Wednesday, July 15, 2009

It's weird what pops into your mind.....

I woke up this morning with an idea, well more the idea of a place to look for the solution - complicated I know. Here's the twisted tale. I have an agglometer in the PI, a fancy name for a glass bowl and drain tap in the fuel filter. The idea for this is that you can see if there's any water contamination and drain the fuel. It also has the added benefit of being an easy way to drain off a small amount of fuel for starting a BBQ in true boys own dangerous cookery style - but that's another story :-)

Anyway, as well as the agglometer thingy I have a clear injector line so I can see what's happening there too. The result of all this transparency is that you see things you never knew were happening - phenomena that you'd be blissfully unaware of if you had a standard system.

What could I see?


No not the one time monkey partner of the deceased King of Pop but bubbles of air/vapour in the glass bowl and the injector pipe. These baffled me - the system was not leaking, it was not cavitating, these were appearing from start up and through out running up to temp (pump temp as well as engine temp). So where were these bubbles coming from? They were worrying as the PI system has no way of bleeding air out once fuel has flowed passed the PRV and then at pressures over about 30 PSI the PRV won't bleed air.

OK so to the point - I woke up this morning and thought "I know where the answer to that is" and I went straight to the article Dave Pearson gave me which emanated from I think a 1990 Club magazine (2000 register maybe?). I had blogged about this in the past. There it was, failing motor shaft seals on the pump unit will allow air in as well as leak fuel out.

Now I have tested loads of pumps and found failed shaft seals on about 60% of them - I haven't looked for air ingress just fuel egress (which is more obvious when bench testing). So it seems highly likely that I can sort this out with new seals.

The article also provides some good advice on blue printing a pump, what and how to modify as well as what to leave well alone!

As I write this, I think I'm going to have to work through this article and do the operations it suggests with camera in one hand and blog in the other.

Whilst the Lucas pump will always be the weakest link I am determined to build a good 'un and run the little bugger to success - I am actually enjoying this.

As soon as work, family and life generally allow me the time in the garage to get some momentum on this I'll be OK.

So far my local hydraulics place have let me down on the parts I ordered but my new best friend Darren at Pirtek Reading is on the case. Today's idle though - I wonder if they can supply injector O rings?

Here's the article, scanned and blogged, I commend it to all PI owners, I just wish I could credit the source properly:-

Jason's Blog: More Lucas PI info - some pearls of wisdom here :-)

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