Hesitation, staggering on acceleration and poor gas mileage.

[MT-2500]

Originally Posted by JoshBarber

thanks MT.
Will spray it anyway just as an attempt. I would think it wouldve set off a check engine light if there was a problem with it though. will check the plugs also. replaced them not even a year ago with properly gapped AC Delco plugs.

HOW IS THAT FUEL PRESSURE?
Do not leave home without it.
MT

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.

[JoshBarber]

Originally Posted by MT-2500

HOW IS THAT FUEL PRESSURE?
Do not leave home without it.
MT

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.

Can you explain the "pinch" off part? How to, where it is, etc?

[MT-2500]

Find the rubber hose on the return line around fuel filter and check pressure with it pinched off.
Also you can get a direct full fuel pressure test at the line going into fuel filter.
Just do not run fuel pump at full pressure over 30 seconds.
Post back fuel pressures.
MT

[JoshBarber]

Originally Posted by MT-2500

Find the rubber hose on the return line around fuel filter and check pressure with it pinched off.
Also you can get a direct full fuel pressure test at the line going into fuel filter.
Just do not run fuel pump at full pressure over 30 seconds.
Post back fuel pressures.
MT

"return line" ????

is the place before the fuel filter a fitting? or do you have to remove the line from the filter? if its just a fitting like the one on the fuel rail, I'd think it would be smart to check BEFORE and AFTER the fuel filter.

Define "full pressure" for the fuel pump? Key on? Or vehicle running?
And if its full pressure with the vehicle running, how in the hell do you get readings WHILE driving like Ive seen so many people suggest?

ALSO - the only tester I can find is at a local AUTOZONE, and they claim it covers all GM vehicles up to 95 or 96. Did it change after that? Or can I use this one on my 98?
If not, anyones suggestions on WHERE TO GET ONE, PRICE, and part number would be greatly appreciated

[MT-2500]

Return line is the fuel return line from engine back to the fuel tank.
You can plug it off or pinch the rubber hose that it has on it fuel filter to engine lines.
Full fuel pressure is all that the pump will put out with return line close/shut/pinched off. oryou can check full pressure at the fuel line going into fuel filter. Hook a gauge right on the end of it.
Running on the road fuel pressure you need to tape the fuel gauge to the windshield or mirrow and drive down the road 15-20 minutes and watch fuel pressure.
Why did they not check your fuel pressure and check the injectors when they done the injector clean? Or were they in to big of a hurry to get your money with a 30 minutes injector clean job?
Get that fuel pressure gauge on there and tell us what the readings are.
MT
MT.

[MT-2500]

Originally Posted by JoshBarber

"return line" ????

is the place before the fuel filter a fitting? or do you have to remove the line from the filter? if its just a fitting like the one on the fuel rail, I'd think it would be smart to check BEFORE and AFTER the fuel filter.

Define "full pressure" for the fuel pump? Key on? Or vehicle running?
And if its full pressure with the vehicle running, how in the hell do you get readings WHILE driving like Ive seen so many people suggest?

ALSO - the only tester I can find is at a local AUTOZONE, and they claim it covers all GM vehicles up to 95 or 96. Did it change after that? Or can I use this one on my 98?
If not, anyones suggestions on WHERE TO GET ONE, PRICE, and part number would be greatly appreciated

You check full pressure with engine off and fuel pump running what ever way you can get it to run. You can jumper the fuel pump prime connecter with a fused jumper or keep fliping the key on with engine off to prime it up to full presure.
Full pressure is checked with return line blocked.
Normal/regular pressure just put the gauge on it.
All 90 and 20 gm engines use the same sise fuel pressure test port on the ones that have a test port.
MT

[BlazerLT]

I'm telling you Josh, go get a new MAF and try it out.

If it doesn't work you can send it back.

May really help you trouble shoot.

Sometimes a cleaning won't help a defective sensor and MAf's aren't that expensive when compared to the cost of the cleaning and treatments and throwing parts at your truck.

[JoshBarber]

The results:

Key Off - 0psi

Key On (engine off/fuel pump prime) - Jumped to 60psi, and then dropped quickly to 0psi

Engine Running - 54psi

WHAT THE HELL!!!!!!!!????????
Is there a check valve? Or is this the fuel pressure regulator!??!?!? Can someone explain exactly WHERE the regulator is as well so I can make sure a vac. line didnt come unplugged etc.

[blazee]

Looks like you have a leak in the system. The most probable causes would be the regulator (in the intake) or the pulsator (in the tank). Does the pressure drop to 0 with the return pinched? A good way to figure out which end the problem is on is to test the pressure at the filter.

[JoshBarber]

Originally Posted by blazee

Looks like you have a leak in the system. The most probably causes would be the regulator or the pulsator. Does the pressure drop to 0 with the return pinched?

I didnt try this yet....do I do it WHILE its running? Because it doesnt keep pressure in the line with the key OFF or ON for more then 2 seconds!

Wheres the regulator and pulsator?

[blazee]

I edited my post while you were replying again.

Pinch it off and then turn the key on. Use a pair of vice grips or get someone to turn the key while you hold it. If the pressure stays then it's most likely the regulator.

[JoshBarber]

Originally Posted by blazee

I edited my post on you again.

Pinch it off and then turn the key on. Use a pair of vice grips or get someone to turn the key while you hold it. If the pressure stays then it's most likely the regulator.

if you pinch it off before turning the key, the fuel pressure will never rise correct? maybe you mean turn the key on and THEN pinch it and watch it?

[blazee]

You pinch the return line not the supply line. After the fuel leaves your tank, it goes to the intake and through the fuel pressure regulator, any extra fuel that you don't need is then sent through the return line and back to the tank. If the regulator is bad it will send too much back to the tank and cause the pressure to drop. Pinching the return line blocks the flow of fuel back to the tank and allows you to see how much pressure your pump can supply. In your case it will let us see if the regulator is sending too much fuel back to the tank and causing your pressure to drop to 0.

[JoshBarber]

Originally Posted by blazee

You pinch the return line not the supply line. After the fuel leaves your tank, it goes to the intake and through the fuel pressure regulator, any extra fuel that you don't need is then sent through the return line and back to the tank. If the regulator is bad it will send too much back to the tank and cause the pressure to drop. Pinching the return line blocks the flow of fuel back to the tank and allows you to see how much pressure your pump can supply. In your case it will let us see if the regulator is sending too much fuel back to the tank and causing your pressure to drop to 0.

I just did what I think you described.
Got underneath, and pinched the fuel return (the only rubber line I saw which was to the rear of the fuel filter.
Again, with the key off, 0psi.
With the key on, UP TO 60psi for a brief second, then drops immediately down to 0psi.
With the engine running it jumps up to approx 54psi, and as soon as the vehicle shuts off, returns to 0psi.

No difference

[blazee]

I'd suggest checking the pressure at the filter itself, if there's no difference there then the problem is most likely the pulsator.