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Strange dying issue....Take a shot..

Stroker Webers

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#1 steve260z

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Posted 2 weeks ago

Ok..Have a stroker with triple Weber 40s, Datsun distributor, 34 degrees all in, carter low pressure fuel pump, plugs look good, brand new fuel filter, dead headed carbs, old return line vented to atmosphere, Crane ignition module...Think thats most of important parts, just ask for whatever I've neglected to mention.
After 10 minutes of driving, when I come to a stop the car will act like its going to die or will die. This occurs about 50% of the time. If this does not occur I can let the car idle in the driveway and it will start acting like its going to die and will eventually within the next 30 minutes. I can then restart in the car with about a 4 or 5 second crank. Now, if its not in this state of just dying I can turn the car off and restart with a 1 or 2 second start...I think the clues lie here in this 4-5 second crank to start. Now, I've but a voltmeter on the battery as the car dies and the meter reads a consistent 14-14.3 volts while running and dying. When the car dies I can still hear the carter fuel pump running. When it dies the O2 meter will drop down to about 10 AFR from the usually 12 at idle. Now, not sure if this richness is caused by the actual problem or just the result of low bouncing idle at the point of dying which would mess with the vacuum signal the carb sees. Obviously I'm freaking stumped. As mentioned above the 4-5 second crank time on restart is interesting. I've been thinking maybe the fuel is getting too hot, pump is crapping out (only 5K miles on it), all kind of esoteric different Weber ideas and many other ideas...

How about your ideas?
Thanks,
Steve

Edited by steve260z, 2 weeks ago.

3.1L Stroker, F54, P90, 9.9CR, .8mm Metal Head Gasket, Schneider Stage 2 Cam,Header, Exhaust, Weber DCOE 40s

Build:  http://forums.hybrid...-antonio-31l-z/

& E92 335i 6 Speed manual, Cobb flash tune: 400hp


#2 30 ounce

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Posted 2 weeks ago

Sounds like vapor lock to me. I wouldn't run the fuel dead headed, run a return line. It will keep the fuel cooler. Also anything you can do to shield the headers from the carbs will help too.

#3 steve260z

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Posted 2 weeks ago

I was thinking that too but everything I've read on Vapor Lock seems to show the car will not start back up. Mine will start back up...on the 4-5 second crank...Is that true about Vapor Lock? Also, thinking about a heat shield under the carbs. Before I do that I'd like to ID the problem first.

Edited by steve260z, 2 weeks ago.

3.1L Stroker, F54, P90, 9.9CR, .8mm Metal Head Gasket, Schneider Stage 2 Cam,Header, Exhaust, Weber DCOE 40s

Build:  http://forums.hybrid...-antonio-31l-z/

& E92 335i 6 Speed manual, Cobb flash tune: 400hp


#4 30 ounce

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Posted 2 weeks ago

I had the same issue with my 3.0 liter but I had SU carbs.  It would restart but it wasn't pretty.  I went from dead head fuel system to return line then added heat shield with heat wrap and wrapped all the fuel lines.  Every little thing helped but the return line was the biggest help.



#5 heyitsrama

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Posted 2 weeks ago

74' should have a return line already on the body. Upper one is for a charcoal canister, the lower one near the feed should be the return.  B) 



#6 HuD 91gt

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Posted 2 weeks ago

Sounds exactly like vaporlock. Mine would start when having the same issue, but as you said would take many more seconds. I was running SUs, ended up wrapping the fuel lines in foil insulation tape. Got rid of most of the issues. Problem started after adding a non coated header. I wouldnt put another one on without having it coated or wrapping it.

Edited by HuD 91gt, 2 weeks ago.

1971 240z - Balanced .040 over L28 w/ Ported P90 head - Colt c542.s cam, SU w/SM needles, MSII (ignition)- LS2 Coils Wasted Spark, MSA Premium Exhaust - 6-3-2 Header

 


#7 steve260z

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Posted 2 weeks ago

I do have unwrapped headers, the fuel line is rubber unwrapped. Yes, the return line is still in the body.
Another note: I checked the connections on the Crane Ignition unit. 2 or 3 going to the distributor, all good.

3.1L Stroker, F54, P90, 9.9CR, .8mm Metal Head Gasket, Schneider Stage 2 Cam,Header, Exhaust, Weber DCOE 40s

Build:  http://forums.hybrid...-antonio-31l-z/

& E92 335i 6 Speed manual, Cobb flash tune: 400hp


#8 BluDestiny

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Posted 2 weeks ago

Almost sounds like you're just boiling the fuel out. After you drive for 10 or so minutes, have you tried just flooring it? and does it sputter and bog out? 


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#9 steve260z

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Posted 2 weeks ago

Yes, it does. Bogs down...runs like crap if I floor it when its acting up.

3.1L Stroker, F54, P90, 9.9CR, .8mm Metal Head Gasket, Schneider Stage 2 Cam,Header, Exhaust, Weber DCOE 40s

Build:  http://forums.hybrid...-antonio-31l-z/

& E92 335i 6 Speed manual, Cobb flash tune: 400hp


#10 steve260z

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Posted A week ago

Messing with it now...The Crane XR700 which is mounted on the inside fender below the coil is real hot. Say touch for 2 seconds thats all. Now, it has heat sinks built onto it, so suppose to be hot to some degree. Basically the entire header/intake side is real hot..Just fishing around..


And....my Amp meter usually has a "tick" in it...ticks to the positive side. As the RPMs dropped lower than usual and car acted like it was going to die the fuel pump was not as noisy and the amp meter did not have the "tick". I reved up back up, tick came back and pump was louder. Need to get the car up on ramps to watch the fuel going into the filter but maybe I have an issue with the relay??? The 260 came with both electric and mechanical pump. Relay maybe?

Edited by steve260z, A week ago.

3.1L Stroker, F54, P90, 9.9CR, .8mm Metal Head Gasket, Schneider Stage 2 Cam,Header, Exhaust, Weber DCOE 40s

Build:  http://forums.hybrid...-antonio-31l-z/

& E92 335i 6 Speed manual, Cobb flash tune: 400hp


#11 HuD 91gt

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Posted A week ago

I was amazed the difference the uncoated headers made vs. the stock manifold.   Everything was hot on that side of the engine as well.   


1971 240z - Balanced .040 over L28 w/ Ported P90 head - Colt c542.s cam, SU w/SM needles, MSII (ignition)- LS2 Coils Wasted Spark, MSA Premium Exhaust - 6-3-2 Header

 


#12 steve260z

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Posted 14 hours ago

Well, here we go. Yes, the car dies. But, the symptom is dying but not the problem. The problem is the idle slowly reduces and the car eventually dies. So, what is causing the slow reduction of idle? Still don't know but I've at least made progress. I increased the idle speed to 1K and it still worked its way back down to 600 and died.

For the hell of it I just changed the dead head to a return line system. Maybe the gas in the line is getting too hot. I'll see shortly

3.1L Stroker, F54, P90, 9.9CR, .8mm Metal Head Gasket, Schneider Stage 2 Cam,Header, Exhaust, Weber DCOE 40s

Build:  http://forums.hybrid...-antonio-31l-z/

& E92 335i 6 Speed manual, Cobb flash tune: 400hp





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