The mysterious FDV fault continued.

tom · Post by **tom** » Thu Oct 23, 2008 10:06 pm

I'm about to take on Rob's Tizzydee and I'll be puzzling out the cause of the problem so that i can sort it out before I go up to collect it. This will be the holding thread which explains my ideas as they occur to me. I'll be back when I've done some reading but it doesn't look too difficult so far.
We'll assume that the pump can provide enough power to lift the car because it will lift when the steering is turned and that the pinion valve is operational because turning the wheel has an effect. The fact that the steering is good suggests that the pump has some pressure and the fact that the stop light stays on points to an absence of pressure downstream of the FDV.

Things to rule out.

Lost ball from pressure regulator?
Faulty pressure regulator.
Determine what is going on in the FDV.

ken newbold · Post by **ken newbold** » Thu Oct 23, 2008 11:35 pm

Welcome back to the land of the loonies.

Knew you wouldn't be able to resist for long

Post by **docchevron** » Fri Oct 24, 2008 12:42 am

Ah ha!
That explains the voicemail!
Alas it's a rather anti social hour to be returning calls now but I'll give you shout at a more reasonable hour!

tom · Post by **tom** » Fri Oct 24, 2008 10:05 pm

Brain engaged, I think it looks like this: Pump feeds directly to FDV.
Pinion valve turns (or rotates, it is after all a matter of a pinion,) and cuts off the FDV. STOP light goes out eventually and car staggers to its knees.
There is a lot of pressure in the FDV because it is getting full pump pressure before it hits the PR and now it is cut off the flow (Which is minimal because one piston is STUCK) has nowhere else to go and heads for the suspension (at high pressure but very little flow). Once the system is pressurised, the normal leakage plus wear causes it to drop again because there is no adequate replenishment of the accumulator
BECAUSE NOTHING IS EVER GETTING TO THE PRV WHICH IS WHY IT NEVER TICKS!

The clue is in the cutting off of the flow when the pinion valve moves. The flow has to go somewhere.

I diagnose a stuck piston in the FDV and Green Globe Gang HQ (West) assures me that a replacement FDV is waiting for me to collect en route to a rescue mission abetted by my trusty partners in crime DLM and Grolliffe. It will be nice to get my hands dirty again. Watchmaking is very satisfying as a hobby, but sometimes you can't beat a cold day and an inert BX!

Philip Chidlow · Post by **Philip Chidlow** » Fri Oct 24, 2008 10:12 pm

Good to see you back Tom. As has been said before, once the BX is in the blood, that's it...

RKM · Post by **RKM** » Sat Oct 25, 2008 1:26 pm

To be fair, I am just pleased that my BX is getting a good home. She deserves it!

B-Hive · Post by **B-Hive** » Sat Oct 25, 2008 1:59 pm

These FDV's can be tricky and temperamental from my brief experience. I only had to swap out a HP pump for a better one to get issues with my FDV's calibration.

They seem to bed in with a known community..once one of the main components are changed then the FDV need recalibration. Also unless you really know what you are doing, an everyman overhaul is limited to seals and filters..do not attempt to touch the screw ring assembly...or kaos will ensue...

tom · Post by **tom** » Sun Oct 26, 2008 5:52 pm

Seems that I was right. Although I chose not to buy the car, Rob rebuilt the valve again, correctly this time, it would seem because it all works now.

RKM · Post by **RKM** » Mon Oct 27, 2008 9:00 am

Still not entirely sure what it was - all I can assume was a stuck piston. However, the suspension now rises and the power steering works well.

Tom spotted a few probs, which I have decided to sort out, especially as I went on a high-speed run yesterday evening in the car and enjoyed it immeasurably!

R

MULLEY · Post by **MULLEY** » Mon Oct 27, 2008 1:14 pm

Good news that you've managed to get your car working again, & well done to Tom for being a gent about it & for offering advice on other issues. Isnt this a cracking club....