Intermittent No Crank

[Broosedamoose]

I've been having this issue for about 4-5 weeks and can't track it down! The truck will be starting fine but then I'll go to start it and it won't crank. Let it be for a bit and it will crank. No rhyme or reason to it. Does it when it's cold, does it when it's warmed up and it doesn't matter what the outside temp is. It hasn't happened for a couple weeks now but I used the truck all day yesterday and it was fine. Went to start it today and it won't crank. The last time it happened I drove to my doctors, went in and when I came out, it wouldn't start! Had it towed to the garage and it cranked as soon as he tried it! Thought it may have been the Neutral Safety switch so we replaced it. It's been fine for a couple weeks but I just went to leave and it won't crank! The starter was replaced about four months ago. It's not the PATS. Battery has 12.4V. I can hear the relay at the passanger side kick panel clicking when I turn the key. I'm not sure what else it could be. Of course my mechanic is on vaccation until the 26th. Any ideas?

 

[superj]

when it does it, have you popped the hood and wiggled the wires at the battery?

just wondering if the wires are a hair loose or maybe have a bit of corrosion built up at the terminals?

 

[RobbieD]

when it does it, have you popped the hood and wiggled the wires at the battery?

just wondering if the wires are a hair loose or maybe have a bit of corrosion built up at the terminals?

^^^ That, and especially check the small S wire (Red/Lt Blue?) on the starter relay for "clean and tight".

 

[RonD]

2007 4.0l Automatic

Try shifting to Neutral and see if it cranks
You changed DTR sensor but could be a loose column shifter, so not moving DTR full into Park every time

There is no Starter relay in SJB(passenger side kick panel)
Starter relay is in the engine fuse box
But key turned to START usually cuts power to cab systems so a relay could be clicking off in SJB

Starter Relay in Engine Bay fuse box should have this pin/slot layout: https://www.gtsparkplugs.com/images/mini-automotive-relay-wiring-840x.jpg

Next no crank pull out this relay
Key on, in PARK
Use a jumper wire to connect slots 30 and 87 together, momentarily, that's what the relay should do when key is turned to START
Starter motor should activate and engine should start

If you hear the starter motor's relay/solenoid "click" but starter doesn't spin then yes could be a problem with larger battery cables, positive or negative
Or starter motor itself


If jumping 30 and 87 works to start the engine then replace the relay with a new one
If that doesn't fix it then its an issue with cab wiring
Starter Relay is not getting 12v at slot 86 or no ground on 85(PATS) with key turned to START


IF...........starter motor activates but engine doesn't start(key on) then it IS a PATS issue, fuel injectors are off line

 

[Broosedamoose]

I've checked the wires and they are all good.
@RonD, I'll run through this and see what I get. I can't say for sure but I'm 99% sure my mechanic checked the relay and it was ok. I also tried wiggling the shifter and putting it in neutral.

 

[RonD]

Jumping 30 and 87 isolates the two sides of the systems

Key---cab wires---PATS------30/87-----starter motor---battery cables

So like a 50/50 test on what side of the system is intermittent

And if jumping 30 and 87 works then you don't have to tow it home, lol

 

[Broosedamoose]

I tried listening for the relay and it's not pulling in. I tried jumping slots 30 and 87 and nothing happens. Of course, after the move, I can't find my meter anywhere so I couldn't test for voltage. But there is something weird going on. The PATS light was not flashing yesterday or this morning but when we were out there earlier it started flashing. I just went out there to see if it was going to start and the light is not flashing anymore! How is that possible? I don't see how it would be ok one minute, bad the next and then ok again. Looks like I'm going to have to get her towed in to my mechanic. Before I do though, is there anything I could do with FORScan that would tell me something?

 

[Broosedamoose]

And if jumping 30 and 87 works then you don't have to tow it home, lol

Thank God it happened at home this time! But it looks like I will need a tow to the garage.

 

[Broosedamoose]

I found my meter and started testing. I'm getting 12V at the relay but nothing at the starter. I hooked up the laptop and FORScan shows no DTC's. So it seems the issue is somewhere from the bottom of the relay socket to the starter connection. I'm thinking there is corrosion on the bottom of the socket. I'll have to pull the junction box to look underneath.

 

[Broosedamoose]

I called that one right! turned out to be a lot of corrosion under the engine fuse box and the wire going to the starter corroded right off. Cleaned it up as best I could but the whole box needs to be replaced. That's gonna have to wait for the weather to warm up though.