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Fuel pressure regulator for Airtex 8012s (5 to 9 psi) fuel pump


jalexquijano

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Stock SU CARBS pressure is anywhere from 3.5 to 4.3 so i will need a regulator for any pump over 4.3 psi. If I run too high of a fuel pressure, the fuel bowl or well will be too pressurized which won't let the needle/seat assembly stay seated at idle or low speed when the carb doesn't require more fuel. The result will be a stinky rich fuel mixture and you'll be fouling plugs left and right while having a stumbling idle.
 
Can´t stand the stinky fuel mixture and the fouling at idle.
 
WHich fuel pressure regulator is recommended? Holley, Mr. Gasket?????? I need a secure one which will not let any gas out and is safe!!
 
 
Edited by jalexquijano
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What's the fuel pressure now ? 5 psi to 9 psi is a pretty big spread, so maybe your fuel pump is adjustable. The better regulators use a bypass (return). If you're using the stock fuel rail, it has a restrictor before the rubber hose that goes to the stock fuel return line. You'd have to block off the return end of the stock fuel rail, and plumb the regulator's return line to the stock return line. The return line is supposed to be the same size as the inlet line but the stock return line should be OK if your pump isn't pushing too much. You'll need a good F.P. gauge to set any regulator. The better ones all have a port to attach the gauge.

I read about some problems with the cheap deadhead regulators on this site and elsewhere. Mallory or Aeromotive are probably way better. Don't need one myself since my stock mechanical pump puts out the right pressure. If I wanted an electric pump I'd probably use the stock one, or get a Mallory 4070LP, which is adjustable and set at 4.0 psi from the factory (but I'd still check it with a gauge).

Anyway, here's a link for some regulators. http://aeromotiveinc.com/products-page/regulators/subcat/Carbureted

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Fuel pressure was measured at the fuel line of the rear carb two days ago an it was measuring around 5 to 5.5 psi. The car does present some hesitation or stumbling when accelarating in first gear or passing through any bumpy road at low speed. I already changed the differential mount but it was not the problem. Need to sort the following issues as soon as posible:

1. Stinky gasoline smell up front even though no flooding off the float bowls.

2. Reduce fuel pressure to 4 psi.

3. Eliminate the back and forth shaking, hesitation or stumbling when accelerating under 2,000 rpms in first gear.

4. Fouling of plugs at idle at traffic jams or intersections, which eventually will cause rough idle and stalling.

Float levels where set by Ztherapy when they sent the carburetors back from rebuilt. They advice not to open or touch the float bowls.

Please advise.

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4 hours ago, jalexquijano said:

1. Stinky gasoline smell up front even though no flooding off the float bowls.

2. Reduce fuel pressure to 4 psi.

3. Eliminate the back and forth shaking, hesitation or stumbling when accelerating under 2,000 rpms in first gear.

4. Fouling of plugs at idle at traffic jams or intersections, which eventually will cause rough idle and stalling.

Float levels where set by Ztherapy when they sent the carburetors back from rebuilt. They advice not to open or touch the float bowls.

Please advise.

You need to drive up to Texas and have a good mechanic really check your engine out.  Even with a fairly poor carb tune, you shouldn't have all of these issues.  Especially the back and forth shaking.  Sounds like you have a dead cylinder.

If you could collect and post all of the information about your engine, including the cylinder pressure readings, cam timing pictures, pictures of the cam lobes, all of that, you might get some good advice.  I wouldn't be surprised if you had a flat cam lobe, since you just installed a new cam.  They usually go bad soon after installation, if they're going to go bad.

Get everything you know about the engine and cam that's in the car now, and take two pictures of the cam shaft, 180 degrees apart.  Start a new thread.

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Okay. Im not driving to Texas. Car is going for paint job in 2 weeks so i need to sort this out with your help. What pictures and infromation do you need so i can post it immediately? Do you think the float bowls need adjustment, could this be the cause of the hesitation below 2000 rpms?

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"  cylinder pressure readings, cam timing pictures, pictures of the cam lobes, all of that,  "  Everything that you know.

The back and forth shaking could be the way the engine runs, or it could be from engaging the clutch.  Which is it?  I know you've been over all of this before, but it's your car so you need to keep the facts organized.  You should be able to summarize all of the problems that you've had, and the suggestions that people have made.  

 

 

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jalexquijano's 240Z problems

1.  Engine shakes during acceleration at low RPM.  Clutch is engaged, so it's not a clutch engagement problem.  New differential mount had no affect.

2.  Plugs foul.  Smell of excess gas.  Fuel pressure measured at rear carb was ~5.5 psi. (before rear carb or after rear carb?  Deadheaded?).

3.  Engine backfires - 

4. Engine overheats - 

 

I would keep a running list of these things and post them in all of your threads.

On your current request for a pressure regulator - you didn't say that you have a regulator now.  If you don't have a regulator and you're seeing 5.5 psi after the carbs, then you'll need to do some plumbing work also to bypass the excess pressure as Stanley suggested.  

And, you didn't respond to his suggestion of an Aeromotive regulator, or a Mallory 4070LP   The Mallory is set to 3-4 psi and can be adjusted over a narrow range.  He made a suggestion and you just ignored it.  That's why people aren't responding any more to your questions.  If someone suggests something you have to at least acknowledge that you saw it.  Otherwise, what's the point of responding to jalexquijano's questions.  He'll just ignore the response.

Good luck.

http://www.jegs.com/InstallationInstructions/600/650/650-4070LP.pdf

Edited by Zed Head
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21 hours ago, Stanley said:

What's the fuel pressure now ? 5 psi to 9 psi is a pretty big spread, so maybe your fuel pump is adjustable. The better regulators use a bypass (return). If you're using the stock fuel rail, it has a restrictor before the rubber hose that goes to the stock fuel return line. You'd have to block off the return end of the stock fuel rail, and plumb the regulator's return line to the stock return line. The return line is supposed to be the same size as the inlet line but the stock return line should be OK if your pump isn't pushing too much. You'll need a good F.P. gauge to set any regulator. The better ones all have a port to attach the gauge.

I read about some problems with the cheap deadhead regulators on this site and elsewhere. Mallory or Aeromotive are probably way better. Don't need one myself since my stock mechanical pump puts out the right pressure. If I wanted an electric pump I'd probably use the stock one, or get a Mallory 4070LP, which is adjustable and set at 4.0 psi from the factory (but I'd still check it with a gauge).

Anyway, here's a link for some regulators. http://aeromotiveinc.com/products-page/regulators/subcat/Carbureted

Thanks Stanley. How loud is the Mallory 4070LP?? Can it be set to 4 psi and hence no need of regulator?

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  • 4 weeks later...
On ‎2016‎-‎02‎-‎28 at 5:08 PM, Zed Head said:

jalexquijano's 240Z problems

1.  Engine shakes during acceleration at low RPM.  Clutch is engaged, so it's not a clutch engagement problem.  New differential mount had no affect.

2.  Plugs foul.  Smell of excess gas.  Fuel pressure measured at rear carb was ~5.5 psi. (before rear carb or after rear carb?  Deadheaded?).

3.  Engine backfires - 

4. Engine overheats - 

 

I would keep a running list of these things and post them in all of your threads.

On your current request for a pressure regulator - you didn't say that you have a regulator now.  If you don't have a regulator and you're seeing 5.5 psi after the carbs, then you'll need to do some plumbing work also to bypass the excess pressure as Stanley suggested.  

And, you didn't respond to his suggestion of an Aeromotive regulator, or a Mallory 4070LP   The Mallory is set to 3-4 psi and can be adjusted over a narrow range.  He made a suggestion and you just ignored it.  That's why people aren't responding any more to your questions.  If someone suggests something you have to at least acknowledge that you saw it.  Otherwise, what's the point of responding to jalexquijano's questions.  He'll just ignore the response.

Good luck.

http://www.jegs.com/InstallationInstructions/600/650/650-4070LP.pdf

I would really prefer a pump to can push steady 4 psi instead of adding a fuel pressure regulator to the engine bay. Does the Mallory 4070LP reaches 4 psi?

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