97 suburban with fuel pressure issue

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#1
My 97 chevy 1/2 ton sub. is giving me fits. The history goes is this, in Jan. the fuel pump stoppped working. Elec. checked out OK, so I changed the pump. ( I was lazy and didn't change the inline filter) Truck started and drove 5 -10 miles before it started dying at stop lights, then it quit starting all together. The pressure was weak at this point(28-40lbs while cranking) so I changed the inline filter. This did nothing for my pressure issue so I changed out the pump again. Now the truck will give 60 - 68lbs. right off the bat, but after running for about 2 min. it starts to surge then die. After dying the pressure is only 40lbs. while priming or cranking. I have now changed the pressure regulator and the problem is still the same. It seems to leak down some pressure while sitting and if given an hour or two it will pressure up and start but only for a short while. I have checked for external leaks and connections in the tank. Now where do I go from here???
 
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#2
this was a change over year from csfi to sfi.....could you ID system....can't remember - I'm too old.
60-68 psi suggests a SFI but that is ASSUMING ....

is the SES light on?


Did you change the pulsator with fuel pump?
try this...pinch off fuel return line- will pressure hold steady?
any evidence of fuel in oil?
black smoke upon start up?

The fuel pressure that continues to fall is caused by one of the following items:

The in-tank fuel pump check valve not holding.
A partially disconnected fuel pulse dampener (pulsator).
The fuel pressure regulator valve leaking.
A central SFI injector and poppet valve leaking.
An SFI injector is leaking
 
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#3
This is a CSFI system. I am basing that on the centrally located injector body with 8 plastic lines going to the ports. The SES light is working but there are no set codes(I checked with an auterra scan tool). I did replace the pulsator but I replaced it with a rubber hose supplied in the pump kit. I tried pinching the return line this morning but the pressure with or without the return pinched is less than 40lbs. and it will not start today. I checked for oil in the gas and it still looks clean, no thinning or gas smell. I have not changed the fuel pump sending unit, is that where the fuel pump check valve is? I am not sure how I would check for a leak at the injectors. Any tips would be greatly appreciated, thanks!
 
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#6
The pump is a Master brand from Advance Auto. I have not changed the wiring on the pump but I did inspect it and the pump is turning on, just doesn't make good pressure.
 

Gus

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#7
What Ford Dude is saying, whenever you change these pumps(hopefully you got a good one), you should check out the harness going into the pump, with an ohm meter, and flex the lines while doing so......saves you headaches later.....have seen bad grounds, bad connections, bad harnesses, that cause a voltage drop, so you don't get max pressure.....should also check the harness to the pump, to make sure you have WORKING battery voltage..to do this, you put a test light AND voltmeter in parallel and attach it to the harness...light should be bright and showing battery voltage...if you don't see battery voltage, there is a voltage drop in that circuit.....

I know WAP is going to argue with me, but I don't like after market fuel pumps.....

But if voltage is ok, AND the pump is ok, then then you have to isolate the leak.....when you checked out the spider assembly, did you notice if the bottom of the intake was "washed" out with fuel?
 
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#8
Ok so I am limited in my knowledge of the electrical system, so I didn't mention that when I changed the first pump out the ring on the end of the ground wire broke off! I replaced it with a crimp on ring and got power to the pump. How can I test to see if the ground is adequate? Does checking for working voltage at the harness tell me that? When I checked out the "spider" lines in the lower intake there was the usual semi dried oil film but not washed out or wet with gas.
 

wap

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#9
Not so much an argument as an experienced opinion. AC Delco/Delphi or Carter. Off shore pumps that a lot of retailers push I have not had good luck with either. That being said, Gus is right about the voltage drop. I have seen a lot of people replace the pumps in late model GM's time and time again only to have the problem resolved by changing the wiring harness going to the fuel pump, the Ignition switch, or the ignition 'jumper' harness. Just because you get a 12 volt reading does not mean you will have 12 volts 'loaded.' A small sealed beam headlight with a couple of wire leads attached to it will burn bright at the fuel pump harness if the harness is ok. It will burn very dim if there is a wiring issue. Be sure to change the fuel filter also. If a new pump has more preessure, you will get trash returned to the tank without changing the fuel filter. This pump will not put up with much /any debris in the tank. Flush tank, and be sure to strain re-introduced fuel. Good luck. I like your parallel idea Gus. .....WAP
 
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#10
Re: 97 suburban with fuel pressure issue

fixed . Well so far so good! I checked my voltage at the harness and it dropped during cranking, so I resoldered the broken ground and replaced the harness at the fuel pump. The truck will now run with no loss of pressure and even passed the test drive without stranding me! ;D I want to thank everyone for all the great advice and instruction. I still cannot belive how helpful evryone here is. I'm almost looking forward to my next breakdown! Thanks again and my "tithe" is on the way for sure!
 

dealer1

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#11
I replaced a pump today on a 98 tahoe.similar system.The carter pump came with a new style connector that had to be replaced.They seem to work fine.I have used some customer supplied master fuel pumps and they are like boomerangs.They keep coming back.I hate doing jobs 2 or 3 times but at least they pay again.