2000 Blazer Fuel pump ?'s

[djd99]

I just installed a new fuel pump this last weekend due to a faulty sending unit the fuel pump it's self worked with no problems.
Now after putting in the new AC Delco pump taking the truck on a hour and a half run you stop it will stall and not start back up for about 3 to 5 minutes.
I did a pressure test and got these readings.
Key forward not running 59 PSI
Running at Idle 55 PSI
2000 rpm's 59 PSI
Even no this pump is still functioning and only doing this at random times would you guys think this is a junk pump(That's what i'm thinking)
I've never had this problem before the fuel pump change.
2000 S10 Blazer 4dr W
4.3 V-6 Auto
New AC delco plug wires, plugs and dist cap 5,000 miles ago
I've taped my pressure gauge to my windshield today and going to drive it this way this week and see what happens.
What are the fuel pump specs for this truck and any opinions would be helpful. Don

[MT-2500]

60/66 lbs are specs.
59 is to low.
Make sure your gauge is good.
On the fuel pressure test you need more testing.
Fuel pressure specs are 60/66 on your engine.
Key on pressure is good.
But we need the engine cranking pressure.
Your engine running pressure is dropping below specs.

Engine running should range about 61-62 full vacuums no load or idle.
A throttle snap or a load on engine no vacuum the pressure should go to 65-66 range.
Steady driving down the road or light throttle it should range 63 -64.

But you need to get a fuel pressure gauge taped to the outside of windshield and drive it 30 minutes to a hr and watch the fuel pressure after the engine and fuel pump has warmed up good.
And also watch the fuel pressure when it acts up.
Like catching it in the act of acting up.

From what you have checked your fuel pressure is dropping down after engine is started.
But that does not always say the fuel pump is bad.
The fuel pressure regulator controls pressure as long as the fuel pump has pressure to control.
You need to check the direct fuel pressure at the fuel filter to check pump.
It should put out 75-85 lbs of direct pressure to be good.
Also a pinch the return line of will give you a fuel pump or fuel pressure regulator check. Which should also be done after fuel pump has been run 30 minutes or more.
So before you replace the fuel pump do the full testing on it.
You could have a fuel pressure regulator problem or other problems besides the pump.
MT

[MT-2500]

Or this.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

[djd99]

Just an update guys I drove this truck everyday since I replaced the fuel pump and for the most part it ran fine with only 60 psi up until winter. Then this pump would not start on cold mornings with 60 psi. I decided to throw another AC Delco pump in this week (290 bucks at Carquest)and now I don't have any problems with cold starts. It does start right up within a couple seconds witch before my remote starter would have to reset itself because it would not attempt to fire. Here's a good lesson guys do not buy ACDELCO fuel pumps on ebay for 100 bucks as your just wasting your money. Lesson learned!

[MT-2500]

Originally Posted by djd99

Just an update guys I drove this truck everyday since I replaced the fuel pump and for the most part it ran fine with only 60 psi up until winter. Then this pump would not start on cold mornings with 60 psi. I decided to throw another AC Delco pump in this week (290 bucks at Carquest)and now I don't have any problems with cold starts. It does start right up within a couple seconds witch before my remote starter would have to reset itself because it would not attempt to fire. Here's a good lesson guys do not buy ACDELCO fuel pumps on ebay for 100 bucks as your just wasting your money. Lesson learned!

Thanks for posting back how it went.
Good luck