[Diy_efi] re: rich/lean and O2
David Cooley
n5xmt at bellsouth.net
Thu Nov 25 19:18:14 GMT 2004
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A real fuel pressure regulator would be needed... the smashed line may w=
ork
at low fuel load, but at Wide open throttle the pressure will drop and th=
e
engine will lean out..=0D
=0D
=0D
-------Original Message-------=0D
=0D
From: RogeranCarol=0D
Date: 11/25/04 14:10:02=0D
To: diy_efi at diy-efi.org=0D
Subject: [Diy_efi] re: rich/lean and O2=0D
=0D
Thanks for the comeback guys--I don't have a scan tool so I can't say wha=
t
the Block learn or the Integrator #'s are. The ECM won't go into closed l=
oop
according to the MIL flashes I see while in the Field Service mode (
shorting pin A to B on the ALDL connector while the engine runs--2 flashe=
s
per second are supposed to indicate "open loop" and that is what I'm seei=
ng)
The ECM is a 16171199 with PROM Broadcast code BDWB--the only California
certified combo for a K1500 5.7L Chevy with an NV4500 manual trans
(according to the local SMOG Ref)! You gotta love SMOG laws. This ECM has=
a
dedicated O2 sensor ground that connects directly to the engine block. I
double checked all grounds and especially those associated with MAP and O=
2
sensors. Even removed ECM connector pins and inspected for damage/corrosi=
on.
All appear good. But I didn't check MAP output above idle (idle =3D1.05v)=
=2E I
ll do that today. Per my Helm manual, a low MAP voltage (high vacuum) cou=
ld
cause the ECM to go into the "Deceleration En-Leanment mode", even though
the vehicle is not moving--this would cause a significant lean-out of the
fuel mixture.=0D
I'm thinking fuel pump, even though my pressure readings are steady 12.5
psi across my test RPM range. What I didn't mention before is that since =
I'm
planning on converting to multi port injection, I didn't want to install =
or
buy a TBI pump, soooo, I jury rigged my current high pressure fuel pump
(original engine was a 4.0L Jeep with sequential multi port injection) to
run at 15psi with the TBI disconnected by running a metal return line fro=
m
the filter output to the original fuel return line, then smashing the tub=
e
until I got 15psi. Seemed to work, except for the cold lean stumble, unti=
l I
got curious about being in Closed Loop. I'm thinking I don't have a grasp=
of
the pressure/volume thingy and even though I have good pressure, maybe I =
don
t have sufficient volume.=0D
Addition thoughts/comments would be appreciated=0D
Roger =0D
=20
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<DIV>A real fuel pressure regulator would be needed... the smashed =
line may work at low fuel load, but at Wide open throttle the pressure wi=
ll drop and the engine will lean out..</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV id=3DIncrediOriginalMessage><I>-------Original Message-------</I></D=
IV>
<DIV> </DIV>
<DIV id=3Dreceivestrings>
<DIV dir=3Dltr style=3D"FONT-SIZE: 11pt"><I><B>From:</B></I> <A href=3D"m=
ailto:rogerancarol at cox.net">RogeranCarol</A></DIV>
<DIV dir=3Dltr style=3D"FONT-SIZE: 11pt"><I><B>Date:</B></I> 11/25/04 14:=
10:02</DIV>
<DIV dir=3Dltr style=3D"FONT-SIZE: 11pt"><I><B>To:</B></I> <A href=3D"mai=
lto:diy_efi at diy-efi.org">diy_efi at diy-efi.org</A></DIV>
<DIV dir=3Dltr style=3D"FONT-SIZE: 11pt"><I><B>Subject:</B></I> [Diy_efi]=
re: rich/lean and O2</DIV></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>Thanks for the comeback guys--I don't ha=
ve a scan tool so I can't say what the Block learn or the Integrator #'s =
are. The ECM won't go into closed loop according to the MIL flashes =
I see while in the Field Service mode ( shorting pin A to B on the A=
LDL connector while the engine runs--2 flashes per second are supposed to=
indicate "open loop" and that is what I'm seeing). The ECM is a 16171199=
with PROM Broadcast code BDWB--the only California certified combo for a=
K1500 5.7L Chevy with an NV4500 manual trans (according to the loca=
l SMOG Ref)! You gotta love SMOG laws. This ECM has a dedicated O2 sensor=
ground that connects directly to the engine block. I double checked=
all grounds and especially those associated with MAP and O2 sensors. Eve=
n removed ECM connector pins and inspected for damage/corrosion. All =
;appear good. But I didn't check MAP output above idle (idle =3D1.05=
v). I'll do that today. Per my Helm manual, a low MAP voltage (high vacuu=
m) could cause the ECM to go into the "Deceleration En-Leanment mode", ev=
en though the vehicle is not moving--this would cause a significant lean-=
out of the fuel mixture.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> I'm thinking fuel pump, even thoug=
h my pressure readings are steady 12.5 psi across my test RPM range. What=
I didn't mention before is that since I'm planning on converting to mult=
i port injection, I didn't want to install or buy a TBI pump, soooo,=
I jury rigged my current high pressure fuel pump (original engine was a =
4.0L Jeep with sequential multi port injection) to run at 15psi with the =
TBI disconnected by running a metal return line from the filter outp=
ut to the original fuel return line, then smashing the tube until I got 1=
5psi. Seemed to work, except for the cold lean stumble, until I got curio=
us about being in Closed Loop. I'm thinking I don't have a grasp of the p=
ressure/volume thingy and even though I have good pressure, maybe I don't=
have sufficient volume.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Addition thoughts/comments would be appr=
eciated</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Roger</FONT> </DIV>
<DIV> </DIV></TD></TR>
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