LS1 Sync issues (again) (SOLVED)

[volospian]

Hi,

A while ago I had sync issues on my new L33 (LS1) install. After fixing a few issues, mainly a bad earth, they seemed to go away. However, now the car build itself is nearing completion I have started to use the engine a bit more (base tune, just to get it in and out of the single garage so I have more room to work on it, that sort of thing).

Basically, if I connect the negative to the battery (leave it disconnected when I'm not in the garage, just in case I have left something on, don't want a flat battery) and try to start the car, it starts pretty much first go. However, if I then shut it down, it usually won't restart. It will sometimes backfire, sometimes it will start for a few seconds, then shutdown, etc. I suspected sync issues, so I looked at the comp logs again today.

Basically, the sync log is OK enough to start it from totally cold, but once started the cam signal goes to pot. I have just spent a few hours fiddling with the MS3X trim pots (R11, R32) to see if I can adjust anything to help, but the sync log remains, basically rubbish.

I think there may be two issues here. One may be the cam signal itself, and I think it's just good enough to get the engine fired, as once it's running, the comp log looks pretty much fine, however, the other issue is that, once fired up and stopped, it really doesn't like restarting, as if it can't even get a good enough signal to fire up.

Anyway, nothing I seem to do affects the comp log patter much. I have adjusted both R11 and R32 lots both ways, and it seems to be about the same signal whatever. At the moment, the setting is with R32 fully CCW, and R11 adjusted to give 2.5v at ZC TESTPOINT.

What do people think causes this pattern? Is this trigger voltage (R11) Hysteresis (R32) or simply a duff signal (noise)?

I've attached todays comp log, and it shows that the signal stays pretty similar no matter what I have done to the MS3X pots...

[jsmcortina]

Do you get the same problems if you set "Wasted COP" ignition and "Semi-sequential" fuel ?

That should eliminate the cam sensor.

James

[volospian]

James,

Just had a chance to test with those settings. Seems to run fine semi-sequential with wasted COP. I didn't actually go as far as to check the timing with a light, but it fired up on the button, every time (well, I tried three times and it fired up first press each time).

I'm sure I tried semi/wasted COP when I first had the issues and it worked then, but couldn't remember for sure, and it's always best to check again just in case something that used to work has broken in the meantime

Rich.

[jeffmarsh750]

Is it fixed ??? if so what fixed it ???

[volospian]

It is fixed!!!!

In an effort to reduce any noise, I replaced the cam signal wire with a shielded pair, as described here... put it all back together, reset it to fully sync and COP, and... it didn't make any difference

I then decided that it must be either the cam sensor itself or a component fault on the MS3X board, so, despite the fact that the cam sensor was brand new when I fitted it, I'v just swapped the cam sensor with another new one. Now, holding the new and old side by side before I fitted it, I thought the new one looked just a smidge, maybe 1mm at most, longer than the old one, but just holding them side by side it was difficult to tell if that was real or just my imagination. Anyway, after an hour struggling to access the rear mounted cam sensor, I connected everything back up, ran a comp log and... the signal was perfect!!!

So I plugged the pump, COP and Injector fuses back in and fired it up.... fine (more or less, idle stepper needs correcting, but a bit of cable tie under the throttle stop was enough to sort it for test purposes). Shut her down, fired it back up, fine, started (more or less) on the nose and the signal was perfect. Tried two or three times more, just to be certain, and it's all hunky dory!!

Now, I don't know if the original cam sensor was actually faulty (no tools to check the operation) or if the new one was, indeed, a smidge longer and that made the difference, but I bought the original off a certain well known auction site, at the cheapest price I could find. While it's true I bought the new one off the same site, it was off a different vendor and it was boxed differently when it arrived (and it cost a bit more). Now, if there is variation in some cheap aftermarket sensors, that could be enough to cause these infuriating signal issues... don't know... but swapping the sensor fixed it and I am ******* ecstatic!