L98: starts, but won't keep running.

Hi group:

I have an 89 L98 conv. I am having a problem with it, first thing in
the morning it will start, rev up to about 12-1500 rpm and then idle
down and die. It will not restart after this unless let sit for 5 or
10 mins. then it will repeat the performance.
No codes are shown, and it is getting spark, even when not starting.
The fuel rails are pressurized (not sure how much pressure) It seems
like the injectors are not putting out gas or perhaps the throttle
position is unknown?
Trying to get it to keep running with the throttle on the initial
start just kills it, I suspect something to do with not getting enough
fuel in the mixture.
Anyone experience a similar problem or have any ideas on how to
diagnose this further?


TIA
Dave G.

Dave Gee wrote:
> Hi group:
>
> I have an 89 L98 conv. I am having a problem with it, first thing in
> the morning it will start, rev up to about 12-1500 rpm and then idle
> down and die. It will not restart after this unless let sit for 5 or
> 10 mins. then it will repeat the performance.
> No codes are shown, and it is getting spark, even when not starting.
> The fuel rails are pressurized (not sure how much pressure) It seems
> like the injectors are not putting out gas or perhaps the throttle
> position is unknown?
> Trying to get it to keep running with the throttle on the initial
> start just kills it, I suspect something to do with not getting enough
> fuel in the mixture.
> Anyone experience a similar problem or have any ideas on how to
> diagnose this further?
>
>
> TIA
> Dave G.
>
The shop manual (Section 6E) and a pressure gauge will save you time and
a bundle of dollars throwing parts at an unknown problem. Without codes
though even that won't be easy.

Gentle throttle tends to rule out an idle air circuit failing to open.

Since you know spark is OK then its time to figure out what's happening
first. Is the fuel pump shutting down or the injectors all shutting off
with plenty of pressure on the rail.

If the engine runs for 2 seconds and then dies of fuel starvation, it
could be failure of the ECM to receive a pulse train from the
distributor --that will shut down the injectors. I've seen that in a
350tpi Camaro. That could be a broken wire from the distributor to the
ECM or a bad distributor module.

You might also pull the vacuum line on the fuel pressure regulator and
see if there's gasoline leaking from the wet side to the vacuum side.

Best to get out the book.

PJ

"Dave Gee" > wrote in message
ups.com...
> Hi group:
>
> I have an 89 L98 conv. I am having a problem with it, first thing in
> the morning it will start, rev up to about 12-1500 rpm and then idle
> down and die. It will not restart after this unless let sit for 5 or
> 10 mins. then it will repeat the performance.
> No codes are shown, and it is getting spark, even when not starting.
> The fuel rails are pressurized (not sure how much pressure) It seems
> like the injectors are not putting out gas or perhaps the throttle
> position is unknown?
> Trying to get it to keep running with the throttle on the initial
> start just kills it, I suspect something to do with not getting enough
> fuel in the mixture.
> Anyone experience a similar problem or have any ideas on how to
> diagnose this further?
>
>
> TIA
> Dave G.

This sounds just like what happened to my 86. It turned out to be a bad fuel
pump. Once replaced the car ran as well as it ever has.

"Bob" > wrote in message
...
>
> "Dave Gee" > wrote in message
> ups.com...
>> Hi group:
>>
>> I have an 89 L98 conv. I am having a problem with it, first thing in
>> the morning it will start, rev up to about 12-1500 rpm and then idle
>> down and die. It will not restart after this unless let sit for 5 or
>> 10 mins. then it will repeat the performance.
>> No codes are shown, and it is getting spark, even when not starting.
>> The fuel rails are pressurized (not sure how much pressure) It seems
>> like the injectors are not putting out gas or perhaps the throttle
>> position is unknown?
>> Trying to get it to keep running with the throttle on the initial
>> start just kills it, I suspect something to do with not getting enough
>> fuel in the mixture.
>> Anyone experience a similar problem or have any ideas on how to
>> diagnose this further?
>>
>>
>> TIA
>> Dave G.
>
> This sounds just like what happened to my 86. It turned out to be a bad
> fuel pump. Once replaced the car ran as well as it ever has.
Fuel filter?

Hi All:

Thanks for all the replies and tips, certainly appreciated. One
thing puzzles me, don't these cars throw a code if the fuel pressure is
low? It seems that this is elementry for a FI system to function
properly and with all the other things that the system seems to monitor
it seems odd to leave this out.

"Dave Gee" > wrote in message
oups.com...
> Hi All:
>
> Thanks for all the replies and tips, certainly appreciated. One
> thing puzzles me, don't these cars throw a code if the fuel pressure is
> low? It seems that this is elementry for a FI system to function
> properly and with all the other things that the system seems to monitor
> it seems odd to leave this out.
>
You mean like the code that the 72,000 pounds of computers that monitor the
space shuttle said "you have a deadly hole in your wing"? **** happens or
should I say it don't happen when it needs to, plus you're dealing with and
older, less sophisticated computer system. You still need to do as you were
doing, is there spark, is there fuel, is the exhaust restricted, and so on
and check the basics before you start looking for an exotic problem. I'd be
glad to post the fuel management codes definition if you can retrieve it.
There are about 400 trouble codes today that can be displayed and I've had a
complete computer failure in a C5 that threw no code pertaining to it's
demise. By the way, in that case it would start but would not move more that
a few inches before shutting down. The good thing was it would run and allow
us to keep the air-conditioning running on a very hot expressway while
waiting on the flatbed.

--
Dad
05 C6 Silver/Red 6spd Z51
72 Shark Black/Black/4spd

It wouldn't happen to have an oil pressure switch go bad or something?
No oil pressure, kill the fuel?

Dave Gee wrote:
> Hi All:
>
> Thanks for all the replies and tips, certainly appreciated. One
> thing puzzles me, don't these cars throw a code if the fuel pressure is
> low? It seems that this is elementry for a FI system to function
> properly and with all the other things that the system seems to monitor
> it seems odd to leave this out.
>

On Wed, 19 Oct 2005 12:01:35 -0400, "Dad" > wrote:

>"Dave Gee" > wrote in message
roups.com...
>> Hi All:
>>

>a few inches before shutting down. The good thing was it would run and allow
>us to keep the air-conditioning running on a very hot expressway while
>waiting on the flatbed.

Gee, that sounds like a fun car for $45,000 or more.

Hi again:

Dad, if you can post the code definitions I would be curious to see
them, I have a small reader and booklet that lists some that are tied
to 'blinks' that give you some information but I don't think it is as
comprehensive as what you are talking about.
Perhaps you could send them as an attachment to me via e-mail of
perhaps an FTP? As to the fuel pressure on these cars, monitoring that
would be as simple as the oil pressure light on a 56 Buick, just turn
it on if pressure falls below a certain value.

I just put a fuel filter on the car, it made no difference. After
experimenting some I am able to keep the car running, (sort of) by
careful throttle positioning so that lets out oil pressure switch
problems or a distributer not telling the ECM to continue spark.
Looking at the plugs it is obvious that the car is running EXTREMELY
lean, IMHO lean enough where engine damage could result from trying to
run it, which should be throwing a code too. Since this is not the
case I am beginning to think the ECM is getting a spurious signal from
some sensor that monitors the exhaust gas makup, or the ECM itself is
not functioning properly. As near as I can tell, there are no exhaust
restrictions.
There seem to be some setups that let you hook up a laptop to the ECM
and, along with some software, see what the ECM 'thinks' is going on.
Has anyone here used these setups on the L98 engines, and does anyone
have an idea as to the
pros and cons of the various setups? It seems like this would be a
very valuable diagnostic and tuning tool.

TIA
Dave G.
89 vert.
69 GTV
Ducatis,BSAs,NSUs,Maicos
And a CBX

<white minority> wrote in message
...
> On Wed, 19 Oct 2005 12:01:35 -0400, "Dad" > wrote:
>
>>"Dave Gee" > wrote in message
groups.com...
>>> Hi All:
>>>
>
>>a few inches before shutting down. The good thing was it would run and
>>allow
>>us to keep the air-conditioning running on a very hot expressway while
>>waiting on the flatbed.
>
> Gee, that sounds like a fun car for $45,000 or more.

Actual sticker price was less than 40k, where have you been? What I paid was
less than that, but then I'm sure you have a fun car for much less.

--

Life is a sexually transmitted condition that is always fatal.