2.7l Will not start when hot - ANY ideas?

Has anyone found a fix to the problem? i have a 96 tacoma 2.7 4x4 and it will not start after being warm 10-20 minutes after i turn the truck off. it is a really annoying problem. please help !!!!

 

I have a 98 doing the same thing. I have replaced a faulty MAF, 2 new coils, wires, plugs and a bad cam position sensor. It cranks better still not cranking correctly. My thought is leading to a faulty CPS, because after a non start I can hear what sounds like a low humming like the FP is running partially(if that make sense)after may attempts the fuel pump will pump really hard like it actually should then within 3-4 attempts it will rumble to life and run perfectly fine until the next time I shut it off. It cranks fine when cold. I think that after the engine is off(hot) the CPS resistance drops and won't send a proper signal to the ECM to turn on the FP. I'm about to go out and replace it to see if it makes any difference. I replaces the CTS(broken and fell apart) earlier today and it does crank easier but still not correctly.

 

My isuzu trooper used to do this. There is a fuel regulator that keeps pressure on the injectors so they can shoot fuel in while starting, then the fuel pump catches up and resupplies the regulator...so when that regulator gets old, the edges of the seal on the accumulator get worn, and when hot, the fuel expands and gets thinner and leaks past. Then it sits in the line by exhaust and gasses off, putting pressure into the fuel tank, causing it to vent. that's what you smell. So now not only do you have no fuel pressure while starting, your pump then starts pumping and the air pocket goes up towards the injectors. Long story short I replaced my regulator and it solved the problem.

 

Did you mean that you replaced the CPS(Crankshaft position sensor)?

 

I have replaced the regulator and checked the fuel pressure neither of which solved my problem. I have also replaced the fuel filter.

 

I only have one question "what is the fuel pressure" ? No I don't want to hear yeah I got plenty of fuel, PSI only. That is the very first thing that should be checked with any hard start or running issues it is the only thing that has a constant every thing else changes and they can not not work properly with screwed up fuel pressure.

 

Mine was in the ok range of 38-44psi, page EG-125 of the service manual. It sucks that Toyota did not use a schrader valve on the fuel rail, but requires a special banjo bolt and fitting to check. Low fuel pressure can also cause a lean condition at WOT(wide open throttle). This can bee seen by looking at the upstream O2 sensor voltage.

I still cannot believe that a Toyota tech has not posted a fix for this problem. I have seen many trucks with this problem and I am sure that Toyota techs know what is going on. My fix(switch/resistor) is more of a work around than a fix.

 

I found my problem. It was the fuel pump and a bad ground (body to engine ground). It was more the fuel pump. The pump would have about 42 psi the first time I cranked it up in the morning, but after it was driven for a little while it would not crank until I had almost completely killed the battery. It started throwing lean condition codes as it got worse, I've had the fuel pump for a couple months and said it can't be the problem because it had good fuel pressure and would run perfectly other wise. So for chits and giggles, I put the pressure tester on the fuel rail when first starting it was around 42psi, then went for a drive to warm it up. I let the truck set for about 15 minutes and tried to crank it. It would crank and try to start, but upon checking the pressure after trying to restart and it only read 22-25 psi(which was not enough to activate the injectors) after continuous cranking it would eventually build up enough pressure to sputter to life. When it was up and running, the fuel pressure varied between 22-30psi and would eventually thrown a lean code. I replaced the fuel pump and cleaned all the grounds(the rear body to engine ground on the back of the motor was almost completely rusted away @ the rear of the engine) on the truck. After that, the truck fired up perfectly. I took it for a test run and let it set for about 15 minutes and fired right up again. It's been 3 weeks now, the truck runs smoother, has more power and believe or not, gets better gas mileage. Don't make the mistake I made and buy the fuel pump and not install it first(the pump really gave no signs of improper functions on initial testing) , because throwing parts at it get's real expensive really quick. My only saving grace was that the truck now has almost 390k miles and has never had any real maintenance done to it other than oil changes and the occasional broken part(original owner neglect). So now, I have a nearly new truck after the last few months. I replaced coils, plugs, wires, crank and cam(the sensor was worn thru the casing and leaking oil through it) position sensors, fuel pressure regulator, fuel pump and filter, fuel pump relay, coolant temp sensor, engine temp sensor, MAF, injectors cleaned and tuned and a VSV.

 

Glad to hear that you found a fix to your hot start problem. Where was the bad ground that you found?

 

On the firewall that hooks to the block on the exhaust manifold side.

 

I've been suspicious of the fuel pump for a while now, too. Although I'm not experiencing this as often as last year, when it did happen I tried holding the pedal to the floor. Instead of trying to start, it just quit trying. When mine acts up, it's as if it's getting some fuel but not enough. When I held the pedal down (clear flood mode), it got nothing. Distinctly different sound. It's always had plenty of spark.

I've been looking at a Denso fuel pump and might just bite the bullet and install it. The only thing I can't figure out is how messing with the IAT seems to resolve this issue. Then again, I've simulated excessive IAT temps (175 F) at normal ambient temps using a potentiometer and the truck started just fine. I'm still thinking fuel evaporation/vapor lock, which can be aggravated by low fuel pressure, ethanol, and cheap gas (I've also been using better quality gas). My only guess is that at lower IAT temps, the computer opens the injectors longer. Colder weather = greater air density = higher fuel requirement. Remember too that the IAT is used only in open loop.

If I replace it, worst case I'll have a new fuel pump on a nearly 20 year old vehicle. I've certainly seen plenty of electric fuel pumps fail at that age or less...

trx125, how big of a job is replacing the pump? Other than the pump kit with strainer and the tank gasket, what else is needed? How long did it take you? It looks pretty simple. Anything tricky to look out for?

As far as the damaged ground, I'd be surprised if that had anything to do with it. Grounds are redundant and my guess is the fuel pump has it's own ground on the connector/wiring harness rather than relying on chassis ground for such a critical component.

 

Took about an hour or so to replace the pump. I took out the front 4 bolts that hold the bed on and loosened the last two at the very back. Cut a 2x4 that was just long enough to reach from the middle of the front of bed to the floor jack. I wedged the 2x4 in between the drive shaft and the muffler and jacked the front of the bed up and braced it off with blocks in between frame and the bed. This gives you enough room to access the fuel pump from the driver's side and put it all back afterwards. I purchased a Denso pump kit off ebay.

 

Nothing tricky, pretty straight forward job. Unplug the harness, undo the fuel lines(cap off to keep dirt out), remove the 8mm bolts, lift out pump assembly and reinstall in reverse order.

 

Thanks for the pic. I hadn't even considered lifting the bed to gain access to the pump. Not sure if I'll do it that way or just drop the tank. We had some warm weather today and although my truck started, it was struggling in the heat. I think I'm going to replace the pump soon.

 

2004 Tacoma, 2.4, AT, 22287 miles. Engine turned over but would not fire off on a 70° April day in a Walmart parking lot. All fuses intact. Engine would briefly start after spraying starting fluid into brake vacuum hose. Towed to independent repair garage. Diagnoses was a deficient fuel pump.

$ 50 tow
290 replacement fuel pump and filter
234 labor
23 supplies
25 tax
$622

No previous issues . . just one of those "your turn today" situations.

 

Dang. That stealership prices?

 

Hi, has anyone found a solution to this problem? It is really frustrating!!

We have a 3.4L V6 (5vz) '98 Taco and we have generally the same problem as you guys. The unique thing about our problem is that it started when our engine was replaced. We burned a hole in piston #3 in December and had a reman'd engine installed, as well as a wideband O2 sensor (air/fuel ratio gauge) installed at the same time. The engine mechanic emailed us and told us the engine was in and running well, but now the truck had developed an excessive cranking/hard starting issue when it's hot. Has to sit for ~30-60 min after it was last brought to full temp, then the problem occurs. Starts great otherwise - cold, or 5 min after last running.

We've replaced:

Fuel Pressure Regulator
Fuel Pump
Fuel Filter
Starter
Battery
Crank Sensor
Cam Sensor
TPS Sensor
Coil Packs
Plugs
Plug Wires
Thermostat

We've tried the following known good used donor parts:

ECM
Igniter
MAF/IAT
Circuit Opening Relay
EFI Relay
IAC Valve

Injectors were serviced, 2 failing were replaced with rebuilt injectors.

We are about to try starter relay, charcoal canister, and ECT sensor.

If those don't work, thinking it's gotta be the tailgate or the steering wheel.

We've had 2 awesome mechanics COMB OVER the entire vehicle over the past 3 months, and they are running out of ideas. They have done a great job trying to diagnose properly but just haven't found it. I have researched this issue SO MUCH and I am amazed at how many people with all different types of Toyotas (from Corollas to 22REs and everything in between) seem to have some variation of this issue. It's crazy! We are getting ready to give up and just live with it, but it's tough to do after trying SO hard for SO long to get to the bottom of it. Especially when the truck didn't have the problem before the engine replacement. That's a real bummer, to have spent all that $ on the engine then have this new issue. Even though it does start every time, it still makes me nervous to take it out of town as long as the problem remains undiagnosed.

Anyway, I've tried to keep an eye on this thread lately and finally decided to say hello and see if anyone has any advice for us (other than to stop throwing parts at our truck!)

 

I would do this, also check all your grounds are hooked up.

 

Thanks for the reply! We replaced the ECT sensor this weekend, so far no change. You guys think it needs a good amount of time/driving to "recognize" the new sensor?

Also thought about just adding a ground wire. Existing ones have been checked/tightened/cleaned up/etc, but would there be any harm in just adding another one to see if any difference?