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4.2 EFI GQ Fuel pressure

Tech Talk for Nissan owners.

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Posts: 1918
Joined: Mon Sep 26, 2005 6:03 pm
Location: Victoria

4.2 EFI GQ Fuel pressure

Post by Jimbo »

Hello all, my 4.2EFI patrol has been running like crap on petrol. Thought is was air flow metre but changed it over and still the same. So yesterday i borrowed my mated fuel pressure gauge and found it to be running at 26PSI

Is this too low? Low enought to make it run really bad?

Anyone know what it should be at?

Could it be the pressure regulator?

Any ideas

Thanks in advance

Jimmy
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Post by Jimbo »

Anyone?
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Post by marko »

26 is correct pressure. Even though it has fuel pressure, have you check the fuel filter. When does it run bad,All the time,idle, just off idle, full load,etc.Does it miss or sound like its running out of fuel?
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Joined: Mon Sep 26, 2005 6:03 pm
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Post by Jimbo »

Ok i just got told 34 psi is correct with vac line in and 42 withought vac line.

Fuel filter is brand new. It runs crap all the time but sometimes its fine under no load. As soon as i try to accelerate slightly it hesitates very bad and i end up slowing down. It also pops and back fires a bit too!!
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Post by Red_MAv »

Mine is a straight TB42 but it had the same symptoms backfiring and running like crap. It was the coil. Tossed a new coil in and ran like a dream again.
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Post by Jimbo »

OK but mine is duel fuel and runs great on lpg.
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Post by Spanners05 »

My GQ 4.2 EFI had a low fuel pressure problem, but the symptoms don't sound like yours, my fuel pressure was getting as low as 14 psi, the car could still be driven, just.
It was just low on power, the backfiring and poping makes it sound more like spark, maybe a computer fault.
You can check the fuel pressure regulator, plumb in the fuel pressure guage and check that it changes when you remove the vaccumm pipe, which is the controller for the regulator.
Does it only backfire on petrol?
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Posts: 1918
Joined: Mon Sep 26, 2005 6:03 pm
Location: Victoria

Post by Jimbo »

Yes all the problems are on petrol. It runs really well on gas.

I dont want to go out and buy a fuel pump if its not the problem. Maybe i should just take it to an EFI joint and let them sort it out...although i prefer figuring stuff out myself first.

Thanks again.
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