87 MR2 has no spark

Sparky · 10-23-2009, 02:04 PM

Ok, little introduction first. I'm actually from the dark side (old school BMWs, I've got a couple 2002s), and haven't played with an EFI Toyota in close to a decade (had a MkII Supra). I recently had an 87 MR2 fall into my lap. It was intended as a parts car, but the other guy never got around to parting it out, and when I was looking through it the car actually seems pretty solid; shifts smooth, good clutch and brakes, cranks easily, but it has no spark... I would love to get it running instead of parting it; I just don't think I have the heart to part an old MR2.

I've run through the list for the 87 BGB, and I'm a little stumped. I'm seeing 2-3v at the hot side of the coil with the ignition on (shouldn't that be 12v?) and the coil checks out ok. I'm getting a bad resistance read from the sender on the distributor (a steady 225 ohms resistance), so I'm assuming it's a bad sender, but not totally sure. I'm thinking the 2-3v means a bad ground somewhere, but where should I start? Also, the plugs coming for the dizzy are gray, but the connectors for the coil are green; am I checking the right thing? I'm 99% sure the gray leads are the distributor sending plugs. New dizzy time? Is it even the right dizzy, with gray plugs? All the ones I've seen online had green plugs that match the coil side ones.

dirocyn · 10-24-2009, 05:31 PM

I'm sure someone will correct me if I'm wrong, but pretty sure the hot side of the coil should see battery voltage--it has on every other car I've worked with. I'd try and figure that out before replacing anything.

A problem I've noticed, and it's not just MR2s--once cars reach a certain age they develop corrosion in the wiring, and they corrosion is a lousy conductor. Once you find where the problem is, it often requires nothing more than cleaning a connection.

Are you getting good battery voltage everywhere else? Where I'm going here is, the easiest way to see 3v on a hot wire is if there's bad corrosion at the + terminal. Which can manifest overnight if it's humid enough. Also check your engine ground. Since the starter grounds through the transmission ground strap, the starter can turn even if you have a bad engine ground--and you won't get any spark without an engine ground.

Sparky · 10-27-2009, 12:14 PM

Hmm, most cars I'm used to depend on the engine ground as the starter ground, so they won't crank if that one is bad. I'll have a look. I'm getting power to all the accessories (locks, windows) and the gauge cluster lights up and shows a CEL like it should, so I'm guessing it's something odd with the coil wiring or a ground related to that. Thanks for the idea.

dirocyn · 10-28-2009, 12:36 PM

That means your battery-to-frame ground is ok. I think you're probably right, that it's in the wiring that leads to the coil. I bet you a plug nickel it's on the hot side, not ground. Wires with a + current corrode more quickly. But check the engine ground anyway.

Checked the BGB and can confirm, you should see battery voltage at the hot side of the coil. Assuming your battery makes more than 3 volts, your problem lies somewhere in between, on the hot side. Only thing in between is wires and the engine main relay. Check what voltage is going into the relay, if it's 12v then in all probability the relay is bad.

Papo J · 10-28-2009, 01:03 PM

Sounds like you may have a bad igniter, not a bad distributor. You should see battery voltage at the coil even with a bad distributor, the power to the coil is filtered and fed to the coil by the igniter.

toyotaspeed90 · 10-28-2009, 03:51 PM

stupid question.... is your ignitor grounded? When it's bolted to the chasis it's self grounding.... if you unbolt it to do some routine checks, it loses it's ground and won't spark.....

Sparky · 10-29-2009, 01:28 PM

No stupid questions when it comes to me and 80's Toyotas, like I said it's been awhile. It grounds through the coil, correct? The ignitor ground through the bracket on the coil, which grounds into the chassis? If so, then yes it's good. I actually have the coil out to check resistance, and cleaned up around there while I was at it.

What's the best way to test the ignitor? Is there an option other than replace? I figure I'm also going to replace the main relay and see if I get a jump in voltage.

toyotaspeed90 · 10-29-2009, 03:27 PM

if you need to replace the ignitor or coil... there are tons of us with lots of spare parts in the garage..... being in OR there are tons of MK1 guys in the PNW.

the ignitor is self grounded through the bracket it bolts to -- which is bolted to the chasis. If it's not bolted to the chasis in it's original location and you have it out for testing, use a jumper cable from the negative to the bracket (or directly to the ignitor). All toyota ignitors are self grounded... meaning there isn't a wire that runs to them for grounding. The coil's "negative" is the pulse signal sent from the ignitor (black wire). The brown wire should be a constant 12V.

The next thing to check.... is there are 2 connectors on the distributor side that are green... pull them both off and look inside (or look at the back of them) to see if the wires have pulled through. Because they're in a horrible location, it's common for people, when disconnecting them, to pull by the wire and not the plastic connector... which makes it REALLY easy to pull the wires out.... go to reconnect and although the plastic pieces connect the wires never actually make contact. This is common in these cars.

Sparky · 10-30-2009, 02:49 PM

Well I feel like an idiot. I'm guessing the missing relay circled in the pic is the main relay. The one that was very corroded and nasty, and I have to get channel locks on to pry out.

After looking at the circuit diagrams from the BGB, that and a blown fusable link on the Head unit line (Line B) would explain 99% of what doesn't work on the car. The 3v was coming from the fact that the last owner had connected the lines by the dizzy wrong (what's the clear one for? That was powering the coil). With green to green (or gray in my case), I'm getting no power, just like it should with the main relay out.

Also, for the benefit of those of use without diagrams on the fuse box lids, are they out there on this site?

10-23-2009, 02:04 PM	#1 (permalink)
Sparky No Skills Join Date: Oct 2009 Location: Beaverton, OR Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	87 MR2 has no spark Ok, little introduction first. I'm actually from the dark side (old school BMWs, I've got a couple 2002s), and haven't played with an EFI Toyota in close to a decade (had a MkII Supra). I recently had an 87 MR2 fall into my lap. It was intended as a parts car, but the other guy never got around to parting it out, and when I was looking through it the car actually seems pretty solid; shifts smooth, good clutch and brakes, cranks easily, but it has no spark... I would love to get it running instead of parting it; I just don't think I have the heart to part an old MR2. I've run through the list for the 87 BGB, and I'm a little stumped. I'm seeing 2-3v at the hot side of the coil with the ignition on (shouldn't that be 12v?) and the coil checks out ok. I'm getting a bad resistance read from the sender on the distributor (a steady 225 ohms resistance), so I'm assuming it's a bad sender, but not totally sure. I'm thinking the 2-3v means a bad ground somewhere, but where should I start? Also, the plugs coming for the dizzy are gray, but the connectors for the coil are green; am I checking the right thing? I'm 99% sure the gray leads are the distributor sending plugs. New dizzy time? Is it even the right dizzy, with gray plugs? All the ones I've seen online had green plugs that match the coil side ones.

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10-24-2009, 05:31 PM	#2 (permalink)
dirocyn Cage Fighter Join Date: Mar 2009 Posts: 133 Thanks: 6 Thanked 12 Times in 12 Posts iTrader Rating: (0/0% )	I'm sure someone will correct me if I'm wrong, but pretty sure the hot side of the coil should see battery voltage--it has on every other car I've worked with. I'd try and figure that out before replacing anything. A problem I've noticed, and it's not just MR2s--once cars reach a certain age they develop corrosion in the wiring, and they corrosion is a lousy conductor. Once you find where the problem is, it often requires nothing more than cleaning a connection. Are you getting good battery voltage everywhere else? Where I'm going here is, the easiest way to see 3v on a hot wire is if there's bad corrosion at the + terminal. Which can manifest overnight if it's humid enough. Also check your engine ground. Since the starter grounds through the transmission ground strap, the starter can turn even if you have a bad engine ground--and you won't get any spark without an engine ground.

10-27-2009, 12:14 PM	#3 (permalink)
Sparky No Skills Join Date: Oct 2009 Location: Beaverton, OR Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Hmm, most cars I'm used to depend on the engine ground as the starter ground, so they won't crank if that one is bad. I'll have a look. I'm getting power to all the accessories (locks, windows) and the gauge cluster lights up and shows a CEL like it should, so I'm guessing it's something odd with the coil wiring or a ground related to that. Thanks for the idea.

10-28-2009, 12:36 PM	#4 (permalink)
dirocyn Cage Fighter Join Date: Mar 2009 Posts: 133 Thanks: 6 Thanked 12 Times in 12 Posts iTrader Rating: (0/0% )	That means your battery-to-frame ground is ok. I think you're probably right, that it's in the wiring that leads to the coil. I bet you a plug nickel it's on the hot side, not ground. Wires with a + current corrode more quickly. But check the engine ground anyway. Checked the BGB and can confirm, you should see battery voltage at the hot side of the coil. Assuming your battery makes more than 3 volts, your problem lies somewhere in between, on the hot side. Only thing in between is wires and the engine main relay. Check what voltage is going into the relay, if it's 12v then in all probability the relay is bad.

10-28-2009, 01:03 PM	#5 (permalink)
Papo J 6SPD GTE Join Date: Sep 2006 Posts: 189 Thanks: 1 Thanked 19 Times in 18 Posts iTrader Rating: (0/0% )	Sounds like you may have a bad igniter, not a bad distributor. You should see battery voltage at the coil even with a bad distributor, the power to the coil is filtered and fed to the coil by the igniter.

10-28-2009, 03:51 PM	#6 (permalink)
toyotaspeed90 No Skills Join Date: Jun 2006 Location: Bellingham, WA Posts: 422 Thanks: 0 Thanked 32 Times in 32 Posts My Google Map iTrader Rating: (0/0% )	stupid question.... is your ignitor grounded? When it's bolted to the chasis it's self grounding.... if you unbolt it to do some routine checks, it loses it's ground and won't spark.....

10-29-2009, 01:28 PM	#7 (permalink)
Sparky No Skills Join Date: Oct 2009 Location: Beaverton, OR Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	No stupid questions when it comes to me and 80's Toyotas, like I said it's been awhile. It grounds through the coil, correct? The ignitor ground through the bracket on the coil, which grounds into the chassis? If so, then yes it's good. I actually have the coil out to check resistance, and cleaned up around there while I was at it. What's the best way to test the ignitor? Is there an option other than replace? I figure I'm also going to replace the main relay and see if I get a jump in voltage.

10-29-2009, 03:27 PM	#8 (permalink)
toyotaspeed90 No Skills Join Date: Jun 2006 Location: Bellingham, WA Posts: 422 Thanks: 0 Thanked 32 Times in 32 Posts My Google Map iTrader Rating: (0/0% )	if you need to replace the ignitor or coil... there are tons of us with lots of spare parts in the garage..... being in OR there are tons of MK1 guys in the PNW. the ignitor is self grounded through the bracket it bolts to -- which is bolted to the chasis. If it's not bolted to the chasis in it's original location and you have it out for testing, use a jumper cable from the negative to the bracket (or directly to the ignitor). All toyota ignitors are self grounded... meaning there isn't a wire that runs to them for grounding. The coil's "negative" is the pulse signal sent from the ignitor (black wire). The brown wire should be a constant 12V. The next thing to check.... is there are 2 connectors on the distributor side that are green... pull them both off and look inside (or look at the back of them) to see if the wires have pulled through. Because they're in a horrible location, it's common for people, when disconnecting them, to pull by the wire and not the plastic connector... which makes it REALLY easy to pull the wires out.... go to reconnect and although the plastic pieces connect the wires never actually make contact. This is common in these cars.

10-30-2009, 02:49 PM	#9 (permalink)
Sparky No Skills Join Date: Oct 2009 Location: Beaverton, OR Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Well I feel like an idiot. I'm guessing the missing relay circled in the pic is the main relay. The one that was very corroded and nasty, and I have to get channel locks on to pry out. After looking at the circuit diagrams from the BGB, that and a blown fusable link on the Head unit line (Line B) would explain 99% of what doesn't work on the car. The 3v was coming from the fact that the last owner had connected the lines by the dizzy wrong (what's the clear one for? That was powering the coil). With green to green (or gray in my case), I'm getting no power, just like it should with the main relay out. Also, for the benefit of those of use without diagrams on the fuse box lids, are they out there on this site?