Hot Engine Won't Start (7 Viewers)

[05LX]

I have an '05 LX that I recently purchased. I've been going through and fixing some minor issues along with some regular maintenance items. My biggest issue is that the truck doesn't want to start when the engine is hot. Symptoms:
-Cold start, cranks right up
-Warm engine shut off for ~10 min, cranks right up
-Warm engine shut off for 20-30min+, fails to crank on first try, cranks right up on second try
-Runs perfectly, no CEL

The P/O was upfront about this issue during the sale and claimed to have narrowed it down to a leaking injector. This made sense since I've had a similar issue with the exact same symptoms on an older Yukon that was in fact, due to leaking injectors. He even gave me a new set of OEM injectors (unfortunately for 06+ engines) to swap out.

So I sent the injectors off to be cleaned/reconditioned. They weren't as bad off as I had hoped, and none leaked before or after the reconditioning. The issue is still present, no better or worse than before. Some other things I fixed/replaced while I was doing this:
-Injector seals
-Fuel damper
-Valve cover gaskets
-Spark plugs
-All vac lines replaced with silicone
-PVC valve and hoses replaced with OEM

What should I be looking at next?

 

[Kamran Khan]

Check your coolant temperature sensor is working properly and the temperature you see on the instrument cluster is the correct temperature of the engine. These engines won't start if the temperature goes to red line, and won't start until it cools off. Maybe that's good the engine isn't starting to prevent damage to the engine.
Second thing to look for is fuel pump, don't change the fuel pump before diagnosing it because you don't want to change parts before making 100% sure it's faulty.

 

[GOLIGHTLY]

Almost sounds like an old vapor lock thing but with a twist lol, weird.

If P/O had a leaky injector, does anyone know the electrical stuff well enough to know if a trashed O2 sensor or EGT sensor could cause something like this?

 

[Fairgame]

Engine hard to start when warm

2004 LX470 randomly hard to start when engine is warm. Changed the fuel filter, spark plugs and ignition coils with no change. No dash lights or codes. Any idea where I should go from here? TIA

forum.ih8mud.com

 

[Wheeliee]

I’m thinking it could be starter related. Does it just click when it doesn’t start or does it turn over and crank and crank and not start?

 

[05LX]

I’m thinking it could be starter related. Does it just click when it doesn’t start or does it turn over and crank and crank and not start?

No it cranks fine, it just won’t start. The LX does that thing where you can bump the key and it tries to crank for ~10sec or however long. If it’s hot and it has sat for 20-30min+, it will crank but not start during that first cycle, then immediately start when I crank it a second time.

If I’m right on the time threshold of where the issue starts (~20-30min) it may stumble and try to start at the end of that first crank cycle, or even catch and start (roughly) near the end of it. Once it’s past that timeframe, it won’t even try to start during that first cycle, but always starts right up on the second try.

Almost sounds like an old vapor lock thing but with a twist lol, weird.

If P/O had a leaky injector, does anyone know the electrical stuff well enough to know if a trashed O2 sensor or EGT sensor could cause something like this?

P/O just suspected a leaky injector. The report I got back from FIS showed no leaks or spray pattern issues before or after reconditioning. They were actually in really good shape and probably didn’t need a cleaning, but at least now I know they are problem-free.

The Yukon would do it because that GM spider injector system was just a bad design, the poppets would get gunked up super easily and stick slightly open allowing fuel to drip in the cylinder(s) and vapor lock. Only difference is then it wouldn’t start at all, you’d have to wait it out. I did have to change out bad O2 sensors on it, but couldn’t say if it was directly related or just coincidence.

 

[GOLIGHTLY]

P/O just suspected a leaky injector. The report I got back from FIS showed no leaks or spray pattern issues before or after reconditioning. They were actually in really good shape and probably didn’t need a cleaning, but at least now I know they are problem-free.

The Yukon would do it because that GM spider injector system was just a bad design, the poppets would get gunked up super easily and stick slightly open allowing fuel to drip in the cylinder(s) and vapor lock. Only difference is then it wouldn’t start at all, you’d have to wait it out. I did have to change out bad O2 sensors on it, but couldn’t say if it was directly related or just coincidence.

Ah ok, my brain was going to older domestics with clogged returns, fouled up reference circuits etc. Doesn't hurt that those injectors are mint now though lol

 

[Wheeliee]

No it cranks fine, it just won’t start. The LX does that thing where you can bump the key and it tries to crank for ~10sec or however long. If it’s hot and it has sat for 20-30min+, it will crank but not start during that first cycle, then immediately start when I crank it a second time.

If I’m right on the time threshold of where the issue starts (~20-30min) it may stumble and try to start at the end of that first crank cycle, or even catch and start (roughly) near the end of it. Once it’s past that timeframe, it won’t even try to start during that first cycle, but always starts right up on the second try.

Gotcha, the only other thing I’m wondering if you have a failing or dirty cam or crank sensor that may be acting up when hot. Like it’s needing to see a few rotations before it fires up. For s***s and grins I’d pull them and clean them off as they can get dirt build up on them. But that’s a WAG. And you aren’t seeing any codes which is baffling. I will say on other cars I have dealt w injectors on I have had reman and serviced injectors be leaky or bad on me right out the box. Are you able to put a pressure gauge inline to see after initial prime if the rail can maintain fuel pressure? Cause if it drops off you definitely have a leak or it’s losing pressure back to the tank and you have to reprime it again.

 

[05LX]

Gotcha, the only other thing I’m wondering if you have a failing or dirty cam or crank sensor that may be acting up when hot. Like it’s needing to see a few rotations before it fires up. For s***s and grins I’d pull them and clean them off as they can get dirt build up on them. But that’s a WAG. And you aren’t seeing any codes which is baffling. I will say on other cars I have dealt w injectors on I have had reman and serviced injectors be leaky or bad on me right out the box. Are you able to put a pressure gauge inline to see after initial prime if the rail can maintain fuel pressure? Cause if it drops off you definitely have a leak or it’s losing pressure back to the tank and you have to reprime it again.

That's my next move, hook up the fuel pressure gauge and the scanner so I can see what my pressures and trims are doing. I'll report back.

 

[2001LC]

I have an '05 LX that I recently purchased. I've been going through and fixing some minor issues along with some regular maintenance items. My biggest issue is that the truck doesn't want to start when the engine is hot. Symptoms:
-Cold start, cranks right up
-Warm engine shut off for ~10 min, cranks right up
-Warm engine shut off for 20-30min+, fails to crank on first try, cranks right up on second try
-Runs perfectly, no CEL

The P/O was upfront about this issue during the sale and claimed to have narrowed it down to a leaking injector. This made sense since I've had a similar issue with the exact same symptoms on an older Yukon that was in fact, due to leaking injectors. He even gave me a new set of OEM injectors (unfortunately for 06+ engines) to swap out.

So I sent the injectors off to be cleaned/reconditioned. They weren't as bad off as I had hoped, and none leaked before or after the reconditioning. The issue is still present, no better or worse than before. Some other things I fixed/replaced while I was doing this:
-Injector seals
-Fuel damper
-Valve cover gaskets
-Spark plugs
-All vac lines replaced with silicone
-PVC valve and hoses replaced with OEM

What should I be looking at next?

First terminology. Crank/cranking. Is when we turn IG key to start engine, and we hear/see the engine (crank shaft spinning) turning-over (cranking) at a normal cranking speed (about 250RPM). This does not mean it started, just that it's cranking. A cranking no start, indicates starter is good.

Crank no start (engine turns over (spins), but will not start), is very often fuel related. Which can be fuel circuit, fuel pump, immobilizer are most common.

Long crank to start. Is most often excessive fuel injector leak down rate.

Long crank, can be spark related. Crank sensor or it's wire. Cam sensor or it's wire. Even a bad MAF could be involved.

Hot soak TSB 05-07 should give a CEL w/DTC P0335 and/or P1340 crank shaft DTC, confirmed. But may just be pending, so needs scanning for as condition happens. Is a, camshaft position sensor issue giving a crankshaft DTC. Toyota updated the replacement sensor.

 

[05LX]

First terminology. Crank/cranking. Is when we turn IG key to start engine, and we hear/see the engine (crank shaft spinning) turning-over (cranking) at a normal cranking speed (about 250RPM). This does not mean it started, just that it's cranking. A cranking no start, indicates start starter is good.

I didn't even think about that when I was typing it up, but yes, I'm only experiencing a crank no-start condition. No issues cranking at any time, just the no-start when it's hot. I'll check out that TSB.

 

[codyvanloon]

What happened? My truck is having the same issues

 

[xeuxaz]

Fuel pressure good? Pump would be next on my list.

 

[ftbshop]

Watching. Have a similar issue on my 00 where if it hot soaks for 20 to 30 minutes, it will sometimes fire, fail to catch idle and die. Runs perfect on the second start. Have replaced fuel pump with an OE Toyota already, no change

 

[05LX]

Finally have some time this weekend to work on it again.

Fuel pressure is good, but stays at 44psi regardless of if I remove the vacuum hose off the FPR. I can apply vacuum to the FPR and get the pressure to drop. There is zero vacuum at the FPR port on the intake. Fuel pressure drops almost immediately when the engine is cut off, and does so much faster once it’s warmed up.

So now I suspect a vacuum issue and possibly the check valve in the fuel pump? Going to continue to dig into it further.

 

[05LX]

Finally solved it:

Fuel pressure was not holding after the engine was shut off, so I suspect the check valve had failed. When I went to access the pump, I saw signs of someone else having removed the seats and whatnot before. A PO had replaced the pump and fuel level sender, and used the crappy Delphi pump (probably the same wonderful person that decided to paint half the seats, that was a blast to remove).

I replaced the entire fuel pump assembly with OEM except the level sender and out of an abundance of caution, also replaced the FPR with OEM even though it appeared to be functioning normally. I read several reports of bad FPRs killing fuel pumps, mine was definitely original, and an extra $60 was not worth the risk.

I just got back from a ~2000mi trip and had zero issues, so I'm pretty confident that I have resolved this. I only found one other post linking a bad check valve to a hot-start issue and had to dig deep for it, so IDK if this is really uncommon or just not discussed, but hopefully this helps someone diagnose their issue.

Also, DONT BUY THAT DELPHI PUMP. I get it, its a third or a quarter of the price, but you get what you pay for.

 

[spaldam]

I had a shop replace my fuel pump, and now this same issue is reoccurring about a month later. I'm suspicious of the fuel pump they put in it now.
I'm also finding people talking about a possibly issues with the fuse box under the hood. Has anyone else experience problems with the fuel box?

PN: 82720-60022

 

[Patron100LC]

Sadly, since Denso discontinued the fuel pump we used to be able to get for $100 or so, replacing it with OEM as a PM became expensive, but carrying one as a spare on a long trip is a pretty good idea.
Not easy to diagnose since a pump issue might not throw any codes, and can be similar to a bunch of other issues as mentioned before, like injectors, fuel regulator, or even a filter.
Same as electrical like cam or crank sensors and Maf.

I’d like to add, mostly for future reference, that I did have a pretty similar issue with mine, and wasn’t related to Any of these issues.

My 2005 LC did it once or twice a day, where it didn’t start on 1st attempt like always, but it will crank for a second or two and not start, only until 2nd attempt.

It bothered me but couldn’t think of the reason it did it, since it didn’t feel like starving for fuel, it felt like my starter auto start feature we have on the newer 100’s was acting up by cutting off mid start.

Well… after a couple weeks contemplating a starter job, I removed an OBD dongle I used for Torque App on a tablet I have semi permanent on my dash.
Guess what? All good again for several months.

No idea what this OBD thing did to my electrics, but the starter or other electrical equipment was acting up while it was installed. Didn’t put it back since, if I use it in the future it’ll be for a specific diagnose or to monitor temps on 1 trip, not as a permanently installed device.