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stock 280Z fuel pump for triple mikuni setup


dsalni

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Hey guys, did some digging but couldn't find an answer, so I'll ask here.

 

I'm running a triple Mikuni setup on my '78 280Z L28, with a stock fuel pump, fuel pressure regulator and inline gauge. I'm getting a constant 4psi before the carbs. My question is - is there any downfall or reason not to use the stock 280Z EFI fuel pump with carbs? I did recently buy a Carter, but money is tight and if I don't HAVE to install it, then I'd rather return it while it's still brand new.

 

thanks in advance!

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The only reason I can see would be that you're overworking it by regulating it down so low. Either the pump will give or the fpr diaphragm will give.

good point. My car is pretty loud, and I'm starting to hear the pump start to whine consistently now. Guessing that's a sign of inevitable failure. 

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What a crock of crap!

 

OVERWORK? It's running at 4-psi with absolutely a FRACTION of the load in the motor windings making  it run cooler. Less pressure means less side loading on the rollers in the pressure elements. This means LESS WEAR. High flow through the pump also means COOLER RUNNING OVERALL....

 

The FPR has the ability to open and bypass. It's not a pulsing pump...THAT wears out diaphragms.

 

And if any of those reasons has not been common sense enough, I've been using a stock Datsun EFI pump to run my Triples since 1985, and the pump was 9 years old THEN....

 

The noise and the wear came from using it a EFI pressures  for likely that same period of time! At 4psi, those Bosch Pumps last forever. And stay QUIET!

Edited by Tony D
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Use of EFI pump on Carburetted Applications.

 

The stock L28ET pump will not supply much power to an EFI'd car, you run  20# of boost and you're within 6# of  bypass in the internal relief and  dropped it's flow quite a bit.

 

But that same pump running at 20psi in a carburetted blowthrough setup will only be running maybe 24~25psi and nowhere  NEAR curtailed flow, or the internal relief valve. I ran 350HP + on a carb blow through using a single N/A EFI Pump with a 3psi booster for the swirl pot (basically 3.5 psi inlet head  to the EFI Pump.)

 

Was that way from 1985 to the mid/late 90's. Tens of thousands of miles driven. Personal Best was 4.5 mpg, worst was daily commuting at 17.5 mpg...

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  • 1 month later...

I just posted a similar ? A few days ago. I am switching to the Holley 4 bbl. The responses I got were that it's a bad idea and you need a fuel pump psi rated for carbs. My thought is that I don't want to take the chance. 100$ isn't a bad insurance policy for a 500$ carb. I think it would work just fine with the bypass regulator I bought but if it does fail you would be sending enough pressure into the carbs to warrant a rebuild x 3. My carb needs 7psi, plan on the 14psi Holley so the regulator does its job and fuel bypasses often to keep the pump cool

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  • 2 weeks later...

For a definite answer: an eBay seller sent me a siezed leaky Holley red pump so I put my OEM pump back in to test the Holley and see if it would run, I regulated it down to 7 psi and ran the return into a 5 gal gas can, it worked but bypassed enough to fill the gas can up 2/3 of the way in less than 10min. I wouldn't want to take the chance w that much pressure and that much flow having a reg go bad or return line get obstructed

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  • 2 weeks later...

I thought there was a definite answer already...what have you added? I'm a bit confused. What you posted adds nothing to the discussion and I'm having trouble finding relevance in any of the tests you did or what they supposedly show.

 

If an FPR fails, it fails opens dropping fuel pressure through the bypass line.

 

If your return line becomes obstructed, full fuel pressure will be dependent on float bowl inlet orifice will be present...(assuming the FPR can not bypass and therefor orifice size becomes the pressure regulation mechanism.

 

In a Holly Red that would be maybe 12-14 psi before its internal bypass opens...

On a stock EFI pump that's maybe 15-17psi once your floats sink (it may have been 8-9psi as this was a condition I saw on my triple when I bought a car)... It will NEVER get to the 60psi of the EFI Pump Internal Bypass Valve because of the floats sinking..

 

Either will sink your floats, flood the bowl, and dump gas into your carb throat.

 

Your fears are totally unfounded. Nothing will be damaged in the carb.

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