Hello all. So my 86 IROC just suddenly started cranking and not starting. I checked to see if I was getting fuel and it is, I checked for spark and its got spark. So I decided to check my fuses for the hell of it and found my crank fuse blown. I replaced it and tried starting it again and she just kept cranking. I rechecked the crank fuse and sure enough it was blown. I checked all the wiring to the solenoid and it all looks fine, (as suggested by youtube.) I'm looking for any help for places to look to find the problem. Any help at all would be grately appreciated!!

 

If the Engine that originally came in your vehicle was a TPI Engine...

Then the Crank circuit is only used for the Cold Start Fuel Injector circuit (often referred to as the 9TH Fuel Injector).

There is an issue in that circuit; high resistance of the Cold Start Injector will definitely draw more current than that minuscule Fuse can handle.

 

Ty for the quick reply! Its still TPI but I put a 350 in it after the 2nd 305 blew up in it. Shouldn't make a difference right?

 

This might help; The schematics are from 87 but they should match your 86. My Guess,.. a bad Cold Start Switch.

* To start: Disconnect your cold start injector AND Switch, install a good fuse and turn the key to START---> The fuse should not blow out. If it DOES - then you have a short on the Cold Start Circuit somewhere on the Injector or Switch's plug itself or in the harness somwwhere. Reconnect the cold start Injector Switch and turn the key to START; If the fuse blows than you confirmed the Cold Start Switch is causing the problem; if it doesn't blow than reconnect the cold start Injector and turn the key to START to check the Injector.

This first image simply shows that the CRANK fuse will only get voltage when the key is turned to START. (The PURPLE wire feeding this fuse comes from the PURPLE Starter Solenoid Wire; meaning if the starter is turning over,.. the CRANK fuse should also have voltage.) With a helper turning the key to START,... the CRANK fuse, the Cold Start Switch, and the Cold Start Injector should all show battery voltage.



This image shows a bit more of the system: The Cold Start Switch is grounded to the intake when it gets screwed into place so the Switch should show GROUND when probed with a voltmeter. When the Cold Start Switch is WORKING it will send ground to the Cold Start Injector to activate it. ( you should probe the 2nd wire on the Cold Start Switch and the same color wire on the COLD Start Injector while a helper turns the key to verify GROUND. That's about it; the system is very basic and with a voltmeter and a helper it should be pretty easy to check these circuits.



Notice that the ECM does not control the Cold Start Injector set-up in any way. While this is true, I have read that the ECM DOES control the other 8 injectors at cold start-up so in a round-about-way so the ECM can still cause Cold Start problems too. There are some sensors that the ECM will look at to decide if the "cold start sequence" should be run or not. The primary sensor you need to consider is the ECM Temp Switch,.... this sensor is a 2-wire sensor that is mounted right next to the Cold Start Switch on the front of the Manifold.

You might perform this testing and all the wiring checks out - but there is still a starting issue. At this point you have verified everything is getting voltage and ground and that the Switch is working,.. but the Injector might not be actually working/operating. You'll have to at least perform some tests to the wiring itself before you should focus on the actual Injector operation. ( It should make an audible "click" when it gets power and ground.... you can "jump" power and ground from a battery to the actual injector plug and listen for this audible "click".)

You can have the cold start function entirely removed from your ECM by sending your '165' ECM to get Tuned . If you ever decide to 'tune' the ECM to remove the cold start I highly recommend: https://tunedperformance.org/ . Just be sure to tell Brian that I said "HI" ! ( he will treat you right. )

 

Hey, ty for the response. when I turn the key to on, the fuse doesn't blow. Only when I turn the key to crank the engine then the fuse blows. Don't know if that means anything worthwhile.

 

Yup,.. 100% as expected.

When you first turn the key and the instrument panels "wakes-up" the key is in the RUN position.

The fuse will only get voltage when the starter solenoid is active. ( AKA: when the key is turned to START )

 

I cleaned all wires and terminals. My brothere suggested it might be a bad ignition switch so he said to jump the starter then check the fuse, if it wasn't blown then its a bad switch. I jumped the starter and checked the fuse, it was blown so it shouldn't be the switch. Any idea where to go from here or where to look?

 

Any idea how to disconnect the cold start injector? Would that eliminate the problem? Or can I use a test light to check the circuit?

 

If you turn the key to START and the starter turns,.... the ignition switch CAN'T be your problem because the ignition is obviously sending voltage thru the Neutral Safety Switch and to the Starter + CRANK fuse as expected ( Starter turns and Fuse blows ). Start searching for your problem AFTER the fuse, not BEFORE the FUSE.

See Post #4; it contains ALL the info and schematics that you will need to find your problem. Follow the directions I wrote out for you and you can verify if the Switch or the Injector is causing your short. The directions are written so that you don't even need to know how to use a voltmeter to check them. ( AKA: if you disconnect the Cold Start Switch,..... turn the key to START and the fuse doesn't blow - the switch is the problem. ) If you test those 2 things and the fuse is still blowing when they are not connected, then you most likely have a short to ground on the PURPLE wire somewhere in your harness or 1 of the plugs.

1 thing at a time - start with the CS Switch, then the CS Injector.