Jump to content
Sign in to follow this  
Rob Y

Injector O ring change

Recommended Posts

And 20 years ago the main concern regarding unleaded fuel was valve seat recession , which seems to have been a non event . All the problems with material compatabilities were missed entirely or glossed over. Such is life.

Share this post


Link to post
Share on other sites

There is a big difference to the application though. Fuel hose in constant contact with the fuel and the resultant effect being fuel permeability, compared to these o rings which are not in constant contact with the fuel and then the only effect is that they might swell slightly, so would not cause any issues. I have seen reports on tests done on o rings in modern unleaded fuels and even nitrile worked fine, so I am not worried about the marginal difference between the 2 Viton grades for this application. I am pretty sure the ones I took out were original and probably nitrile, so after 40 years you start to see an effect and even then it's not actually critical.

The only bit that you missed is that the original O rings for the injectors had a swelling agent in the compound that gave a 10% swell! This was added so that the O ring would give a good seal when exposed to petrol and stop drain down when the engine is switched off. The currently supplied O rings do not do this? I suspect that the current restorers of PI do not know this?

 

Bruce.

Share this post


Link to post
Share on other sites

And 20 years ago the main concern regarding unleaded fuel was valve seat recession , which seems to have been a non event . All the problems with material compatabilities were missed entirely or glossed over. Such is life.

Spot on Mike!

And the fact that it was a lucrative business convincing people to strip engines (probably leading to other work too) and seeking un needed additives.😱

Edited by Rem18

Share this post


Link to post
Share on other sites

The only bit that you missed is that the original O rings for the injectors had a swelling agent in the compound that gave a 10% swell! This was added so that the O ring would give a good seal when exposed to petrol and stop drain down when the engine is switched off. The currently supplied O rings do not do this? I suspect that the current restorers of PI do not know this?

 

Bruce.

Interesting.

And so?

Share this post


Link to post
Share on other sites

Hi Bruce,

That was an interesting solution!

And a very good memory:)

Viton O-rings will not/hardly swell in our fuels.

Using a softer grade of Viton may be helpfull.

There are different grades for sale.

I made a note in my BB to use 75 Shore hardness Viton B, not sure where I got that from.

Regards,

Waldi

Share this post


Link to post
Share on other sites

Hi Bruce,

That was an interesting solution!

And a very good memory:)

Viton O-rings will not/hardly swell in our fuels.

Using a softer grade of Viton may be helpfull.

There are different grades for sale.

I made a note in my BB to use 75 Shore hardness Viton B, not sure where I got that from.

Regards,

Waldi

I bet if Lucas did this there was a good reason to spend more time and money sourcing supplies.

Sounds like this be a case of 'if it ain't broke don't fix it'

As maybe replacements might actually be worse?

Edited by Rem18

Share this post


Link to post
Share on other sites

M

 

To answer your questions:

My tank is bare steel currently, no internal coating yet, and it is not severely corroded internally, but I plan to apply an internal coating before installation, but want to increase the outlet diameter first. I had a flake of rust in the tank outlet when I dismantled it, non sure where it came from, so a coating may be a good pre-caution.

I also plan a decent size fuel filter between tank and pump, so this will catch most of the particles that could still be released.

 

 

The slosh also locks down loose particles.

I used the one from Moss 18 years ago.

But this time I may use an American two pack product if I can figure out how to remove the old liner first!!???😱

Share this post


Link to post
Share on other sites

Interesting.

And so?

In my day in the 1970's when I used to buy millions of O rings it was very common to have the swelling agent added to the compound to react with oil or petrol to give better sealing!

Bruce.

Share this post


Link to post
Share on other sites

And of course now I said it what do I find?

N*2 injector has stopped spraying.

Swapped 1&2 and it's better but still not right as now 1 doesn't spray and 2 sprays iffish.

Pulls fuel when you put them back but doesn't spray when removed.

Funny thing is I replaced MU only just before and primed everything and it was all working.

Wondering if the new MU has a slightly different pressure?

Will go for a blast to see but not very happy.

May have to take MU off and check banjo.

Dahhhh.... Might take injector apart but concerned as with all things once you start taking stuff apart you end up doing loads more.

This ethanol petrol thing is beginning to cause depression....

Share this post


Link to post
Share on other sites

Try disconnecting them at the union to the fuel hose and blow through clean air at 80 psi - check the Lucas PI red book for details.

 

The fuel in Australia is now is such that it attacks nitrile rubbers easily -my MU and injectors are going off tomorrow to be fitted with viton seals , a viton fuel diaphragm and a full recalibration. They were supposedly rebuilt for unleaded fuels 9 years ago for the then expected composition of unleaded fuel. Interesting a lot of our local historic racers running Lucas injection systems on high octane road fuel are adding small amounts of 2 stroke oil to the fuel- they believe that the lubricating properties of our current unleaded is far less than the leaded 100 octane of 20 years ago.

Share this post


Link to post
Share on other sites

Yes Mike of course I know regards testing.

I generally lightly pull the nosle while running but it's not working this time.

More likely I will dismantke the culprit.

I also have a spare but it's a screw type and this is a push and fading around under the sn I couldn't get the white holder put.

My concern is that like with all car things once you fix something then something else further fuel the line goes.

After changing fuel pipes I now have to look at the 18 year fuel tank liner.

I will dismantle filter then check lines and as last resort MU in case a banjo is not seated.

But my guess is injector.

It's Sods law because here I wrote a few days ago that I has never had modern fuel trouble with injectors.

 

Going for an Italian tune up later in PM.

Let's see how she runs under pressure once I get out of town centre.

 

I have reeboks MU in bits and going to re seal.

Where did you order viton for MU ?

T

Edited by Rem18

Share this post


Link to post
Share on other sites

A company in Sydney called BowerPower Auto Technologies is rebuilding the MU. They have the viton components made for their rebuilds. Summer's on the way and I don't want to risk importing components that may or may not work.

 

Good luck with the Italian tune.

Edited by Mike C

Share this post


Link to post
Share on other sites

I wrote to prestige in the UK but he didn't answer .

Will update you regards Italian tune up on a few hours.

Talk to Neil Ferguson 07977001571 or contact him on here (k Raven-smith)

Stuart.

Share this post


Link to post
Share on other sites

Metering units DON'T alter the pressure ONLY the amount of fuel delivered to the injectors/engine. Neil

Of course all it does is switch it from one injector to another.

But I was thinking maybe I had pinched a banjo OR when fitting.

But I swapped over 1&2 and saw it was an injector.

All sorted now cheers.

As soon as I got out of town and hit the 'Italian tune up button' everything came on song literally.

Half a turn advanced on ignition distributor wheel and away we go.

Neil I need to speak to you about refitting my old MU to viton etc as my spare I just put on is 20 years old stored but obviously with period seals.

I want to overhaul it myself with up to date seal kit.

Can you pm your email at some stage please.

Thanks

Tony

Edited by Rem18

Share this post


Link to post
Share on other sites

Resurrecting this one. If not I will order from UK.

Can someone give me the measurements of the orings for the injectors In but also Out so maybe I can see if I can source locally in Italy?

Share this post


Link to post
Share on other sites

Rem18, these are the O-rings inside the injectors, right? The originals were, I believe, 3/16" x 1/16" which works out at 4.5mm x 1.6mm (all inside diameter x cross section). As Viton takes more of a set than the original rubber, I fitted a slightly larger cross-section 4.5 x 2.0mm and used a little silicone grease during assembly - they went in without a problem.

 

Cheers, Richard

Share this post


Link to post
Share on other sites

Yes Richard I am referring to the o'ring on the spring body which is the only one inside I think.

Right? As I wasnt going to play around opening the spring body up if I can help it and just clean up the seating of the sleeve body.

So you just greased and slid these Viton versions over the front to drop on right?

Or looking it might be better to slide from the back right?

Viton b right?

Thanks Tony

Share this post


Link to post
Share on other sites

Hi Tony. The one I was referring to is indeed inside the injector. You have to open up the injector which requires pinging off a tiny circlip. There was an excellent article in TR Action several months ago. I think this is what you must mean when you say "opening the spring body" - yes, it's fiddly but do-able if you aren't fazed by small fiddly mechanical things. The grease helps with the first part of assembly but in particular helps to ease the over-sized - hence tight - O-ring (already on the internal body) into the outer body.

 

Sorry I'm not more help. My memory has faded and I don't have the article to refer to.

 

Cheers, Richard

Share this post


Link to post
Share on other sites

No I have already taken an injector spring body out of the injector casing (which is just a metal pipe) by releasing the circlip.

I was referring to the cylindrical spring body inside, I dont think one should unwind that part as it will affect the pressure setting of the injector its just the o'ring on the outside of the spring body right?

Question... Are these injector bodies all same size, I imagine you can you swap them between injector out casings?

It seems to me that the seal is created more by the machined tapered surface of the injector assembly when under fuel pressure mating up against the machined facing of the injector outer casing and that maybe the oring is just for sealing when the engine is stopped and the system is not pressurised.?

In fact the fact that the sping bodu slides so easily back and forth in the injector body implies to me it really isnt high tollerance along the barrel.

Am I wrong?

Edited by Rem18

Share this post


Link to post
Share on other sites

Here we go, TR Action Issue 289 - April 2016, Page 37 which should tell you all you need to know - well, more than I know anyway!

 

Cheers, Richard

Share this post


Link to post
Share on other sites

Hi. Would it be possible for someone to copy the article and PM me. I would like to keep as I will be doing my injectors in the future. I can't seem to copy or save to my laptop.

Cheers

Brian

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.