Sunday, September 26, 2010

Battery of Tests

Well, its been too long since my last post, but I didn't want to post anything until I got a breakthrough. Unfortunately, I haven't had one, but I figured I'd left the blog out in the cold too long. Speaking of "out in the cold"... the weather has been a regular topic in this blog, and in conversations with fellow Pacific North-westerners all Summer. Now that Fall is officially here, most folks are expecting the rains to set in. My wife and a few of her friends are trying to stay optimistic, but I'm not betting on any more warm, dry days. This makes for a very unpleasant effort on the bus project, exacerbating my current frustrations.

Feeling Fuelly
After getting the engine to run for a few seconds here and there, I thought my troubles were to be quickly resolved. I felt that if I could get the air bubbles out of the fuel system, I could get the engine to run reliably. I moved the large stock fuel filter operation from where Hal had installed it (you can see the mount holes in the top picture there), up to near the top-hatch (see bottom picture). I figured part of the problem was that the Injection Pump was the high point of the system, so air bubbles were getting trapped in the pump. I checked my Jetta and noticed that the fuel filter was right next to the coolant bottle, so I thought, "maybe the height matters". There's a picture here to the right. I don't know if it does at this point, because the engine still doesn't start. I pulled the clear filter I put in between the tank and the stick filter as well. I thought maybe this was allowing air in, or at least giving it a place to collect. This didn't help either.

Battery of testing
With all of the attempts to start the engine, the battery keeps running down. I find that the quick 10Amp charge doesn't actually work, and I need to charge the battery on the slower 2Amp cycle. This introduces a considerable amount of lag between starts. As I write this, the battery is getting charged again. I have noticed that the primary cable running from the battery to the starter gets warm at one of the splices. I am a little concerned about that. Of course, the engine should start quite quickly under most conditions, and little current runs through there other than to start the engine.

My latest attempts have been surrounding the fuel supply again. I have routed the return line from the injection pump to a jar that's 1/2 full of diesel. As the engine start attempts are run, I can watch the fuel level move up and down, as well as watch the air bubbles appear. I'm hoping this is helping to bleed the air out. The port on the fuel filter that the return line connects to has been closed off, so no new source of air is introduced. I have not had much luck with this arrangement yet. I am starting to worry that I messed something up the last time I had it running and it got a little rough-sounding. To me, it sounded like it was running out of fuel, so I shut it off. Maybe something more worrisome happened. :(

That's it for now. If you have any ideas for why its not catching, I'd love your input. They say insanity is repeating an action with a different result expectation. With that, I'll keep trying to start this thing while trying to think of what could be the cause other than air in the fuel system.

Pictures:
top - where the fuel filter was mounted before. Note the clear plastic filter has some air in it.
middle - fuel filter in the Jetta.
bottom - new fuel filter location to mimic the height of the filter in the Jetta

2 comments:

Hal said...

Just as a thought, it might be worthwhile to put an electric fuel pump inline between the tank outlet and the fuel filter. At the very least, it would help eliminate the possibility of fuel starvation.

.. you *did* keep the electric pump from the gasoline engine, right?

PdxPaulie said...

the old '72 had the mechanical fuel pump :( In the few short drives I've taken, I haven't had a problem. Between the MB primary filter and the TDI main filter, there's lots of fuel close to the engine.