2003 LC100 Hot Starting Issue

[Runge92]

I have an issue that has stumped two shops and now need to turn to the experts.

About a month back, my 2003 LC100 (104K) starting experiencing issues starting hot. For example, in the morning (cold engine) you can put the key in and it will crank right up without issue. If you run it a bit and then stop for some gas forget it. It will turn over without issue but not start. It doesn't even start to catch. I will continue to turn it over for about 10 seconds or less waiting for a couple of minutes between attempts until it starts up and runs without issue. Once started, it doesn't have any noticeable issue. You just can't turn it off!! The issue is extremely consistent i.e. every time I'll stop for gas or shut it off for more than a couple of minutes ...I'm sunk..

The first shop kept it a week ... kept telling me nothing was wrong... and then finally reproduced the issue and changed the fuel pump and filter.... fix lasted less than 8 hrs

The second shop has had it a week (Toyota) and has reproduced it only one time...they once again can't find anything wrong based on the computer feedback

Any ideas??

 

[overhanger]

For the 3FE, this was always related to the fuel pressure regulator going bad. Replace the FPR, in a 3FE, and the problem disappears. I'm too new to 100s to know if the solution applies here, though.

 

[NMuzj100]

FSM DI-23 Problem Table says to check the following for Hot Engine (Difficult to start).
1. Starter Signal Circuit DI-141
2. Fuel Pump Control Circuit DI-121

The starter signal circuit tells the fuel system to add fuel for hot starts for a rich mixture. Need a Toyota Scan Tool to read the signal.

 

[Runge92]

Thanks for the ideas...I recieved a new bit of information that's unexpected
my local Toyota shop called Toyota corporate and they state the issue resides either with 1) the ignition switch not reconigizing the key (requires replacement of ignition switch) or 2) the computer doesn't recognize the key.... they state the key isn't the issue
Does this sounds logical??

based on symptoms to date I'm not convinced...

 

[Kenso]

I would think if it was related to the security/immobilizer system, the security light on the dash would continue to flash when the key is inserted and the problem occurs. Something to observe next time it occurs maybe. I know on Hondas the key receivers will fail occasionally, haven't ever seen it on a 100 but seems plausible.

 

[DWNUNDR]

any thoughts on crank or cam sensors??

 

[NMuzj100]

I can't see the key issue being heat related unless there is a heat caused short.

Does the security light (key shape in center dash) react the same cold and hot?
Is there an aftermarket security system on the truck ?
Do you have other smart keys on your key ring ?

 

[PJCB]

Try your spare key and see if that makes a difference - might well be transponder related. I know of several cruisers which had intermittent starting issues due to the transponder in the key failing.

 

[sleeoffroad]

Next time this happens, try pressing the gas pedal all the way to the floor before you start it and then keep it there until it starts. We have seen these trucks flood themselves when you drive them for short distances and turn them off.

 

[Runge92]

Thanks for all the sugguestions...I'll try them this weekend
answering questions from above
1) Security System is standard Toyota
2) I used the alternate key without any change in symptoms for about a week...doesn't seem to be related to the key
3) I did notice a difference a couple weeks back by pushing the gas pedal to the floor a couple of times which seemed to help it start.... The solution has not seemed to make a difference for the past two weeks

 

[agaisin]

OK - I am admittedly talking out of my ass, but based on the symptom you describe and searching, here are some other ideas:
1) Vapor Lock? Not sure what can really be done to prevent this.
2) Bad Cold Start Fuel Injector (or associated electrical component)? Does the LC100 have a cold start injector? I just see numerous threads where the cause of hot start issues was related to the cold start injector. Not sure if it's relevant to LC100s.
3) Ignition Coil - saw people describe hot start issues that could be due to bad ignition coils.
4) Bad Engine Coolant Temperature Sensor. Apparently if the sensor is bad (at least for other vehicles) the computer thinks the engine is always cold and the air/fuel mixture is too rich to warm start but ok when cold.
5) Bad EFI Main Relay - apparently common problem in hondas that would cause hot start issues. Not sure if it's relevant here.

I realize I'm just throwing ideas at the wall to see what sticks...

Also curious - what temperatures and altitude are you driving in when you have the issue (and in general)?

 

[scottm]

I've had this exact problem on an Audi, it was the crank position sensor. I'm not sure where that is on a 100, maybe it uses the cam position sensor?

On my Audi I would pour cool water over the sensor after stopping for gas and it would start right up, maybe there's a way to cool the offending sensor to see if that makes the difference.

This is the cam position sensor, under the driver's side timing belt cover.

 

[sleeoffroad]

3) I did notice a difference a couple weeks back by pushing the gas pedal to the floor a couple of times which seemed to help it start.... The solution has not seemed to make a difference for the past two weeks

Just keep it pressed all the way before start and during cranking until it takes.

 

[sleeoffroad]

Also, replace the EFI fuse. We had a customer that had a similar issue and it turned out to be a hairline crack in the efi fuse. Just trowing up weird ones that might be the culprit.

 

[scottm]

If it's flooding it could be leaking injectors. After shutdown they dribble fuel into the cylinders until the fuel rail runs out of pressure. It takes a while for the fuel to drain past the piston rings and clear, so it seems like it goes away when the engine is cool. It also rinses the oil off the piston rings and cylinder wall, causing more rapid wear on startup.

This seems less likely as it should start rough initially as the flooded cylinders clear, but you didn't mention that.

 

[Runge92]

I wanted to close the thread out with the solution but also wanted to thank everyone for the very helpful information.

The problem ended up being with the EFI Main Relay. I replaced it ($79) and no problems for 2 months.

Once again thanks for the help.

 

[overlandish]

I am having this exact same issue right now. Hopefully it is something as simple as a relay! Thanks for the easy to find post. - Daniel