rick lambert

Morgan, maybe this quote from the FSM will help you understand.
" As a backup system to the fuel pump relay, the fuel pump can also be turned "ON" by the oil pressure switch". a little more-" If the fuel pump relay fails, the oil pressure switch will close and run the fuel pump.

No where in the FSM does it state the oil pressure switch will kill the supply of fuel in the event oil pressure is less than 4 pounds.

Maybe time to look at codes 44 and 45 simply because of what the scann showed.

CFI-EFI

What you agreed to "......i agreed in part........" was:

---------------------------------------------------------------------
Which is totally false and wrong. Ease into your FSM for a while and LEARN how your car works.



Your FSM says all three of those lines? Your FSM believes "this is true"? At best, I think you have taken something out of context. If you keep reading you will find what I have written.



YOU not understanding something, doesn't make it untrue. Yes, I "Can you explain that". The purpose of the oil pressure switch is to act as a back up, in case of fuel pump relay failure. You will find THAT in your FSM, also.



1989 was the first time since early 1984 that the gauge sender and the oil pump switch were in the same housing. You can tell they are one in the same, by the three wire connector. The sender uses one wire and the switch uses two.

I didn't say that you did. I had lumped a response to both you and jcsr72, who said, "MAYBE his digital dash gauge shows good oil pressure from the oil pressure "sensor", but the circuit between the ECM and the oil pressure "switch" may be faulty.". It appears you agree, there is no such circuit.



Are you going to publish your own FSM? You may have a problem with the "F" part of your FSM, as the factory has already designated an author/printer. Even the old, imperfect, FSM has plenty we can all learn from. Better to study IT, rather than add "what i think is correct", because, in some cases, as demonstrated in this thread, you are wrong.

RACE ON!!!

byebyeL98

This is not correct. The MAF sensor is used in open loop as well; the ECM still needs to know how much air is entering the engine in order to fire the injectors appropriately.

Aardwolf

The 02 is used in closed loop and not open. The MAF is read in both states.

morgan_kane

Here is scanned picture from FSM schematic:
http://finnshark.com/gallery/files/3...p_original.jpg
Tell me where i was wrong?

Why fuel pump needs backup? Why not ignition system, alternator or even airbags have backup, if fuel pump needs it?


Hmm.. my -87 manual has this picture:
http://finnshark.com/gallery/files/3...h_original.jpg
It seems to me that they share same housing. Maybe they can be separated, but i just answered to kopbet's question.

Nop, this is where those pictures are taken from:
http://finnshark.com/gallery/files/3...s_original.jpg

It is original GM manual.

morgan_kane

OK, so it is.
Maybe different years have different protocols?

EDIT:
I checked my FSM (not electrical supplement) and it states backup version too. So you both right. There is some lack in the electric supplement manual, because it says that relay is on only when starting.

Still, it is hard to understand, why backup circuit is made through oil switch? Why just another relay? It just feels logical that it was made to protect engine. Now there is no protection, in spite of oil pressure switch.

CFI-EFI

About which point? You were going to prove where *I* was wrong, remember? Your schematic is either 344 pixels wide, too small to read, or 2294 pixels, about 4 pages wide, where one can't see enough of it, without extensive panning and scanning, to make sense of it. However, if you will spend some time with it, you will possibly be able to see how your car works. Maybe you can rescale that scan to readable dimensions and you can explain to me (us) how everything works as you say.



I don't design them. I only figure out how they work. It is futile to ask why, but if you must, see if they can help you at GM.com.



They don't have to be separated. They already are. As it is clearly shown in your illustration, the oil pressure switch, with it's two wire connector, screws into the pipe tee from the top. The oil pressure switch, with it's single wire connector screws in from the 4:00 o'clock position. Your illustration proves my point that from part year 1984, and up to near the '90s, they were two separate devices. Luckily for you, they changed back to a single unit in 1989, makomg your answer correct, but you didn't know that when you said they were one unit. Your illustration proves that.



Your source of info appears to be impeccable. Now all you have to do is learn to interpret it properly.

RACE ON!!!

morgan_kane

I never said that.

It is very easy to zoom it whitch size you want. A3 size schematic is hard to put little size so, that it is readable. You should know.


Nop, as i said, i only responded to kopbet's question
citing (kopbet89c4) "So where is my oil pressure sensor and oil pressure switch? Are they in the same vicinity or are they way apart in different areas of the car?"
I NEVER SAID THEY ARE ONE UNIT, I ONLY STATED THAT THEY ARE NEXT TO EACH OTHER.

As you can see in the schematic, in the link upper, if you are able to zoom it (it is not hard), It says exactly: Fuel Pump Control (During Startup only).

How in your opinion i should interpret it??

tequilaboy

I would be concerned with the BLM of 108 from the original post.

This means that you are very rich and at the limit of the ecm's ability to provide rich mixture compensation while in closed loop. From this infomation, it can be inferred that you're also running very rich in open loop at this rpm/load condition.

Things that may cause you to be very rich in open loop:
Too much fuel pressure
injectors too big (if > 23 #)
leaking injectors
tune open loop a/f increase vs temp, open loop a/f increase vs load, startup fuel vs temp, injector constant, bpw vs load, MAF calibration, etc.
MAF calibration (Over estimated airflow from MAF skews the load calculation and resultant fueling)
Low vacuum -> increases fuel pressure
Not enough spark advance -> contributes to low vacuum and also tends to raise the load due to increased airflow requirement.

Things that you can do to influence the open loop mixture:
Fuel pressure: reduce if you have an AFPR
Injectors: replace if too big, or leaking.
MAF calibration: reduce output if you have an adjustable MAF, or chip tuning capability.
Tune: if you can work with a tuner or tune your own chips, lots of possibilites here (injector constant, MAF tables, Target AFR, etc.)
Correct ignition timing

Adjusting fuel pressure should help to put your blms in the ballpark try to target 128. I would try this first.

If the MAF is acting flaky and erratic, it can be disconnected forcing limp home mode where the airflow is calculated instead from the tps sensor (no guarantee that the resulting signal is a good fit to your car's appetite for air). If you go this route, you will still likely need to adjust fuel pressure to improve the resulting mixture.

jcsr72

Let's think about this for a second.
-Fuel supply at time of stall...........x (fuel pump, relay & oil switch)
-Stable fuel pressure (44 psi) at time of stall......x (FPR)
-Injector pulse at time of stall..... existent, but correct pulse duration??

We should investigate spark... or less likely, the injector control system.

kopbet89c4, morgan_kane, CFI-EFI and others... do you disagree?

kopbet89c4

Could there be a small air bubble in the fuel line while starting up??? Is it possible that the air bubble can form once the car cools down? I think that could cause possible stalling on part throttle while warming her up again...

Today, I warmed her up to about 180 degrees before I started driving. I felt the roughness in the idle about 5 minutes before driving. That rough idle lasted for about 1 minute meaning if I pressed the pedal down while it was idling that way, it would stall out...

I can see how the car would idle roughly when that happens... temporary lean condition...

Funny how when this stalling happens, there are no codes.

If this is indeed an air bubble forming in the fuel line during cool down, what can be done to prevent it???

If I have 44 psi of fuel pressure when the car stalls, could that "air bubble at 44 psi" be fooling the fuel pressure gauge as well?

Remember, the car will literally drive forever once warmed up.

Da Mail Man

..........****i thought i eased out of this discussion for a bit?

CFI-EFI

Don't sweat the air bubble. If one were to form (doubtful) it wouldn't stand a snowball's chance in Hades of sticking around. The second you turn the key, the pump runs for 2 seconds. after you start to crank the engine, the pump continues to run. The regulator bypasses excess fuel and pressure back to the fuel tank, via the return line. Any possible air bubble will be long gone before the car gets a chance to start.



I admit, I'm totally stumped. I mostly joined this thread to correct all the misstatements being made about how the fuel system functions. To me the clue is in the fact that it runs well after it is warmed up and in closed loop. The fuel system is more effected going to closed loop than any other. I have to believe the problem is fuel. Not the fuel supply. There is plenty of pressure, but SOMETHING that affects the fuel system, is malfunctioning in open loop. I don't picture this as an ignition problem. Most ignition problems become aggravated by heat, not allayed by it.

RACE ON!!!

rick lambert

Time to get back to helping this guy. I can't go with air bubbles in the line. Just a few thoughts, what were the IAC counts when you were scanning? And have you checked the voltage at the TPS? I'm leaning toward eliminating any fuel delivery problems with the fuel pressure you have, and the fact you're running rich. You may even want to check the air duct and look for anything that could introduce more air, any leaks.BTW, I'd check those plugs.

CFI-EFI

How can you bow out without answering the challenges to your erroneous statements? Do you have a position, or not? Can you back up your statements?

RACE ON

aminnich

All Good Thoughts.

CFI-EFI

No you didn't. I challenged you to prove me wrong, and thus far, you've ignored the challenge. Make your schematic readable and explain to me how the oil pressure switch is wired to shut down the engine. With the diagram in front of the whole world, explain how the oil pressure switch output doesn't join up with the output of terminal "A" of the fuel pump relay, on circuit #458 with both being capable of powering the fuel pump, independently of the other. That almost sounds like the description of parallel circuits.



How does one do a zoom? I see two sizes; as it is, and larger after clicking on the icon. You can resize the photo before you up load and link it, here. If you can explain how to do a variable zoom and make your circuit explanations, I will be happy to follow along.



What was this from post# 60:

I can see that. Now read the circuit description in the text of the main book. The electrical manual probably has it stated correctly in the text, too, but we can't see it.



As presented in it's entirety, not solely by an unsupported blurb in a drawing.

RACE ON!!!

kopbet89c4

I saw today that the IAC counts were surging rapidly from 30-130 when the car was running roughly. The TPS has been set at .55 like it should be from the factory. The TPS voltage does not stick either. Smooth all the way up to 4.42 volts and smooth back to .55 volts.

But is there a possibility that the resistance in the TPS has skewwed over time? I checked the boot, as well as the connection to the TB. My traffic cone boot is completely free of any air leaks.

So I set the fuel pressure to 36 psi before a cold start. Same problem... stalls in roughly 2 minutes; the same amount of time as it would stall even if the fuel pressure was at 44 psi.

At both fuel pressures, the BLM was 128 on a cold start, and at both times it stalled.

Once warmed up in closed loop mode, the BLMs seem to get lower and today they were between 108-120 when idling. On part throttle, the BLM was 124 and WOT it was 128. Any yes, since it was fully warmed up with the coolant temps at the 170s to 190s, it ran perfect, not a skip, miss, sag, or stumble.

The car is as unreliable as a beat up 1989 Ford Escort a few minutes after start up. Needless to say, it acts like a POS. Once its fully warmed up, its acts exactly how a Corvette should be. Fast and throttle happy!

I compare it to a kid that doesn't like getting up for school in the morning. But once she's up, she's ready to rumble and run with the big boys!

SupaVette

Hmm, i thought closed loop happend pretty much after about 2mins of engine running time, in which is enough time for proper temp etc for it to go into closed loop. I don't think open/closed loops is your problem. Have you checked your temp sensor for the ECM? put it in a bowl of boiling water with themometer and checked resistance at various temps. Could be that when sensor gets to around the 115 mark it gives an incorrect reading and ECM thinks water is cold and so richens the fuel way up. Just a thought, good luck

kopbet89c4

Well, I know that on the scan CTS actually displays 1-3 degrees more than the coolant temp on the dash.

The moment it stalled, the laptop, aka the scanner displayed 117 degrees. Another time it stalled it read 119 degrees. I can't see how that sensor would be bad if I had valid readings from the scan. And if there was an intermittent open in the sensor, I'd be seeing -30 something degrees for the coolant temp and get a code. If there was an intermittent short in the sensor, the coolant gauge would read like over 300 degrees for the coolant temp and also get a code.