Help Any Ideas???

[1987ss]

Its a 1999 tahoe. today it was warm out and truck started actin up after 1 1/2 hours of driving.. at first it hesitated on accelartion but if you gave it gas graudaly it would get up to speed fine. if you kicked it down it would hesitate and rpms wouldnt go past 3000 rpms.. from a dead stop same thing about 2500 rpms and would hesitate.. in park it acts normal.were do i start? no ses light and it has 130k on it tranny fluid looks clean!! PLEASE HELP!!


ok just went out and pressed on accelerator in park and it spits and spudders threw intake when steped on rpms only go to 2300 or so.. it idels fine THANKS PLEASE HELP

[MT-2500]

Got fuel pressure?
What engine?
Hard to start cold.
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.

[1987ss]

it is a 350
engine OFF key ON 37-38 psi
in park engine on 51 psi accelarate in park 60 psi
accelarate while driving 60 psi
pinch what?
now that the truck cooled down its running normal again???

also for like the past month it seemed the truck would turn over a little bit longer than normal b4 it would start

[MT-2500]

Pinch off the rubber part of the return line only.
Between engine and frame you will find the rubber part of fuel lines.

Your fuel pressure is low.
If pinching off or blocking off the return line does not raise pressure to 75-85 lbs of pressure.
Check the direct pressure where the fuel pump line goes into the back of fuel filter.
If you do not have full pressure of around 75 lbs there you fuel pump is bad.

[1987ss]

thanks for the help!

i left preassure tester on it over night it went down to 10 psi
key on engine off went up to 60 psi (cold motor)
ideled at 52 psi

im a try to pinch line and ill post back in a little bit

[MT-2500]

Fuel pressure is low.
A cold start requires 64-65 lbs of fuel pressure to squirt the injectors good.
Do not leave home without good pressure.
Check the full fuel pump pressure .
If it is not 75-85 lbs and the fuel pump is getting good 12-13 volts and good ground.
It is time for a new fuel pump.
If it has good full direct pressure have a look at your fuel pressure regulator.

[1987ss]

ok i pinched off return line first time i got 74 psi, second time i got 70 psi and third time it was 71 psi..

the snap on fuel preassure tester i borrowed dosnt have a fitting to test line going in to fuel filter..

[MT-2500]

Originally Posted by 1987ss

ok i pinched off return line first time i got 74 psi, second time i got 70 psi and third time it was 71 psi..

the snap on fuel preassure tester i borrowed dosnt have a fitting to test line going in to fuel filter..

Your fuel pump is putting out good pressure then.
Better check fuel pressure regulator for holding or regulating the right pressure or leaking off.
MT

[1987ss]

how do i do that?

[MT-2500]

Originally Posted by 1987ss

it is a 350
engine OFF key ON 37-38 psi
in park engine on 51 psi accelarate in park 60 psi
accelarate while driving 60 psi
pinch what?
now that the truck cooled down its running normal again???

also for like the past month it seemed the truck would turn over a little bit longer than normal b4 it would start

On this test it may also be a weak fuel pump.
I would jumper the fuel pump and let it run for a hr or so and recheck pressure with fuel line pinched off.
It could have a bad fuel regulator and a bad fuel pump that loses pressure after it runs for a hr and gets hot and weak.
Good luck and let us know how it goes.
MT

[1987ss]

how do you jump fuel pump? cant i just let it run normaly?

im a start it and run engine for a hour.. ill post back as soon as i can

[1987ss]

ok i let it idel for 40 min and drove it for 30 more min..
and the readings stay the same 50 psi driving 60psi when i step on it

it is running normal it is also 25 degrees cooler outside todat than yesterday..

[MT-2500]

50-60 is not normal.
Go back up to post 2 and read it.

[1987ss]

so should i change pump or regulator? were is regulatror located?
I APPRECIATE THE FEED BACK!!!! THANKS MT

[MT-2500]

That is for you to test and figure out.
All I can tell you is your fuel pressure is low.
Proper testing.
Go threw the test.
They will tell you what is what.
Fuel pressure regulator controls the pressure but you need pressure to control.
Is the fuel pump putting out full pressure all the time hot or cold?
Have you also checked for good 12 volt power and ground to fuel pump?

From what you have told us so far it may be both regulator and fuel pump.
But makes always make sure .
Like Have you also checked for good 12 volt power and ground to fuel pump?


If fuel lines runs into the top of the engine you will find the fuel pressure regulator in there.

Run a search on how to.