when i first turn the car on fuel pressure when to 62 psi as soon pump goes off it drop down to 56 psi.when i start the car it’s around 58 psi.i was told by someone that had a blazer and he said when car runing it should around 60 to 66 psi and he said it’s to low
when car is running 56 psi at idle
What you just described sounds normal to me. There is a range of what’s considered acceptable fuel pressure for your system, and you’re on the lower end of normal.
I’m saying that because we have lots of cars with your exact fuel injection system in our fleet
I’ll say it again, look elsewhere for your problem
Your vehicle starts on its own
That would NOT be possible if the pump was failing and had low pressure
ESPECIALLY not with your specific fuel injection system
The problems you described a few months ago are due to something else
Have you measured that exhaust backpressure, as some of the other guys mentioned earlier?
yea i had that done by 3 shop and thay all said exhaust is fine.
Acceptable fuel pressure at idle so the engine idles normal. What is the fuel pressure while accelerating?
No one is asking the obvious question here so I will. Is the check engine light on?
no check engine light on.with 2000 rpm it around 56 psi
Is that full throttle while driving?
no
Well, two professionals here (Tester and pete peters) say that this fuel injection system doesn’t work properly at pressures under 60 psi, so it sounds like the fuel pump is in fact your problem.
And one professional here . . . me . . . says OP’s fuel pressure is normal, so it sounds like the fuel pump is in fact not your problem
I’m not always right, and maybe the pump is the problem. But what I’ve heard so far wouldn’t make me head down that direction
But right now, it seems we’re playing a game of “the majority wins” . . .
Ok I had my car look at by 3 shops this week. And they all said I need a new fuel pump.I get new pump put in and still getting low fuel pressure 62 psi with key on soon pump goes off it drops to 56 psi. With car running at idle it’s around 56 psi.I did a link down test and in 30 mins psi was still at 56.I really don’t know where to start now.and new pump is acdelco
i done a leak down test today psi was 60 and 10 mins it was 52 psi and i let it set 10 more mins it went from 52 psi to 44 psi
What matters is fuel pressure with the engine running, so I wouldn’t be worrying about the leakdown test. As long as the engine starts after sitting, the check valve is working well enough.
So you replaced the fuel pump, and the fuel pressure at idle hasn’t improved. Have you gone for a test drive and still have the sputtering/ loss of power problem?
yes it still has no power
Tester said the fuel pressure must be 60 psi or higher for this injection system to work properly. If he’s right, then your fuel pressure is still too low. You might try adding an electric fuel pressure booster pump, but that’s an expensive experiment.
If he’s not right, the problem could be elsewhere, for example in the injection system itself.
at idle it was 54 psi
There’s nothing wrong with your fuel pressure. These poppet-nozzle style injectors do need high pressure to begin working-60 psi or more. I’ve seen no start conditions caused by fuel pressure being 59 1/2 lbs. Just that little difference will keep the injectors from opening. But once the engine has started and is running that spec is no longer critical. You could be driving around with the pressure as low as 45 psi and probably wouldn’t even know the difference.
Furthermore, do you even know if your car still has the poppet-nozzle injectors? If they have ever been serviced in the past they were probably replaced with the updated conventional style injectors, making that fuel pressure spec even less important.
I find it hard to believe that three shops did a proper diagnosis including test drive to duplicate the concern and all other testing needed and you still don’t have the answer. Do you have any of the information that the shops gave you as results? This is a simple system and I would bet a competent mechanic would have the problem figured out from the driver’s seat without even opening the hood.
Maybe a leaking fuel pressure regulator?