noboost

Taking my injectors out, I noticed the infamous pulsation damper (PD) loose screw, complete with gas leaks. Not wanting to add my car to the list of roadside BBQ hosts, I want to stop the leak. They way I understand it, there are three options.
1.) Replace with a new PD $124.51 (Mazdatrix Price) 2.) Swap fuel rails with a 88 - 91 which have built in PDs. Or 3.) Replace PD with a banjo fitting bolt.

Has anyone replaced their pulsation damper with a 12mm x 1.25 banjo bolt? If so, did you notice any adverse changes in how the engine ran?

I've got a feeling that a leaking PD with a screw missing isn't doing a great job of dampening anyway. So replacing it with a bolt may be alright.

tesla042

http://haxx0r.net/car/rx7/pulsation.html

I got *TWO* 89-91 fuel rails, each for under 30$. If you aren't under a time constraint, i suggest you look around on the for sale section here, and at http://www.thepartstrader.com for people parting out 89-91's..

-Tesla

noboost

OOpps on my first post I meant to say '89 - '91 fuel rails have the built in PD.

Do used '89 - '91 have rubber diaphragms built in? If so, aren't they likely to be cracked being at least 10 years old?

Anyone out there with banjo bolt experience?

akageals

No but I wanted to do it! I'm not sure that the PD really does much that you could tell just by feel. Let us know what happens if you do it.

Todd

wankelhead

another option for ya... i bought a new one for my 87n/a,but,was unable to use it 'couse i'm using a 89-91 intake manifold,and there is not enough clearance for the older pd under there.so,if you want it,make me a offer.i'm thinking in the 80$ range.
david

ItsNiceToBurnRice

uhhhh, if the damper is suppose to smooth about the fuel pump bumps wouldnt just a bolt defeat the purpose? I jsut wanna know, ****, Ill put a banjo in there if it means no way of leakin.

noboost

If the pulsation damper has a loose screw and is leaking (which mine was), I don't see how that does a good job a smoothing out the fuel pulses. So my thought is, a damper may not be necessary.

I am having a hard time finding a 12mm x 1.25 banjo fitting bolt. Anyone know where to search? I have looked into local fastener houses, J&L, McMaster Carr, some Aeroquip catalogs, made some calls and still haven't find one.

-john

tesla042

Yeah..they're REAL hard to find.. You may want to consider cutting the dampener off the bolt, and welding the end closed.. I was going to do that before I found the 89+ rails..

The 89+ rails have the pulsation dampner built in. It's integral to the rail, and is designed so that it isn't as prone to leaking as the 88's are.. In fact, I've never heard of an 89+ with an engine fire, or a leaking PD.

Someone on here has an animated gif of the difference between the two.. he'll prolly chime in in a bit..

-Tesla

mprime

Summit sells them for around 15 bucks heres the part number I got from Earls Performance products

12mmx1.25

EAR-807691

mprime

If any one has questions to the exact specs heres the web page from Holley/Earl

Banjo Bolt Page info Click Here

noboost

I ordered a metric banjo bolt from Goodridge,

http://www.goodridge.net/cat/topframe.html

-john

Pinfield357

so what is a banjo bolt and what does it do?

RX-7Impreza

a banjo bolt is a bolt that has the center drilled out up to the head and a
....................___.....
______ ...__l.....l
l______l..l__.....l
__________l.....l
l_________ ......l
...................l___l....

hole drilled in the side so that fliud can pass through it, above is a cross section

Justin

RX-7Impreza

ok on this picture aboveyou have to ignore the dots and just look at the lines

Pinfield357

how would that help where would the gas go then? im still confused about this...

scathcart

The pulsation dampner "damps" pulses from the fuel pump, a mini gasoline shock absorber. As I see it, this allows the fuel injectors to see an ABSOLUTELY constant fuel pressure. Otherwise, the injectors could fire at either a pump pulse or the time in between, where fuel pressure would be higher or lower. Higher or lower fuel pressures would allow minute differences in air fuel ratios, and with the engine running at the very edge of it safe level, you *could*go lean....
I would keep it if at all possible, unless you switch to a better style pump, such as an Aeromotive A1000 linear pump or the likes. That's what I run.... (almost). I have a sweet fuel set up.
Sean Cathcart

RX-7Impreza

despite the strength of the fuel pump you have you will still endager your car somewhat by doing the banjo bolt fix. with the injectors flicking open and closed so often you can create "dry spots" where the injectors open with not enough pressure to inject much fuel. this is minor but in high hp/ boost engines it can be a danger.

it is much better to get teh S5 fuel rail, they arent hard to locate...

Justin

noboost

Pinfield357,

The Banjo bolt takes the place of the pulsation damper. On the end of the primary fuel rail there is a pulsation damper that sandwiches a banjo fuel hose fitting (called a banjo fitting due to it's banjo shape). The pulsation damper can be removed and a banjo bolt can be installed. The banjo bolt sandwiches the stock banjo hose fitting onto the fuel rail.

So to answer your question "where would the gas go?" It would flow through the banjo bolt, which is hollow.

FWIW, I replaced my PD with a banjo bolt and saw no ill effects of idle quality.

-john

stockrex

can some pls point out the PD in this pic I found on ebay?
TIA

7Rebel

I circled the PD in red

Pinfield357

ok i understand the the banjo bolt is hollow and the fuel flows threw it but where does it go once its threw the bolt? it has to go some where

Pinfield357

maybe im just thinking to much into it...

7Rebel

In the pic .... look at the fuel rail right under where the PD is .... the fuel flows throught that into a Fuel hose that goes to the secondary fuel rail.

HAILERS

JPG OF A BANJO BOLT:

HAILERS

BANJO TWO: