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

[eaglescout526]

I mean you could hunt down a special test bulb but something like a courtesy light would also work for the test bulb. The only other ground would be the one from the engine to the fire wall which you have cleaned and replaced in your pic. The injector pulses, that's all I know. My guess is it pulses and the fuel enters and the injector pulses it down into the throttle body in mist like fashion so the fuel atomizes when it gets to the combustion chamber. But yes there needs to be a good 14-15PSI of pressure for the fuel system.

 

Everything except the CPS is VDC. 

[SoCalManche]

2 hours ago, eaglescout526 said:

I mean you could hunt down a special test bulb but something like a courtesy light would also work for the test bulb. The only other ground would be the one from the engine to the fire wall which you have cleaned and replaced in your pic. The injector pulses, that's all I know. My guess is it pulses and the fuel enters and the injector pulses it down into the throttle body in mist like fashion so the fuel atomizes when it gets to the combustion chamber. But yes there needs to be a good 14-15PSI of pressure for the fuel system.

 

Everything except the CPS is VDC. 

Alright, well I did the ignition testing. 

 

With probes in both D1_3 and D1_4, it sits at ~ -5V. When I crank, it sits at ~5.6V.

[eaglescout526]

So the book says it should be zero volts after engaging the starter motor. Then says repair the harness as necessary.  Then it says to check the MAP sensor and repair as necessary. And of course the last test I wish I had is the MS 1700 ECU scanner.

[SoCalManche]

5 minutes ago, eaglescout526 said:

So the book says it should be zero volts after engaging the starter motor. Then says repair the harness as necessary.  Then it says to check the MAP sensor and repair as necessary. And of course the last test I wish I had is the MS 1700 ECU scanner.

So basically back to the idea of "start opening up the split looms to try to find toast wiring.

[eaglescout526]

Sounds like fun doesn't it? Otherwise the book doesn't really say what else to do other than repair the harness. 

[SoCalManche]

9 minutes ago, eaglescout526 said:

Sounds like fun doesn't it? Otherwise the book doesn't really say what else to do other than repair the harness. 

Crap...haha. 

 

Want to come take a work vacation in San Diego and help? It's only a 5 1/2 hour drive! Haha

[eaglescout526]

Sure!! If we weren't in this current situation the world is in, lol. First thing I would look at before absolutely diving into the harness is cleanliness. How clean are the FP relay and the starter relay contacts. Possibly a connector could be loose on that relay. Had that happen once, wouldn't even engage the starter until I found a connector coming unplugged yet it had started the day before that incident. Are there two 5 pin connectors by the passenger side shock tower by the relay center?

[SoCalManche]

2 minutes ago, eaglescout526 said:

Sure!! If we weren't in this current situation the world is in, lol. First thing I would look at before absolutely diving into the harness is cleanliness. How clean are the FP relay and the starter relay contacts. Possibly a connector could be loose on that relay. Had that happen once, wouldn't even engage the starter until I found a connector coming unplugged yet it had started the day before that incident. Are there two 5 pin connectors by the passenger side shock tower by the relay center?

There are three. The B+ latch relay (closest to firewall), fuel pump, and I forget the third.

[eaglescout526]

Do you have AC or Fog lights? Possibly O2 relay.

 

I meant the other 5 pin connectors, the GM weatherpak ones.

 

Gonna need TNT to blow this stump.

[SoCalManche]

6 minutes ago, eaglescout526 said:

Do you have AC or Fog lights? Possibly O2 relay.

 

I meant the other 5 pin connectors, the GM weatherpak ones.

 

Gonna need TNT to blow this stump.

Here are a few pictures. The first two relays disappear into the harness, and the third relay is connected to that silver connector which is attached to a fusible link.

[SoCalManche]

Whoops, my bad. That silver component does NOT attach to a fusible link. The wiring goes into that silver box and splits off a third direction as you can see, somewhere else. When I looked initially, it looked like the fusible link was connected.

[eaglescout526]

I wonder where your starter relay is. I looked at my 86-87 parts book and saw a couple like that silver one but I know its not the anti diesel timer so it could be the power steering relay. 

[SoCalManche]

1 minute ago, eaglescout526 said:

I wonder where your starter relay is. I looked at my 86-87 parts book and saw a couple like that silver one but I know its not the anti diesel timer so it could be the power steering relay. 

From what I gathered, I thought there wasn't a starter relay. I thought the only thing close was the starter solenoid with all the fusible links.

[eaglescout526]

Relay, solenoid, they do the same thing. Man 86 is an animal that's for sure. On the side of the TB is an allen head bolt snugged away by the fuel lines facing the drivers side fender. If you can manage to find a pressure gauge to fit that port you can see what the fuel pressure looks like. Have you seen any fuel leaks around the TB area?

[SoCalManche]

1 minute ago, eaglescout526 said:

Relay, solenoid, they do the same thing. Man 86 is an animal that's for sure. On the side of the TB is an allen head bolt snugged away by the fuel lines facing the drivers side fender. If you can manage to find a pressure gauge to fit that port you can see what the fuel pressure looks like. Have you seen any fuel leaks around the TB area?

Trust me, I know. I've been calling it "The Unicorn" for some time now. Haha

 

I haven't seen any fuel leaks. When I pop the jumper wire in the fuel pump relay circuit, it cycles the fuel back to the tank no problem, with no leaks in the lines. I'll have to see if Autozone is still doing loan-a-tool right now for a fuel pressure gauge.

[eaglescout526]

This one definitely is a unicorn of issues. I'm not sure if they have a kit for all fittings but hopefully they have the right one for our TB's. If they do let me know, id permanently hook one up. 

 

Ok looking at the 86 electrical book, from 87 on the FP relay, that wire goes to splice "K" which goes up to C113 that goes to splice "N" then one of the five other orange wires goes to the fuel pump with C100 then to C200 then to the Sending Unit. So theres only two connectors between the splice and tank. Two other orange wires go to the laod swap relay which is probably that silver one in the pic and another one goes to the PS switch. Another orange wire goes to C219 which is not used. 

 

Thank goodness for dual monitors.

[SoCalManche]

3 minutes ago, eaglescout526 said:

This one definitely is a unicorn of issues. I'm not sure if they have a kit for all fittings but hopefully they have the right one for our TB's. If they do let me know, id permanently hook one up. 

 

Ok looking at the 86 electrical book, from 87 on the FP relay, that wire goes to splice "K" which goes up to C113 that goes to splice "N" then one of the five other orange wires goes to the fuel pump with C100 then to C200 then to the Sending Unit. So theres only two connectors between the splice and tank. Two other orange wires go to the laod swap relay which is probably that silver one in the pic and another one goes to the PS switch. Another orange wire goes to C219 which is not used. 

 

Thank goodness for dual monitors.

Just called, and they are still doing loan-a-tool. Must be O'Reillys that stopped doing it. 

 

Anyways, this kit looks like it has a ton of fittings, so it should be good to go hopefully. And yeah, I saw Jeep Driver's setup on here with a permanent Fuel pressure gauge at the TBI, and I dig it. His whole setup makes my MJ look so basic, ha.

 

I'm headed to go pick that up, and hopefully pick up a noid light too, to check the pulse coming from the fuel injector harness. So which voltage or resistance do I check to figure out which wires are fried?

[eaglescout526]

Both would indicate open loop but I would test for both just to see what we could be looking at. And let me know on that tool kit and ill see if I can hunt down a semi cheap kit to add a pressure gauge to mine. 

 

Also the injector is not supposed to have more than 10 Ohms of resistance.

[SoCalManche]

6 minutes ago, eaglescout526 said:

Both would indicate open loop but I would test for both just to see what we could be looking at. And let me know on that tool kit and ill see if I can hunt down a semi cheap kit to add a pressure gauge to mine. 

 

Also the injector is not supposed to have more than 10 Ohms of resistance.

Sorry, I mean how do I check? Neg battery post and Fuel pump relay circuit pin 87? Remember, I'm a novice when it comes to knowing how to test for stuff. 

[eaglescout526]

10 minutes ago, SoCalManche said:

Sorry, I mean how do I check? Neg battery post and Fuel pump relay circuit pin 87? Remember, I'm a novice when it comes to knowing how to test for stuff. 

Right right right. My brain is going a mile a minute. But we can confirm that jumping the relay causes the pump to run, so we can test the voltage and see if we are seeing 12V or not.

Back up the line to 30 on the relay, it goes to a red fusible link.

Then 86 on the relay goes to splice "B" which is a yellow wire all the way to splice "E" then splice "D" to the ignition switch. I wonder what T3 shows at the ECU connector? 

Splice "B" also shows to go to D1_2. 

 

Looks like the MAP and TPS share the same 5V circuit from the ECU. 

 

Ill admit, I'm learning right here with you.

[SoCalManche]

1 hour ago, eaglescout526 said:

Relay, solenoid, they do the same thing. Man 86 is an animal that's for sure. On the side of the TB is an allen head bolt snugged away by the fuel lines facing the drivers side fender. If you can manage to find a pressure gauge to fit that port you can see what the fuel pressure looks like. Have you seen any fuel leaks around the TB area?

Just got back and the fuel pressure at TBI is 15PSI when I throw the jumper wire in there.

[SoCalManche]

34 minutes ago, eaglescout526 said:

Right right right. My brain is going a mile a minute. But we can confirm that jumping the relay causes the pump to run, so we can test the voltage and see if we are seeing 12V or not.

Back up the line to 30 on the relay, it goes to a red fusible link.

Then 86 on the relay goes to splice "B" which is a yellow wire all the way to splice "E" then splice "D" to the ignition switch. I wonder what T3 shows at the ECU connector? 

Splice "B" also shows to go to D1_2. 

 

Looks like the MAP and TPS share the same 5V circuit from the ECU. 

 

Ill admit, I'm learning right here with you.

Didn't really understand this, ha. Well, I understand what you're saying, I just don't know how or what I'm testing for.

[eaglescout526]

Ok pressure is good, pump is good. That takes care of the fuel system as far as delivering fuel. What is the number for that pressure gauge kit so I can hunt one dow if you don't mind me asking?

 

Your guess is as good as mine for the fusible links. Its all in that electrical diagram I posted in thirds. I would imagine the splices would be soldered pieces of wire in the harness.

 

T16 on the ECU is the 5V supply for TPS and MAP.

 

D1                                                D2

 

4    1                                     3   6   9   12   15

5    2                                     2   5   8   11   14

6    3                                     1   4   7   10   13

 

 

Which pins are you jumping on the FP relay? 30 to 87? That will rule out the fusible link for that area if you are jumping those two.

Were just looking for voltage of some kind, not resistance.

[Ωhm]

 

[SoCalManche]

7 minutes ago, eaglescout526 said:

Which pins are you jumping on the FP relay? 30 to 87? That will rule out the fusible link for that area if you are jumping those two.

Were just looking for voltage of some kind, not resistance.

Yes, I throw the jumper on pins 30 and 87 to turn on the fuel pump.