96 Tahoe fuel injected takes too long to start

[trouble]

Hey, My 96 tahoe starts like an old carburated truck, not a fuel injected
carb. Only after just stopping and trying to restart, does it actually start
right away. This was after a set of plugs and cap was installed and a
flywheel and starter. Any ideas? Now it takes about 8 seconds to start then
rtuns fine. no other problems.

[KenG]

Try this:
1. Turn key to run, but don't start. Listen for the fuel pump to run for
2 seconds. If you can't hear it run, then you might look at the BCM.
2. If you can hear it run, then turn the key off and on again. Then
after it stops, one more time.
3. Now start the motor.
4. If it is still hard to start, then you might look at the fuel pump.
There is a check valve that maintains pressure in the line when the
motor stops.
5. Another possibility is an injector that is leaking, bleeding the
pressure off overnight. Results are similar to the check valve, but
takes longer to evidence itself. Consider this if it does start
immediately, but still starts hard in the morning.

KenG

[Future]

Thanx, Sure enough, when I follow step 2 the truck starts exactly as is is
suppossed too. what is the signifigance of the two times? please explain. I
think I understood you to say that I should be looking into a leaky
injector? any words of advise as to where to look for the drips of gas. I am
assuming I would see some at the injector? thanx again

[KenG]

This gives you 3 possibilities, but only 2 posible fixes. Could actually
be any of the 3.
1. Fuel pump is putting out insufficient pressure. Not likely, as you
would have many other symptoms (poor driveability).
2. The check valve in the fuel return line. If it is leaking, your
residual fuel pressure will leak down. How bad it leaks controls how
long after you stop does it take to restart normally.
3. One or more injector can be leaking. Usually takes overnight to
result in a problem in starting. More injectors leaking shortens the
time. If you have one or more injector leaking, try this: About an hour
after you stop for the day. Remove the air cleaner. Smell for gas in the
intake, if you have a strong smell of gas, suspect one or more
injectors. Note that there will always be a faint smell of gas in the
intake, unless the motor has not been run in days.

1 and 2 require a fuel pump change.
3 obviously requires further troubleshooting to identify the leaking
injector.

KenG

[Future]

Hi again. I have more news/findings. Although the running of the fuel pump
thing twice worked yesterday during shorter time periods, it didn't work
this morning. I took off the air filter and only smelt a slight odor of gas
after an hour last night. I believe you hit the nail on the head about the
overnight pressure drop. Could you explain to me why the turning on till it
stops then on again , seems to work. I don't understand. I guess I will be
calling my dealer soon to ask about the replacement of the injector/s. Is it
really expensive? Thanx again.

[Lonely G-Monkey]

Horribly. I might think about looking into replacing yourself. I have
a TBI engine, just one fuel injector. A "standard" (it's a company)
fuel injector set me back $98. Thats with 0 labor. If you buy your
own, BUY AC-DELCO. Yes it is more expensive, yes it will last 4x
longer than anything else (no matter what part it is)

A great example:
Energizer Batteries (I think this is the "top of the line" at PepBoys)
2 year replacement warranty. Not bad huh? Most batteries only last
about 3-4 years right?

AC-Delco battery, 6 year free replacement, and some amount of time for
a no-dead battery warranty: free jump start. (can't remember how long)
NOT BAD - My father generally gets 10 years service out of an
AC-Delco, and retires it before it gets "too dangerous" to run during
the winter...IE not because it's dead.

I think of money spent on AC-Delco as an investment.....

-The Lonely Grease Monkey
1985' K5 305CUI TH700R4 NP208
KJ's successor

"Ignorance is preferable to error; and he is less remote
from the truth who believes nothing, then he who believes
what is a wrong."
- Thomas Jefferson

[KenG]

Check Valve:
In the fuel feed line is a check valve that only allows fuel to flow to
the fuel rail and not drain back into the tank through the pump (when it
is not running). This check valve ensures that there is always fuel in
the pump and in the fuel line to the fuel rail hopefully still under
pressure.

Fuel Pump:
The fuel pump feeds gas under high pressure to the fuel rail. There two
different paths to run the pump: 1. If the ECM senses that the motor is
running (it has oil pressure) the motor runs. If there is no oil
pressure, then the pump stops. This is to prevent a situation where the
motor is not running but the fuel pump is, as in an accident, where
there is a high likelyhood of fuel leaking. 2. The two second burst when
you turn the key to run. This "refreshes" the pressure in the fuel rail,
so that full pressure is available when you crank.

Injectors:
Feed fuel into the intake system, usually at the rear face of the intake
valve.

Pressure Regulator:
The pressure regulator bleeds off the pressure from the fuel rail that
is in excess of the needs of the engine. The fuel that is bled off is
returned to the tank, via a fuel return line.

There are a few ways this pressure can be compromised.
1. The pump is producing less than optimum pressure. This usually
results in driveability complaints like poor throttle response, or surging.
2. There is a leaking injector/s. Usually only evidenced at idle, may
cause the engine to "load up" during long periods of idle. Might even
stall. Usually takes all night to bleed the pressure down to a level
that causes starting problems. A leaking injector WILL cause a strong
gas odor about one hour after stopping the engine.
3. The pressure regulator is defective and is venting more pressure than
necessary, or just plain leaking. Usually a slow leak, but faster than
an injector. Might bleed down pressure over a few hours.
4. There is a defective check valve allowing fuel to drain back into the
tank. This is the most variable failure. It might have a slow leak,
resulting in any of the symptoms above, or it might be fast and vent
pressure as soon as the motor is shut off. If the fuel drains out of the
rail, and back to the tank, then the pump might lose it's prime. If the
prime is lost, then it will take an extended amount of pump on-time to
regain the prime. If the tank is full it will be short, as the pump is
submerged, if the tank is low it could take some time to prime the pump.
If you leave the tank low and the pump loses it's prime on a regular
basis, it will damage the pump, as the pump is cooled by the gas it is
submerged in.

Many systems have a schrader valve in them that allows checking the fuel
pressure. Attach an approved gas pressure guage, run the engine, turn it
off and monitor the pressure. The pressure may drop a little overnight.
It should never drop to zero overnight. It sounds like yours is.

Clear as mud eh?

[Future]

how much pressure should be at the test port during , running, and how much
when stopped? Thanx

[Future]

New info. I put the gas pressure gauge on the test port when I got home last
night and restarted the engine. as soon as I turn the key 52 pound
immediately. when I turn it off, it starts to drop off slowly. down to 40
lbs in 3 minutes down to 20 lbs in 20 minutes 10 pounds in an hour, this
morning pressure was at 2lbs.
Question is, when I first turn on the key, the gauge goes right to 52 but
the truck still takes 5 to 6 seconds to start. this a hint at all? thanx

[Rita A.. Berkowitz]

"Future" <fut...@tomorrow.com> wrote in message
news:3i5rb.56542$Gq.11...@twister.nyc.rr.com...

The above confirms that your fuel pressure regulator and fuel delivery
system is working as designed. Your problem will be found elsewhere. My
next step would be to confirm, as they say in the hood, that your Cadillac
converter is not clogged. I'll bet that the catalytic converter is on its
last leg. How many miles on the truck?

Rita

[Future]

I don't get it Rita. why would the CC be involved? Wouldn't the fact that
the pressure is leaking out kinda point be to a leaky injector or bad check
valve? Please explain

[KenG]

Now you have real data to look at. The rate you describe the drop is
pretty rapid. As I read your post, it is down to 2 lbs in the morning.
Obviously this is not enough pressure to operate under. It takes 6
seconds to start because the 2 second burst from the pump is not enough
to bring the pressure up to a sufficient level to provide enough fuel to
start on. While you are cranking the oil pressure is going up and
eventually the ECM starts the fuel pump. The ECM doesnt know that the
engine is not running, it only senses that there is oil pressure ans
starts the pump. In a good system, I would expect to see 40 PSI +/- 5
overnight. A single injector leaking might let it drop to 10 PSI
overnight, but the 2 second burst in the morning should bring the
pressure up to near full pressure, and the engine would start
immediately. The fact that the pressure drops to 2 PSI overnight in the
morning tells me that the check valve is leaking. The fact that it takes
6 seconds of cranking to start in the morning tells me that the fuel is
completely draining back into the tank leaving air or at least bubbles
in the fuel line/rail. This would mean that the check valve is leaking
very bad. To have a definitive isolation, try this.
1. Disconnect the fuel line at the fuel filter (very easy, just squeeze
the white plastic tabs, and pull it off).
2. Get a piece of fuel line and connect it to the filter with a hose
clamp.
3. Connect the pressure guage to the other end of the hose. You should
have them connected in this order, tank, filter, hose, pressure guage
4. Turn the key to run not that the pump runs for 2 seconds.
5. Check the pressure. It will likely be above 52, as there is no
pressure regulator. Keep watching the pressure. If it drops
significantly, then the pump/check valve is bad. If it stays up, then
the problem is injector(s) or regulator.

Good Luck..
KenG

BTW, please quote some from the previous message, it make it easier to
follow the flow of the thread.
L8rs

[KenG]

You've been paying attention...

[Donavon]

Any updates on this Future? I am having a simular issue.

Thanks.

[Gerry]

Sounds like a bad fuel injection pressure regulator..

"Donavon" <nospam...@yahoo.com> wrote in message
news:Ta6sb.22743$mb5.17385@fed1read02...

[Chris]

Sounds like I have a similar one on my 96 Jimmy. I'm starting a new post
with a better description of the trouble. See "Erratic Starting Problem in
96 Jimmy"

"Donavon" <nospam...@yahoo.com> wrote in message
news:Ta6sb.22743$mb5.17385@fed1read02...

[Corey Scheich]

Funny thing. I was having the same problem with my 99 Yukon. I just kind
of ignored it. I don't really know if I was getting pressure loss because I
never tested it but I had the same symptom cranked for 5-8 seconds before
starting, and ran fine once it was running. It seemed to be related to my
failed attempt to replace the DARN fuel Filter so I wrote it off as a small
pressure leak and when I had time I was going to cut the fuel line in front
of the DARN fuel filter and fix the problem. Well I hadn't gotten to that
yet and my battery went bad. I replaced the battery and it seems that the
truck starts like a champ now. It no longer takes 5 seconds even over
night. I guess the battery just couldn't take the load of both the pump and
starter. Any comments would be welcomed insight.

Corey

"KenG" <Ke...@dont.spam.me.ec.rr.co> wrote in message
news:tt8rb.100416$IA2.3...@twister.southeast.rr.com...

[PN...@webtv.net]

fuel pressure should NOT drop after pump stops running. you either have
a bad fuel pump or regulator. most likely pump.