Ok, so here is a little background info on the car.

It's a '93 Si, bought it stock. Ended up putting a cheap header on it because I cracked the stock one. That is the only thing I have bought besides parts for regular maintenance.

After discovering I was having headgasket issues, I started saving for a new engine instead of trying to fix it, as it had about 150k on it. I ended up getting a jdm D15b vtec since it was close to the stock Z6. Replaced the entire ignition: cap, rotor, and took the semi new coil and ignitor out of my Z6 dizzy and threw them in there. I also changed the t-belt, tensioner and water pump. Oh and a new clutch and flywhell. Typical stuff for installing a new engine. I swapped intake mani's and used the stock P28. Great mileage and ran well.

I have had zero problems with it until recently. After getting gas and attempting to pull away from the pump, the car died and refused to start. I pushed it into an empty parking spot, thinkin it would be a bad coil or ignitor. It turns over but doesn't hit a lick. I had no check engine lights before this happened. I jump the service plug and get codes 10 (intake air temp. sensor), code 16 (fuel injectors), and code 41 (oxygen sensor heater).

The first thing I did was check all related fuses, and eventually every fuse under the dash and in the engine bay. None were broken. Next thing was to check for spark. Each plug showed a healthy spark when grounded. This is where it got above my level. I pulled very plug and they were all dry after priming and attempting to start. I took the fuel injectors off with the fuel rail, and had a friend turn the car to on to prime the fuel system. The pressure shot an injector out because I wasn't holding it and gas got everywhere. After holding them in the next time and turning the engine over, the car started and ran from the fuel previously spilled into the combustion chamber via the open fuel injector holes. It ran four about 4 or 5 seconds surprisingly smooth until it got starved for fuel. However, I noticed that the injectors were not opening at all.

I decided to go ahead and try my main relay at this point. Took it out and apart, contacts look good. It's only about a year and a half old. However I don't think it is the main relay, because the fuel pump primes with good pressure and all of the injectors get 12 volts. They are all ~12ohms and I know 10-13 is normal.

I had also learned the ECU pulses ground signals to the injectors with 12v on them already to make them fire. I though maybe there was a chance the ECU was bad. Put it in another friends civic and she started right up.

I'm kind of lost as to where to go next. I've never really ran into any fuel issues before, they have all mostly been ignition related.

Any help would be greatly appreciated. I'm living about 3 hours away at college and don't have much money to throw at this, however, with the help of you guys, I think it will get solved.

One of the couple of pics I have of my hatch, just for ***** and giggles.

 

1) Test your main relay.
----------------------------------------------
Then check continuity of the wires running between:

2) Main relay connector terminal 2 and ECU connector terminals A23 and A24.

3) Main relay connector terminal 8 and ECU connector terminals A7 and A8.
---------------------------
4) Then test continuity to body ground at ECU connector terminals A26 and B2.

 

Thanks for the quick reply.

One question...
Is it possible to do the continuity check on the main relay using a 9v battery as the power source? I only ask because I have the main relay here in the apartment with me and there has been a hurricanado outside for the past 26 hours. I will more than likely get the chance to test the rest tomorrow.

 

I'm not sure.

 

Fair enough.

I should update tomorrow after doing the tests you provided. Thanks again for the info and the schematics.

 

Correct me if I missed something, but it started right up with another ECU and you're still looking for the problem? I'm confused.

 

Sorry, I wasn't really clear there. I meant to say I tested the ECU from my car in a friends to make sure my ECU was ok.

 

That makes a lot more sense, looks like I didn't read close enough.

 

Well I didn't get any sleep last night because of a paper I had due this morning, and everything is kinda starting to run together. Ha I hate college.

 

I actually just tried it. It was enough to make the relay click on each of the three tests, and there is also continuity. So I guess the main relay is good then, correct?

 

yes

 

I got lucky and managed to grab an open window from the rain. I did each test from the relay connector to the ECU connector, as well as testing the 2 ECU connector pins to ground. Every connection had continuity.

 

If you reset the ECU (by removing the hood Back Up fuse for about three minutes) and then crank the engine for about 30 seconds, do all or only some CEL codes return? And when you jump the service connector to pull codes, does the CEL blink the codes and then remain on steady or does the CEL just continue to blink the codes repeatedly?

If you remove ECU connector A and turn the key to ON(II), do you measure battery voltage to body ground at ECU connector A terminals A1, A2, A3, and A5 (fuel injectors)?

 

The battery is pretty dead, and only got it to turn over about 6 times. No CEL's came on, but like I said it didn't turn over but a few times. I'll have to get my neighbor to give me a boost tomorrow so I can check. Plus it's sleeting outside now and my hands go numb after about 5 minutes. It was hard enough just getting the main relay and computer back in. I'll crank her tomorrow and also check for voltage at the injector terminals.

 

Been kind of busy the past couple of days with school and a new family member.

Checked for voltage at A1, A2, A3, and A5. All have around 12 volts.

Next, I cleared the codes by way of the backup fuse, got the battery charged, and cranked it for a while. It came back with codes 16, 21, and 41. I'm not sure if 21 and 41 are even related, but it threw them at me.

I also checked the injectors for voltage and resistance again just to be sure, and it is still all up to specs.

This one is really stumping me.

 

When you jumped the service connector to pull codes, did the CEL blink the codes and then remain on steady or did it just continue to blink the codes repeatedly?

 

It would blink the series of codes and start repeating them when finished.

 

With the key in ON(II), is there battery voltage to body ground at both ECU A25 and B1?

Is there any damage/corrosion in the A23 or A24 terminals in the ECU or ECU connector sides?

 

Had voltage to ground at both A25 and B1.

I looked at A23 and A24 and both were shiny and corrosion-free. They did not appear bent or damaged in any way.

 

It really sounds like an ECU problem, but I can't explain why your ECU worked in your friend's car.

If you follow the service manual troubleshooting for code 10 (IAT/TA sensor), does the IAT connector get 5 reference volts and good ground from the ECU and is the IAT sensor resistance within spec, again pointing to the ECU?

 

I climbed into the engine bay, and hovered over the back of the engine bay. The IAT sensor was in spec as far as resistance goes, but it was only showing .3 volts

 

This is what the service manual is showing me. Is the test harness necessary or is there a way to do without it?

 

You don't need the test harness. Just carefully pierce the insulation on the wires to do any multimeter tests requiring the test harness. If anything isn't clear, just post your questions.

 

I just checked the voltage between D15 and D22, and it's 3.74 volts. This still seems pretty low to 5 volts. I don't understand why it shows 3.74 right past the computer and .3 at the plug for the IAT/TA sensor. This is confusing the life out of me

 

What voltage do you measure across the two battery posts?

You may want to re-measure voltage at the IAT plug. At this plug, measure voltage of the Red/Yel wire both to body ground and to the Wht/Grn wire. Are they the same or different?