1996 S10 Blazer Low fuel pressure ????


fedorajim
03-23-2005, 11:00 AM
Hello all I followed the thread
http://www.automotiveforums.com/vbulletin/t377176.html to gauge where my truck stacked against his problem and did some testing. Here are the issues I'm dealing with.

~Long cranking to get the truck to start. sometimes 3-5 minutes of on/off cranking

~once started - accelerating just sucks! seems that the truck can't get out of its own way. it does downshift but seems to take forever to reach a rpm in which it will shift again.

~limited funds just rebuilt the rear differential (the whole thing)

~ No engine codes

~ all new O2 sensors

Fuel system pressures
Fuel Pressure
@KOEO 52 PSI
@KOER 50-52 PSI
@KO 58 PSI
@KO 5 minutes 50 PSI
(intially jumps to 60 PSI right after you turn the truck off then bleeds down to the above PSI)

Battery Voltage
@KO 12.5 Vlts
@KOER 14.7 Vlts

LEGEND
KOEO- Key On Engine Off
KOER Key On Engine Running
KO Key Out
KO 5 minutes- Key Out sitting for 5 minutes


Vehicle specs
~ 4.3 w engine
~ 124,600 miles
~ replaced intake gaskets upper & lower 1.5 years ago
~ oil change on regular interval
~ no towing
~ new battery 6 months old

BlazerLT
03-23-2005, 11:02 AM
Fuel pressure should be @KOEO 60-66psi

fedorajim
03-23-2005, 11:03 AM
Ok it should be @ 60 - 66 PSI what would cause this to be low?

BlazerLT
03-23-2005, 12:19 PM
Ok it should be @ 60 - 66 PSI what would cause this to be low?

-Fuel pump
-Improper battery voltage
-plugged fuel filter
-bad fuel pressure regulator.

fedorajim
03-23-2005, 01:12 PM
-Fuel pump
-Improper battery voltage
-plugged fuel filter
-bad fuel pressure regulator.

replaced the fuel filter just now, battery voltage never drops below 10 volts while cranking. Pressure regulator, where is it? in line in the tank? If i'm that far into it, might as well replace the fuel pump as well?

I'll most likly replace the pump & regulator in the next day or so, I'll reply whether this solves the problem

tom3
03-23-2005, 01:57 PM
Seems like 96 and 97 were really bad years for fuel pumps and level sensors. Have to buy the whole assembly too, serious money there. Bad news.

mike2004tct
03-23-2005, 02:21 PM
Seems like 96 and 97 were really bad years for fuel pumps and level sensors. Have to buy the whole assembly too, serious money there. Bad news.

'97 & '98s have the bad sensors,and they use the same pump assemblies.
Lucky for '96 owners, it's not the same pump assembly/fuel level sensor as the '97s. The pump is about $240.00, much cheaper than what I paid for my '97 ($358.00 for the 2dr model, $328.00 for the 4dr model- Carter pump from NAPA).

BlazerLT
03-23-2005, 04:53 PM
replaced the fuel filter just now, battery voltage never drops below 10 volts while cranking. Pressure regulator, where is it? in line in the tank? If i'm that far into it, might as well replace the fuel pump as well?

I'll most likly replace the pump & regulator in the next day or so, I'll reply whether this solves the problem

Check the battery voltage with a voltmeter with the engine off.

Should be 12.8-13.8 volts with the engine off and over 14.4 volts with the engine running.

Use a voltmeter , NOT the dash gauge.

thomasrn
03-23-2005, 05:02 PM
replaced the fuel filter just now, battery voltage never drops below 10 volts while cranking. Pressure regulator, where is it? in line in the tank? If i'm that far into it, might as well replace the fuel pump as well?

I'll most likly replace the pump & regulator in the next day or so, I'll reply whether this solves the problem

I wouldn't worry about the fuel pressure regulator, at least not yet. It cost about $70.00 for a new one, but it's kinda scary taking apart the upper air intake manifold.

Your Fuel pump is able to do 60 PSI, probably not the electric motor in the pump assembly itself. It does make the 60 PSI!

You probably have a leaky Fuel Pressure Pulsator, or the float valve in the sending unit needs cleaning and is leaking. If you're short of cash, and don't mind spending the 4 hours to pull the fuel tank out, you could try that. I would hunt around google to learn as much as you can.

I ended up opting for a $125.00 used fuel pump that seemed to fix my problem. Meanwhile, the old pump is in the garage waiting for me to go check it out.

Regards,
---- Robb -----

blazee
03-23-2005, 05:08 PM
He should also test to see how long it takes for the pressure to bleed off, if I interpret his post right, it says the pressure dropped 8psi in about 5 min. A leak in the system would cause him to have low pressure. A leak is not limited to the regulator. It can be one of the following as well:
leaking fuel injectors
damaged injector o-rings
damaged or split fuel pulsator
leaking check valve
leaking fuel lines

tirrem08
03-24-2005, 10:42 AM
I'm having the exact same problem on my 1996 s10 blazer. I replaced the fuel pump and fuel filter 2 weeks ago and it felt a lot better for a while but now its starting to do the same thing. What would be the next course of action? replace the fuel pressure regulator? I'm gunna have the pressure checked tomorrow so we'll see if that pump is supplying that 60psi. I'm considering pumping a couple of .357 slugs into the engine, at least that will give me some piece of mind. This thing has given me nothing but trouble from the beginning.

BlazerLT
03-24-2005, 12:13 PM
did you replace the fuel filter when you put the new pump in?

tirrem08
03-24-2005, 07:39 PM
Yeah I replaced the fuel filter. I've talked to a few mechanics that have told me to never put an aftermarket fuel pump in your car. I just couldn't seem to fork out the extra $150 for the OEM pump.

fedorajim
03-26-2005, 12:11 AM
Your Fuel pump is able to do 60 PSI, probably not the electric motor in the pump assembly itself. It does make the 60 PSI!

Only when I turn the truck off is when the PSI jumps to 60 PSI

BlazinUP
04-29-2005, 10:29 PM
tirrem.........did you get the pump looked at....
have you got the problem fixed?
iv a similar situation........could you let me know

Add your comment to this topic!