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

[Ωhm]

I just want you to be safe. Vapors/static electricity are the danger.

[SoCalManche]

2 minutes ago, Ωhm said:

I just want you to be safe. Vapors/static electricity are the danger.

Yessir.

[SoCalManche]

But like I said, my only option currently is small jumper cables, and if you would like me to proceed, I'd need a little more idea of what exactly I'm doing. Where am I attaching to fuel pump?

[eaglescout526]

On the pump itself should be two prongs. If the clips are attached wrong, the pump will blow bubbles and if they are clipped on the other way, it pump the fuel. 

 

But one of the wires going to the pump should be black indicating ground.

[Ωhm]

5 minutes ago, SoCalManche said:

But like I said, my only option currently is small jumper cables, and if you would like me to proceed, I'd need a little more idea of what exactly I'm doing. Where am I attaching to fuel pump?

What I was looking for is to disconnect the fuel pump from the vehicle wiring and powering the pump right off of the battery. Even another battery would work. Hook plus to plus and neg to neg at the fuel pump connector.

[eaglescout526]

What Ωhm said.

[SoCalManche]

1 minute ago, Ωhm said:

What I was looking for is to disconnect the fuel pump from the vehicle wiring and powering the pump right off of the battery. Even another battery would work. Hook plus to plus and neg to neg at the fuel pump connector.

Okay, that's what I thought. Yes, I've done that test before and it fires right up. I will do it again. I was told in my thread about this a year ago that testing directly like that doesn't do anything. At least that's what was said. 

[Ωhm]

In this set up once the pump is running, attempt to START vehicle.

[SoCalManche]

30 minutes ago, Ωhm said:

In this set up once the pump is running, attempt to START vehicle.

Same thing occurs;

 

Did not add fuel to TBI. Had someone else crank while I held the leads to my TJ's battery (disconnected from TJ, of course). She showed intermittent FIRING, not quite catching fully to gain full START.

 

Same thing occurs if it is connected normally through the harness.

[Ωhm]

Good news to hear this testing went well, only it didn't solve anything. Do you own a timing light?

[SoCalManche]

2 minutes ago, Ωhm said:

Good news to hear this testing went well, only it didn't solve anything. Do you own a timing light?

I do not. You think the timing is off?

[Ωhm]

No, not the timing. Somewhere I read you can hook up a timing light and look at the injector spray pattern while cranking the engine. May have to move pickup to different spark plug wires, but you should be able to see the spray pattern.

[SoCalManche]

19 minutes ago, Ωhm said:

May have to move pickup to different spark plug wires, but you should be able to see the spray pattern.

Can you elaborate on this point? I'm not following.

[Ωhm]

12 minutes ago, SoCalManche said:

Can you elaborate on this point? I'm not following.

Hook up a timing light and point it down the TB. The strobe effect will freeze the spray pattern. Different spark plug wire (timing light pickup) will give different views.

[SoCalManche]

Alright, I'll have to snag one tomorrow to check the spray pattern.

[eaglescout526]

I still wonder if the fuel pump can put out but not enough pressure to keep up with the demand of the ECU and engine. Like yes we saw the pump can build the pressure but can it maintain that pressure when fuel is needed?

[SoCalManche]

1 minute ago, eaglescout526 said:

I still wonder if the fuel pump can put out but not enough pressure to keep up with the demand of the ECU and engine. Like yes we saw the pump can build the pressure but can it maintain that pressure when fuel is needed?

I have a spare I can go hook up to see.

 

Even so, only 4V at FP connector with KEY ON; 3-something V when cranking.

[eaglescout526]

That just doesn't sound like enough voltage for anything. But even applying 12V directly to the pump itself yielded near firing of the engine.

[SoCalManche]

19 minutes ago, eaglescout526 said:

That just doesn't sound like enough voltage for anything. But even applying 12V directly to the pump itself yielded near firing of the engine.

So basically applying 12V directly or 3-4V through harness yield same results, so pump may be bad?

[eaglescout526]

Yes and no, I would hold off on the pump thing until we get this fuel injector thing figured out but it could be the pump, but 3-4 volts still doesn't sound right unless that's all it really needs but if that was the case then why would they have put a ballast on the later years?

[SoCalManche]

So here is a video of it starting, everything hooked back up to normal, with same pump. Looks like the ISA is working properly now? Idle shoots through the room now before dying.

 

https://drive.google.com/open?id=14qRsMq6PkL9HlcRitcJSioziefSfxxFN

[eaglescout526]

Heyyyyy the ISA works!! I know that sound after shut down anywhere. I think we are moving away from the bad ECU idea.

[SoCalManche]

11 minutes ago, eaglescout526 said:

Heyyyyy the ISA works!! I know that sound after shut down anywhere. I think we are moving away from the bad ECU idea.

So just terrible grounding on top of what was already terrible grounding. Lol

[eaglescout526]

Very well could've been. Still need to figure out this fuel problem. So pump constantly running with 12V applied and relay in place, it kinda wants to start but it acts like its not getting enough fuel to meet the demand of starting. Sound right? 

 

So I wonder if power loss is at that bulk head met with resistance from the tar inside. Just a working theory for now.

[SoCalManche]

1 minute ago, eaglescout526 said:

Very well could've been. Still need to figure out this fuel problem. So pump constantly running with 12V applied and relay in place, it kinda wants to start but it acts like its not getting enough fuel to meet the demand of starting. Sound right? 

 

So I wonder if power loss is at that bulk head met with resistance from the tar inside. Just a working theory for now.

Yes. Regardless if fuel pump was connected directly at 12V via second battery, or connected through harness on normal setup (which hits 3-4V on crank), the engine acts like it wants to FIRE without pouring fuel in TBI, yet it will not catch and actually fire.