*vibrates excitedly*

Filed under: truck by tamber
2 Rhagfyr 2022 @ 01:19

I'd given it a go trying to start it a couple of weeks back, Saturday afternoon after work, with no success; nothing but backfires, at one point it tried to lob the carb off the manifold (I'd forgotten I'd only plopped it on there for mockup purposes and not bolted it down! Whoops! ), and the timing light was showing nothing of any use. Some playing with sensor offset got a couple of promising slight speed-up moments, but no real firing.

I packed in after an hour or so, as my knees were making their complaints known, but I had an idea of what might be wrong...

So I headed down on Tuesday evening, armed with my laptop, to double-check sensor settings. (Tooth 1 offset, etc.) Set fixed timing at 10BTDC, so I should see somewhere in the region of the nice stamped '10' in the flywheel; but I was seeing nothing that even vaguely resembled a mark.

Next step: Unplug the coilpack, and with some bodge-wires, hook up an old-style coil so I could crank the engine with all the plugs out and still have it fire a spark to the block such that I can use the timing light. (Just in case the resistance of cranking against compression was causing enough of a slowdown/current draw that it was dropping things out.)

Still no visible marks. Re-check tooth 1 offset. (50 degrees.) Re-check fixed timing. (10 BTDC) Move bodge-wire over a pin on the plug: Still no visible timing marks. Move bodge-wire over a pin on the plug again: Timing marks suddenly become visible! And they're right where they should be, in the region of 10 to 15 BTDC.

So, one of two things has happened:

  1. I have managed to wire the coil pulldowns backwards by swapping wires in one of the plugs, miraculously managing to get it entirely backwards rather than merely shuffled.

  2. The scant documentation I found on the Vauxhall Omega coilpack I'm using, is wrong.

So when I had it set to fire at 10 BTDC, it was in fact firing at 70BTDC. No wonder it was trying to explode the carb off! Documentation updated, and coil wiring adjusted to reflect the new reality, and I briefly had it running on ether; which took some juggling! And, unfortunately, I'd forgotten my gopro so you don't get to see me trying to simultaneously spray ether, work the throttle & choke, and run the starter, all at the same time.

Spirits suitably buoyed, I made another run down to the unit on Wednesday, once again armed with the laptop. Timing table was re-enabled, a great big handful of timing sprimkled onto the table for good measure...

...the world's worst fuel tank hastily constructed, and we were ready for a real test-fire.

As you can see in the video, it startled me when it fired up; it's a lot louder on gasolene than it is on ether! And it's running on all 6, too! While I was trying it on ether, number 5 cylinder didn't appear to be firing, because the exhaust runner was cold for that cylinder; hence me burning myself on it this time around...

I've not tried to really rev it out yet, seeing as it's only on a lightly-wibbly cradle meant to be used to remove it from the truck, rather than for running it; and I dread to think what would happen if I revved it right out to the hard-cut limiter and it tried to make a break for it...

Also, I think I've got a decent location for the coilpack now. I'm just waiting on some longer bolts to do a better job of mounting it, but it should be workable there! And new resistor caps throughout! In red, too, cuz der red ones go faster!

Don't worry, I've since neatened up the leads. Shortened one very slightly too much, but it's fine, I'm not making a new one. It's fine. Just got to find my plug-lead clips, and then we'll be golden!

As far as the rest of the engine management stuff goes, there's a good list yet: