25th March 2007

Back in the garage at last. Before I start, apologies for the complete lack of updates here between then and now. Only one notable thing happened. I continued to use the car over the summer, but at some point, I noticed that the oil pressure seemed to be very high at high revs. Paranoid as ever about all things involving the oil system, I decided that I had to investigate, it seemed a bit like the PRV wasn't opening fully. So the car was out of use for a while, whilst I removed the sump to try to find out what was going on. I didn't really come to much of a conclusion, although I did slightly modify the pressure relief valve as it looked like it was being slightly obscured by it's surrounding tulip. I don't think it was any different to how it always had been though. When I put it all back together, it seemed to be a bit better, but still tends on the high side. When the tax ran out at the end of October, I pushed it into the garage, and there it has remained, touched only to push it out to start the engine sometime just before Christmas.

So I now finally have time to get back to the garage. Once again, I am booked to go on tour in the car in May, so there is a target, but there isn't much that is critical to make that happen. The one thing which was a bit of an unknown quantity was that the car struggled a bit with emissions at the last MOT - the test was not quite right and the tester sent me out to make sure it was all good and hot, but when he retested it the probe melted.
I've been thinking about how to resolve this, and what the problem might be, and having read some bits of the Haynes manual, have a few ideas of things to try. First thing I'd discovered from the manual was that the ECU stores fault codes, and I have wondered whether there is a faulty sensor on the engine (although it has always driven just fine). Fortunately when I reworked the dash I connected up the lamp for the ECU, so I just need to have a fiddle with the service connector and it should tell me if anything is wrong. What it tells me is that there is a fault with the air intake temperature sensor. So I check out the sensor going from test spec in the manual, and it seems to be ok. The ECU also provides a method to clear the fault codes, so I do this, and run the engine again, and check for fault codes again. All clear, so I guess that might be a fluke, and will find out in time, but it does seem unlikely (though possible) cause of the emissions problem.

After some diagnostic chat with Richard, I decided to try connecting up the PAIR valve. Keen readers may remember that I removed the air injection kit a while ago, based on being told that it is only effective on overrun. Having read the Haynes manual it turns out that this is correct for the carbed version of the Blackbird, but on the fuel injection engine, the valve is "controlled by the ECU". Working on the theory that it might not only be open on overrun, it seemed the easiest way to prove this would be to connect it up and try it with the engine running. This showed that the valve is open at idle (and therefore allowing air to be drawn into the exhaust), and closes when the engine is revved a little bit. Testing it with a helper showed that it closes at approx 3krpm, which is good news for the emissions test which is done at fast idle. Based on this test, I decided that this is probably the cause of the problem, and that I would refit the PAIR system to the car. This I did, but reworked the plumbing of it so that it all fits a bit better. Hopefully once the cat is back on, it should be ok on the emissions test now. I've borrowed a wideband lambda device which I will do another test with at some point.

Another thing which needs fixing is that the headlights stopped working shortly before I stopped using the car last year. They went a little bit intermittent to start with, then just stopped working altogether, although this is only the dipped headlights, the main beam was still working ok. So I was suspicious of the changeover relay I fitted, which swaps between dip and main beam - this was my first port of call for investigation. Checking with the multimeter, the relay seemed to be working ok, and I was seeing 12 volts in the right places at the right time (when I remembered to turn the ignition on for main beam!). So I checked at the headlamp connector end of things, and I was getting the sidelight here, but not the dip. Narrowing it down, I checked out the fuses (not sure why I didn't think of this first), and they check out ok, and I had continuity between the fuse and headlamp connector. A bit more fiddling with a helper, and I tracked the problem down to the connectors where the dash loom connects to the main chassis loom - when I wiggled it, it worked, briefly. When I pulled the connectors apart, I could see there was a definite problem. It looks like a mechanical failure on the pin for the dipped headlights, which has caused it to overheat at some point. I ran out of time for further investigation on this, but at least I know where I'm looking now. Hopefully it isn't a fundamental problem that the connector cannot handle the current of the headlamps being on for long periods?

One final thing is that whilst I was working in the engine bay, I eyeballed the fuel hoses, and it reminded me of the problems I have been having with them perishing. The ones I replaced last year look fine, but when I checked under the rear of the car, I found two more that have perished! Crazy. I must have had some dodgy hose in my original kit. I thought I'd replaced these two, but it looks like maybe I replaced them with some more of the original hose. Oh well, have to drain the fuel tank, yet again, and get it sorted. Fortunately there's not alot of fuel in it at the moment, and I need to have a good grovel underneath to check it all over anyway.

©2002-2009 David Hackett