I have a starting problem with my stock 1985 C4. The car does not like to start cold. Cranks fine. Will run after being cranked sveral times. Runs fine. Yesterday I took out the 5A fuse labelled "crank". Now it start not problem. Runs fine. I think i may need anew thermo time switch. Any help would be appreciated.

 

You're not making any sense. Or at least I'm not understanding you.

You took out the "Crank" fuse and what ?? Was it blown? Did you just leave it out? What? Explain. I assume you have a shop manual to have known that fuse was the voltage source for the cold start injector which it is.

Since this fuse is burried behind the dash on my '86, I would hope that you used a voltmeter to first verify no voltage at the engine side before you even bothered to take the dash apart to check it.

"Now it start not problem"

What are you trying to say? That now it starts fine cold? If so then why are you asking if you need a thermo switch? If it starts up fine cold then obviously not. Those things aren't cheap and it would be stupid of you to just toss one in there just guessing.

If you suspect an inoperable cold start system start by unpluging the cold start injector. Connect a noid light to the plug and crank the car when cold. The light should stay light for the same amount of time that the starter is spinning. When this same test is done with the engine hot the noid light should not come on (thermo switch open and not grounding the brown injector wire). This is what
is supposed to happen when everything up to the cold start injector connector is working properly.

You can pick up a noid light kit at Autozone for rent or purchase.

Part# 27161




Harbor Freight also sells a good noid set.

Item# 97959

http://www.harborfreight.com/11-piec...set-97959.html

 

I'm sorry for not being clear. It was clear to me.

The crank fuse was not blown when I removed it. The engine starts when cold with no issue when the crank fuse is pulled out. The car does not want to start with the fuse in place when cold. The car runs fine with or without the fuse. It starts easier without the fuse.

 

Do you have the wiring diagram? I'm going by '86 wiring so I don't know how different '85 is on this.

The Crank fuse is the main voltage source that feeds the thermo switch and cold start injector. Without the fuse there is no voltage supply to both of those plain and simple. Unless your wiring is different the opposite should be true.

If you get a noid light on the cold start injector plug and crank the car with and without the fuse you'll know for sure if that's really what is happening at the injector plug.

 

85 is the same as the 86. Power feed is from the starter interrupt relay through the crank fuse to the cold start injector and the thermo-time switch. There is no way the removal of the crank fuse could/would allow the car to start easier unless there are other things happening.

 

Yes the true voltage source originates from the ignition switch through the starter enable relay first to be exact.

The Crank fuse is what allows or breaks that feed to the cold start injector and thermo-time switch. The time switch is simply a temperature controlled ground switch on the Tan ground wire of the injector. Closed to ground when cold (injector sprays on crank as starter spins) and opens when hot (no ground no injector spray on crank). The purple voltage feed wire always gets voltage in the forward crank position weather cold or hot. It's the switching on/off to ground by the thermo-switch on the Tan ground wire that allows for the cold start enrichment spray.

So I can't see how no fuse would be making the cold start work. Before you go buying parts you don't need that is why I suggested a noid light test at the cold start injector plug with and without the fuse to verify that's actually what's really happening. If it's not you're wasting your time looking in the wrong area.

If '85 cold start is the same as '86 then this is how it's wired.

 

So what if the Start Injector is Dumping way to much Fuel and is Fooding the Engine? Yea I know Cold Engines love lots of Fuel but its an Idea.

 

If this was happening then disconnecting/reconnecting the cold start injector directly instead of the fuse/no fuse should have an identical effect. If it does I would then look into this as a possibility.

 

Looking at the schematic, it appears pulling the fuse or the cold start injector connector would have the identical effect - basically deactivating the cs injector.

It sounds like there are other leaking injectors and when the cold start injector actuates it is flooding the engine when "cold".

I would put a fuel pressure gauge on the rail and check how quickly the fuel pressure bleeds off after the 2 second pump cycle or after engine shutdown. I'm betting it drops like a rock.

 

Def sounds like too much fuel to me. The cold start injector actuating puts it over the top and killing the power stops the extra fuel from entering an already too rich system. Test yer injectors and post up the results.

 

Let us not forget the palmetto bugs....... You can saddle them and ride em...