88 S-10 Blazer 4x4 fuel not getting to Throttle Body

4.3 engine.My s-10 Blazer was cutting off.So I put in a new fuel pump,because the fuel pump had been loud.So I replaced the fuel pump,with a bosh,from advance auto,life time warrenty.also replaced
strainer on pump and inline filter.It ran good for about a month and started doing the same thing,no fuel to TBI.Now it runs for about a minute and cuts off.Cranks will not start.Next day same thing,runs cuts off.Could this still be the new fuel pump?I also just rebuilt the TBI again,so it's not that.I thought it may be the engine computer,but wouldn't it set a code?Soon as weather permits I'll be back out there,trying to get this figured out.In the mean time,I'm hoping some one here can give me some clues on what to look for.Thanks for any and all suggestions! Bobby
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bobby swift wrote:

What is the fuel pressure Key on engine off? What does it do when you shut off the key? Usually if it's the pump it won't run at all. Sounds more like a bad regulator or a problem somewhere else.
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I've got the manuals for the S-10 Blazer.I just went out and got a fuel pressure tester,booklet says not for GM TBI systems,but i'll figure a way to get it hooked up.I put a new spring and diaf phram,in the regulator,it could maybe be the meter cover?The engine cuts off when ignition is turned off.Hope I don't have to remove the fuel tank again.It ran good after the fuel pump was installed,it even had more power,drove it about a month and it started doing a tempory shut down,that got worse over a short time.I let it sit here and let it run for a long time,but now it won't start.It usualy starts when I let it sit over night,but only runs for a minute and shuts down.It's almost like it's sucking something closed.Thanks for any suggestions.
Bobby
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bobby swift wrote:

What you need is the fuel pressure when you just turn on the key. Then the pressure drop when you turn off the key (ideally it shouldn't drop) Then the pressure as it's running.
The pump should turn on for 2 seconds or so then shut off if the engine isn't running.
One thing you may want to check is the oil pressure switch that feeds the pump voltage. If it goes bad the engine will only run for a couple seconds and quit.
--
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Just a thought here guys. Considering the age of the vehicle, would it be likely that the fuel filter is simply plugging up? Could be a lot of crap in that 22 year old tank. Regards, JR
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I'm gonna have to wait on checking fuel pressure,because of heavy rain.The pump does run about 2 seconds after key is turned on.I don't know what the chances of a new fram filter being plugged,I guess it could happen.The tank is new,so is the sending unit and pump.I even removed fuel cap to see if it runs,with no luck there.I do have acess to compressed air to blow the lines out.Could the fuel pump strainer be sucking together?I even thought maybe it could be the ECM,but no codes have been set.If it was the oil sending switch,wouldn't it not start up and run after sitting over night?Thanks! for the suggestions! Bobby
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bobby swift wrote:

There is an EASY way to determine if it is the pump. There is a jumper line near the FP relay that you connect 12 volts onto. Jump it and see if it runs OK.
If it runs OK with the jumper in place check the OP switch and the wiring. The 2 seconds run is a good sign.
I would doubt it's the filter. They can handle a LOT of crud before they plug.
I would wait till you can get dry. Then check the pressure. If it's in spec jumper the pump and see what it does.
Good luck.
--
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I checked the fuel pressure today it puts out 12lbs.I got the fuel pressure tester mounted near the fuel tank connected in parallel so I could view it with engine running.It finally started after I connected it,after running for about 5 minutes,it cuts off and wouldn't start.When I turned the switch ,I could hear the relay kick in,but no start.I hooked the pump on the test connector to the battery,it fired right up,un hooked the wire...thinking it was gonna cut off,but it kept running...ran for 10 minutes.....so I turned it off and it starts every time.But I'm not brave enough to take it for a trial run yet.Any clues?I've got another ECM,I got from the junk yard a while back...so I may try that later.I also unhooked the fuel pump relay,while it was running and it kept running....good oil sending switch.Thanks! Bobby
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bobby swift wrote:

Well 12 psi is in spec. 9-13 is what they call for.
I would swap the OP switch. and check the wiring near it VERY well.
I don't think it's the ECM.
--
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It cut off again,after running for a while.The pressure still holds with it straight wired,but will not run,sometimes it doesn't build pressure with ignition turned on.I'll get the oil switch and let you know,if it does the trick.Thanks! Bobby
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Can't find my wrench for the oil pressure switch.Any way i took the air cleaner top off.Then I sprayed some throttle body cleaner in it....and it fired right up....so I go back to check fuel pressure....it was steady 12 psi.When the engine cut off...I noticed the pump was still running,for the 2 seconds after the engine died....then the pressure guage dropped to O.Yesterday I put 20 lbs. air pressure through the fuel line from the tank to the inlet line on the tbi.into a cup and it put about 8oz.of fuel in the cup,so the line wasn't blocked.Could it be something in the TBI...???Got me really puzzled on this one.Thanks! Bobby
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On 1/27/2010 3:38 PM, bobby swift wrote:

What does the pump do under the same scenario? Meaning, divert the line to the TBI and turn the ignition on/off, making sure that you have a large enough container and that you are doing so from where the gas line connects to the TBI. If you get fuel flow then you need to look at the TBI, such as verifying all electrical connections are good.
I had an '88 S-10 that would drop one of the injectors when it got cold outside. Once the engine warmed up it ran fine, but I got rid of the truck before I resolved the issue. So, who knows...
Anyway, I'd verify that the injectors actually worked.
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The injectors were spraying,I looked down in the throttle body,before I walked to the back,to see what the pressure gage was doing when the engine died.Once the engine stopped,about 2 seconds the gauge dropped below 10 lbs then the pointer jumped a little before,droping to-(o)guess that jump was the relay cutting off.I got another fuel fiter.I'll put that on tommorrow.....and the oil sending switch.If any body has any more ideas,I appreciate them.I'm determend to figure this out,Thanks for all the replies! Bobby
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On 1/27/2010 6:28 PM, bobby swift wrote:

If possible, place the pressure gauge in the engine compartment so you can monitor everything from one place.
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The fuel filter seems mostly the problem.I ran it for about 15 miles and back this morning.I thought the problem was fixed.So I went back out,just a short ways from the house it cut off again.Cranked it several times before it started...drove it to the store and back...a couple miles,with no problems.Now it's gonna snow here...so it will have to wait.Thanks! Bobby
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On Fri, 29 Jan 2010 19:45:02 -0500, snipped-for-privacy@webtv.net (bobby swift) wrote:

Golly, how very annoying. :-) This morning I had a cinch on the saddle break while moving the cows via horse, which I suppose is much the same problem only a different era.
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I want to connect a fuel pressure guage to the inlet line,a permanent connection,so I'll be able to check it any time.I will have to cut the line to make a place for it.Is it possible with out it leaking and starting a engine fire?Thanks in advance! Bobby
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It's back to doing the same thing.I let it sit over night...it starts up runs fine for about 2 minutes...then shuts down.Won't start again till next morning.I replaced the oil sender switch.I guess it could be the ECM not sending pulse signal to the injectors...so i will get a noid light.It's like when the fuel filter gets saturated with fuel it loses fuel pressure.Not enough space to pull the inlet fuel line back to install pressure gage,unless i cut the line.Thanks! Bobby
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bobby swift wrote:

If the pressure is holding with it wired but it still cuts out then I would check to make sure you have spark. Especially if you saw the injectors spraying after it cut off. Toss a timing light on it and see if the spark is OK. If you crank it and it isn't starting make sure you have spark.
Some days I HATE long distance diagnostics....
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