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Fuel pressure issue - 95 Astro - please help



 
 
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  #51  
Old February 12th 05, 02:15 AM
Lawrence Glickman
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On Sat, 12 Feb 2005 00:31:13 GMT, aarcuda69062
> wrote:

>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.


OK. Myself, I've recorded what should be "normal" numbers for my own
engine using a data logger and storing the file(s) on my hard drive
for future reference.

I've also used my Scantool to record what parameters that reveals:
e.g.
long term fuel trim bank 1 % = 5.5, 4.7, 1.6, 2.3
short term fuel trim bank 1 %= 0.00, -2.3, 1.63, 3.9

long term fuel trim bank 2 %= 3.1, 3.9, 7.0, 7.8, 7.0, 7.8, 3.9
short term fuel trim bank 2 %= 2.3, 2.1, 0, -.08, -2.3, -3.1

and I am lead to believe, from my readings, that it is perfectly
NORMAL on my engine for bank 1 to be quite different from bank 2,
although I can't put my finger on the source of that information at
this moment.

Now goody for me, I can program my data logger to record all of the
above values in a continuous stream if so desired, so if I see any
MARKED deviation from my baseline reading, I've got a "clue."

There are many many other parameters I've recorded for baseline
purposes, too many to list here. Point is, I would have reference
values to consult. Maybe this is asking too much for anybody to do.

>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.


Wouldn't he get what's called Freeze Frame? IOW, my data logger has
the ability to show all engine parameters it is capable of reading at
the moment a malfunction occurs. I've never had the pleasure of
seeing this happen, so I can't be more specific, IOW, I can't give you
the parameters delivered because it hasn't happened to me =yet=. But
if and when it does, I may post for General Information purposes.

>It's also entirely possible that it isn't a fuel problem.


Could be electrical. Intermittent loss of power to fuel pump, etc.
But I'm wondering if that wouldn't throw a DTC. Again, I've never
experienced ( on this car ) a malfunction so I can't be more specific.

Lg

Ads
  #53  
Old February 12th 05, 02:43 AM
aarcuda69062
external usenet poster
 
Posts: n/a
Default

In article >,
Lawrence Glickman > wrote:

> >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.

>
> OK. Myself, I've recorded what should be "normal" numbers for my own
> engine using a data logger and storing the file(s) on my hard drive
> for future reference.


Good idea. It's always better to know what normal looks like
then trying to figure it out once things go wrong.

> I've also used my Scantool to record what parameters that reveals:
> e.g.
> long term fuel trim bank 1 % = 5.5, 4.7, 1.6, 2.3
> short term fuel trim bank 1 %= 0.00, -2.3, 1.63, 3.9
>
> long term fuel trim bank 2 %= 3.1, 3.9, 7.0, 7.8, 7.0, 7.8, 3.9
> short term fuel trim bank 2 %= 2.3, 2.1, 0, -.08, -2.3, -3.1


Add the long term fuel and the short term fuel to determine the
total fuel correction at that instant, anything over 10-12
percent is cause for suspicion.

> and I am lead to believe, from my readings, that it is perfectly
> NORMAL on my engine for bank 1 to be quite different from bank 2,
> although I can't put my finger on the source of that information at
> this moment.


Yes, that is true.

> Now goody for me, I can program my data logger to record all of the
> above values in a continuous stream if so desired, so if I see any
> MARKED deviation from my baseline reading, I've got a "clue."
>
> There are many many other parameters I've recorded for baseline
> purposes, too many to list here. Point is, I would have reference
> values to consult. Maybe this is asking too much for anybody to do.


It becomes a question of whether it is possible.

> >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.

>
> Wouldn't he get what's called Freeze Frame? IOW, my data logger has
> the ability to show all engine parameters it is capable of reading at
> the moment a malfunction occurs.


His is a 95 model year, not yet quite OBD2, his system may not
have the capability to record freeze frame data, I also believe
that he's posted that he's not getting any fault codes, so if no
fault is being detected, no freeze frame.

> I've never had the pleasure of
> seeing this happen, so I can't be more specific, IOW, I can't give you
> the parameters delivered because it hasn't happened to me =yet=. But
> if and when it does, I may post for General Information purposes.


Just booby-trap something.
Loose gas cap, disconnect the EGR, pop the purge flow sensor off,
etc.

> >It's also entirely possible that it isn't a fuel problem.

>
> Could be electrical. Intermittent loss of power to fuel pump, etc.
> But I'm wondering if that wouldn't throw a DTC. Again, I've never
> experienced ( on this car ) a malfunction so I can't be more specific.

  #54  
Old February 12th 05, 03:12 AM
Lawrence Glickman
external usenet poster
 
Posts: n/a
Default

On Sat, 12 Feb 2005 01:43:38 GMT, aarcuda69062
> wrote:

>In article >,
> Lawrence Glickman > wrote:
>
>> >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.

>>
>> OK. Myself, I've recorded what should be "normal" numbers for my own
>> engine using a data logger and storing the file(s) on my hard drive
>> for future reference.

>
>Good idea. It's always better to know what normal looks like
>then trying to figure it out once things go wrong.
>
>> I've also used my Scantool to record what parameters that reveals:
>> e.g.
>> long term fuel trim bank 1 % = 5.5, 4.7, 1.6, 2.3
>> short term fuel trim bank 1 %= 0.00, -2.3, 1.63, 3.9
>>
>> long term fuel trim bank 2 %= 3.1, 3.9, 7.0, 7.8, 7.0, 7.8, 3.9
>> short term fuel trim bank 2 %= 2.3, 2.1, 0, -.08, -2.3, -3.1

>
>Add the long term fuel and the short term fuel to determine the
>total fuel correction at that instant, anything over 10-12
>percent is cause for suspicion.
>
>> and I am lead to believe, from my readings, that it is perfectly
>> NORMAL on my engine for bank 1 to be quite different from bank 2,
>> although I can't put my finger on the source of that information at
>> this moment.

>
>Yes, that is true.
>
>> Now goody for me, I can program my data logger to record all of the
>> above values in a continuous stream if so desired, so if I see any
>> MARKED deviation from my baseline reading, I've got a "clue."
>>
>> There are many many other parameters I've recorded for baseline
>> purposes, too many to list here. Point is, I would have reference
>> values to consult. Maybe this is asking too much for anybody to do.

>
>It becomes a question of whether it is possible.
>
>> >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.

>>
>> Wouldn't he get what's called Freeze Frame? IOW, my data logger has
>> the ability to show all engine parameters it is capable of reading at
>> the moment a malfunction occurs.

>
>His is a 95 model year, not yet quite OBD2, his system may not
>have the capability to record freeze frame data, I also believe
>that he's posted that he's not getting any fault codes, so if no
>fault is being detected, no freeze frame.
>
>> I've never had the pleasure of
>> seeing this happen, so I can't be more specific, IOW, I can't give you
>> the parameters delivered because it hasn't happened to me =yet=. But
>> if and when it does, I may post for General Information purposes.

>
>Just booby-trap something.
>Loose gas cap, disconnect the EGR, pop the purge flow sensor off,
>etc.


That's a good idea ! ;0
I can just disconnect for example the EGR vacuum line or something
simple like that while the engine is running so I can see what will be
recorded at the moment the MIL is lighted.

Good Idea. Beats wondering what and how much information I would get
when a DTC pops up. What I mean by that, is I am currently monitoring
4 out of a possible 23 engine parameters. So when a DTC is thrown, I
don't know how much information of WHAT parameters will get logged to
the chip. This is the perfect way to find out.

Lg


>
>> >It's also entirely possible that it isn't a fuel problem.

>>
>> Could be electrical. Intermittent loss of power to fuel pump, etc.
>> But I'm wondering if that wouldn't throw a DTC. Again, I've never
>> experienced ( on this car ) a malfunction so I can't be more specific.


  #56  
Old February 14th 05, 05:38 PM
[email protected]
external usenet poster
 
Posts: n/a
Default

Update.

I double checked my work on the CPI install and found a problem. One
of the fuel lines was not all the way in and it was slowly leaking. I
oiled (really helped) the lines up real good and made sure it was all
the way in this time.

I gas fouled all the plugs so I have to change the plugs before I can
let you guys know if that fixed it. Also, it is still bleeding off
pressure with the key off. It has been going all the way down to
10psi.

My current guess is it is the pulsator since it was never replaced.
>From what I understand this might not cause problems after the van has

been started.

I will try and change the plugs before work tomorrow and let you guys
know . I might not get finished because it is not the easiest job on
that van.

  #57  
Old February 23rd 05, 11:04 AM
Jessie Herrera
external usenet poster
 
Posts: n/a
Default

Hi,
I'm assuming you have fuel injection. Your pump should pump around 35
psi. You can put a pressure gauge on your fuel line and check the
pressure. First though, I would suspect a dirty fuel filter. Sometimes
fuel injected vehicles have 2 in line filters. when one plugs up it can
cause your problem. It can also be your fuel regulator.
Good luck to you.
Jessie

wrote:

> Can someone please help me figure this out? I am really stuck.
>
> I have a 1995 CHEVROLET TRUCK ASTRO VAN 2WD
> 6 Cylinders 262 W 4.3L CPI. 105,000 miles
>
>
>
> Symptoms:
> The van is cutting out like it is running out of fuel while driving.
>
> I let the van warm up first before a test drive. It drives okay (not
> great) at first, then it starts acting like it is running out of gas.
> It bogs down and stalls when I accelerate. I tried flooring it and it
> wants to die. This problem is progressive meaning it is getting worse;
> now it happens after just a couple miles of driving. The problem will
> go away (van drives much better) after turning off the van and then
> back on.
>
>
> History:
> Fuel pump quit working over new years. I replaced and it drove fine.
> I drove one 300 mile trip then another 300 miles of city driving with
> no problems.
>
> It got real cold (irrelevant?). I drove for 25 miles with no issues.
> I filled up with gas (irrelevant?) after work and drove 10 miles and it
> started acting up.
>
> The problem got worse over the next couple days (60 miles city
> driving).
>
> I changed the fuel filter which was clogged and appeared to be the
> original filter. It seemed to run fine. I drove several very short
> trips 5 miles which may have been too short to notice symptoms. I
> filled up again, then drove 15 miles.
>
> It acted worse than ever.
>
> I checked the fuel pressure. It was about 62psi with the pump running
> but dropped to 6psi when not running.
>
> I replaced the CPI unit and the nut kit (fuel lines). The fuel
> regulator was leaking. I could see where the gas had cleaned the
> inside of the plenum.
>
> I retested fuel pressure. It was 62psi with the pump running but
> dropped to 22psi with the pump off. My Haynes manual said it should
> only drop 3-10psi with the key off.
>
> I road tested the van and it has the same symptoms.
>
> Shouldn't I be able to see or smell the gas that bleeds off? I
> don't see any gas (I will double check tonight).
>
> Now I do not know what to do. I am stuck. Can anyone offer any
> suggestion?
>


  #58  
Old February 26th 05, 04:08 AM
[email protected]
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Posts: n/a
Default

I finally got it fixed. I suspect it was the pulsator.
I ended up dropping the tank and replacing the pump, threw out the
pulsator and replaced with fuel line, replaced the main gasket and a
missing o-ring on one of the fuel lines to the tank. I am not sure if
the o-ring was lost when I dropped the tank or some other time.

It runs great now. Thank you guys so much for all you help and
suggestions!!!!!

  #59  
Old May 10th 18, 03:18 AM posted to rec.autos.tech,alt.trucks.chevy
Drewsky
external usenet poster
 
Posts: 1
Default Fuel pressure issue - 95 Astro - please help

replying to daveg.01, Drewsky wrote:
I have the same problem with my van same model w vin. Did you ever find the
problem?

--
for full context, visit https://www.motorsforum.com/chevy_tr...elp-35769-.htm


 




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