Engine Won't Crank When Car Is Warm...why?

[jjeffri]

Howdy All:

 

It's been a while since I posted in here, mostly cause my Pathy has been doing pretty well for the past year. However, as the stars have aligned to give me car troubles, I am back to request help from the experts.

 

The problem: I drove my Pathy down the freeway for about 1 hour. I parked, turned off the truck, and went inside for about an hour. When I came out to drive away, I couldn't start the truck. When turning the key to "Start," I simply heard a clicking sound (like a relay), but the starter didn't engage. I tried jumping the truck, but nothing, the same clicking noise was the only indication that the key was getting to "Start." I called AAA and the tow truck driver came out after about an hour (about 2 hours since the engine had last been running). He asked what it sounded like, so I stuck the key in the ignition and voila, the truck started; pretty embarrassing. I drove the truck home, another hour up the freeway, and when I stopped the truck, I turned off the engine. I tried to start it a few seconds later, and nothing, just the relay clicking sound.

 

I've toyed with it enough to find out that it systematically doesn't start when the engine is "warm." It cold starts just fine, like in the morning or after sitting for a couple of hours.

 

Any thoughts? Maybe a problem with the starter solenoid or starter itself? I suppose the transmission interlock could also be faulty, but I wouldn't expect it to be so temperature sensitive.

 

Thanks in advance for any suggestions.

[unccpathfinder]

have you checked for corrosion at both the battery terminal and at the starter...and that the cable is tight at the starter...it could also be a bad spot on the solenoid? and after several attempts at starting it moves off of the bad spot and then starts? just throwing some ideas out there

[SaKaNa]

Mine was having some weird problems like that, I'd be running fine, I'd go to turn it off to go in a store... I go back to my pathy 5 minutes later, go to start -- cranks a weak one then dies. I try again, just a clicking relay. Turned out my timing was way off on my timing belt...I dont know how it actually woks, but after having that fixed, I havent had the problem at all.

[jjeffri]

have you checked for corrosion at both the battery terminal and at the starter...and that the cable is tight at the starter...it could also be a bad spot on the solenoid? and after several attempts at starting it moves off of the bad spot and then starts? just throwing some ideas out there

 

There is corrosion on the battery terminals, although I'm not sure what the temperature dependence of that would do to starting the engine. I suppose if the alternator is humming along just fine while the car is running the current can just overpower the corroded contacts. I may try cleaning off the battery.

 

Haven't checked the starter. I think I have to get under the car to do all of that, and so far haven't had the time to borrow a buddies garage. Thanks for the suggestions.

[Zilverado]

There is corrosion on the battery terminals, although I'm not sure what the temperature dependence of that would do to starting the engine. I suppose if the alternator is humming along just fine while the car is running the current can just overpower the corroded contacts. I may try cleaning off the battery.

 

Haven't checked the starter. I think I have to get under the car to do all of that, and so far haven't had the time to borrow a buddies garage. Thanks for the suggestions.

It may be that the temperature issue is a coincidence, but I have read (and have experienced it myself) that these vehicles are quite sensitive to voltage when trying to start. So start by cleaning the battery terminals WELL, before going to the extent of replacing the starter, since it's a bit of a bear to do - especially on the 4wd.

 

I say this because, earlier this year, I had a similar problem. I suspected corrosion, so I took everything apart and wire brushed it. Still no luck. Battery measured a strong 12.5 volts at the terminals. So I was on the verge of replacing my starter. I tried one more time to boost the vehicle and whalla - - it started no problem every time.

 

I took the terminals apart again and this time used a light sanding drum on my rotary tool to clean them up. Put 'er all back together and haven't had an issue since.

 

So give it a try and see what happens.

[unccpathfinder]

voltage

 

should be amps correct? you can read 12v and not have enough amps to crank correct?...someone correct this statement if im wrong...i have heard this and witnessed it a couple of times...but dont really know the y behind it...i will assume that the resistance across the battery has somehow decreased with the amps decreasing as well resulting in 12V

[88pathoffroad]

Darnit 88, such a bearer of bad news

 

Any thoughts on repair time/cost?

 

When mine went, I ordered new brushes for it from a local parts store, then pulled the starter and rebuilt it with the new brushes in about two hours. Cost me about $7 IIRC. That's what usually wears out, the rest of the starter is mostly solid-state parts that don't move or wear excessively.

[adamzan]

When mine went, I ordered new brushes for it from a local parts store, then pulled the starter and rebuilt it with the new brushes in about two hours. Cost me about $7 IIRC. That's what usually wears out, the rest of the starter is mostly solid-state parts that don't move or wear excessively.

 

thats what my dad had the shop do to mine

[yozsi]

starter relays are also known to take a @!*%.

[87pathy]

The starter is usually shot when it fails when hot.

 

Get me to rhyme again, whydon'tcha?

 

won't start when hot??? ya, starter is caput

[Ultrafinder]

I just had this same problem on my 94'. a few months ago i found a corroded connection from the ignition. I just cut the connection out and that worked for a while then the problem came back. I installed a 30 amp relay and that definetly fixed the prob. for some reason Pathys need 12+ volts to start well.

[Geoff B]

Before blaming the starter, do some more diagnostic with a voltmeter. Check the voltage at the starter "s" terminal (the wire that engages the solenoid), or as close as you can conveniently get checking that wire. You must have a complete circuit (i.e. all wires connected) when this check is made. More often that not, it will be in the 8 - 10 volt range, which is too low to properly engage the starter solenoid.

 

What happens is that the 8-10 volts generates enough magnetic force to pull in the plunger in the solenoid (so you hear the solenoid pull in), but not quite enough to pull it firmly into the contacts that make the starter motor turn. Why is the voltage low? Too much voltage drop from a marginally engineered circuit. On a good day, everything works OK, but ANY shortcoming in the circuit or solenoid will cause the no crank problem. A slightly weak battery, corroded terminals, slight drag with the solenoid plunger, etc and it won't work. Heat only aggravates the problem more, causing a slight decrease in the effieciency of the circuit.

 

The solution is to add the commonly available Bosch relay mentioned in a previous post. This takes the strain off of the OEM starter circuit (which covers a huge distance and goes through many connectors and components) as the relay only demands .25 - .5 amps to operate, and then provides a full 12V battery voltage to the starter solenoid. I'm sure I can come up with a wiring diagram for the relay if anyone needs one.

 

I dealt with this problem about 8 years ago with my '95 Pathy, and numerous other pieces of construction equipment over the years professionally. Interestingly, it is usually a Nippon Denso starter application with the problem, so they seem to be very particular about having a full 12V to operate properly. In the case of my Pathfinder, the relay solved the intermittent no crank 100%.

[jjeffri]

Thanks for all of the suggestions. I had an autoparts store check my battery, they said it was good; and, since I've heard so many folks suggest the starter as the problem, I just bought a remanufactured one from the store. I first pulled the old starter to avoid the $100 Core fee, then turned in the old one and picked up the new one. Cost near $160. I have a 1996 Pathy, and y'all were right, that's a bear to get out, found it above the oil pan on the passenger side. I finally unbolted it, which is hard enough given all the other stuff in the way, and then wrestled with it to get it out for about 15 minutes. Finally, it just kind of fell out, I had no idea what rotations and contortions I did, but it fell out, so yay. The new starter went in relatively easy and seems to work. I haven't had time to drive far enough to really get the engine warmed up, at least not to the degree that I was experiencing problems before. Again thanks for all of the help.