I've scratched my head over this a few times over the past couple years and just wasted some money on a part I didn't need, so it's time to see if anyone in here can help.

The problem:

94 3vze 4runner is hard to start when warm. It starts great when cold and when hot (turned off and re-started immediately). BUT it is really hard to start if it is brought to operating temperature and then turned off and re-started after 15 minutes to an hour or so. After an hour or so of sitting it starts fine again.

When it is warm (hard start condition): It cranks fine, and will fire occasionally and almost run (rpm less than 100) if you pump the gas while cranking. It can take anywhere from 1-10 minutes of cranking and pumping the gas before it finally starts. When it finally does start, it is as if the problem goes away suddenly. It abruptly runs normally, idles fine, has power, etc. However, on a couple of occasions it has run poorly for 20-30 seconds (sounded like it was missing) after particularly long cranking and pumping sessions. The issue happens in all weather conditions.

Often it is possible to avoid the cranking / pumping ordeal by flooring the accelerator when turning the key. The truck will fire and start to rev, stumble and want to die at about 1k, then recover and rev up to 3k after which it runs perfectly. Sometimes it doesn't recover at 1k and dies instead, in which case it's pumping and cranking time.

I've replaced the fuel filter and cold start valve (thought it might be leaking / in-effect flooding the truck - this was a waste of time and money b/c it had zero effect whatsoever). There is no gas smell during the no start shenanigans, and it has spark.

Anyone seen this before? Have thoughts on what it might be? Thanks in advance for any ideas.

 

The 3VZE has a "fuel pressure control" system to combat vapor lock. http://web.archive.org/web/201503060...ne/99fuelp.pdf The FPR usually connects to engine vacuum (so that the fuel pressure is always a constant pressure ABOVE the intake pressure). The Fuel pressure control opens a VSV when warm. This connects the FPR to atmospheric, which is higher than intake vacuum, which raises the rail pressure.

Your problem sounds a little like vapor lock, and this is the system that addresses it. Start by tracing your FPR vacuum line to see if it is connected to a VSV.

 

Alright. Thanks for the tip! Guess I'll investigate a potential vacuum issue.

 

 

 

Diggin up a 4 year old thread! Nice searching! I had this exact issue that the op is describing 3.0, it was the fuel pump.

 

Exact problem as OP.... I guess I'll start with fuel filter and, then pump and distributor cap? Currently stranded... so frustrating

When it does start up it sometimes it's misfiring /chuggy but I had all injectors machined 2 yrs ago. Not sure what is involved with the vaccum system?

I know its an old thread but more tips if anyone else has dealt with this would be awesome!!

 

Start with the fuel pump.

 

Similar side effects as a bad knock sensor or knock sensor harness, check you check engine light code if there is one though. A bad MAF or TPS will also have similar side effects. All of which had failed on me. I had also replaced on of my injectors recently for a misfire of mine, injector 1 had shorted out. Could happen too. But... Again if your having problems of starting while the engine is hot, also likely a bad distributor.