1996 Chevy Astro 1996 Astro fuel distribution issues

1996 CHEVROLET ASTRO
24,000 MILES • 6 CYL • AWD • AUTOMATIC
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BRIAN1911
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1996 Astro Van. Currently will start after 12-20 bumps of the ignition. Will not start with a constant crank of the ignition. Once it starts, the rough idle will smooth out (due to the 12-20 bumps of the ignition) and it will idle just fine. It will engage into any gear fine as well. It will also crawl in gear across the parking lot without a problem. Once the accelerator pedal is pushed, the engine will stumble and stall.

Prior to this issue, there has been no other issues with this van. No codes, no problems.

Due to this issue, we have checked the ignition system, which has excellent spark & good timing. Fuel pressure was at 56, so we changed the fuel pump & strainer as well as the filter. This resulted in no change of the symptoms.

Currently, we are about to look into the fuel pressure regulator, and I assume that it must be under the plastic upper intake. Sounds like a pain. What's your thoughts?
Apr 22, 2008 at 10:10 AM
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RASMATAZ
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If its the 4.3 with the Vortec CPI system, your pressure should be 60-66 psi-Did you recheck the fuel pressure with the new pump?

Checking the fuel pressure regulator-you need to remove the IMTV-if the passenger side is washed out-the regulator is leaking

Also you might want to test the throttle position sensor? I'll be here waiting upon your return for further assistance.
Apr 22, 2008 at 11:14 AM
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BRIAN1911
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[quote:def4624461="rasmataz"]If its the 4.3 with the Vortec CPI system, your pressure should be 60-66 psi-Did you recheck the fuel pressure with the new pump?

Checking the fuel pressure regulator-you need to remove the IMTV-if the passenger side is washed out-the regulator is leaking

Also you might want to test the throttle position sensor? I'll be here waiting upon your return for further assistance.[/quote:def4624461]

I just completed taking off the upper plenum. There is no washed out area, and everything is as typical as it would be with 200K+ miles on it. I'm going to replace the regulator anyway (nasty black fuel was behind the regulator).

Fuel pressure is good at the test schrader valve.

I have not tested the TPS as of yet. Since it has been years since I finished ASEP, I'm not to knowledgeable on the 1996 TPS circuit.
Apr 22, 2008 at 12:01 PM
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RASMATAZ
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The TP sensor output voltage should be .85 or less at idle ( Closed Throttle ) and its not non-adjustable.
Apr 22, 2008 at 4:53 PM
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BRIAN1911
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[quote:18eba4fb10="rasmataz"]The TP sensor output voltage should be .85 or less at idle ( Closed Throttle ) and its not non-adjustable.[/quote:18eba4fb10]

Just finished replacing the fuel pressure regulator. No change... problem still exists.

here's some more info on the truck.
~~~~~~~ TRUCK IDLE ~~ TRUCK OFF
TPS ~~~~~~~~.0-.4~~~~~ .8 (does go to 100% WOT)
RPM~~~~~~~~ 700 ~~~~~ 0
Calc load ~~~~~ 1.6 ~~~~~ .4
MAF~~~~~~~~ .60 ~~~~~ .26
MAP ~~~~~~~~ 10. ~~~~~ 27.8
Coolant~~~~~~122 ~~~~~ 100
IAT~~~~~~~~~ 81 ~~~~~ 81
Ign Adv ~~~~~ -20 ~~~~~~~ 0
ST FTRM1~~~~~ 21 ~~~~~ 0
ST FTRM2 ~~~~~ 25 ~~~~~ 0
Fuel sys ~~~~~ open ~~~~~open
O2sII ~~~~~ .16-.40 ~~~~~ .095
ST FTRM11 ~~~~ 30 ~~~~~~~0
ST FTRM21 ~~~~ 30 ~~~~~~~0
O2S12 ~~~~~ .30-.70 ~~~~.115
Apr 23, 2008 at 3:00 PM
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RASMATAZ
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Have you recheck the fuel pressure. Also open up the EGR and investigate.

Also test the oil pressure switch-
Apr 23, 2008 at 6:05 PM
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BRIAN1911
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[quote:08fef43c02="rasmataz"]Have you recheck the fuel pressure. Also open up the EGR and investigate.

Also test the oil pressure switch-[/quote:08fef43c02]

Fuel pressure = 68
EGR = torx screw on bottomside moves freely, no plugups.

Not sure why the Oil press switch is a factor. regardless, dash gage reads oil pressure at 40psi at idle.
Apr 23, 2008 at 7:55 PM
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RASMATAZ
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EGR = torx screw on bottomside moves freely, no plugups. Could be sucking in air diluting the A/F mixture

Not sure why the Oil press switch is a factor. regardless, dash gage reads oil pressure at 40psi at idle. The OPSU has a contact in it that closes when oil pressure is above 4lbs to power the fuel pump after the initial 2secs while engine is being crank. When the engine fires up the switch powers the fuel pump.
Apr 24, 2008 at 10:19 AM
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BRIAN1911
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[quote:a7d09deb67="rasmataz"]EGR Could be sucking in air diluting the A/F mixture
The OPSU has a contact in it that closes when oil pressure is above 4lbs to power the fuel pump after the initial 2secs while engine is being crank. When the engine fires up the switch powers the fuel pump.[/quote:a7d09deb67]

Correct, but if there was a problem with the OPS, then the truck would not start & idle as it does now. Right? At this moment, I can only test on baseline resistance and by dash gage. Since they both seem to look fine as well as the engine running/idling, the OPS subject may be moot. Agree?

I saw no evidence of a gasket sealing issue with the EGR. Pushing on the Torx screw on the moveable EGR valve is easy and not obstructed. I might look at a new EGR to feel the tension while pushing on the Torx screw for comparison. otherwise, this may be another dead end.

So far, we're both batting zero. How about any other suggestions?
Apr 24, 2008 at 10:58 AM
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BRIAN1911
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I take it that you gave up on this since you have not replied back in several days.
Apr 30, 2008 at 4:24 AM