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Fuel pressure issue - 95 Astro - please help



 
 
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  #41  
Old February 10th 05, 04:14 AM
ed
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Posts: n/a
Default

Steve W. wrote:
> An engine needs thre things to run
> Air, Fuel, Ignition source
> Air is a given unless your covering the air cleaner with a bag.
> Fuel - about the only thing you didn't replace was the tank, so I would
> say your OK there
>
> The symptoms point to a heat related failure. Some component is getting
> hot enough to shut down the engine.
> Since you still have fuel pressure when the engine dies it isn't a bad
> pump.
> It also isn't likely the EGR since they don't normally shut down an
> engine and then clear up when they get cool. They are either stuck open
> (which causes REAL bad idle on the 4.3 and an engine that will not idle
> hot or cold) or they don't work at all.
>
>
> Ignition?
> You said you found a cruddy wire end. One usually won't do much but
> cause missfiring in that cylinder. I has a problem with the wifes 94 4.3
> that was a bad set of plug wires. It caused massive missfiring but no
> real problem with running or acceleration. Just bucking under load.
> (common symptom FYI).
>
> Bad plugs- Not likely since they fire OK when cold. Plus for the engine
> to quit they all have to stop working.
>
> Plug wires- Same as above BUT they could cause crossfiring.
>
> Cap - Usually causes missfires if the cap is bad.
>
> Rotor - possible but not real likely.
>
> Coil- very possible- it could be shorting out internally when it gets
> warm enough.
>
> Ignition Module - possible for the above reason, but they usually just
> fail.
>
> Computer - It's not showing codes which is not unusual for an OBD I.5
> vehicle (oddball that GM used in 95 on some vehicles) they mainly show a
> code only when an item totally fails, unlike OBD II that can tell you
> that a sensor is just getting weak. It could have a bad connection on
> the main connection though.
>
> Main wiring harness connection on the firewall - It has been a culprit a
> few times for heat related problems. It gets warm and the connection
> opens.
>
> It is also possible that it could be a bad connection to one of the
> above components.
>

I think I'd elmintae fuel entirely for the most part and at least slap a
gauge on that fuel pressure. Run it and shut it off see if it holds
pressure. See what the presure is when it stops running for the hell of it.

Sure the EGR is carboned up inside?(it should be getting close by now).

Ads
  #42  
Old February 10th 05, 04:16 AM
ed
external usenet poster
 
Posts: n/a
Default

Steve W. wrote:
> An engine needs thre things to run
> Air, Fuel, Ignition source
> Air is a given unless your covering the air cleaner with a bag.
> Fuel - about the only thing you didn't replace was the tank, so I would
> say your OK there
>
> The symptoms point to a heat related failure. Some component is getting
> hot enough to shut down the engine.
> Since you still have fuel pressure when the engine dies it isn't a bad
> pump.
> It also isn't likely the EGR since they don't normally shut down an
> engine and then clear up when they get cool. They are either stuck open
> (which causes REAL bad idle on the 4.3 and an engine that will not idle
> hot or cold) or they don't work at all.
>
>
> Ignition?
> You said you found a cruddy wire end. One usually won't do much but
> cause missfiring in that cylinder. I has a problem with the wifes 94 4.3
> that was a bad set of plug wires. It caused massive missfiring but no
> real problem with running or acceleration. Just bucking under load.
> (common symptom FYI).
>
> Bad plugs- Not likely since they fire OK when cold. Plus for the engine
> to quit they all have to stop working.
>
> Plug wires- Same as above BUT they could cause crossfiring.
>
> Cap - Usually causes missfires if the cap is bad.
>
> Rotor - possible but not real likely.
>
> Coil- very possible- it could be shorting out internally when it gets
> warm enough.
>
> Ignition Module - possible for the above reason, but they usually just
> fail.
>
> Computer - It's not showing codes which is not unusual for an OBD I.5
> vehicle (oddball that GM used in 95 on some vehicles) they mainly show a
> code only when an item totally fails, unlike OBD II that can tell you
> that a sensor is just getting weak. It could have a bad connection on
> the main connection though.
>
> Main wiring harness connection on the firewall - It has been a culprit a
> few times for heat related problems. It gets warm and the connection
> opens.
>
> It is also possible that it could be a bad connection to one of the
> above components.
>

I think I'd elmintae fuel entirely for the most part and at least slap a
gauge on that fuel pressure. Run it and shut it off see if it holds
pressure. See what the presure is when it stops running for the hell of it.

Sure the EGR isn't carboned up inside?(it should be getting close by now).

yeah I hate the OBD on that year. My 95 would be so much easier to fix.

  #43  
Old February 10th 05, 04:16 AM
ed
external usenet poster
 
Posts: n/a
Default

Steve W. wrote:
> An engine needs thre things to run
> Air, Fuel, Ignition source
> Air is a given unless your covering the air cleaner with a bag.
> Fuel - about the only thing you didn't replace was the tank, so I would
> say your OK there
>
> The symptoms point to a heat related failure. Some component is getting
> hot enough to shut down the engine.
> Since you still have fuel pressure when the engine dies it isn't a bad
> pump.
> It also isn't likely the EGR since they don't normally shut down an
> engine and then clear up when they get cool. They are either stuck open
> (which causes REAL bad idle on the 4.3 and an engine that will not idle
> hot or cold) or they don't work at all.
>
>
> Ignition?
> You said you found a cruddy wire end. One usually won't do much but
> cause missfiring in that cylinder. I has a problem with the wifes 94 4.3
> that was a bad set of plug wires. It caused massive missfiring but no
> real problem with running or acceleration. Just bucking under load.
> (common symptom FYI).
>
> Bad plugs- Not likely since they fire OK when cold. Plus for the engine
> to quit they all have to stop working.
>
> Plug wires- Same as above BUT they could cause crossfiring.
>
> Cap - Usually causes missfires if the cap is bad.
>
> Rotor - possible but not real likely.
>
> Coil- very possible- it could be shorting out internally when it gets
> warm enough.
>
> Ignition Module - possible for the above reason, but they usually just
> fail.
>
> Computer - It's not showing codes which is not unusual for an OBD I.5
> vehicle (oddball that GM used in 95 on some vehicles) they mainly show a
> code only when an item totally fails, unlike OBD II that can tell you
> that a sensor is just getting weak. It could have a bad connection on
> the main connection though.
>
> Main wiring harness connection on the firewall - It has been a culprit a
> few times for heat related problems. It gets warm and the connection
> opens.
>
> It is also possible that it could be a bad connection to one of the
> above components.
>

I think I'd elmintae fuel entirely for the most part and at least slap a
gauge on that fuel pressure. Run it and shut it off see if it holds
pressure. See what the presure is when it stops running for the hell of it.

Sure the EGR isn't carboned up inside?(it should be getting close by now).

yeah I hate the OBD on that year. My 95 would be so much easier to fix.

  #44  
Old February 10th 05, 04:27 AM
Lawrence Glickman
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Default

On Thu, 10 Feb 2005 03:16:28 GMT, ed > wrote:

Mr Ed,

I know nothin about your vehicle, can you answer a question?
Is it fuel injected?
Are any of your injectors sticking *open* allowing for the complete
loss of pressure sometimes?

Just asking.

Lg

  #45  
Old February 11th 05, 06:01 PM
external usenet poster
 
Posts: n/a
Default

yes it is fuel injection. i just replaced the CPI (injector/spider).
Lawrence Glickman wrote:
> On Thu, 10 Feb 2005 03:16:28 GMT, ed >

wrote:
>
> Mr Ed,
>
> I know nothin about your vehicle, can you answer a question?
> Is it fuel injected?
> Are any of your injectors sticking *open* allowing for the complete
> loss of pressure sometimes?
>
> Just asking.
>
> Lg


  #47  
Old February 11th 05, 09:07 PM
aarcuda69062
external usenet poster
 
Posts: n/a
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In article >,
Lawrence Glickman > wrote:

> On 11 Feb 2005 09:01:10 -0800, wrote:
>
> >yes it is fuel injection. i just replaced the CPI (injector/spider).

>
> That's probably what is called the "fuel rails" on my vehicle.
> There is one rail for bank 1, another for bank 2, they are tied
> together with a piece of high pressure hose.


Nope, his set up is different.
Central Port Injection (CPI)
One centrally mounted injector (the solenoid component) with six
plastic tubes, each one extends into an intake port, at the end
of each tube is a spring loaded poppet valve.
The central injector fires one time for each intake event, when
this occurs it's the combination of fuel pressure and intake
vacuum (pressure differential) that allows the poppet to open
against spring pressure.
There is also a fuel pressure regulator mounted to the side of
the CPI, inside the manifold plenum.
here's a picture;

http://www.lindertech.com/reconinj.htm

It's the fourth one down on that page.

> At the end of each rail is a "test port" which is a female threaded
> opening, presently each plugged with a Teflon-wrapped bolt. This is
> where you can tap in with a fuel pressure gauge if so desired. Each
> rail feeds 3 injectors. Appears to be a simple enough affair.


His fuel pressure tap is at the left rear side of the intake
plenum where the fuel lines enter the intake plenum, he has
already mentioned testing the fuel pressure and posted the
results.

> I'm wondering if you had this problem before you replaced your
> *injector spider* and if that is why you replaced it. OR, if this
> problem suddenly appeared -after- the spider was replaced.


IIRC, most or all of the problems were there before replacement
of the CPI, the fuel pressure regulator was leaking, he knew this
because he removed the manifold tuning valve which allowed a
direct view of the fuel pressure regulator, evidence of a leak is
apparent if one sees the normal gunk found inside the manifold
washed clean in the vicinity of the fuel pressure regulator.

> And if you didn't replace the injectors, but left the old ones on, I
> can't help but wonder if one is sticking open on occasion, allowing
> fuel to bleed-off into the cylinder and take down the pressure in your
> fuel lines when the engine is off.
>
> Otherwise, the fuel pressure regulator is suspect, but I'm certain
> you've already ruled that out.


All of these parts are new or re-built.
  #48  
Old February 11th 05, 10:58 PM
Lawrence Glickman
external usenet poster
 
Posts: n/a
Default

On Fri, 11 Feb 2005 20:07:29 GMT, aarcuda69062
> wrote:

>In article >,
> Lawrence Glickman > wrote:
>
>> On 11 Feb 2005 09:01:10 -0800, wrote:
>>
>> >yes it is fuel injection. i just replaced the CPI (injector/spider).

>>
>> That's probably what is called the "fuel rails" on my vehicle.
>> There is one rail for bank 1, another for bank 2, they are tied
>> together with a piece of high pressure hose.

>
>Nope, his set up is different.
>Central Port Injection (CPI)
>One centrally mounted injector (the solenoid component) with six
>plastic tubes, each one extends into an intake port, at the end
>of each tube is a spring loaded poppet valve.
>The central injector fires one time for each intake event, when
>this occurs it's the combination of fuel pressure and intake
>vacuum (pressure differential) that allows the poppet to open
>against spring pressure.
>There is also a fuel pressure regulator mounted to the side of
>the CPI, inside the manifold plenum.
>here's a picture;
>
>
http://www.lindertech.com/reconinj.htm
>
>It's the fourth one down on that page.
>
>> At the end of each rail is a "test port" which is a female threaded
>> opening, presently each plugged with a Teflon-wrapped bolt. This is
>> where you can tap in with a fuel pressure gauge if so desired. Each
>> rail feeds 3 injectors. Appears to be a simple enough affair.

>
>His fuel pressure tap is at the left rear side of the intake
>plenum where the fuel lines enter the intake plenum, he has
>already mentioned testing the fuel pressure and posted the
>results.
>
>> I'm wondering if you had this problem before you replaced your
>> *injector spider* and if that is why you replaced it. OR, if this
>> problem suddenly appeared -after- the spider was replaced.

>
>IIRC, most or all of the problems were there before replacement
>of the CPI, the fuel pressure regulator was leaking, he knew this
>because he removed the manifold tuning valve which allowed a
>direct view of the fuel pressure regulator, evidence of a leak is
>apparent if one sees the normal gunk found inside the manifold
>washed clean in the vicinity of the fuel pressure regulator.
>
>> And if you didn't replace the injectors, but left the old ones on, I
>> can't help but wonder if one is sticking open on occasion, allowing
>> fuel to bleed-off into the cylinder and take down the pressure in your
>> fuel lines when the engine is off.
>>
>> Otherwise, the fuel pressure regulator is suspect, but I'm certain
>> you've already ruled that out.

>
> All of these parts are new or re-built.


So what is left over that could be causing his symptom of loss of ALL
fuel pressure on occasion?

What would you want to look at next as a probable cause of his
difficulties?

Lg

  #49  
Old February 12th 05, 01:31 AM
aarcuda69062
external usenet poster
 
Posts: n/a
Default

In article >,
Lawrence Glickman > wrote:


> > All of these parts are new or re-built.

>
> So what is left over that could be causing his symptom of loss of ALL
> fuel pressure on occasion?


It could be any of the parts he's already replaced.
The fuel pressure bleeding off at rest can only occur in three
places;
1) Injector (CPI) assembly
2) Fuel pump check valve
3) External fuel line between #s 1 and 2

It's not hard to isolate sections of the fuel system to determine
where the leak off is.

> What would you want to look at next as a probable cause of his
> difficulties?


If it is fuel starvation or over fueling, it will show up on the
O2 sensor voltage and/or the fuel trim numbers viewed on a scan
tool, I mentioned this to him in a post a while back at the
beginning. He procured a scan tool but went no further with it.
He could have posted the scan data here and myself and a number
of others could have given out opinions of what was there.

He did mention in one post that his running fuel pressure dropped
to 50 psi, this is 4 psi below the absolute minimum required to
open the poppet nozzles in his CPI system ( pressure
differential)

He'd be best off with a scan tool with recording capability, that
way he can trigger a recording on a test drive at the moment the
problem occurs, and then review the movie from the trigger point
for anything unusual.

It's also entirely possible that it isn't a fuel problem.
  #50  
Old February 12th 05, 01:33 AM
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Default

The CPI is the enitre injector assembly. I replaced it after I started
having problems.

I fuel pump died about 800 miles ago and i changed it. Then i started
have problems so I changed the CPI, exaust, EGR valve, and all other
items listed above.

Now I am really stuck. I am thinking about taking to Pep boys
tomorrow. But they will probably just run an engine diagnostic and
check the codes and fuel pressure. So I dont know what good that will
do.

 




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