1999 5.7GSI PWTR. Running really rich in driveway

[mylesm260]

1999 5.7GSI PWTR

Ran fine 2 years ago. (has not run in 2 years)

Went to wake the motor up.
New plugs
New fuel filter
Had been flogged so I expected it to be a little rough getting it started up.

Engine is running very rich. Black smoke, barely idling.


- added fresh fuel to the tank
- dumped the fuel from the filter into a glass jar. Looks good
- tested TPS: center-tap 0.6 to 5.0 volts (0-100% throttle)
- tested coolant temp sensor: 930 ohms with the engine "warm" and 1400 ohms after it had cooled down some
- tested the map sensor

no obstructions / no leaks
5.0 volts with engine off
only drops down to 3.9 volts at idle (idling like crap)
used my oil extractor to create vacuum, managed to get 2.5 volts

- tested fuel pressure. 29PSI at the test port
- Fuel pressure regulator looks rusty, but pressure checks out


The one thing I did notice, a connector for what I believe to be the oil pressure switch has corroded away.

I believe there are 3 sensors on that side of the motor:

-oil pressure sender (for the gauge, which works)
-oil pressure switch (which I believe is not connected) which I believe looked like
http://www.iboats.com/mall/image/view/7/9/9-57990_2.jpg
-Knock sensor

all the symptoms for a disconnected oil pressure switch that I could find were to do with the alarm, and cutting out above a certain RPM, nothing I could find suggested that it might cause the motor to run rich.

I am not at the boat right now, so I cannot verify for 100% certain that it is the oil pressure switch that is disconnected.

Am I missing anything?

anything that might be causing the motor to run so rich?

While it's idling, there is fuel pooling up on the butterfly valves. If I disconnect the fuel injectors, the motor actually runs better for about 6 seconds before it dies.

The spray coming out of the injectors looks good, but there is just too much fuel.

My initial thought was a faulty sensor, but the main fuel controlling sensors all seem to check out.

 

[Tail_Gunner]

Re: 1999 5.7GSI PWTR. Running really rich in driveway

It will puddle in the butter fly at idle even when its at top form. Take a neon light and light up your injector pusle's they may well be sticking open....if this engine is TBI that is.

How to Check a Fuel Injector | eHow

 

[mylesm260]

Re: 1999 5.7GSI PWTR. Running really rich in driveway

I've been trying to find an example of this test somewhere.

I see lots of tests using a "noid" light to verify the ECU signal to the injector, but in my case, the signal is definitely there, I can see the injectors both firing.



Do you think the problem could be caused by the oil pressure switch directly above the filter? mine's disconnected (connector rusted off)

I've got one on order, it should arrive tomorrow.

It will puddle in the butter fly at idle even when its at top form. Take a neon light and light up your injector pusle's they may well be sticking open....if this engine is TBI that is.

How to Check a Fuel Injector | eHow

 

[mylesm260]

Re: 1999 5.7GSI PWTR. Running really rich in driveway

Here's a youtube video of the engine running

in the water
in neutral
throttle opened up about 5-10% to keep it running... it's doing about 900 RPM
MAP sensor disconnected

https://www.youtube.com/watch?v=hTuuPG1Wrws&feature=youtu.be

https://www.youtube.com/watch?v=hTuuPG1Wrws&feature=youtu.be

the spray patterns look consistent to me (left vs right)

my plan is after I get the new oil pressure switch installed, if that doesn't solve the issue, I will pull the plugs, compare the right bank vs left bank, and do a compression test to make sure all is well mechanically....

Has anyone heard of these injectors "sticking"

Like I said

Fuel pressure's good
Coolant temperature sensor is good
MAP sensor's good
TPS is good

There isn't a whole lot to these earlier TBI motors......

 

[Tail_Gunner]

Re: 1999 5.7GSI PWTR. Running really rich in driveway

You have some kind of elec short going on..you should never be able to see the spray interupting that's a complet shut down..Why is the map disconnected....

Take a neon light and watch the puslations you injector's and missing badly..miss firing

Read it a bit closer...

Ran fine 2 years ago. (has not run in 2 years)

Went to wake the motor up.
New plugs


New fuel filter
Had been flogged so I expected it to be a little rough getting it started up......:sleeping:

Engine is running very rich. Black smoke, barely idling..


Pull your injectors and have them cleaned..call around there are mnay injector cleaning service's around ..I found one at Napa.

 

[mylesm260]

Re: 1999 5.7GSI PWTR. Running really rich in driveway

Listen, Tail-Gunner....

I appreciate the help and all, but if your not certain about something, maybe don't comment.

that "interrupting" is completely normal for an EFI system.

It's called pulse width modulation, and it is the fundamental basis for pretty much every type of "electrical throttling".

You want to control how fast an electric forklift goes? PWM.
You want to vary the speed on your electric drill? PWM.
You want to dim your lights? PWM.
You want to vary the amount of fuel an injector puts into an engine? PWM.

If you don't believe that's normal, go to youtube and type gm tbi.... you will find dozens of trucks with the identical setups working in the exact same manor.

I was asking on this form to see if anyone had any specific knowledge about that specific motor.

And the map sensor was disconnected to lean out the fuel mixture... the engine did not run at all with the map sensor connected.

The map sensor outputs a voltage from 0-5 volts that corresponds to a fueling table in the ECU.

The lower the voltage, the leaner the fuel table (the more engine vacum, the lower the pressure, the lower the voltage)

14.7KPA (atmosphereic) is 5.0 volts.
0 KPA (absolut vaccuum) is 0.0 volts (in theory)

absolute vaccum (or the closer you get to it) translates to less engine load, and therefore less fuel
14.7KPA (or the closer you get to it) translates to WOT, and therefore MORE fuel

So I disconnected the map sensor to lean out the fuel mixture to try to mitigate the running rich to the point of stalling the engine situation.

 

[Tail_Gunner]

Re: 1999 5.7GSI PWTR. Running really rich in driveway



I guess ive looked to much at my own injector's a bit to much i once tried lifting them up off the body for clearance...anyhow i do understand the modulation and you are quite right..but the modulation is so brief you cannot see it with out a strobe effect and i am quite sure i saw brief interrupts yes you have voltage but injectors do stick open...close etc..peace out good luck.