Cranks, no start nightmare

Todd B · Postby **Todd B** » Sat Mar 12, 2016 12:54 pm

Ok, I've taken the crank pulley off, and can confirm that the timing plate is not on backwards. I mentioned early on that the coil was new, but I still have my old coil... so I swapped them out and still nothing. Tach doesn't move. I checked my timing, all good.

I'm really frustrated.

manga_blue · Postby **manga_blue** » Sat Mar 12, 2016 1:09 pm

OK then, I'm trying to think what else might have changed when you did the engine work. The next common mistake (at least on NA motors, I think NB8As are the same) is to swap over the fuel supply and return lines where they hook up to the fuel rail. It means you get a tiny bit of fuel to the injectors, enough to make it cough a bit but never enough to start.

There are also earth straps at the front of the alternator mount and back of the intake manifold on an NA. Not sure of their exact location on NBs but they must be there somewhere. These provide the earths for the engine sensors, the coilpacks and the injectors. Spark fails and various things go pear-shaped when these are dirty or loose.

and1 · Postby **and1** » Sat Mar 12, 2016 2:18 pm

Couldn't find if you had mentioned it, but have you checked compression? Being NB it would have solid lifters and if the head was reco'ed the tolerances between the cams and lifters could be off and valves might not be fully closing. This happened to me during my engine rebuild.

Todd B · Postby **Todd B** » Sat Mar 12, 2016 2:26 pm

I haven't checked compression because I don't see how that would effect spark. That to me is just a whole different category.

As for swapped fuel lines, and I've wondered that too, but they check out fine as well. I even pulled both hoses off, cranked it to make sure fuel would come up... and it did. So the fuel definitely gets to the front of the rail.

This is what is driving me so crazy!! Everything is checking out fine and still nothing!! I mentioned at the beginning that the coil was only a few months old, well, I still had my old coil pack, where I KNEW that one of them was bad, figured hey, if it works at all it is better than what I've got... and no surprise, there was no change.

So I've got a new crank sensor, new (out of a wrecker) ecu, nearly new coil, timing is good, I've got fuel, I've got power AT THE COILS, but no $#%@! spark!!

Throughout all of this I've been inclined to think it is a bad ground somewhere, but I can only find two ground points and I've cleaned them both quite thoroughly.

93_Clubman · Postby **93_Clubman** » Sat Mar 12, 2016 2:33 pm

Todd B wrote:As for the cam sensor, I think what I'm going to do is take mine off, and ask my neighbor if I can put it in his car. If his car won't start, then I know mine is bad.

Did you get a chance to try the above?

manga_blue · Postby **manga_blue** » Sat Mar 12, 2016 3:42 pm

At this stage I'd be beginning to wonder if I have good solid power at the coils. I have been known to run a temporary 10A lead through a 10A switch (an old house light switch will do) from a solid source such as the battery + and spliced into a 12V power input lead at one of the couils. Then turn it over to see if you can get at least 2 cyls to fire.

It also occurs to me that NB8A engine looms have a reputation for copper failing inside the wire very close to the coil connector plugs. Maybe the disturbance finished those off? Paul (93_Clubman) probably knows more about this than me.

93_Clubman · Postby **93_Clubman** » Sat Mar 12, 2016 3:58 pm

manga_blue wrote:NB8A engine looms have a reputation for copper failing inside the wire very close to the coil connector plugs.

Yeah, came to mind yesterday, but dismissed it at the time as it usually causes missing or stumbling revs. But as you say a head removal & refit could have been the last straw depending on how the loom was handled & stored, & how it's been treated over the last nearly 20 years.

93_Clubman wrote:Could be the usual NB8A coilpack wiring loom weakness, ie a lack of support to the wiring where it bends near the coilpacks results in wires breaking inside the plastic insulation. To check for this, after a decent drive, with vehicle idling, move the wiring loom in this area - if you get a variation or stumble in idle revs then some of the wiring could be on the way out.

Todd B · Postby **Todd B** » Sat Mar 12, 2016 5:40 pm

I've not been able to do the cam sensor swap with my neighbor as he's been out today. Inconsiderate jerk! LOL. Nah, actually he's been great so far.

As for a wire loom failure... that's a solution that makes sense to me, but yet I'm showing 12V power there... isn't that an indication that the loom is fine? Or at least the power connection is fine. Is there a way to test the ground wire there? Maybe I could splice a ground in instead?

This afternoon I went down to Jaycar to get a led to get the diagnostic codes out of the computer... but the instructions I've found say that I'm to jump the B+ to the FEN... yet the picture I have of the connector doesn't show a FEN terminal on the 99-00 cars. So what am I supposed to jump it to?

Here's where I'm getting the instructions: http://www.miata.net/garage/Engine_Diagnostics.html

And here's the image for the datalink:

manga_blue · Postby **manga_blue** » Sat Mar 12, 2016 6:08 pm

This could help ... or else just give you more to worry about.

viewtopic.php?f=55&t=60915

Todd B · Postby **Todd B** » Sat Mar 12, 2016 7:49 pm

Well $%$*. I just tried my diagnostic LED... didn't work. Didn't flash at all. Since it wasn't working, I thought maybe there was a bad connection, so I was wiggling it around and am pretty sure I shorted something out in the process. There was a humming sound underhood before... but not anymore!! It's dark now, so I'll check the fuses in the morning.

Anybody want a 98 MX5? It's got a refurbished head! New radiator, tires, coil, ecu, crank sensor, vinyl top, radio... I'm about ready to trade it off for $20 and a bucket of peanuts.

Todd B · Postby **Todd B** » Sat Mar 19, 2016 5:11 pm

Ok, here's the update: I swapped out the cam sensor with my neighbor's car, and the cam sensor is definitely NOT the problem.

So what is left to check? New coil, ecu, wires, plugs, crank sensor... power everywhere. It just screams to me that there's a bad ground somewhere.

I keep thinking there's a ground that hasn't been attached, but I can't find any...

... I'm open to suggestions.

manga_blue · Postby **manga_blue** » Sat Mar 19, 2016 10:33 pm

I lent 2 Toyota CoP coils to Patrick Bramston once at Eastern Creek. He was trying to chase a recurring miss. His car ran well with my CoPs for a few laps and then started to miss again. Those coils were too hot to touch, even after they'd been out for a few minutes. When I put them in my car the car barely fired and the tacho never budged off zero. Does your car have 4 wire coil plugs, i.e. the ones where a signal from the coils drives the tacho?

Todd B · Postby **Todd B** » Sun Mar 20, 2016 7:12 pm

Well, I think some progress was made. As mentioned at the start of this thread, all this occurred after a head replacement. As I was reassembling the car, I decided that before I would take it off the jack stands and do the final reassembly I would test to see if it would start. One of the things I didn't reassemble was the two large bolts that attach the intake to a big bracket. I didn't think anything of it. Well, figuring, what the hell do I have to lose and maybe they're part of the ground that I'm chasing, I decided to put those bolts back in place. The car still doesn't fire, but now the tach flutters. Not constantly, but it does do something some of the time. So hey, this is exciting! Something different! Now I've just got to figure out what this means...

In response to manga_blue, my car has 3 wire coil connectors.

93_Clubman · Postby **93_Clubman** » Mon Mar 21, 2016 12:22 am

Todd B wrote:One of the things I didn't reassemble...

Great that you're getting some life signs from the tacho now that the intake manifold support brace is connected.
Believe it's different on an NB8A or NB8B, as the TB assembly differed, but on the NA8 if you haven't got the IAC pipe connected to the intake pipe it won't run.
If this principle more broadly applies, & if you've been trying to start the car before fully reassembling, then something similar might be causing the problem.

Todd B · Postby **Todd B** » Mon Mar 28, 2016 4:08 pm

IT RUNS!!

I wanted to close the loop on this thread in case anybody else comes along... here's what happened...

I had notice that the wire harness that goes to the cam sensor seemed like it was pinched, and had me thinking that perhaps the wire was broken inside. There are three wires in this harness and two of them just didn't feel right. So I went out, and spliced in some new bits of wire with my soldering iron. Still no start.

A friend came over who is a more skilled backyard mechanic than I am, and he did some poking around and couldn't find anything wrong either. Except that the immobilizer light was on. He put the stock ecu back in and suddenly, there was spark!

This has left me confused. I understand why the wrecker ecu didn't work in my car. I didn't have the right key for it. But, what still isn't answered is what along the way was actually fixed in order for the stock ecu to work. Was it perhaps the wire that I spliced in? I didn't actually take all the rubber insulation off to see if it was broken. Sure felt like it... but I don't know for certain.

Anyway, thank you all for all of your messages, public and private.