gospeed81

iTrader: (51)

What about your trigger outputs on the MS...?

I may remember poorly, but I imagine this isn't an issue since you were running the car on MS3 prior.

This makes me sad.

From the above advice I'd keep running compression checks, hitting the bleed button after every two cycles, and seeing if you ever get a cycle where it doesn't compress. If so then look at your intake cam again.

lordrigamus

iTrader: (14)

It should do something at least. It may not start up and run but it should pop a few times to give an indication if it's an ecu glitch or not. Mine ran for about a minute on the stock ecu with 460CCs and a 255LPH pump before it loaded up with fuel and shut down.

Might be worth a try if it's an easy swap.

shuiend

iTrader: (24)

Video of what it does when we try to start it.

lordrigamus

iTrader: (14)

Man it sure sound like the timing is off. Is it hissing like it's blowing the compression out an open valve or am I hearing things?

Either way, it still doesn't explain why it's cranking so slow. What did you guys use for assembly lube? What bearing clearance are you running?

Braineack

iTrader: (62)

sounds a lot better/faster than it did before. but i agree sounds like it's completely off on the cam/crank timing.

lordrigamus

iTrader: (14)

It kinda does, yeah. At the beginning of the vid it sounds like it's trying to compress but not firing at the right time. During the rest of the vid, though, it frespins like it's not compressing at all. It sounds like cam timing is off and it's blowing compression through an open valve and echoing in the manifolds.

Wierd.

Shuiend, did you guys verify it was definately at TDC when the cam timing was set? Is it a known good balancer with no chance of a slipped timing mark?

shuiend

iTrader: (24)

The strange noise on the second half of the video is from the throttle being pushed down for flood clear. We did not want to flood the engine.

Yes we verified that the crank was at TDC when we did timing. We put a dipstick in cylinder 1 and made sure it was at the highest point then.

After trying to crank the car all day we also manually turned it tell the crank was at TDC and timing marks on the cam gears still lined up perfectly.

Stealth97

iTrader: (5)

a local guy who swapped in a VVT head tried forever to get it running... tuned out to be a problem with the VVT pulley, and he ended up swapping a non-vvt head on and it fired right up..

shuiend

iTrader: (24)

Don't ******* say that ****. Actually swapping on my 94 head from my old motor is seriously one of my next steps.

y8s

iTrader: (8)

So here's the weird part about shuiend's setup:

We whipped out the timing light, set the timing in tunerstudio to a fixed 10 degrees BTDC and futz with the trigger offset until #1 cylinder plug wire makes the light flash at the right place.

we unclip the thing and go about trying to crank it a few times and then after a few minutes re-check the timing with the timing light. It'll be out 90 degrees one way or the other from where it was.

All timing / rotation information is coming from a stock 1994 CAS and looks normal on the tooth logger screen. Here's is a Joe Perez posted picture that shows about what Lars' looks like:


(ganked from this thread: https://www.miataturbo.net/megasquirt-18/sanity-check-inverted-primary-trigger-required-jimstim-29726/ )

so unless there's a rising/falling edge problem where it gets correct sync about 50% of the time and incorrect sync about 50% of the time, I am not sure what is going on.

gospeed81

iTrader: (51)

I have a spare CAS I'll send your way if you feel that's the culprit.

Braineack

iTrader: (62)

he has a spare CAS. nothing should have failed from when he pulled the motor the day before until we put the new one in the next day. it was running perfectly fine on the stock motor, nothing changed but the motor.

shuiend

iTrader: (24)

I really do not think the CAS is the problem. IT was working perfectly fine before the swap so I have no reason to assume that it would randomly have died in the 2 weeks it sat on my floor.

gospeed81

iTrader: (51)

You say that....

Mine failed on the maiden voyage after doing the exact same thing...backfired so hard when it happened it knocked timing belt off a few teeth, but I thought I'd done blown up the motor we'd just swapped in.

I'm sure ya'll've checked trigger inputs though.

Braineack

iTrader: (62)

yeah composite logs shows a normal cas/crank signal.

fooger03

iTrader: (2)

I'm going to assume that what I'm about to mention has absolutely nothing to do with the problem, but I just wanted to mention it as a random, albeit extremely remote, possibility.

Is the exhaust clogged up? old mouse nest? Potato? Water? Disconnect/ unbolt the DP from the cat, and try it out.

*Oh no ****!? 500 posts! LOL*

shuiend

iTrader: (24)

On a serious note, do you have any more information about this? What ended up wrong with his head?

Downpipes test pipe were both clear when I put them back on the car, and the rest of the exhaust never came off.

curly

iTrader: (25)

I don't want to discount your diagnostic skills or the fact that your car ran great on the previous motor, but you've been assuming A LOT since the beginning of these problems. All of which have to do with things you didn't touch. Don't forget to take a look at those, **** happens.

Faeflora

iTrader: (2)

Said assumptions are?

shuiend

iTrader: (24)

I will say,

I did assume that I had put on my cam caps correctly, this is the first VVT head I have ever messed with and the cam caps do not have arrows on them pointing which way to go like the earlier heads. So I put them on what made the most sense based on how I had the head oriented on the table when I assembled it.

I did assume that I had the timing correct when I did it with the motor outside of the car. Yet again I have never done timing on a VVT motor and the intake cam definitely is not as user friendly as the other intake cams on earlier heads. Although at most the timing was only off a tooth or so on either side so it should still start, probably would not run great, but start none the less.