'83 AMC Eagle SX4

[Eagle_SX4]

Spoke to soon. The car still doesn't turn off with the key. It worked for the first 3 times I turned off the car after the new alternator and now it is back to how it was before. Not shutting off with the key. The only way I can get it to shut off immediately is to press the e-brake after the car is off. But if I set the e-brake before I turn off the key, the engine doesn't shut off immediately. It continues to run for about 30 seconds.

[89 MJ]

So is it dieseling? My car occasionally has the same issue and it’s because I’ve got quite a bit of timing in it. Of course, that’s with a stock 258 with a carb and you’ve got fuel injection. 

[eaglescout526]

Alt isn’t back feeding anything is it?

[Eagle_SX4]

1 hour ago, 89 MJ said:

So is it dieseling? My car occasionally has the same issue and it’s because I’ve got quite a bit of timing in it. Of course, that’s with a stock 258 with a carb and you’ve got fuel injection. 

Yeah I am sure it is not dieseling. My dad's eagle diesels occasionally so I do know what that is like. I can rev it just like when the key is on.

 

I know it has something to do with the alternator circuit. I have separated all the positive leads near the battery and pulled them off one by one to see which wire is causing the issue. The only wire that lets the key function properly is when I disconnect the alternator wire from the battery. But that is not a good solution because then the battery would die pretty quick. 

1 minute ago, eaglescout526 said:

Alt isn’t back feeding anything is it?

How would I test that? I know after the key is off I still have 3 volts on the ignition circuit that eventually fades off after about 1 minute, but not immediately.

[Ωhm]

With KEY OFF and ENGINE RUNNING can you kill the engine by removing FUSES? Might help with what circuit(s).

[eaglescout526]

I know with my 84 there was the choke heater relay that the alt powered along with some other stuff that was spliced to the relay. 

[Eagle_SX4]

11 hours ago, Ωhm said:

With KEY OFF and ENGINE RUNNING can you kill the engine by removing FUSES? Might help with what circuit(s).

I know that if I remove the fuse for the computer it shuts off but I haven't tried any other ones. I will try some others tonight.

 

11 hours ago, eaglescout526 said:

I know with my 84 there was the choke heater relay that the alt powered along with some other stuff that was spliced to the relay. 

I will look into that because it is possible there is something else I need to remove from the eagles harness. I did already remove the carburetor/ignition computer and wire harness.

[Eagle_SX4]

On 3/10/2024 at 7:44 PM, Ωhm said:

With KEY OFF and ENGINE RUNNING can you kill the engine by removing FUSES? Might help with what circuit(s).

I pulled every fuse and wire out of the fuse block except the computer and it still doesn't shut off.

 

I moved the computer to the accessories circuit but that doesn't work because it doesn't maintain voltage on that circuit while cranking meaning the computer has no voltage and won't start.

 

The other thing is that after I shut the key off the alternator Indicator bulb illuminates and stays on while the engine is running and key off. Here is the schematic for that.

T7 on the second picture is the lug that bolts the the back of the alternator. I separated those wires and ran them both back to the starter relay. Which is where the + battery cable is located. If I remove either of those wires the car shuts off just fine, but doesn't charge the battery.

 

Any thoughts other than I got 2 bad alternators in a row?

[Eagle_SX4]

Got the "new" alternator tested today and if failed all the tests. So another one is on the way. Luckily the parts store is honoring the warranty and another one is coming but won't be here till next Wednesday. I will update when the new one comes in.

[89 MJ]

Hopefully that solves it!

[Eagle_SX4]

Thinking more about my problem I think I may have figured out what is happening. The 91-95 high output fuel injection system uses 2 relays to function. The auto shut down relay and fuel pump relay. Both those relays are triggered by the ignition switch. While the engine is running and the key is on the relays close the circuit for the computer and fuel pump giving them battery voltage.

 

So if you have a relay that was powered on by 12 volts but then only has 3 volts it is still enough to keep the relay triggered and full voltage going to the computer and the fuel pump. Making the engine continue to run after the key is off. 

 

My theory is that the alternators have both failed and back fed enough voltage on the ignition circut to keep those 2 relays open.

 

Guess I will find out when the new alternator gets here.

[89 MJ]

I know that you bought this car with this engine swap mostly completed, but would you do it again? My car is getting to the point that it will need an engine in the next few years (or this summer if I decide to take it to school) and I'm not sure the route that I want to go. 

I'm considering a 4.0 with either an AW4 or an AX15 and an NP231J swap, which would be the easier route, or I'll do an LS with a 5 speed and an NP241C. 

[Eagle_SX4]

@89 MJ the 4.0 in the eagle is awesome. I really like it especially with the fuel injection. I did a Cherokee tank swap because the sx4 and Cherokee tanks are almost identical but the wagon ones are different. The Cherokee tank might still fit however. 

 

An LS eagle would be awesome. I actually sold my sx4 tank to guy that has a spirit he shoehorned a big block Chevy 454 into. So an LS will have no problem fitting in there. 

 

Guess it just depends on how long you want your tires to last. I know that if I put an LS into my Eagle my tires would be gone very quickly.

 

But what ever you decide make sure you run fuel injection. Carbs can be made to work but fuel injection is so much easier to maintain and tune.

[89 MJ]

36 minutes ago, Eagle_SX4 said:

@89 MJ the 4.0 in the eagle is awesome. I really like it especially with the fuel injection. I did a Cherokee tank swap because the sx4 and Cherokee tanks are almost identical but the wagon ones are different. The Cherokee tank might still fit however. 

 

An LS eagle would be awesome. I actually sold my sx4 tank to guy that has a spirit he shoehorned a big block Chevy 454 into. So an LS will have no problem fitting in there. 

 

Guess it just depends on how long you want your tires to last. I know that if I put an LS into my Eagle my tires would be gone very quickly.

 

But what ever you decide make sure you run fuel injection. Carbs can be made to work but fuel injection is so much easier to maintain and tune.

Good to know, thank you. Any swaps will get fuel injection. 

[Eagle_SX4]

Well more alternator problems. The parts store ordered 2 more alternators in and both of them had bad bearings but tested good. My car still won't shut down even with a properly functioning alternator.

 

I went to a different parts store and ordered another alternator from them. It will be here tomorrow morning. Hopefully it tests good and has good bearings.

 

Found this forum post and I think it might be the solution I have been looking for. 

https://www.jalopyjournal.com/forum/threads/how-do-i-wire-a-gm-3-wire-alternator.30629/

It talks about using a diode on the switched ignition wire to stop any back feed voltage that the alternator puts out.

 

There is a simple harness available that adds a diode to the switched ignition wire. I ordered one and will see if that fixes my issue. It looks like this.

[Eagle_SX4]

I got the harness installed inline with the alternator plug and now my car shuts off like it should. 

 

This seems to be a common problem with the GM 3 wire alternators.

 

Also I got my new tires out on.

[89 MJ]

What size tires did you put on? 215/75R15? They look a little smaller than my 225s on roughly the same size lift.

[Eagle_SX4]

Yeah they are 215/75R15

[89 MJ]

They look really good!

[Eagle_SX4]

Yeah I am very happy with them so far. Although a little mad because I lost one of the hub caps somewhere on the road shortly after swapping out my snow tires. Luckily I have a spare.

[Eagle_SX4]

Got a '94 Cherokee fuel pump sending unit from the junkyard and got a Deatschwerks DW200 pump mounted on it with no modifications. I will be installing it on Saturday.

[89 MJ]

I’m back again with another question haha. I’m looking into doing a 4.0 head swap in the (hopefully) new future. I think I know what route I’m going to go for the intake, but how does the XJ header fit with the front diff? Is it a stock one and what year?

[Eagle_SX4]

The XJ header does fit the Eagle. It is further away from the engine block than the Eagles is. This creates 2 problems. 1st the diff hanger that bolts to the engine block is directly in the path of the header. 2nd the exhaust moves to the outside of the slave cylinder and you need to make a new heat shield or you will melt the rubber seals inside of it.(personal experience on that one).

 

As for the diff hanger you can just cut it up and weld it back together with a curved middle section that will then clear the exhaust. I will get some pictures of mine tomorrow.

[89 MJ]

21 minutes ago, Eagle_SX4 said:

The XJ header does fit the Eagle. It is further away from the engine block than the Eagles is. This creates 2 problems. 1st the diff hanger that bolts to the engine block is directly in the path of the header. 2nd the exhaust moves to the outside of the slave cylinder and you need to make a new heat shield or you will melt the rubber seals inside of it.(personal experience on that one).

 

As for the diff hanger you can just cut it up and weld it back together with a curved middle section that will then clear the exhaust. I will get some pictures of mine tomorrow.

Thank you! That's good to know, a picture would be great, but I'm not in any rush for one. Whenever you're under the car next would be fine. No need to crawl under it for me, but I appreciate it. And good to know with the heat shield. I am thinking my car might get an AX15 at some point.

[Eagle_SX4]

6 minutes ago, 89 MJ said:

Thank you! That's good to know, a picture would be great, but I'm not in any rush for one. Whenever you're under the car next would be fine. No need to crawl under it for me, but I appreciate it. And good to know with the heat shield. I am thinking my car might get an AX15 at some point.

Your welcome. The rest of the exhaust follows the original eagle routing I tried to use an XJ tail pipe on the passenger side but you would need to move brake lines and reroute the stock fuel line.