Crank no start EFI Fuse? (1 Viewer)

[musthave]

Looking at the diagram, by removing the Fuel Pump Relay, I have eliminated anything downstream from that. So where is this Circuit Opening Relay located? Doesn't that have to be the issue? Or at least the next point?

 

[musthave]

Is it the bottom one?

 

[musthave]

To test, I've done the following:

1. Unplugged both O2 sensors
2. Unplugged Neutral Switch
3. Unplugged Fuel Pump Relay (This should eliminate anything downstream from there, ie. fuel pump, etc.)
4. Unplugged what I believe is the Circuit Opening Relay, the relay on the bottom. (Which tested fine by FSM)

Plugged in new EFI Relay and new 15A fuse. Turn the ignition to On, fuse blows instantly.

What do I look at next?

 

[jonheld]

You are only seeing part of the equation here.
If the EFI fuse blows as soon as the relay closes, then you need to divide and conquer.
The EFI relay feeds the VSV valves for the EGR and FPR, the IAC valve, the 2 O2 sensors, the OBD2 connector, the ECU, the MAF sensor, as well as the fuel pump circuit.

Somewhere along the line, you have a direct short to ground. This was proven when you tested from pin 4 of the EFI relay to ground and had continuity. Obviously, you'll be popping fuses all day long in this condition. I would leave the meter on a continuity beep tone and start disconnecting items on that list. You'll know pretty quickly when you touch the right spot.

 

[musthave]

You are only seeing part of the equation here.
If the EFI fuse blows as soon as the relay closes, then you need to divide and conquer.
The EFI relay feeds the VSV valves for the EGR and FPR, the IAC valve, the 2 O2 sensors, the OBD2 connector, the ECU, the MAF sensor, as well as the fuel pump circuit.

Somewhere along the line, you have a direct short to ground. This was proven when you tested from pin 4 of the EFI relay to ground and had continuity. Obviously, you'll be popping fuses all day long in this condition. I would leave the meter on a continuity beep tone and start disconnecting items on that list. You'll know pretty quickly when you touch the right spot.

Alright, I will use pin 4 and ground for continuity get a steady tone until something happens when I disconnect items 1 at a time. I have OBD2, FPR, and COR all unplugged so that leaves VSV Valve for EGR, IAC, MAF, ECU and OBD2. Not sure where to disconnect OBD2, is that on the port under the hood and by fusebox? Disconnect ECU by right speaker completely?

 

[jonheld]

I am assuming at this point you have THOROUGHLY checked the areas mentioned earlier in this thread regarding the possible chafe points.
1. the harness that runs close to the EGR pipe in the engine bay
2. the harness that runs along the bottom support of the glovebox
3. the harness that runs under the truck attached to the front of the frame rail
4. the fuel pump harness that is under the left C-pillar

The ECU is mounted horizontally and lives above the glove box. Follow the harness that you already inspected to find the 4 dark grey connectors for the ECU; E4, E5, E6, and E7.

 

[musthave]

I am assuming at this point you have THOROUGHLY checked the areas mentioned earlier in this thread regarding the possible chafe points.
1. the harness that runs close to the EGR pipe in the engine bay
2. the harness that runs along the bottom support of the glovebox
3. the harness that runs under the truck attached to the front of the frame rail
4. the fuel pump harness that is under the left C-pillar

The ECU is mounted horizontally and lives above the glove box. Follow the harness that you already inspected to find the 4 dark grey connectors for the ECU; E4, E5, E6, and E7.

Thank you for all of your responses, I really appreciate it. The harness by the EGR looks fine, better than my other cruiser. The harness on the frame rail for the O2 senssors looks great, as does the harness by the C-pillar and the one by the bottom of the glovebox. So for testing the ECU, unplug the grey plug at the bottom completely. Getting ready to head out in an hour or so and give it my best this morning.

 

[musthave]

@jonheld Started the troubleshooting. Went through the connections, didn't take long. Found the issue. As soon as I unplugged IAC connector, I noticed the beep stopped. Put it back on, still stopped. Then I started wiggling the cable from top to splice. On / off. Finally found that with tension on it it stays off. I have it positioned nicely now and it starts and runs fine. I actually can't move it to a position where it fails now.

I will need to pull off the throttle body etc. to get better access and get a look at the splice and the harness. Meantime, it's working. A sense of accomplishment on this front.

 

[Chester]

Brother, this sounds like the demon has been found.
Fixed is not going to be so elusive I hope.

 

[davidp14]

wow. there is some good education here, a little over my head but I'm glad you shared.

thanks