'86 MJ 2.5L ECM....good?

[Ωhm]

50 minutes ago, eaglescout526 said:

I wonder what T3 shows at the ECU connector?

 

When ECU wants fuel pump relay ON, T3 will switch to ground. Internal to the ECU.

[eaglescout526]

Ok that eliminates the fusible link being blown. Could pin 86 be tested on the FP relay during crank to see if the ignition switch is sending voltage to energize the relay?

 

Thanks Ohm!

[SoCalManche]

9 minutes ago, eaglescout526 said:

Ok that eliminates the fusible link being blown. Could pin 86 be tested on the FP relay during crank to see if the ignition switch is sending voltage to energize the relay?

 

Thanks Ohm!

I'm assuming that question was for Ohm, lol.

[Ωhm]

Fuel pump relay block (86) is HOT with KEY ON or engine CRANKING. 

[Ωhm]

Remove FP relay. Check FP relay block (86) for battery voltage with KEY ON. Same circuit as D1-2.

[eaglescout526]

7 minutes ago, SoCalManche said:

I'm assuming that question was for Ohm, lol.

Both of ya but mostly you. But lets do see what our voltage looks like where Ohm said.

[SoCalManche]

Just now, eaglescout526 said:

Both of ya but mostly you. But lets do see what our voltage looks like where Ohm said.

 

3 minutes ago, Ωhm said:

Remove FP relay. Check FP relay block (86) for battery voltage with KEY ON. Same circuit as D1-2.

 

 

D1_2 and FPR Pin 86 are not battery voltage. They are ~12.05V.

[eaglescout526]

So both are getting power to them? So then it should be energizing the relay for the fuel pump.

[SoCalManche]

9 minutes ago, eaglescout526 said:

So both are getting power to them? So then it should be energizing the relay for the fuel pump.

Unicorn.

 

This is why I try to stay away from electrical. Ha

 

Yes, I have power to both. I also do not understand why this is an issue still.

[Ωhm]

7 minutes ago, SoCalManche said:

D1_2 and FPR Pin 86 are not battery voltage. They are ~12.05V.

That's close enough.

 

Need to take two (2) voltage drops. Connect DVOM as follows:

Battery terminal plus (+) and D1_2. CRANK engine and take reading.

Battery terminal plus (+) and D1_6. CRANK engine and take reading.

Both readings should show 0vdc.

 

 

[SoCalManche]

15 minutes ago, Ωhm said:

That's close enough.

 

Need to take two (2) voltage drops. Connect DVOM as follows:

Battery terminal plus (+) and D1_2. CRANK engine and take reading.

Battery terminal plus (+) and D1_6. CRANK engine and take reading.

Both readings should show 0vdc.

 

 

D1_2 + Batt Pos = ~0.4V during crank.

D1_6 + Batt Pos = ~9V during crank.

 

Edit: With Fuel Pump Relay installed.

[Ωhm]

5 minutes ago, SoCalManche said:

D1_6 + Batt Pos = ~9V during crank.

Try this voltage drop again. This time remove FP relay and install jumper wire (30-87).

[SoCalManche]

4 minutes ago, Ωhm said:

Try this voltage drop again. This time remove FP relay and install jumper wire.

With jumper wire installed:

 

D1_2 + Batt Pos = ~0.3V. That was the initial readout, but it continued to descend as I continued to crank.

D1_6 + Batt Pos = 0.231V. This voltage was maintained regardless of crank or not.

[Ωhm]

Pass on both VD test. Good readings.

[SoCalManche]

3 minutes ago, Ωhm said:

Pass on both VD test. Good readings.

Well I suppose that is good and bad. Glad it's a good readout, but continues confusion to the underlying problem.

[SoCalManche]

1 hour ago, eaglescout526 said:

So both are getting power to them? So then it should be energizing the relay for the fuel pump.

Also, here is the fuel pressure test kit I rented. I wouldn't recommend getting it since it's $150 for one piece to fit, but here it is, haha.

[eaglescout526]

Just now, SoCalManche said:

Also, here is the fuel pressure test kit I rented. I wouldn't recommend getting it since it's $150 for one piece to fit, but here it is, haha.

 

All I needed was something to go off of. Thanks.

 

So with the relay installed do you see pressure on the fuel rail?

[SoCalManche]

20 minutes ago, eaglescout526 said:

 

All I needed was something to go off of. Thanks.

 

So with the relay installed do you see pressure on the fuel rail?

No pressure at TBI with fuel relay in circuit, key ON.

I also swapped a different relay in to verify, and no fuel pressure, both times.

 

I also just picked up a noid light set to verify pulse on the injector harness, and it does light up when i switch key to ON, as well as crank.

[eaglescout526]

WTF! Its like everything checks out. So I wonder what voltage is getting to T6(if any goes there) at the ECU connector, perhaps a voltage signal is not going to the relay to energize it. 

[SoCalManche]

4 minutes ago, eaglescout526 said:

WTF! Its like everything checks out. So I wonder what voltage is getting to T6(if any goes there) at the ECU connector, perhaps a voltage signal is not going to the relay to energize it. 

I need to just take out a loan to do a 4BT swap, lol.

[Ωhm]

2 hours ago, Ωhm said:

When ECU wants fuel pump relay ON, T3 will switch to ground. Internal to the ECU.

 

My mistake, NOT T3, but T6. T3 would have IGN SW voltage on it.

 

13 minutes ago, eaglescout526 said:

So I wonder what voltage is getting to T6(if any goes there) at the ECU connector, perhaps a voltage signal is not going to the relay to energize it.

 

[SoCalManche]

1 minute ago, Ωhm said:

 

My mistake, NOT T3, but T6. T3 would have IGN SW voltage on it.

 

 

Should I check this?

[SoCalManche]

Also, would a bad injector in itself cause this issue to happen? I'm not looking to drop $100+ on an injector, but I don't know how to check to see if it works or not. I only know that the harness is working.

[Ωhm]

Its would be a quick test. Disconnect ECU connector. Check for voltage on T3 with KEY ON.

[SoCalManche]

1 minute ago, Ωhm said:

Its would be a quick test. Disconnect ECU connector. Check for voltage on T3 with KEY ON.

Where do I ground?