Just because I write in uppercase letters does not mean I am shouting, yelling or anything such as that...it just is used to bring attention to them.

I NEVER wrote that the signals ONLY told the ECM that the engine was being cranked.

I wrote:
Once the engine is being cranked...and the reference signals go to the computer to let it know it is being cranked...and that is ALL these signals do...other than the OBVIOUS other components to make the engine run needing this signal. These signals do NOT have anything to do with the fuel pump relay being "turned back on" after the engine is running...PERIOD. These signals from the distributor work in conjunction with the internal software program in the ECM. They are very important...but not for the fuel pump relay. DOUBT ME...ask Gordon.

"ask Gordon" I bet you have not done that but instead have spent hours finding information...but this issue can be easily cleared up in ONE phone call. Your choice...obviously.

You can disagree if you wish.

Why don't you do yourself a favor and talk to the guy who knows what he is talking about.
Unless you still insist that what Gordon has stated to me which is what I already knew as correct.

Even under your own admission...you are learning things that you did not know...why stop there...talk to Gordon...because no matter what I write...there is going to be some form of dissection and disapproval. Tell him what you are finding....and let him tell you what GM found to be bad....and changed and how the system actually works.

I wish you the best of luck in your "quest".

DUB

 

That was the impression I got from the words I bolded above.

I deliberately avoided mentioning him in my previous post because I didn't want to get into a discussion about what he knows or doesn't, but since you brought him up again…

I am retired. My income is very limited. I have a very low cost telephone plan, which known as a "measured rate" plan. That means that I have to pay for every minute I talk. This makes me VERY resistant to making long distance telephone calls. [ EDIT ] According to Gordon's web site: "Gordon's fee is $10.00 per call, plus $3.00 per minute" -- out of my budget range. [ /EDIT ]

I suspect Gordon "forgot more than most people know" about C4 Corvettes. How many years has it been since the last C4 was built? That makes me call into question whether he accurately remembers this esoteric detail of how the fuel pump relay works. Since I wasn't part of the conversation I have no way of knowing how you posed the question or how he answered it or the discussion that followed.

Personally, it doesn't seem reasonable to me that the ECM only turns on the fuel pump relay for 2 seconds at key on and then never turns it on again. I'm a retired electronic engineer with 50 years of experience in electronics and programming microprocessors and as a co-worker of mine used to say, "**I** wouldn't have done it that way".

Concerning recollection of details: Two years ago I rebuilt the 700r4 that is in my car (I wrote a post on that). Now I sometimes just don't remember some details when people post questions on the Forum, like the names of the parts (and there are a lot of them -- a friend of mine told me (jokingly) they named it 700r4 because there are 700 parts in it).

The reason I'm pursuing this is that I want accurate information to be out there so people don't go down the wrong path while troubleshooting a problem. The people on the Forum have a vast range of skills and experience from basically none up to experts. Obviously the people on the low end of that scale need the most help. They lack the experience to say, "That doesn't sound right", so we need accurate info.

I did think of another test I can do. I took the oscilloscope down to the garage with the plan of measuring the fuel pump signal coming out of the ECM. I'll do that later when the car (I just got back from going out to get groceries) and the garage cool down. it's 80+ degrees here right now and I don't like working in a hot garage on a hot car.

 

The oscilloscope screen shot below shows the signal I measured on pin C of my fuel pump relay. This is the signal that turns on the relay and it comes from pin A1 of the ECM. The wire color is green with a white stripe.

The scan rate is 1 second per each vertical division. The vertical scale is 2 volts per division. The arrow on the left with the 1 (for channel 1 on my 'scope) is at zero volts.

The ignition was turned on at 1 second and the voltage jumps up to 12 volts for 2 seconds. This turns on the fuel pump and pressurizes the fuel rail in preparation for starting the engine. After 2 seconds the fuel pump is turned off so that it doesn't run continuously if the ignition is turned on but the engine is not started. Note the inductive kickback as the magnetic field collapses in the relay when it turns off at the 3 second mark (the voltage goes negative briefly).

At the 5 second mark the ignition was turned to the crank posisition. The ECM detected DRPs (Distributor Reference Pulses) and turned on the fuel pump. The voltage is low (about 10 volts) because the starter is cranking the engine and loading down the battery. As the engine comes up to speed the voltage rises because the starter motor isn't working as hard. When the engine starts the voltage jumps up to about 14 volts because the alternator is now supplying the voltage. I thought it was interesting to see the battery voltage varying as the starter motor cranked the engine.

 

But what you quoted from my post and "bolded-out" and what you took from it...was only a part of the sentence. If you read it fully....you would have understood that these signals supply information to the OBVIOUS. For me ...what these signals go to is OBVIOUS. I am not a "shade-tree" mechanic....not writing that you are saying that I am.

Once again...
I wrote:
Once the engine is being cranked...and the reference signals go to the computer to let it know it is being cranked...and that is ALL these signals do...other than the OBVIOUS other components to make the engine run needing this signal. These signals do NOT have anything to do with the fuel pump relay being "turned back on" after the engine is running...PERIOD. These signals from the distributor work in conjunction with the internal software program in the ECM. They are very important...but not for the fuel pump relay. DOUBT ME...ask Gordon.

I can appreciate your tests. I REALLY CAN!!!

If calling Gordon is out of the question due to the issues you mentioned. TRUST ME...HE IS VERY SHARP and can give out so much information so quickly...that is it hard for me to write it in shorthand and get it all down. So this belief that he has forgotten "stuff". I seriously doubt it. He knows so much. The problem with sensors and who made them...when they changed sensor manufacturers and a lot more. Call him on his 1-800 number on so you are NOT paying for the phone call. And in 3 minutes...you will have your answers and it would only be around $20.

Gordon knows "things" about many systems that are not written in the factory service manual...and he has proved it to me when I find "problems" in descriptions and repair test procedures that I KNOW are not right...and he confirms it.

So...if I read what you wrote...you finally DO ADMIT that the fuel pump is turned on for 2 seconds...like I wrote in past posts. Test to your hearts content. But I seriously doubt that if you come up with anything different that what I was told and have know...there must be an issue in your system somewhere. But do as you wish...this is America...but before you post your findings..don't you think it would be wise to confirm it with Gordon. Because like when I was talking to Gordon...he was telling me how a friend who came over actually had a bad system because the fuel pump was running all the time when the key was on...and the engine not running.

You are aware the GM only intended the ECM's to last 5 years (NOT MY words...but that from the guy who rebuilds my ECM's, BCM's, etc). And that your ECM can be bad if it is still original....or an aftermarket piece of "junk'...which I have encountered way too many times. NOT writing that yours is bad...because the 2 second shut-down appears to be correct....but I have seen "crazy" stuff happen electrically over the years.

It seems that you have the time to test ideas...maybe running your findings past Gordon may shed some light on this issue.

DUB

 

I NEVER said that the fuel pump is not turned on for 2 seconds. What I was disputing is YOUR claim that the ECM does NOT turn the fuel pump on when it receives DRPs if more than 2 seconds elapses after the ignition is turned on.

YOU said the oil pressure switch takes over if the engine is not started within 2 seconds and is the ONLY source of power to the fuel pump. THAT is what I said was incorrect. I think I proved that was wrong by my oscilloscope screen shot. According to what you said earlier that means that my ECM is bad -- I think not.

As far as what goes on inside the ECM, you apparently did not go to the link I posted earlier:

http://home.earthlink.net/~cliff_har...5/BUA/BUA.html

I spent about 6 months going through the code in my ECM. A lot of stuff is unknown and there is no way to find out because it's GM proprietary information. The timer chip that controls all the timing functions (like injector pulse width, ignition timing, etc.) is totally opaque, for example. It's a GM trade secret, and they aren't telling. So yes, I DO know what the ECM does with the DRPs, like calculate RPM and, as I said earlier, synchronize the pulsing of the injectors to the rotation of the engine.

I spent a LOT of time correcting the original "hac" file because it had many errors. One of my favorite examples is that it said the VATS frequency is between 33 and 66 Hz, which is wrong. It's between 20 and 40 Hz. Compare the original "hac" file (which I posted for reference) to my version and you'll see what I'm talking about.

 

Yes you did...here it is...Post #6

And in Post 13
Then you evidently proved what I wrote was correct.

I am getting tired of this and I am signing off on this post. I wish you the best...again...in your quest of whatever you are searching to prove..or disprove...or whatever. And knowing you will not talk to Gordon....I can not understand how you can test anything unless you know without a doubt that that the end result of the "test" is what it is supposed or designed to be. Gordon surely had access the proprietary code and was at his disposal. Something he knows that WE do not know.

BEST OF LUCK,

DUB

 

After repeated misinterpretations, misquotations and misunderstandings of what I said, I deem this thread to have grazed off into the weeds, without possibility of redemption.

The key word here is "HAD". Back in those days they archived code on 5-1/4" floppy disks. Remember those? Do you have a 5-1/4" floppy drive on your computer? As I have said, I doubt GM could even FIND that information. Archived in a warehouse somewhere and long forgotten…

I hope the original poster resolved his problem.

 

I do not know how I can misinterpret what you wrote when it was so clearly written. Re-read what you wrote and then ask how I came to any other conclusion than you writing that YOUR year car does not have a 2 second "on" feature for the fuel relay...then you proved it...but can not agree that I was correct on the 2 second issue with the fuel relay. I tried to reply to your comments to the best of my ability...and I proved many of them even though you wrote "things" were not in your book...but then you found some of them. But going "round-and round" on the same issue when information can be obtain from an excellent source(Gordon)...and it is not being utilized...it a total waste of time. This is just like Geometry class. Postulates and theorems. A postulate is a statement that is assumed to be true without proof. A theorem is a statement that can be proved to be true. Though you have performed tests with results. It is hard to know how the test is supposed to conclude if you do not actually know everything about the issue you are testing. Because if Gordon contradicts any information you have read, found in a test or otherwise...it then makes the result of the test(s) you have performed that ended with a different result than what it should be...then this should be a sign that there is a problem in your system....and knowing the correct end result if a test is performed...a repair can be made to get it to factory correct again. .

Once again...without you calling to find out the wealth of knowledge Gordon has...you can not make a statement without KNOWING for a fact. Gosh almighty...typing for you is a strain. I have to use words that make you not be able to dissect my comments to death. The word "HAD" was in reference that he worked with the tightly guarded software...and knowing NOW that he is retired...he no longer works with it...so HAD fit well for most people. Gordon could use and see line data that you or I can not access. Such a shame you do not want to know what he can offer you. Your choice. And has talented as your are in electronics....and spending hours of making test jigs, etc to test "something"...does it not cross your mind that when you are "testing, probing, connecting things together, or whatever term suits you" inside the computer...and repairing issues you may have..or have previously repaired...that there can not even be a SMALL chance that the code in the computer can go into a sub-routine if currents (voltage or ground), resistance values spike(s) past a prescribed level or whatever you care to fill in that suits you here....thus telling the code, program or whatever you want o call it to go into another routine. Much like how the computer goes into "flood-mode" when a major sensor goes bad and the computer throws all it can at the engine to get you to a service center. Can you honestly tell me that this is not possible...seeing how you do not have the code to find out. I know it is possible because I did it way back in the day when taking computer classes in school. But then again....I may be wrong...due to I have not called Gordon to see if this possibility exists.

At least we agree on something.

DUB

 

I think he is hiding under his bed. Now you two shake hands and become friends. LOL

 

He has spent more time than I would running intricate tests on an ECM. His findings would be very helpful. I would not even attempt to do what he is doing because I would rather send out the ECM and get it repaired. Because my luck. I would THINK I fixed it and then something else would pop up and let me know that I did not fix it. What stops me is getting to the point of tests and then needing "proprietary information". It then becomes a situation of like entering in a Haunted House...you do not know what is coming up next....or what needs to happen next.

DUB

 

Wow I feel sorry for the the guy who needed information regarding a misfire. It's been 6 years think he still needs help? Not the place to argue who's right or wrong. The guy needed help and didn't get any..