mkIII no spark

[luka]

recently removed the head and had it worked from a machinist and re-installed it back onto the block...upon putting the engine back together, I'm having issues have the engine start.

crank is good, fuel is present, just no spark.

searched around and found 7m-ge won't start!!!! however i'm not sure if i'm having the same problem...

I did notice that the fuel pump relay is buzzing as soon as the battery is re-connected and i'm thinking it interfering with the process to have the spark sent to the distributer.

found the Toyota service repair manual online and have been reading through it, but still have been unable to find the problem.

its a 91 7MGE.

searched around online at various places and looks like a somewhat common problem after doing a good amount of work on the engine...

has this happened to anyone else?

[Jeeves]

Well... What symptoms are you having? Does the relay buzz for a long time? or just a short momentary buzz then it turns off? Any number of things will prevent spark, that's the safety switch for the ECU. Not getting a timing signal or any number of other signals will prevent spark generation. Have you pulled codes? That's a great place to start. What happens when you try and start it? Does it ever try and catch? Or just lots of spinning?

[luka]

the relay buzz's indefinitely once the battery is connected. also once the battery is connected the check engine light turns on but when I turn the key to acc/on it turns off. tried downloading for a code, but there isn't anything. everything else functions, the engine cranks, just won't start. I pulled the distributer and re-checked the timing.

there is also a light on the far left of a yellow bird cage...don't know what thats for and don't remember ever seeing it before.

I do remember that there is a blank bolt on the flange where the upper and lower intake manifold meet. I'll try adding a ground to there, but not sure if that will do it.

A lot of the connectors have lost the locking feature so i've been double checking the security of loose connections.

[Jeeves]

The birdcage light means "low coolant", It's important when running, not so much if the car itself won't even start.

The sensor and ecu grounds are a bundle of white and brown wires (can't recall how many) with two copper ring connectors that can be grounded together on a stud.

I'd investigate that relay more closely, maybe look at any plugs related to it. When you hook up the battery for the first time there's a short relay click but it shouldn't hang buzzing like that.

[luka]

thanks for the pointers.

that relay wiring bundle go right into the body and possible into the dash area...all of the wiring has been re-wrapped in crappy conduit wrapping, so i'll cut those open and go from there.

[Yohaninator]

i'm having a similar problem then him...
i have a 90 with a 88 n/a motor
i had to remove the intanke manifold... Because i had a injector seal brocken
and i've put every thing back together
i start the engine..nothing
It turns...and no spark...
i trie just removing the wire form the distributer
and pitting on my engine to see if i have spark or something
nothing yesterday it was working fine today..nada
any suggestion

btw i've checke every thing that could be wrong (timing.. fuse..wires)

And hmmm when i pass a wire from the positive born on the battery and go right to the red wire on the oil...A spark goes on
but when i start the car ..No spark

[bgrieger]

I hate to sound like an ass, but clearly you haven't checked everything as something is still not right if you have no spark. Start with a complete recheck of the fuses with a multimeter. Don't trust that because it looks good that it is. A multimeter will also allow you to test the circuits we are going to get into next.

There are only a few things on the intake manifold itself, and none of them should influence whether you get spark or not. To this end, how are the grounds? Did you disconnect one while you took the manifold off and forget to put it on? Are they badly corroded? In removing the manifold, you will have had to push and or pull on the wiring harness. It is possible you pinched or broke a wire in the loom, or tugged a connector down stream loose? I would then test the coil and see if it is operating correctly first. Then the distributor to see that it is operating correctly if the coil tests out alright.

Once you have performed the tests, let us know and we can start pointing you at the next group of issues.

[luka]

I ohm'd out everything from the igniter to the plugs and everything has good continuity.

all the fuses are still good.

i'm thinking my problem is with the grounds...the guy I got the car from (BHG) had a ricer pizza pie on the neg battery terminal with 10 or so ground wires going all over the place. In purging them I may have removed 1 that I actually needed.

I'll give an update Thursday night, been following the schematics for a couple other possibles.

[Jeeves]

Originally Posted by Yohaninator

i have a 90 with a 88 n/a motor

You may have another issue entirely:

The injectors changed. One year had low impedence another had high. If you didn't swap them you could have problems,

All 7mgte's are low impedance (black top) 430cc/min.
86.5-88 7mge's are low impedence (yellow top) 295cc/min
89+ 7mge's are high impedence (lt. green top) 315cc/min

[img]http://www.**********s.com/supra/toyo_injectors.gif[/img]
http://www.toysport.com/webpages/Tec.../injectors.htm

[luka]

spent a couple hours checking stuff out earlier today...

replaced the battery connections to clean it up, pulled out my multimeter and start poking around.

found I have 12V running though the engine(multimeter positive on positive battery and negative on the head) while the car is off (no key in ignition). tested the same thing with my celica and it was -12V...when I turned the celica to the 'on' position, it showed 12v...

so my problem is I have too much power running through the system right?

[bgrieger]

All you managed to test there again was that the positive and negative leads of the battery are indeed connected to the car, and that you have ground from the engine to the battery. That really doen't tell you how good the ground is. A tiny 18 gauge wire would likely give enough for the multimeter to see. The 12v is what you should see. I suspect you had the leads reversed on the celica to see -12v, but regardless all it tells you is that you have 12v present. Too much voltage would be IMO >14v steady state.

Again, start with the grounds, and inspect the connectors related to the ignition system. Electrical sucks to diagnose, but it is at least something you can follow one step at a time.

[luka]

hmmm...when I connect a test ground from the block to the negative on the battery, theres quite a bit os sparks...more then I think there should be.

according the to celica, everything is working correctly...i'm wondering if theres a switch stuck "on"...

on the 7M, where are the grounds supposed to be located on the engine? I have 1 from the block to the battery, 1 from the rear mount support to the firewall, 1 from the upper/lower intake manifold flange to the battery, and 3 from the body/firewall to the battery.

[Jeeves]

That sounds about right. I think there's one missing off this diagram:


MODERATOR EDIT: Sorry Jeeves...I hate to keep removing the online TSRM links, but with TN being a commercial for profit site at heart, you have no idea the seriousness of the cease and desist order toyota's lawyers passed over to TN for copyright infringement, and that our very existence relies on us continuing to remove these links where we can find them.

I can only suggest to the OP that it is common knowledge that the Online Supra MK3 TSRM (Toyota Service and Repair Manual) and TEWD (Toyota Electrical Wiring Diagrams) are out there on the net, and that a simple google search with some of those terms will get a bunch right off the top if that is the route you want to go. That said, the TSRM is also still available for the most part from your local Toyota dealer.

[luka]

Thanks Bob,
I have downloaded 2 different copies of the TSRM and neither that I can find have been very helpful.
the instructions tend to be a little dry in some areas.

opened up under the dash and found a couple of wire taps into the ignition harness and a lot of extra wires that arn't factory....so...I might have to tow the car to a friends place to pretty much yank all the wiring and start from the beginning....

felt there isn't much more I can check.

[bgrieger]

Thank jeeves...he pointed out the TEWD route.

If you've found a bunch of non factory connectors and such spliced in, find out what they are and if they are needed before simply yanking stuff. Again, the TEWD will help you out more in following all of this.

Bob