As posted previously, I installed my SAFC, Walbro and FCD and had the car running nicely. At one point, when running at idle, the car just died…I blew the top 30 amp fuse. I replaced the fuse and tried to start the car. The starter turns and with the connector jumpered, the fuel pump works (I can hear the rails pressurizing.) I've determined that I'm not getting any spark. I pulled the wires and had a friend check for spark at the ingniters. Nothing. Just to be sure, I disconnected the SAFC from the ECU and tried to start it, no go. I tested the main relay and it clicks with 12v applied and I also get continuity. I'm also getting 12v at the two-prong connector on the main relay. I checked all the fuses in the engine bay and at the driver's kick panel, all good. I checked voltage at the ECU pinouts. The only one that is off is the AFM input. I'm getting 12v at the ECU. The AFM tests fine. I'm lost and really need help now diagnosing this problem. ANY input is appreciated.

THanks all,

Brian

 

AIR FLOW METER......Is it pin 2A or 2E that has 12v on it?

2A is the reference voltage of 4.5 to 5 volts and I wouldn't expect 2E to have anymore than that, should be less.

I'd rid myself of any part of the SAFC and see what the voltage is at those two pins (I think you might have done that already). If you have 12v on either, I'd say ECU kaput.

So, what pin has 12v??????

If you look at the schematic on page 50-25 of the 88 manual online, you'll see pin 2A supplies the reference voltage for the tps, variable resistor, boost sensor, and atp. If the reference voltage is bad or non existent, then the car will not run. Corrupt ECU. No real definite location of the bad part is known to me...yet.

 

join the club...

do you get 12v at the connectors for the coils like the fsm tells you to check?

when you and your friend tested for spark, did you only test one wire at a time and have the rest plugged in to the plugs? (this might only matter for leading, not sure, but i only test w/ one off at a time)

did you check the resistance of the coils by fsm method?

if all checks out good, and still no start... i'd check compression and then make absolutely sure its not flooded before looking elsewhere


good luck
mike

 

yo hailers! maybe you can help me w/ this one... you've helped me out w/ lots before

what if the reference voltage is non existant at the ecu for 2Q? my ecu shows no voltage at 2Q w/ key in on (car off) and stuff like the boost guage doesnt work. "meter" fuse is good and boost guage will work when i put 12v to it. in 87 fsm, wiring diagram on 50:20, it looks like 2Q supplies power for that.
Bad ecu you think?


one more question: are the sensors (such as boost sensor) supposed to have 5v or 12v? 5v right?

 

My bad. Previously checked the pinouts with the connector disconnected from the ECU. Readings are now as follows—2A Vref at 5v and 2E AFM at 4v. Now I'm really stumped because I thought it may be a short in the AFM circuit. The only relay I haven't checked is the opeing circuit relay. I'm not sure where it is or if blown would have an affect on the ignition and cause a "no-spark" scenario.

 

On the LEAD coil assy, the little two wire plug that is WHITE. Do you have 12v at the black/yellow wire?

 

Hailers, I just ran out and checked. I'm only getting 1.3v at the lead coil connector with ignition on.

 

Attached is a jpg. It seems that 12v comes to the little white plug from the MAIN RELAY and it comes to the main relay from the 40 amp fuse in the engine bay fuse box. Check the 40 amp fuse and if thats good find the black/green wire at the main relay and see if its got the 12v. Should be there 24hrs a day at the black/green wire. If its there.....duh. Ohhhhh, if its there, then the fuse that feeds that relay is blown. Its in the crew compartment. Yeah. Thats it. Its blown. It should be on the third row from the bottom of the fuse box. Second fuse from your left when looking into the fuse box.

Sorry about being tardy. Had to go home and eat etc.

 

Forgot the jpg: Its here. But forget the first part of that other post and look for the fuse in the crew compartmet first. Then the other if need be.

 

I'm getting 12.5v to the black/green wire into the main relay.

 

Yeah. I was thinking out loud as I wrote that. It seems the relay is not pulling in due to the fuse in the crew compartment. I mentioned that fuse in one of the upper posts. Third row, second fuse over if I remember right. How does that check out??????? Betcha its blown. I'm pretty sure its called the ENGINE fuse.

 

I checked the cabin fuses—all of them—and they are all good. SInce I'm getting full voltage (12.5v) TO the master relay and I'm getting only 1.3v at each of the coils is it safe to assume that the problems lies in the master relay? Is the master relay the last point in the circuit before the coils?

Brian

 

Go to the MAIN RELAY and with the key to on, see if there is 12v on the black and white wire. I think its a large gauge wire. What is the voltage?

 

In on position and 4-prong main relay connector disconnected, I get 2v on the black and white lead in the 4-prong. I'm assuming that is the one going into the relay as opposed to the 2-prong white connector.

 

Somethun is screwy here. Yeah, I was talking about the black/white wire at the MAIN RELAY. Its.....oh! Its the round plug at the main relay, not the rectangular one. One wire is black/white the other is pure black. Look at the schematic and you will see(no you won't, I forgot to add the picture that shows that there are two plugs for the main relay) that the black/white wire pulls the relay in and there is a black wire going to ground. Sorry. Check the round plug, two wires. Should be 12v at the black/white wire. What happened???????

 

See the schematic? Where it shows the MAIN RELAY??? See the Ba-05 and Ba-06 next to it. That means there are two plugs going to it. Two seperate plugs. Both have a black/white wire. Thats where we went wrong. So what volts did you find on the round plug with the key to on????????

 

plugs:

 

OK. When I disconnect the white plug, the electric fan goes on and the relay clicks off. The voltage on the b/w lead fluctuates from 9.98v to 10.02v.

 

That would be the BA05 connector I checked. Does that come from the opening circuit relay?

 

Round white plug at the MAIN RELAY????? Does it have 12v on its black/white wire??? Probably does, but I want to make sure we're talking about the same plug.?

 

Yassir. The ba05 connector is the round white plug with two leads. The b/w lead is giving me a vacillating reading between 9.98 and 10.02v. Hence the thread title

B
p.s. thanks for the help!

 

Ok. We were writing at the same time. Since you have approx 12v at the round connector, and you heard the relay drop out as you disconnected it from the harness, then the relay has taken a dump. UNLESS the pure black wire on that connector is not making a good ground. Put your meter on ohms and the neg on the batt neg post and the pos lead on the pure black wire. Should read 0.0000 or at least less that one ohm. How does it read???? If it does read to ground, then the contact in the relay went south and the main relay is bad. It may pull in (you heard it click) but the contacts are not making. OR, the black/yellow wire is broken b/t the relay and the little two prong plug at the LEAD coil assy. Not likely. But possible. Whats happening??????

 

The fan coming on as you disconnect the round white plug with the key to on is normal. I've traced down why that happens before. No worry. The vacillating voltage is probably a slightly low battery and the fan running dragging the volts down.

Tell you what.Connect EVERYTHING BACK UP. But the little white plug at the LEAD coils assy. Put your meter on the black/yellow wire in it. No reading?? TAP the MAINRELAY with a whatever while watching the meter. Did it momentarily show some voltage?????? I'm here until the talking heads on tv go off the air. They've got me talking back to the tv. Darn blockheads.

 

0.00 between ground and battery.

 

OK, put it all back together, hooked up the trusty Radio Shack dmm and while manipulating the relay and it's connectors only got a max of our original reading of 1.3v at the b/y lead on the leading coil.