RE: Fuel pump going, questions:
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RE: Fuel pump going, questions: - 3/18/2008 8:26:51 AM
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swartlkk
Posts: 15304
Joined: 5/1/2005
From: Waterloo, NY
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I didn't take any pictures when I did my spider replacement...
Here are the pics from the manual with the upper plenum off:
The first manual pic above doesn't show the #1 and #6 fuel lines & poppet nozzles for some reason...
The original SCFI system has 6 electronic injectors located in a central pack which are fired sequentially, feeding fuel to pressure actuated poppet nozzles located in the intake runners directly ahead of the intake valves. These poppet nozzles can gum up over time, causing problems.
In mid-02, GM released an updated version, the MFI system, when they did some more tweaks to the 4.3L engine. Below is a picture of a v8 MFI spider assembly (v6 assembly is very similar less 2 injectors).
Courtesy of Lindertech.com
The MFI spider is an upgrade in the sense that the often problematic poppet nozzles are gone, moving the electronic injectors out of the injector pack to the ports. The MFI spider is backwards compatible in all '96 thru mid-'02 SCFI motors (the only motors available in the Blazer in this time period) although the '96 thru '98 may require a different injector pack mount. One thing to note is that the MFI system cannot flow as much fuel as the older SCFI system can which may present a problem if you are planning on pushing the limits of your motor through upgrades.
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RE: Fuel pump going, questions: - 3/23/2008 10:44:06 AM
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Pur_SSyn
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Joined: 3/17/2008
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That sucks that you couldn't take the truck Friday.
There wont be any air in the fuel line. It's not a closed system like brake hydraulics, or clutch, so any air would have been purged
when we fired up the truck.
It's odd that the engine would develop a ticking sound the day after the fuel filter swap. I can't see how it would be related, but
anything is possible? We'll have a look under the hood in case I dislodged a vacuum line while connecting the fuel pressure gauge.
Other than that, we can scan the port and see if anything else developed over night (weird).
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RE: Fuel pump going, questions: - 3/23/2008 5:37:47 PM
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swartlkk
Posts: 15304
Joined: 5/1/2005
From: Waterloo, NY
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Unless you are continuously getting air in the fuel lines, air isn't the problem. All of the air would be purged on initial start up after the filter replacement.
Ticking would either be a VERY violent misfire, an exhaust leak, or an oil supply problem. You really need to narrow that selection down for us... A misfire of that magnitude would cause a check engine light. An exhaust leak could cause the engine to run rich which could explain the loss of power, but not the random nature of the problem as you described it. An oil supply issue should have resulted in a hard part failure if it was bad enough to cause a loss of power...
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RE: Fuel pump going, questions: - 3/26/2008 7:53:55 AM
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swartlkk
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Yes, a misfire can cause a code, but a misfire typically is accompanied by a flashing check engine light.
Check the codes and let us know.
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RE: Fuel pump going, questions: - 3/27/2008 7:50:07 PM
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swartlkk
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From: Waterloo, NY
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B1S3 has nothing to do with engine operation. It is a catalyst monitoring sensor only. If you were watching the actual mV output, the post cat sensor will be flat lined under normal conditions as it shows that the converter is working properly.
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RE: Fuel pump going, questions: - 3/28/2008 6:45:19 AM
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Pur_SSyn
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If I recall correctly, the LT's are showing ~ + 10%. Short terms
are also + 7-10%.
quote:
If you were watching the actual mV output, the post cat sensor will be flat lined under normal conditions as it shows that the converter is working properly.
That's interesting as the scan shows a dead straight and steady
output. I was expecting to see some deflection +/- from the
nominal value.
Mind you, the motors I'm used to monitoring are performance
engines with tweaked out fuel curves, and high flow inefficient
cats.
These types of engines say a prayer, and roll dice before their
emissions tests 
So...if you're saying that a dead flat line is fine, then we'll
move onto other areas.
When we pulled the plugs last night, I had a look. There were
certainly a couple that looked richer than normal, however this
was after the Seafoam test so it's tough to say whether the
plug read was indicitave of the positive trim readings.
Besides that, a plug read should be done with a fresh plug of
course.
We're getting closer to a solution. Everything that has been
done has certainly improved the performance. During the cruise
last night, there were zero misfires.
The previous numbers showed tens of thousands on some cylinders.
#4 was over 40,000!
Next step is to look for an exhaust leak between the flange
and catalytic, as well as check the coolant. There is an odd
'gurgling' sound just behind the dash area which I suspect are
the heater core lines.
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