95 4.3 vortec (Jimmy) ignition switch question on fuel del..

Blazerman: thanks for the suggestions!

Ok... I am in the midst of repllacing both the ECT and the oil pressure
sender (I have another post with some access for removal concerns). I have
a decent scanner that shows no codes or strange freeze frame data, etc. The
vehicle has a crate motor with maybe 50k km. The distributor along with
cap,rotor, plugs, wires, pcv, coil and all newly replaced (LOF also done in
last month). The throttle body and butterfly valve are spotless, the TPS
was replaced and calibrated to factory specs. The gas tank and fuel pump are
new also (although I hear horror stories of folks going through fuel pumps
like undewear!). I did have a slight vac leak at the throttle body but that
was just fixed with new ducting.
Fuel pressure tests at 60psi with the pump and holds at 60 for over 15min
(engine off). The pressure drops to about 50psi within 2 hours - I'm not
outruling a dying pressure regulator or leaking nut kit/injector issue. I
thought about leaving the gauge on all night to see if any excess pressure
is lost. The O2 sensors test ok also. As well, the engine passes emissions
maybe one month ago (cold start issue existed then also though).

I have been pining my money on a lazy ECT causing fuel starvation at the
injectors but I am having a tricky time figuring out the best way to remove
it.

Thanks and take care,
Andrew.


in article 1169414850.743155.257960.TakeThisOut@q2g2000cwa.googlegroups.com, blazerman
at jerry.TakeThisOut@peru-motors.com wrote on 1/21/07 4:27 PM:

>
> Andrew-have owned many, many 95's and can't ever remember putting in a
> ignition switch in any-have put many in 97's but 95's, not many. Hard
> start-how long on the tune -up? Plugs, wires, cap, rotor, fuel filter,
> air cleaner. If that warrants doing, I'd do it-won't be bad money
> spent plus it may solve your problem. Besides that...Not costing much,
> if any, is fuel pressure check. Key on initial 2 second fuel pump
> pressure should be around 60 psi and then drop to 54ish when pump goes
> off and hold. Beyond that... temperature sensor possibly..in that this
> senson may be sending the wrong info to the computer thus leaning or
> richening out the initial fuel mixture. Hope this helps and let us
> know the results as we have many more suggestions! Good luck
> jery.TakeThisOut@peru-motors.com
>
>
> AWN wrote:
>> Sorry if this is a stupid question but if there's a bad ignition switch in
>> my Jimmy, is it possible that the engine will crank but fuel delivery will
>> be sporadic or cut off? I'm starting to suspect the ignition switch as a
>> possibility for my poor cold starts.
>> Thanks.
>> Andrew.
>
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

AWN-I'd lean towards the temperature sensor. If you have a scan tool
on a cold morning scan it and look at the temperature screen and
compare that to the ambient temperature-may cost only your time.(then
hopefully a sensor). Keep us posted. Certainly don't know the answer
to your problem for sure but at the moment I peresonally had had more
issues with this sensor than oil pressure senders. Also doubt fuel is
your issue based on what you've wrote but some injector(good quality)
may help. in case of a varnished injector. Sounds like your doing the
best you can-good luck and keep us posted when you get it so the rest
of us will know! jerry DeleteThis @peru-motors.com



AWN wrote:
> Blazerman: thanks for the suggestions!
>
> Ok... I am in the midst of repllacing both the ECT and the oil pressure
> sender (I have another post with some access for removal concerns). I have
> a decent scanner that shows no codes or strange freeze frame data, etc. The
> vehicle has a crate motor with maybe 50k km. The distributor along with
> cap,rotor, plugs, wires, pcv, coil and all newly replaced (LOF also done in
> last month). The throttle body and butterfly valve are spotless, the TPS
> was replaced and calibrated to factory specs. The gas tank and fuel pump are
> new also (although I hear horror stories of folks going through fuel pumps
> like undewear!). I did have a slight vac leak at the throttle body but that
> was just fixed with new ducting.
> Fuel pressure tests at 60psi with the pump and holds at 60 for over 15min
> (engine off). The pressure drops to about 50psi within 2 hours - I'm not
> outruling a dying pressure regulator or leaking nut kit/injector issue. I
> thought about leaving the gauge on all night to see if any excess pressure
> is lost. The O2 sensors test ok also. As well, the engine passes emissions
> maybe one month ago (cold start issue existed then also though).
>
> I have been pining my money on a lazy ECT causing fuel starvation at the
> injectors but I am having a tricky time figuring out the best way to remove
> it.
>
> Thanks and take care,
> Andrew.
>
>
> in article 1169414850.743155.257960 DeleteThis @q2g2000cwa.googlegroups.com, blazerman
> at jerry DeleteThis @peru-motors.com wrote on 1/21/07 4:27 PM:
>
> >
> > Andrew-have owned many, many 95's and can't ever remember putting in a
> > ignition switch in any-have put many in 97's but 95's, not many. Hard
> > start-how long on the tune -up? Plugs, wires, cap, rotor, fuel filter,
> > air cleaner. If that warrants doing, I'd do it-won't be bad money
> > spent plus it may solve your problem. Besides that...Not costing much,
> > if any, is fuel pressure check. Key on initial 2 second fuel pump
> > pressure should be around 60 psi and then drop to 54ish when pump goes
> > off and hold. Beyond that... temperature sensor possibly..in that this
> > senson may be sending the wrong info to the computer thus leaning or
> > richening out the initial fuel mixture. Hope this helps and let us
> > know the results as we have many more suggestions! Good luck
> > jery DeleteThis @peru-motors.com
> >
> >
> > AWN wrote:
> >> Sorry if this is a stupid question but if there's a bad ignition switch in
> >> my Jimmy, is it possible that the engine will crank but fuel delivery will
> >> be sporadic or cut off? I'm starting to suspect the ignition switch as a
> >> possibility for my poor cold starts.
> >> Thanks.
> >> Andrew.
> >
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

Ok here's the latest... I replaced the ECT and the IAT... ALthough I
think the fuel economy may have gotten a little better, I still have
the cold starting problems. I have replaced the fuel pump relay 3x
with known working replacements. When the relay 'clicks' and the pump
whirls, it will start on a dime. I still think that there may be a
chance that a faulty ignition switch is causing this problem.

As stated previously, fuel pressure tested over 60psi at the rail
shraeder test port, the pump will run with 12V to the test connector
under the hood EVERY time, the battery and alternator tested fine
(battery over 12V and alt constant at just over 14.6V), all tune up
stuff has been done (plugs, cap, rotor, wires, etc).

I thought that either the ignition switch, crank sensor, or oil
pressure sensor may be at fault here. Can anyone comment? I have a
baby on the way as we speak (due date was yesterday) so I'd like to
get this damn Jimmy off my to-do list).

What else should I be checking?? I checked nearly every 5V reference
sensor and they came back fine (slight adjustment to the TPS but that
was unrelated).

Thanks in advance!
Andrew.

blazerman wrote:
> AWN-I'd lean towards the temperature sensor. If you have a scan tool
> on a cold morning scan it and look at the temperature screen and
> compare that to the ambient temperature-may cost only your time.(then
> hopefully a sensor). Keep us posted. Certainly don't know the answer
> to your problem for sure but at the moment I peresonally had had more
> issues with this sensor than oil pressure senders. Also doubt fuel is
> your issue based on what you've wrote but some injector(good quality)
> may help. in case of a varnished injector. Sounds like your doing the
> best you can-good luck and keep us posted when you get it so the rest
> of us will know! jerry.RemoveThis@peru-motors.com
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

in article 1171084875.010556.44760.RemoveThis@v33g2000cwv.googlegroups.com, neex at
anixon1.RemoveThis@cogeco.ca wrote on 2/10/07 12:21 AM:

> Ok here's the latest... I replaced the ECT and the IAT... ALthough I
> think the fuel economy may have gotten a little better, I still have
> the cold starting problems. I have replaced the fuel pump relay 3x
> with known working replacements. When the relay 'clicks' and the pump
> whirls, it will start on a dime. I still think that there may be a
> chance that a faulty ignition switch is causing this problem.
>
> As stated previously, fuel pressure tested over 60psi at the rail
> shraeder test port, the pump will run with 12V to the test connector
> under the hood EVERY time, the battery and alternator tested fine
> (battery over 12V and alt constant at just over 14.6V), all tune up
> stuff has been done (plugs, cap, rotor, wires, etc).
>
> I thought that either the ignition switch, crank sensor, or oil
> pressure sensor may be at fault here. Can anyone comment? I have a
> baby on the way as we speak (due date was yesterday) so I'd like to
> get this damn Jimmy off my to-do list).
>
> What else should I be checking?? I checked nearly every 5V reference
> sensor and they came back fine (slight adjustment to the TPS but that
> was unrelated).
>
> Thanks in advance!
> Andrew.
>
> blazerman wrote:
>> AWN-I'd lean towards the temperature sensor. If you have a scan tool
>> on a cold morning scan it and look at the temperature screen and
>> compare that to the ambient temperature-may cost only your time.(then
>> hopefully a sensor). Keep us posted. Certainly don't know the answer
>> to your problem for sure but at the moment I peresonally had had more
>> issues with this sensor than oil pressure senders. Also doubt fuel is
>> your issue based on what you've wrote but some injector(good quality)
>> may help. in case of a varnished injector. Sounds like your doing the
>> best you can-good luck and keep us posted when you get it so the rest
>> of us will know! jerry.RemoveThis@peru-motors.com
>
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

Sorry to double post. I have a few tech questions if anyone wants to
entertain them...

Does the 95 4.3L W series motor on this Jimmy SLT 4x4 have an
accumulator/reservoir for residual fuel pressure capacity? As well, does
this block use a 'cold start injector'? I have also pulled the intake
manifold tuning valve and looked in with a light a mirror for clean, shiny
hose connections, etc. to indicate a leak at an injector or the FPR (as
stated there's no problem with fuel pressure that I can drill down). I have
fuel and spark and no codes are printing currently with the engine running
in perfect time, etc. I just cannot drill down this damn intermitent
starting problem. Does this sound like a worn crank sensor??

Thanks and sorry once again for the duplicate rants.
Andrew.
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

In article ,
AWN wrote:

> Sorry to double post. I have a few tech questions if anyone wants to
> entertain them...
>
> Does the 95 4.3L W series motor on this Jimmy SLT 4x4 have an
> accumulator/reservoir for residual fuel pressure capacity?

No.

> As well, does
> this block use a 'cold start injector'?

No.

> I have also pulled the intake
> manifold tuning valve and looked in with a light a mirror for clean, shiny
> hose connections, etc. to indicate a leak at an injector or the FPR (as
> stated there's no problem with fuel pressure that I can drill down). I have
> fuel and spark and no codes are printing currently with the engine running
> in perfect time, etc. I just cannot drill down this damn intermitent
> starting problem. Does this sound like a worn crank sensor??

Not if you have spark when the no-start is occurring.

> Thanks and sorry once again for the duplicate rants.
> Andrew.
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

Thanks for the response. Do you have any ideas what else I should be
looking into diagnostics-wise? The MAP reads dead on also at 28.9in Hg
(with about +800 ft above sea level). I'm beside myself as to why the pump
will power up with the test connector but not so every time with the ign
(key in engine off). When it finally starts, it runs like a top.
Thanks. Would it help to post the outputs from my scanner??
Andrew.



in article nonelson-CF20D4.21115910022007.DeleteThis@newsclstr02.news.prodigy.com,
aarcuda69062 at nonelson.DeleteThis@sbcglobal.net wrote on 2/10/07 10:12 PM:


>
>> I have also pulled the intake
>> manifold tuning valve and looked in with a light a mirror for clean, shiny
>> hose connections, etc. to indicate a leak at an injector or the FPR (as
>> stated there's no problem with fuel pressure that I can drill down). I have
>> fuel and spark and no codes are printing currently with the engine running
>> in perfect time, etc. I just cannot drill down this damn intermitent
>> starting problem. Does this sound like a worn crank sensor??
>
> Not if you have spark when the no-start is occurring.
>
>> Thanks and sorry once again for the duplicate rants.
>> Andrew.
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

In article ,
AWN wrote:

> Thanks for the response. Do you have any ideas what else I should be
> looking into diagnostics-wise?

You need a wiring diagram and a test light to solve this problem.
When no-start, check for voltage and ground at the pump and then
work your way forward to the fuel pump relay and the ECM signal
to it. Concentrate on any splices and grounds since thhat is
where trouble usually shows up first.

> The MAP reads dead on also at 28.9in Hg
> (with about +800 ft above sea level). I'm beside myself as to why the pump
> will power up with the test connector but not so every time with the ign
> (key in engine off). When it finally starts, it runs like a top.
> Thanks. Would it help to post the outputs from my scanner??

Nope, doesn't sound like the problem is with anything that would
be seen in the data stream.
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

"aarcuda69062" wrote in message

> In article ,
> AWN wrote:
>
> > Thanks for the response. Do you have any ideas what else I should be
> > looking into diagnostics-wise?
>
> You need a wiring diagram and a test light to solve this problem.
> When no-start, check for voltage and ground at the pump and then
> work your way forward to the fuel pump relay and the ECM signal
> to it. Concentrate on any splices and grounds since thhat is
> where trouble usually shows up first.
>
> > The MAP reads dead on also at 28.9in Hg
> > (with about +800 ft above sea level). I'm beside myself as to why the
pump
> > will power up with the test connector but not so every time with the ign
> > (key in engine off). When it finally starts, it runs like a top.
> > Thanks. Would it help to post the outputs from my scanner??
>
> Nope, doesn't sound like the problem is with anything that would
> be seen in the data stream.

OBD I and II both cycle the fuel pump relay on initial 'key on' for about a
second and a half to initially pressurize the fuel rail. The relay then
turns off and stays off until the computer either registers oil pressure
and/or rotation via the crank sensor/distributor.

I would have to check a service manual but I believe 60 psi is a little
high. Anyway, if the vehicle maintains fuel pressure during cranking then
that rules out fuel pump problems. Move on to injector triggering and
ignition.

Our intermittent starting problem occurred in high humidity, turned out to
be a defective new part, distributor cap arcing only in high humidity would
it short so bad as to not start.
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

"Charlie B" wrote in


>
> "aarcuda69062" wrote in message
>
>> In article ,
>> AWN wrote:
>>
>> > Thanks for the response. Do you have any ideas what else I should
>> > be looking into diagnostics-wise?
>>
>> You need a wiring diagram and a test light to solve this problem.
>> When no-start, check for voltage and ground at the pump and then
>> work your way forward to the fuel pump relay and the ECM signal
>> to it. Concentrate on any splices and grounds since thhat is
>> where trouble usually shows up first.
>>
>> > The MAP reads dead on also at 28.9in Hg
>> > (with about +800 ft above sea level). I'm beside myself as to why
>> > the
> pump
>> > will power up with the test connector but not so every time with
>> > the ign (key in engine off). When it finally starts, it runs like
>> > a top. Thanks. Would it help to post the outputs from my scanner??
>>
>> Nope, doesn't sound like the problem is with anything that would
>> be seen in the data stream.
>
> OBD I and II both cycle the fuel pump relay on initial 'key on' for
> about a second and a half to initially pressurize the fuel rail. The
> relay then turns off and stays off until the computer either registers
> oil pressure and/or rotation via the crank sensor/distributor.
>
> I would have to check a service manual but I believe 60 psi is a
> little high. Anyway, if the vehicle maintains fuel pressure during
> cranking then that rules out fuel pump problems. Move on to injector
> triggering and ignition.
>
> Our intermittent starting problem occurred in high humidity, turned
> out to be a defective new part, distributor cap arcing only in high
> humidity would it short so bad as to not start.
>
>
>

actually i see 55 to 60 normally on the system being discusssed (keyon,
engoff), dropping to about 52 with engine running....any security feature
should also be considered...........kjun
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

Do you mean security as is OEM fuel/ign cutoff? This truck has no security
features other than standard power locks. Thanks for all the recent
responses.

Andrew.



in article 45d86d12$0$24744$4c368faf@roadrunner.com, Kjun at
wrote on 2/18/07 10:13 AM:

> actually i see 55 to 60 normally on the system being discusssed (keyon,
> engoff), dropping to about 52 with engine running....any security feature
> should also be considered...........kjun
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del.. 

Charlie,
Thanks for the input. When you mention checking injector triggering are you
talking about using noid lights? I guess the procedure for checking the
poppets is a little different as they don't test like regular EFI systems as
far as I know. I still can't for the life of me access the oil pressure
switch. Any tips on this? Do I have to pull the plenum or the distributor?
Thanks again!
Andrew.


in article BKWdnb6qU61mQEjYnZ2dnUVZ_segnZ2d.RemoveThis@centurytel.net, Charlie B at
aniceguy.RemoveThis@centurytel.net@centurytel.net wrote on 2/16/07 11:41 AM:

> OBD I and II both cycle the fuel pump relay on initial 'key on' for about a
> second and a half to initially pressurize the fuel rail. The relay then
> turns off and stays off until the computer either registers oil pressure
> and/or rotation via the crank sensor/distributor.
 >> Stay informed about: 95 4.3 vortec (Jimmy) ignition switch question on fuel del..