEEP THEM RUNNING!

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post #7 of 12 (permalink) Old 08-06-2014, 02:16 AM
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MBTF on a spring diaphragm is pretty high. I don't think 30 years is unreasonable life. The first generations Bosch stuff in many cases is still running, terribly overbuilt. This was second generation, so it's a bit more delicate.
For reference, go check out the pulsation dampner on a '68 VW Type III!!! Been going strong almost another 20 years over our stuff!

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post #8 of 12 (permalink) Old 08-07-2014, 02:10 PM Thread Starter
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Updated Update

The coincidental failures are the ones that can mislead you. It was indeed the Fuel Damper that was the source of the leak, but not the miss.

Turns out that the miss, which went from intermittent to permanent, had naught to do with the FD. It was the result of a separated wire in the FI connector on cylinder #5 .
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post #9 of 12 (permalink) Old 08-07-2014, 08:43 PM
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I would have assumed that, but the clarification will help others to be sure!

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post #10 of 12 (permalink) Old 08-10-2014, 01:15 AM
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Looked up SR-71 - it was the titanium air frame that would stretch at high speed temps (over 800* F) and the the fuel was also used to help cool the plane.

Ed and Jeanne's ZXelda 1981 280ZXT ZXita 1987 300ZX 2+2 ZXena 1990 300ZX 1941 Buick Special Sedanette (Betty) 1956 Dodge Royal (Dorothy) 1971 Buick Riviera (Rita) 1984 Ford F-150XLT (Freya) 1987 Pontiac Firebird TA Convt (?)
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