5VZ-FE Hard Start

[PilbaraPrado Lurker Find all posts View Profile Close PilbaraPrado]

Hi guys,
im new to this forum and ive found some great info on my prado but there is just something i cant quite find here or anywhere. I read posts from some people but they dont update as to what the issue was. Im having an intermitent hard starting fault.
When it cranks over when cold it could crank for about 10-15 seconds before starting then shut it off and it starts straight away and sometimes i could jump straight in on a cold morning and it fires straight away. So am i really looking towards a fuel issue? Now i always thought that when you turned on the ignition the fuel system should prime but when i removed the delivery line to the rail and turned on the ignition absolutely no fuel came out. When i bridged B+ and FP terminals on the diagnostic connector the pump works so im pretty sure the pumps are ok. I also tested the sub tank pump aswell. Im just not sure how much should come out over a period of time and i dont have the gauges to check system pressure which from memory should be 36-44 psi ?? Correct me if im wrong.

Am i looking at a intermitent fuel pressure reg fault bleeding off pressure to the return when the engine is shut down so when i crank it when cold it has to rebuild the pressure in the rail? No fuel is coming out of regulator vacuum. When it runs it runs like a dream and gets good economy. Do these engines run a cold start system ? Can the ISC or the MAF sensor give hard starting ? I have cleaned the MAF sensor aswell.

Any info would be great. Im just scratching my head a bit as when i think its ok it plays up again.

Thanks guys and have a good one.

Aaron.

[spectral Lurker Find all posts View Profile Close spectral]

What if the relay was faulty and occasionally failing to kick in and activate the pump? Thats the easiest thing to try. From then it could get a bit trial and error. I've seen similar when the ECU has been a bit flakey.. also immobilizers can cause similar issues.

[PilbaraPrado Lurker Find all posts View Profile Close PilbaraPrado]

What if the relay was faulty and occasionally failing to kick in and activate the pump? Thats the easiest thing to try. From then it could get a bit trial and error. I've seen similar when the ECU has been a bit flakey.. also immobilizers can cause similar issues.

Do you mean the efi relay? If that's the one you mean then I swapped it with the power outlet relay. I might try at get ahold of another ECU.

[spectral Lurker Find all posts View Profile Close spectral]

No the fuel pump relay.

[PLAYDOE Lurker Find all posts View Profile Close PLAYDOE]

I have the same issue and have had it for a while I can't seem to work it out I have replaced nearly every sensor ie crank,coolant but not cam also replaced fuel filter,fuel pressure regulator and is getting fuel pressure also holding it. But still un solved and unsure

[PilbaraPrado Lurker Find all posts View Profile Close PilbaraPrado]

I have the same issue and have had it for a while I can't seem to work it out I have replaced nearly every sensor ie crank,coolant but not cam also replaced fuel filter,fuel pressure regulator and is getting fuel pressure also holding it. But still un solved and unsure

Where about's is the fuel pump relay located and is there 2 (one for each pump)?

[PLAYDOE Lurker Find all posts View Profile Close PLAYDOE]

Where about's is the fuel pump relay located and is there 2 (one for each pump)?

I didn't think there was a fuel pump relay on them

[PilbaraPrado Lurker Find all posts View Profile Close PilbaraPrado]

Neither did I

[PilbaraPrado Lurker Find all posts View Profile Close PilbaraPrado]

Neither did I

Ok so myself and a sparky mate just went through a few things any checked all the relays which seem to be fine. The only small thing we found was at the efi relay under the bonnet we had 12.5V supply from the battery and 11.3V from the keyswitch. When cranking the keyswitch voltage drops to about 9.5V which sounded a little low to me but my sparky mate assures me the relay should still kick in which it must do as the car does start. As to the subject of the pumps priming when the key is turned on, according to the wiring diagram the ECU will give earths to the circuit opening relay and the sub tank relay once the ECU sees an earth given by the crank/cam sensors hence why the pumps only work when the engine is cranking. My sparky mate thinks I may have a dodgy crank sensor which I will test when I do the to I do the timing belt next week.

When I removed the main fuel line from the rail and cranked the engine, heaps of fuel came out so I'm going to rule out the pumps until I can check pump pressure.

Any way guys I will update some more when I progress next week. Still feel free to drop an suggestions as I feel there Is a lot of people out there who's prados have this niggling problem and can't find the answer.

Cheers.

[spectral Lurker Find all posts View Profile Close spectral]

Good to see the pumps look ok.. the relay I was referring to sits behind the sub tank gauge?

I guess if you have plenty of fuel.. the next thing to check is spark?

[Torrie 72 Senior Member Find all posts View Profile Close Torrie 72]

Sounds like it could be the crank angle sensor, although when they start to go on commodores they will first play up when starting after a short run then begin playing up when they get hot. Would still be worth looking at - hope they're not tool expensive!
Cheers, Ben.

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Yeah very common on the older commodores Ben either had to wait for it to cool down or carry a bottle of water with you and pour it over the sensor just above crank pulley ooor get a new sensor lol...... Cheers Steve

[PLAYDOE Lurker Find all posts View Profile Close PLAYDOE]

I don't think it is the crank sensor I replaced that, also coolant temp sensor but not cam sensor I had a look at work to as I work for Toyota and found something it may be its called the starter signal circuit which leads to the ecu ill try and see if I can put the wire diagram up as I haven't checked it yet

Ok so myself and a sparky mate just went through a few things any checked all the relays which seem to be fine. The only small thing we found was at the efi relay under the bonnet we had 12.5V supply from the battery and 11.3V from the keyswitch. When cranking the keyswitch voltage drops to about 9.5V which sounded a little low to me but my sparky mate assures me the relay should still kick in which it must do as the car does start. As to the subject of the pumps priming when the key is turned on, according to the wiring diagram the ECU will give earths to the circuit opening relay and the sub tank relay once the ECU sees an earth given by the crank/cam sensors hence why the pumps only work when the engine is cranking. My sparky mate thinks I may have a dodgy crank sensor which I will test when I do the to I do the timing belt next week.

When I removed the main fuel line from the rail and cranked the engine, heaps of fuel came out so I'm going to rule out the pumps until I can check pump pressure.

Any way guys I will update some more when I progress next week. Still feel free to drop an suggestions as I feel there Is a lot of people out there who's prados have this niggling problem and can't find the answer.

Cheers.

[PLAYDOE Lurker Find all posts View Profile Close PLAYDOE]

Here is the diagram

[[email protected] Lurker Find all posts View Profile Close [email protected]]

hey there pilbara i have a problem with mine and think it may be the MAF sensor coming from the air cleaner,, i have poor accelaration pickup and when i clean the little fuses bits inside it seems to go ok and i think that might be part of my start troublles some times.. just check.