ST165 with no spark - again.

___Scott___

Active member
Not so fast. The problem has returned. It wouldn´t start this morning and as before there is no movement in the tach needle when the starter is cranking the engine over.

As a recap, I´ve swapped in the following:
- Spare ECU
- Spare Distributor
- New Ignitor
- New Coil
- Bypassed the harness with the NE, G1, G2, G- wires.

Maybe next I´ll bypass the IGT and IGF wires between the ECU and ignitor and see if that helps at all. At least it´s home in the garage now and I have most of the weekend to work on it.
 

___Scott___

Active member
I'm back to the original ECU And distributor. I haven't Investigated yet, but the symptoms are the same.

There can't be much left to check at this point.
 

___Scott___

Active member
Today verified that it still didn't want to start. Then I soldered wires to the IGT, NE, G1, G2, G- and E1 pins on the back side of the circuit board of my spare ECU so could be assured of getting a good connection with the scope. I then unplugged the original ECU and plugged the connectors into the spare ECU and set up the scope to look at the IGT signal. Turned the key and it started right up. GRRRRR!

I can't pinpoint the problem if it goes away when I'm set up to look for it. Anyway I probed around for quite a while and everything I looked at looked like it should. I let it cool down while I did some other stuff. Came back later and removed my bypass of the NE, G1, G2, G- signals and reconnected the original connections. Then I swapped back the original ECU and tried it again. It wouldn't start. :D I know, crazy that I'd think that's a good thing but I need to pinpoint this problem. So I jabbed a wire into the back side of the IGT connection at the ECU and setup the scope to look at it again. Turned the key and it started right up. GRRRRR!

I haven't added a ground wire from the ignitor to the ECU yet, that's next... after I find something to eat.
 

___Scott___

Active member
I'm not ready to give up on it yet. And I'm not really a red-car-kinda-guy. Even though I've been driving a red Z4 for nearly a month.

Update:
I added the ground wire from the ignitor to the E1 connection on the ECU connector. The car started right up, but is idling higher than before. I don't think I knocked a vacuum hose loose, but I'll have to look around. The fact that it started right up doesn't mean anything. I still haven't identified the cause of the problem.

Also, the check engine light is on and the code is 54. I have a jumper installed in the connector to the level sensor to bypass it, and that has worked for a few years but it's not working now. Of course the IC pump isn't running either.
 

Theman88b

New member
I know you have been checking for spark this whole time but have you checked for an injector pulse when it doesn't run? Check the distributor ground, run a new one if you have to. Have you checked the EFI main relay?

I pulled this from Identifix, wire color may be wrong but good info:

"No start No Spark";

1. Verify that the Check Engine Light stays on while cranking too and if not, check the +B terminal in the diagnostic check connector for battery voltage while cranking.

2. At the igniter, scope the White Ignition Trigger (IGT) wire for a 0-5 volt square wave signal while cranking. If there is a signal, but there is no pulse on coil negative, the igniter may be faulty.

3. Verify battery voltage to the igniter on the Black/Orange wire.

4. Verify ground for the igniter through its mounting.

5. Check the coil negative White/Blue wire at the igniter for battery voltage key on and for a pulse signal to ground while cranking. If it is pulsing, the problem may be a faulty coil.

6. Check the tachometer signal wire out of the igniter on the Black wire for battery voltage key on. Remove that wire from the igniter connector and check for spark. If it gains spark, run a new tachometer wire.
 

___Scott___

Active member
Theman88b":2ai9j376 said:
I know you have been checking for spark this whole time but have you checked for an injector pulse when it doesn't run?
I checked that with a test light to verify there was power at the injector wires at the ECU, but that doesn't mean they were pulsing. I think the ECU needs the NE, G1 and G2 signals to know when to pulse an injector. I didn't look at the injector signals with a scope, but that's something to look closer at if the problem returns.

Theman88b":2ai9j376 said:
Check the distributor ground, run a new one if you have to.
Done that, that's the G- wire.

Theman88b":2ai9j376 said:
Have you checked the EFI main relay?
Verified power to the ECU, which comes from the EFI relay.

Theman88b":2ai9j376 said:
I pulled this from Identifix, wire color may be wrong but good info:
That's all good info, thanks for posting that. Even if I don't end up needing it, someone else may need it later.

At the moment the engine starts every time and I've tried it probably more than 20 times over the course of several hours. I don't know what the deal was with the fast idle after the first start after adding the ground wire between the ignitor and the E1 wire at the ECU, but that went away and it idles normally now.
 

Theman88b

New member
Hopefully you will not have any further problems. The Japs know how to wire a car so usually not this hard to diagnose lol.
 

___Scott___

Active member
I agree, this one was harder to diagnose than most. I've been an ST165 owner since 1996 and I don't remember anyone mentioning a problem like this one before.
 

wakkjobb

New member
These are picky special cars; bet the root of the problem is something really simple and random... like a wire that is halfway worn through grounding out some circuit intermittently.
 

___Scott___

Active member
Oh yeah, I´ve been through that with my other ST165. The harness that goes over/behind the cam gears melted enough to short several of the wires together. That was a hassle to figure out which wire went where since they were all intertwined into a black blob.

I knew that relying on the body for ground current paths is doomed for eventual failure. I also knew the ignitor did that, that´s why I ran a ground wire from it to the engine years ago. It turns out that wasn´t enough. In hindsight, I should have tied a ground wire into the ECU at the same time.
 

___Scott___

Active member
Thread revival...

I was afraid the problem wasn't actually fixed since I never found a "smoking gun" problem. The problem has returned but this time I spotted a problem:
ST165_Fuse_Box.jpg


That melted fuse socket is for the EFI fuse. Strangely enough, the fuse is fine. Apparently there was enough resistance in the contact that it heated up and melted the fuse box. Unfortunately I can't access the contact from the bottom of the fuse box, there seem to be contacts inside an enclosed cavity between what's accessible on the top and bottom.

I assume the fuse box is unique to the ST165, does anyone happen to have a spare?
 

___Scott___

Active member
I dug around in the melted mess and found the connector, cleaned it up and bent it to make better contact with the terminals of the fuse. Then I put everything back together and tried to start it but the same problem persists. The engine cranks over fine but won't start and the tach needle doesn't move at all.

After doing some other stuff, I came back to it and decided to pull the EFI relay and bang it on one of the strut bolts and see if that did anything. I plugged it back in and tried again and it fired right up. Maybe it's a coincidence or maybe I have a flaky EFI relay.
 

88gt4DE

Active member
Wow ... what an irritating problem. I would say that or the contacts in it are dirty ... I have a few relays laying around. Whats the number on it ?
 

___Scott___

Active member
I didn't get the number off the the suspect relay, but I do have it. I picked up a new one on the way to work this morning and so far so good. That doesn't mean anything though. It'll go thousands of miles without any sign of problems, then one day it will refuse to start... or worse it will shut off while driving down the road. That makes it tough to troubleshoot since I never know if I actually fixed the problem, it's just wait and see.

The last time the relay in my "starter relay mod" started getting flaky I opened the relay, removed the guts so that I only had the body and terminals, then replaced the guts with solid state electronics. No more flaky relay, it's been working great for months. I may do the same thing to the EFI relay I pulled out. I'm really beginning to despise relays.
 

88gt4DE

Active member
Those suckers get stupid hot ... I was shocked when i messing with all mine when i was having fan issues ....
 
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