integrawillie

I've searched and searched the past few days, and I can find no resolution for my issue. I've noticed that you two guys have answered the majority of questions surrounding issues like this, so here goes...

1990 Integra LS
Piston/rod b16, garrett 60-1, blah blah blah

I had the car tuned this week. Ran great, 385@21 psi. I get it off the dyno, fire it up, back it out, go to pull out of the lot and the thing dies. No big deal, probably this pesky main relay, so I give it a little tap (thing has gave me little problems like this for a couple years, was too lazy to solder it.) Fires back up but quickly dies again. Pump is coming on intermittently with key switch. I take the relay out, resolder all of the connections, and reinstall it. Pump is on everytime with key on, mil light is on, then off, I can hear all the clicks. Car has fuel to the rail, and has spark, but has no injectors opening. I'm checking things over and I find the back up fuse blown. Still has the same condition though. Went through the oem service manual on fuel and emission systems and ended up with the following:
Mil light comes on
Mil light goes off after 2 seconds
*this is where I get confused..manual says to check for battery voltage at A23, A24. I have a jumper harness from obd0 to obd1, so I checked at the obd1 connector at the ecu. A23 is 0 volts, but A24 has battery voltage. According to the manual, it doesn't have a good connection with G101. I check, double check, triple check the connection. Everything looks good.. so I run a long jumper from 101 to the A24 pin. I turn the key to the start position and the pgmfi relay fuse on the under hood fuse box blows. I'm automatically assuming there is a short somewhere. I'm checking the wiring diagram in the manual, and it shows pin #1 at the relay is battery connection, and runs to the fuse box. I can't find anything wrong with the wire, and I get frustrated. I popped a 30A fuse in there, and searched quickly for smoke. I found that the wire from the box to the #1 pin started peeling the insulation from the heat. Wire continuity checks ok, I even run a jumper from the box to the relay just to check, same results. At this point I'm in the same boat..car will not start, no fuel at all on the injectors. When I remove the G101 jumper wire and replace the blown fuse the relay comes on, pump primes, mil comes on/goes off..as soon as I attach the jumper the fuse blows. So what am I overlooking here? A23 and A24 both go to G101, so why am I blowing pgmfi relay fuse everytime I add the wire? I checked the relay straight to the battery in all positions, and the relay tests great. What the heck is going on here? Sorry for the wordy entry, just trying to be thorough.

racebum

post in forced induction

fcm

Sure sounds like a dead short on the lead/point that you jump to, [101] from A24, [that you say has power].

Hint, NEVER replace fuses with bigger ones, no matter how "frustrated" you get, your lucky all that happened is some "peeling" of insulation, I have seen cars pretty much burnt to the ground because the owner or somebody else replaced a fuse with a bigger one.

What is 101?

According to your manual are both A24 and A23 supposed to have power and are A23 and A24 IGP1 and IGP2?


If so, de-pin A23 and use a jumper from A24 to A23, see if that works.

Question, you said you have a OBD0 to OBD1 jumper harness, does that mean you are jumping from the 90 Integra ECU/ECM harness plug(s) to an OBD1 ECU/ECM, I am assuming so?

If so, what are the colors of the A23 and A24 leads on the stock plug, [before the jumper]?

If they are yellow/black, then they are indeed IGP 1 and 2, and they get their power from the injector relays output, fuse 38 -10A, [hot at all times] in engine bay fuse box, that lead will be a blue/white at the PGM-FI Main Relay.

If the above is correct then A23 is shorted out and cut off, [or fuse would blow without jumper] from the PGM-FI Main Relay, [yellow/black], so de-pinning or just cutting the A23 lead and running a jumper from A24 to A23 should solve the problem. 94

integrawillie

Not around the car (at work), so I'll answer as much as I can. The jumper harness is just what you said. 90-91 Integra ecu connectors rerouted into obd1 connectors. I've had the harness for a couple years now. On the flow chart, the manual states to check at pins A23 and A24 for less than 1.0v. If there is more than 1.0v at either terminal, fix the short for whichever pin/wire it is. The obd1 pinout diagram (which is what I'm working with) shows A24 and A23 as being PG! and 2. A25 and B1 are IGP1 and 2. As far as jumping A23 and 24, this is another confusing one. In the jumper harness they are already connected together. A23 and 24 run into each other, and one wire runs to the factory ecu connector. When I check A24 at the ecu connector, it is 0v..when I check A23 I get battery voltage. How is this even possible?? One wire turns into two wires, and one of them has batt volt, and the other is 0? That's why I ran the ground wire from directly after the ecu connector, all the way around to the G101 thermostat housing ground. I suspected the ecu at this point, so I installed a stock obd1 p06, but had the same results. With jumper from G101 to A24, fuse blew at key on, without the jumper the relay sounded correct, pump primed, cranked and no start/no fuel from the injectors. (wouldn't run the car due to injector size and different map sensor and all that, but would grossly overfuel the cylinder on priming when the injectors opened *if it worked). I can't recall the color of the oem wire that A23 and A24 run to right now, will have to check that in a bit. Also, when I jumped A24 to G101, the yellow/white wire that runs from the under hood fuse box to the relay was the one that got very hot. Looks to be pin #1, which is batt power.

fcm

OK, PG1 and PG2 are grounds, there should be no voltage on then at all, they should both have full continuity to chassis ground, that is why the fuse blows when you install a jumper.

I am also confused as to why your manual would ask you to check for voltage at PG1 and PG2 when they are grounds, I am also not sure why the jumper harness connects PG1 and PG2 to the same pin on the OBD0 harness side although it should make no diff., they ground to the same point on both OBD0 and OBD1 Integras, but both OBD0 and OBD1 ECU/ECMs have both PG1 and PG2 inputs.

Test A23 and A24 for continuity to chassis ground, both should show full continuity to ground, it also confuses me that you would get two diff. readings on A23 and A24 when they are connected together at the the harness end of the jumper harness, it would indicate there is a problem with the jumper harness.

Unplug the jumper harness, at both ends and test for continuity of the A23 and A24 pins on ECU/ECM side to the pin on harness side where they join together.

Also test for voltage at IGP1 and IGP2, [A25 and B1] with ign. switch on, jumper harness plugged in. 94