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1996 Chevy Astro 1996 Astro fuel distribution issues

Tiny
BRIAN1911
  • MEMBER
  • 1996 CHEVROLET ASTRO
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 24,000 MILES
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?
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Tuesday, April 22nd, 2008 AT 10:10 AM

9 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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.
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Tuesday, April 22nd, 2008 AT 11:14 AM
Tiny
BRIAN1911
  • MEMBER
  • 6 POSTS
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.
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Tuesday, April 22nd, 2008 AT 12:01 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
The TP sensor output voltage should be.85 or less at idle ( Closed Throttle ) and its not non-adjustable.
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Tuesday, April 22nd, 2008 AT 4:53 PM
Tiny
BRIAN1911
  • MEMBER
  • 6 POSTS
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
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Wednesday, April 23rd, 2008 AT 3:00 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Have you recheck the fuel pressure. Also open up the EGR and investigate.

Also test the oil pressure switch-
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Wednesday, April 23rd, 2008 AT 6:05 PM
Tiny
BRIAN1911
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  • 6 POSTS
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.
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Wednesday, April 23rd, 2008 AT 7:55 PM
Tiny
RASMATAZ
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  • 75,992 POSTS
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.
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Thursday, April 24th, 2008 AT 10:19 AM
Tiny
BRIAN1911
  • MEMBER
  • 6 POSTS
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?
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Thursday, April 24th, 2008 AT 10:58 AM
Tiny
BRIAN1911
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I take it that you gave up on this since you have not replied back in several days.
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Wednesday, April 30th, 2008 AT 4:24 AM

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