1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Stock fuel pressure

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Old Sep 20, 2021 | 10:09 AM
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Stock fuel pressure

I plan on upgrading my fuel pump this weekend from stock to a mr gasket setup. I was going to run their mini 12s with the fuel pressure regulator. What would happen if I were to run it at 5 or 6 psi. Would there be a power difference? Also any tips on wiring would be appreciated.
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Old Sep 20, 2021 | 11:49 AM
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running that much pressure will likely cause flooding and possibly other issues as well. start at around what the recommended pressure is, and then (if necessary) adjust it to what your car likes.

as far as tips go, use quality wires (won't hurt to go a little larger gauge). if it were me, instead of just splicing it into the car, i would create a new circuit straight from the battery and use the factory wiring to turn on the "new" relay. it's your choice though. either way should be fine.
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Old Sep 20, 2021 | 12:00 PM
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Originally Posted by diabolical1
running that much pressure will likely cause flooding and possibly other issues as well. start at around what the recommended pressure is, and then (if necessary) adjust it to what your car likes.

as far as tips go, use quality wires (won't hurt to go a little larger gauge). if it were me, instead of just splicing it into the car, i would create a new circuit straight from the battery and use the factory wiring to turn on the "new" relay. it's your choice though. either way should be fine.
so the mr gasket pumps are good? Also can you explain the wiring part please I’m not very good with electrical
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Old Sep 20, 2021 | 01:05 PM
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i have no idea about the Mr. Gasket pumps. i've only recently started hearing about them. sorry. i assumed it was something you sought out for your own reasons.

as for the wiring, if you're not into that sort of thing, then just keep it simple. splice the new pump into the existing circuit. i assume you know how to figure out which wire is positive and which is negative/ground. splice the pump's connector onto the new pump with some sort of safe connection (use heat shrink and good insulation), then plug it in.
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Old Sep 20, 2021 | 01:14 PM
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From: https://www2.mazda.com/en/100th/
i would suggest finding a container with the volume marked on the side, and do a volume test, the Mazda pump does ~700cc in 30 seconds and is right on 2.75psi. you new pump needs to do the same volume or more in that same time, and pressure needs to be stable, and the same.

the holley regulators are crap, it kills flow and pressure is all over the place....
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Old Sep 20, 2021 | 04:08 PM
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Originally Posted by diabolical1
i have no idea about the Mr. Gasket pumps. i've only recently started hearing about them. sorry. i assumed it was something you sought out for your own reasons.

as for the wiring, if you're not into that sort of thing, then just keep it simple. splice the new pump into the existing circuit. i assume you know how to figure out which wire is positive and which is negative/ground. splice the pump's connector onto the new pump with some sort of safe connection (use heat shrink and good insulation), then plug it in.
yeah that makes more sense most I’ve done wiring wise is light pods and bars so it should be similar
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Old Sep 20, 2021 | 04:10 PM
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Originally Posted by j9fd3s
i would suggest finding a container with the volume marked on the side, and do a volume test, the Mazda pump does ~700cc in 30 seconds and is right on 2.75psi. you new pump needs to do the same volume or more in that same time, and pressure needs to be stable, and the same.

the holley regulators are crap, it kills flow and pressure is all over the place....

I have a feeling my pump won’t put those numbers out lol
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Old Sep 20, 2021 | 05:03 PM
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Wait! What does it mean to upgrade from the OEM fuel pump? You won't find a better fuel pump for these cars than the stock one. Any other pump is almost guaranteed to give you problems with fuel pressure, unless its properly regulated.. but to do that, typically you need to run a larger return fuel line... And you also need to deal with wiring it in, finding a proper way to mount it, etc.

All this extra work and hassle for nothing. Unless your engine is ported, the stock pump will work fine and they seem to run for 30-40 years.

By the looks of the filter, you have big problems in your fuel tank. No pump will help that.


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Old Sep 20, 2021 | 05:50 PM
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Originally Posted by j9fd3s
the holley regulators are crap, it kills flow and pressure is all over the place....
never realized this. so many years down the line, and i'm seeing a trusted source say this. it's all water under the bridge now, but it explains so much of the issues i was having with tuning my Dell'Orto way back when.
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Old Sep 20, 2021 | 05:54 PM
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I had very good luck with Holley regulators, in 2000.
The regulator I put in my '81 last year floats around from 2 to 6 psi. It's a mess.
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Old Sep 20, 2021 | 06:33 PM
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Originally Posted by tommyeflight89
Wait! What does it mean to upgrade from the OEM fuel pump? You won't find a better fuel pump for these cars than the stock one. Any other pump is almost guaranteed to give you problems with fuel pressure, unless its properly regulated.. but to do that, typically you need to run a larger return fuel line... And you also need to deal with wiring it in, finding a proper way to mount it, etc.

All this extra work and hassle for nothing. Unless your engine is ported, the stock pump will work fine and they seem to run for 30-40 years.

By the looks of the filter, you have big problems in your fuel tank. No pump will help that.
fuel tank was getting dropped and cleaned when I do the pump maybe I’ll try just cleaning the pump out instead. Thanks!
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Old Sep 21, 2021 | 10:25 AM
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I have a holley regulator and it works fine but its maybe 8 years old, so they could be crap now a days. i would stay away from any Mr. Gasket crap. Agree that by the looks of that filter you have a huge problem in your tank. Get it sorted/cleaned/lined whatever first and blow out the lines and a new filter then see what the pump does. Nikkis are very particular and like the pressure to be in the 2.5-3.0 psi, anything over that and problems will happen.
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Old Sep 21, 2021 | 10:39 AM
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Originally Posted by t_g_farrell
I have a holley regulator and it works fine but its maybe 8 years old, so they could be crap now a days. i would stay away from any Mr. Gasket crap. Agree that by the looks of that filter you have a huge problem in your tank. Get it sorted/cleaned/lined whatever first and blow out the lines and a new filter then see what the pump does. Nikkis are very particular and like the pressure to be in the 2.5-3.0 psi, anything over that and problems will happen.
is there a place that does that kinda stuff to gas tanks I’m planning on dropping it
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Old Sep 21, 2021 | 08:07 PM
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Yes find a local tank shop, they will dip the tank, clean it out, and refinish it. I think mine was around $400 or so.

Dropping the tank is pretty straight forward. Pay particular attention to the sending unit, it is held in place with small screws and a gasket. You should plan on replacing the sending unit, gasket (available from Mazda), and all the rubber fuel hose. Mazda will also have a new OEM filter for you. I know it sounds like a lot but all of that will probably take the same amount of time as hacking things up to install an aftermarket pump!

Not sure where you are in Michigan, but a state that is home of Detroit muscle should have some shops around that are good at bringing old tanks back to life!

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Old Sep 21, 2021 | 09:36 PM
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Originally Posted by 85_whiterx7
is there a place that does that kinda stuff to gas tanks I’m planning on dropping it
in addition to what tommyeflight89 posted above, you can also check your local radiator shops as well.


Originally Posted by peejay
I had very good luck with Holley regulators, in 2000.
Originally Posted by t_g_farrell
I have a holley regulator and it works fine but its maybe 8 years old, so they could be crap now a days..
if they turned to trash only recently, then mine may have been okay. mine would have been somewhere around 2003-04. i never really had reason to suspect mine of bad behavior (so much so that i got one for my brother's car with a Holley), but when i saw j9fd3s' post it got me thinking what if ....
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Old Sep 21, 2021 | 09:45 PM
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Originally Posted by tommyeflight89
Yes find a local tank shop, they will dip the tank, clean it out, and refinish it. I think mine was around $400 or so.

Dropping the tank is pretty straight forward. Pay particular attention to the sending unit, it is held in place with small screws and a gasket. You should plan on replacing the sending unit, gasket (available from Mazda), and all the rubber fuel hose. Mazda will also have a new OEM filter for you. I know it sounds like a lot but all of that will probably take the same amount of time as hacking things up to install an aftermarket pump!

Not sure where you are in Michigan, but a state that is home of Detroit muscle should have some shops around that are good at bringing old tanks back to life!
yeah I’m in the Detroit area. I replaced the sender last weekend. Is there anything I should know before I clean the fuel pump?

Last edited by 85_whiterx7; Sep 21, 2021 at 09:52 PM.
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Old Sep 23, 2021 | 01:56 PM
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Sending units are NLA, no?
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Old Sep 23, 2021 | 03:04 PM
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Originally Posted by peejay
Sending units are NLA, no?
i just got mine off of Mazdatrix for 130
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