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Clement, Diagnostic Technician
Category: Australia Car
Satisfied Customers: 208
Experience:  VW, BMW & GM Holden factory trained, Applied Design (Auto), Diploma in IT
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Toyota Hilux 3rz-fe 2.7 petrol.Motor is hard to start.

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Toyota Hilux 3rz-fe 2.7 petrol.

Motor is hard to start. I know from previous diagnostics that fuel pressure drops whilst motor is not running. After 15-30 seconds of cranking motor coughs and splutters to life and gives off all symptoms of having been flooded. Just installed a new fuel pump and now problem seems worse. 250000 kms on clock. Would this be an issue with the injectors, the pressure regulator or an airflow meter? Other suggestions? Hope you can help.

When you say the fuel pressure drops, how much does it drop by and over how long? Have you had it scanned for fault codes?
Customer: replied 5 years ago.

Hi Clement,


I can't quantify the pressure drop. I had some issues with it running really lean a couple of years ago and the techo with the dyno machine had a pressure guage on the fuel line and he showed it to me and you could visibly see the pressure dropping as we spoke. He suggested that this was why it would be hard to start. My gut feeling is given enough time it drops to almost nothing. Interestingly if I leave it for a couple days it starts straight away (like it should in my opinion). Although I have only run one tank since I replaced the fuel pump (a bosch unit) fuel economy has jumped from a long term average of about 12.5l/100km to about 15l/100km (not good for my wallet). I t drives ok once it's running. No I haven't had it check for fault codes should I take it to Toyota.



You are right to say that loss of residual fuel pressure will cause a hard-to-start situation. Once the engine has been turned off, residual pressure should not drop to under 1 bar (100kpa) after 20 mins. If you can see the pressure dropping rapidly then you have a problem somewhere.

With the loss of residual pressure, fuel vaporisation can occur in the fuel lines, which will cause hot-start issues. When the vapor has been given time to disperse (usually long enough for a cold start), the engine will fire up again.

A few components can contribute to loss of pressure:

  • fuel pump check valve
  • fuel rail regulator
  • injectors
  • external leaks from hoses, fuel filter etc

A good way to test this is to hook up a fuel pressure gauge, run the engine, turn it off and then clamp the return line. If the pressure holds, you have a faulty regulator.

If the pressure does not hold, get another clamp and clamp the supply line. If the pressure holds, you have a faulty fuel pump check valve (which should not be the case if you have had a new Bosch unit!).

If the pressure still does not hold, you have faulty/leaking injectors and will have to get them checked/flow tested and serviced.

Fault codes can be checked by any good auto workshop, it is not necessary to go to Toyota. Fix up your loss of residual fuel pressure first and see if that helps your fuel consumption.

Hope this helps shed some light!
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