Having 3.4 Hot Start Issue

[UnderFire]

Alright, so we've been working on this for a long time and haven't made any progress. So I figured I'd ask for help.

The problem is on a 99 Tacoma, 3.4 auto. Basically, it starts and runs great, no problems the whole time it's running. Shut it off after it's hot and between 10 and 45 minutes after it will not start again. Just cranks, sounds like no fuel.

So far we've tried:

Cleaned and swapped TB
Cleaned and swapped IAC
Cleaned and swapped MAF
New TPS
New Coolant Temp Sensor
Swapped Different Injectors and FPR
Replaced lots of vacuum lines

Nothing's changed.

Stumped...

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[99problems]

Alright, so we've been working on this for a long time and haven't made any progress. So I figured I'd ask for help.

The problem is on a 99 Tacoma, 3.4 auto. Basically, it starts and runs great, no problems the whole time it's running. Shut it off after it's hot and between 10 and 45 minutes after it will not start again. Just cranks, sounds like no fuel.

So far we've tried:

Cleaned and swapped TB
Cleaned and swapped IAC
Cleaned and swapped MAF
New TPS
New Coolant Temp Sensor
Swapped Different Injectors and FPR
Replaced lots of vacuum lines

Nothing's changed.

Stumped...

Sent from my Z981 using Tapatalk

How's your fuel filter looking? If original, that would be a good place to improve the situation I would think.

 

[19963.4lsr5]

If you suspect it's fuel related shoot some starter in the throttle body. If still no run check for spark.

If no spark the ICM could be failing.


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[UnderFire]

How's your fuel filter looking? If original, that would be a good place to improve the situation I would think.

Forgot that. Did a tune up on the truck maybe 2-3k ago. Plugs, wires, fuel filter, air filter, all good. Also tried swapping the ECU out for another and it didn't change.

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[UnderFire]

If you suspect it's fuel related shoot some starter in the throttle body. If still no run check for spark.

If no spark the ICM could be failing.


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I should try that. I may try swapping out the igniter.

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[gamefreakgc]

Just cranks, sounds like no fuel.

Sounds like or has no fuel? Next time it happens, pull a spark plug immediately after trying to crank it over (have your tools ready). If it smells like fuel or is wet, you're obviously getting fuel but no spark. You can then ground the spark plug on the body and have someone crank it over (watch a video on this before trying) to see if you have spark.

If you have spark but no fuel, a sensor, wiring, or computer issue is keeping it from getting fuel. Often after a failed start you can hook up a code reader and it'll spit out a code. This happened to me when my MAF failed. I see you swapped the MAF, also check the wiring on the harness for any damage. The only sensors that I know of that cause a non-start is the crank sensor, camshaft sensor, and MAF sensor.

 

[UnderFire]

Confirmed today, no fuel. Sputters a bit, assuming burning what's left in the rails, then just cranks. Starter fluid in the intake starts it up fine.

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[19963.4lsr5]

Confirmed today, no fuel. Sputters a bit, assuming burning what's left in the rails, then just cranks. Starter fluid in the intake starts it up fine.

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There is a relay that controls the pump, plus a filter or the pump motor is failing.


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[Nate_GB]

You may want to check fuel pressure at the rail. It is my understanding that these trucks have a check valve in the fuel pump to keep pressure at the rail when the truck is shut off while hot. If the check valve isn't holding the pressure at the rail when the truck is shut off, then you'll have a vapor lock type of issue where no fuel will get to the rail until the truck cools down. As a disclaimer, some of this info is stuff I've read elsewhere so I haven't had personal experience with this issue. Seems like a reasonable explanation though for the problem you're having so it may be a good place to start.

 

[Unner]

You may want to check fuel pressure at the rail. It is my understanding that these trucks have a check valve in the fuel pump to keep pressure at the rail when the truck is shut off while hot. If the check valve isn't holding the pressure at the rail when the truck is shut off, then you'll have a vapor lock type of issue where no fuel will get to the rail until the truck cools down. As a disclaimer, some of this info is stuff I've read elsewhere so I haven't had personal experience with this issue. Seems like a reasonable explanation though for the problem you're having so it may be a good place to start.

That seems very likely. Probably the check valve in the pump that has failed.

I don't know how it works on 3rd gens, but I know on MK3 Supras you can jump 2 pins in the diagnostic box and it will turn the fuel pump on. If you can figure out how to turn the fuel pump on and let it run for a little bit before starting the truck and it starts up normal then your problem is the check valve.

 

[Unner]

So I think you should be able to jump the pins labeled FP and B+ to get power to the pump. Do this for 30 seconds or so and then try to start it. If it starts just fine it's most likely a bad check valve in your fuel pump that isn't holding pressure like it's supposed to when the motor gets heat soaked.

 

[k2damfc]

I’m having a similar issue, however mine stalls while driving. Usually only happens on those hot days and driving higher in elevation. It will stall like it’s not getting any gas, press gas pedal and nothing happens until it does then vroom then reappear the stalling. Happened bad last night and got to the top of a hill then proceeded to coast to a stop, get out, pop gas cap and then start and it will start but then usually such a fluctuation in Rpms, as if stalling but not completely stalling. Everytime, even if 5 mins later, the gas cap reveals some kind of pressure/vacuum. Already got a cap about a year ago and fixed it for a bit but I don’t want to have to buy a new gas cap every year. Also usually letting it sit for a little while, she fires up and purrs like normal and rides great. I’ve replaced fuel pump, sending unit, filter and (can’t remember off top of my head) fuel rail regulator(some regulator) about 2-3 years ago (gas gauge problem). I tend to replace my spark plugs way more often then most so I know it’s not them.
More curious if the pressure control previously posted is something in the pump? How does one go about diagnosing it directly and replaceing? Going to try the pin jumping when it happens next. Dropping a tank on something that I have no idea to tell how full it is(gauge hasn’t worked in long time), is something I’m going to try and avoid at all costs, but I’ll do what I have to.