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Category: Chevy
Satisfied Customers: 26244
Experience:  ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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My 96 suburban initially has fuel pressure of 55 then drops

Customer Question

My 96 suburban initially has fuel pressure of 55 then drops to 47 while running. Increase roms andthe pressure increases. Have done many diagnostic test replaced many fuel related parts. Truck will run but as soon as you put into drive or reverse it bucks and nearly stales
JA: How many miles are on the vehicle? And when was it last serviced?
Customer: 105000
JA: Are you fixing your Suburban yourself? What have you tried so far?
Customer: One second please let me get my list
JA: Anything else you want the mechanic to know before I connect you?
Customer: I replaced fuel pump, new computer, idle control sensor, mass air flow sensor, ips, two O2 sensors and egr
Submitted: 7 months ago.
Category: Chevy
Expert:  AMEDEE replied 7 months ago.

Hello and welcome!

My name isCustomerand I can assist you with your question.

Expert:  AMEDEE replied 7 months ago.

I will try my best to answer all of your questions.

However, before we get started, please let me mention a few things.

1. If at any point you would like to speak on the phone, please feel free to request a phone call on your end and I can call you right away.

2. If you dont understand any technical terms or anything that I mention (component tests or theory or operation), please let me know and I will provide you with a more in debt explanation or answer.

3. Please understand that I am here to help you anyway I can.

Does the fuel pressure leak down key on engine off or with the key off??

Customer: replied 7 months ago.
Pressure does not drop
Customer: replied 7 months ago.
That is reason I did not replace fuel regulator
Expert:  AMEDEE replied 7 months ago.

What is it at with the engine at idle? Is it t 47 psi? Does it go up a bit when you step on the gas pedal?

Customer: replied 7 months ago.
Initially it is about 55 but running idle about 47
Expert:  AMEDEE replied 7 months ago.

I am sorry, I see you that you indicated this in your initial post.

May I get your VIN?

Thank you!

Customer: replied 7 months ago.
Expert:  AMEDEE replied 7 months ago.

Can I get the complete VIN?

Customer: replied 7 months ago.
Expert:  AMEDEE replied 7 months ago.

I am sorry but the image did not come through..

Customer: replied 7 months ago.
Expert:  AMEDEE replied 7 months ago.

Thank you for the VIN!

It is very important that the fuel pressure is within specs on this engine.

Key on engine off and while cranking the fuel pressure NEEDS to be between 60 and 66 psi. Hands down

Because we have a low fuel pressure issue when the engine is running, there is something that needs to be addressed. Was the fuel filter replaced? Was power at the fuel pump checked? What about the ground to the fuel pump? If that all checks out good and there are no restrictions in the fuel pressure line and nothing is leaking fuel causing this low fuel pressure, you have a faulty new fuel pump and it will need to be replaced under warranty.

Customer: replied 7 months ago.
Filter was replaced
Customer: replied 7 months ago.
Power at pump was checked and old pump was only 3 years old, switched outfit new one figuring that the pump went bad
Customer: replied 7 months ago.
I am assuming that if the pump run the ground is sound
Customer: replied 7 months ago.
I was thinking that if a line is pinched I would get a surging fuel pressure
Expert:  AMEDEE replied 7 months ago.

No sir, your last two replies are not correct.

Just because the pump runs does not mean it has a good ground.

No, a pinched fuel pressure line will cause low fuel pressure.

Customer: replied 7 months ago.
What is the voltage supposed to be at the pump?
Expert:  AMEDEE replied 7 months ago.

Battery voltage

Customer: replied 7 months ago.
Ok on first reply, second where is most common place for a pinched fuel line? Can old lines cause this issue as well?
Expert:  AMEDEE replied 7 months ago.

If the old lines are restricted in anyway, yes, they can cause this. I have found that the most common place for the lines to be pinched is the rubber part where it goes up to the throttle body (before the throttle body)

Customer: replied 7 months ago.
For ground is there a common place for an issue
Expert:  AMEDEE replied 7 months ago.

No there is a no common place that it goes bad, but I would recommend to check the ground strap from the tank to the frame. Just follow the black wire from the fuel pump module and it will go to a ground and you can remove it, clean it up and re attach it.

Another test you can do is to dead head the fuel pump (restrict the return line) with the engine at idle and the fuel pressure should reach 70 psi.

Expert:  AMEDEE replied 7 months ago.

Would you be willing to speak on the phone? I have sent over an offer with my phone number in it..

Customer: replied 7 months ago.
I wouldn't mind talking but I would like to try the suggestions you sent over. Will this offer be available after my test
Expert:  AMEDEE replied 7 months ago.

To be honest, I think the offer may expire after some time. When it does, I am not able to send another offer over again. So I would recommend that you accept the offer now before it expires..

Customer: replied 7 months ago.
I would but I am not with my truck
Expert:  AMEDEE replied 7 months ago.

You dont have to be at your truck when we talk. But I understand you may not be able to talk at work.

You can always accept my offer not and then call me later when it is convenient for you..

Customer: replied 7 months ago.
I'm going to be honest I have dumped a lot of money into parts that I didn't have and reached out to you and service as a last ditch effort to see if I find the answer. Is there anything else besides what you have suggested so far. I truly appreciate your expertise.
Expert:  AMEDEE replied 7 months ago.

Hello and sorry for the delay!

As far as the fuel pressure issue? No, we have covered everything. As long as nothing in the fuel system is leaking and the pressure line is not restricted and the power and ground check out good, the problem is a bad fuel pump.

Expert:  AMEDEE replied 7 months ago.

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "5 STAR SERVICE" for assisting you today.

Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!

Also, if you are a member or if you have a subscription to the site, you still need to rate my answer in order for me to get credit for assisting you with your question.

Please let me know if you have any further questions.

Expert:  AMEDEE replied 7 months ago.


It'sCustomerand I just wanted to check in to see how things are going and to see if you need any further assistance?

Let me know!