Monday, April 11, 2011

It's been a long time.....

.... since I updated this blog. That's probably because not a great deal has been happening. You see after the the International Auto Ecosse last year I was somewhat disheartened with the car and my own ability to get it running right.

I'd been all through the injection and the ignition systems, twice. I was systematic and careful, or so I thought. It didn't seem to matter what I did or indeed what issues I found and fixed, the engine still would not pull strongly and didn't sound smooth. It wasn't quite a misfire but it wasn't right. Pulling plug leads off didn't isolate a real misfire but a chance piece of night driving revealed that full beam could make it worse. As would sounding the horn (air horns).

Now I have an electronic pressure gauge that doesn't really instil confidence - it seems to register 102 PSI no matter which pump or PRV goes on. I'm not sure it's ever been accurate despite being new and specified properly - it should register up to 150 psi. Anyway, full beam did seem the pressure drop to 100psi. The car will run down to about 85psi so I kind of thought it wasn't injection related. I know that's not good and never a long term prospect.

I've changed everything in the injection system from throttle bodies to metering unit to prv and pump.

So I then decided the problem was ignition based, wiring to the low tension side - you know how it is, you turn it over and over in your mind and you know it's the cause and you know how to test it and fix it. So you go out there and wire the coild directly to the battery and turn it over and ......

...she runs.....

...... but it's no bloody different! The rough running is still there.

So, back to square one. What else can it be - fuel pressure? It doesn't make any difference which pump of prv combination, I still see 102psi.

Now those you who know me well also know I am crap at electrickery - it's black magic as far as my small brain is concerned. I know I'm crap at it so I tend to avoid it but there was one modification that I hadn't done and that was to rewire the pump with a relay. You use the existing wiring to switch a relay and power the pump from a new chunky cable direct from the battery.

I'm indebted to Paul "Bodders" Bodiam who, after a chat at a club meeting last week, sent me an email with some test to do before I started re-wiring things. The tests showed me that there was a 2.1 volt loss in the original wiring. That is not good for the pump!

So, a quick re-wire (which revealed my less than adequate supply of wire!) and I still got 102psi on the gauge but it didn't drop. I did see 103 psi briefly but so briefly I'm not sure it was real!

Whilst the car was sticking over I did a stupid thing. I should have taken it for a test drive and tried to figure out if my modification had really made a difference before I did anything else. Of course I didn't!

I continued to fiddle.

In previous fiddlings I had managed to mangle the throttle return spring and found something I thought was suitable, nailed it on and created a totally crap throttle pedal, too hard. So I found some suitable replacement springs on eBay - E type Jag ones (apparently), perfect!

Whilst fiddling with return springs I started looking at the throttle butterflies and how t hey opened. It was then that I realised they were not exactly synchronised - blocking the air bleed didn't kill the engine. So, yet more fiddling and I got them synchronised, I can't quite figure out how they got out of whack as they were the first thing I checked (I've already changed the throttle bodies once).

So, having messed up my logical approach to problem solving, I took the car for a spin. It's better! I can't quite believe it, so I don't. I only got to give it a quick spin down the road and so I'm not going to pronounce it "fixed" just yet.

So, was it the power to the pump or was it the throttle butterflies? More work needed I think.

In the meantime, I have noticed one of the anti-vibration straps on the rear suspension is broken so I need to get a new pair. I've replaced all the flexible hoses and the pedal feels better, after the first pump - which means I need to bleed the brakes properly this time!

Right, there's lots more odds and sods been going on but I'll save them for another time - next mission is renew the MOT and get the car to the Isle of Wight at the end of the month :-)



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