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nOW wHAT ? by Lou6t4gto
Started on: 03-03-2014 07:20 PM
Replies: 21 (534 views)
Last post by: Lou6t4gto on 03-07-2014 11:38 PM
Lou6t4gto
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Report this Post03-03-2014 07:20 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
So the 3800SC is "installed", and it will "start" WITH a shot of Ether. BUT, with the fuel pump hot wired it will build 52PSI, but "as soon as I cut the current", it drops almost immediately to 23-25. No visible Leaks, no smell of gas. I tried to start it with the pump running continuously (52 PSI) but it won't start. Already "changed" and checked the fuel pump, and Fuel Inj FUSES. *The engine Ran fine when still in the donor car, But had a serious lack of power . Has since been totally rebuilt (because it had a broken crank shaft key slot). So, What's the deal with this "won't start" even with fuel pressure, and why is it Dropping Pressure so fast ???? with 50 psi, shouldn't the injectors be" injecting" ? Exactly HOW do I check to see if the injectors "Have a pulse" ? Thanks
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cmechmann
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Report this Post03-03-2014 07:25 PM Click Here to See the Profile for cmechmannClick Here to Email cmechmannSend a Private Message to cmechmannEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did the donor car have VATS/PASSKEY? If it was not turned off by programming/flash will shut the injectors off.
As far as the fuel pressure drop. And it does not drop right to zero. Flakey fuel pressure regulator.

[This message has been edited by cmechmann (edited 03-03-2014).]

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Lou6t4gto
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Report this Post03-03-2014 07:53 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Donar car did have vats, Hopefully the" reprogramming" took that out ! I just went out and put in a NOID light, and there's no signal to the injectors ! :-(
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olejoedad
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Report this Post03-03-2014 11:34 PM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
You should have 12v to the pink wire on the injector plugs with key 'ON'.
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Lou6t4gto
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Report this Post03-04-2014 12:59 AM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
There IS indeed 12 volts going to them with the key on, they just don't "Pulse" when the engine is cranked over. All fuses are fine.
And the fuel pump still refuses to work, when" jumped", it goes to 50 psi, and drops off to nothing when the pump stops. more than 1 problem ?
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phonedawgz
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Report this Post03-04-2014 07:37 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Can you connect to the PCM with a scanner? Key on engine off. You should.

Assuming you can do that does the scanner show the engine rotating while cranking? It should. Once you get these two things going you will most have solved your fuel pump not priming problem.

+12v unswitched on Blue 20?
+12 switched on Blue 19?

Any check engine light when you first turn the key to on?

A non functioning PCM (most likely because it doesn't have supplied to it what it needs) will give you the problems you are experiencing.

[This message has been edited by phonedawgz (edited 03-04-2014).]

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Lou6t4gto
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Report this Post03-04-2014 03:39 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
I plugged in the "hand held scanner", it says "no Codes". Now ,when "Cranking", the Noid light IS Flashing ! , so I guess it is pulsing, just no fuel pressure ! haven't checked blue 20 and 19 yet.
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phonedawgz
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Report this Post03-04-2014 04:43 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
If the noid is flashing then the PCM is running. No need to check 19 / 20.
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Lou6t4gto
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Report this Post03-04-2014 06:34 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Is it Possible (with the fuel pump,) it's still the original,(2.8) that it won't hold the 50 PSI, pressure and it is draining Back through the pump ? The regulator was fine when I pulled the engine. can't think of another reason for it to lose it's prime" immediately". ALSO, On the Fuel pump "RELAY", the orange wire going IN (12 volts) is hot, what other wires ON the Relay, can I "check" (and HOW to check them) (at the relay and at wherever they are going)as to WHY the ump is Not getting Power when the key is turned on. seems like I'm SOOO Close ! Thanks
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cmechmann
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Report this Post03-04-2014 09:26 PM Click Here to See the Profile for cmechmannClick Here to Email cmechmannSend a Private Message to cmechmannEdit/Delete MessageReply w/QuoteDirect Link to This Post
The pump would be able to make that much pressure but won't be able to supply the volume needed when in boost. Something that would cause your earlier problem of dropping down to around 25 could be the anti cavatation unit on the fuel pump and now you may have blown it off, now that it is trying to reach a higher pressure with the 3800 regulator, but you should be getting no pressure now if that was the case.
If it is going to 50, then dropping off to 0 with no power, something is leaking down.(open injector, open regulator)
You should have 4 terminals at the relay. One from the Battery. One to the pump. One to key power and one completing the ground through the ECM/PCM.
Now since this is a swap, your fuel pump relay wiring has changed. Before you had battery. Fuel pump. Key power. Prime from ECM. And continuous run from the oil pressure switch.
You should have 12v key off at one terminal. If you put your test light on the positive side of the battery, it should show a ground through the fuel pump circuit on another terminal. Back with the test light to ground you should find another 12v on a different terminal with key on(of course this depends on how the swap was done). With the test light back on the positive, The last terminal should show ground for 2 seconds when you turn the key on and come back on when you crank it.
Are you using the stock wiring for the fuel pump relay with the 2.8 oil sending unit on the 3800?
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Lou6t4gto
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Report this Post03-05-2014 12:22 AM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thus far, the way it is wired IS: Relay A - dk green/white to C2-3 FP relay control, "B"to 203 "L", "C" black/white to ground, D orange/black to 203 "B".
Using the original 2.8 Oil Sender with only the wire for the gauge hooked up. Am I misunderstanding something ??
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zkhennings
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Report this Post03-05-2014 12:41 AM Click Here to See the Profile for zkhenningsSend a Private Message to zkhenningsEdit/Delete MessageReply w/QuoteDirect Link to This Post
Could be leaking at connection from pump to sender, I have had that happen and it acted similarly, would get pressure, but then it would drop. Could be check valve in the pump too. I would block the return line and see what happens. If the same scenario is happening, then it's not the regulator. I would (maybe do this first) hook the gauge up to the fuel line itself from the pump with some hose clamps and hose before it gets to the fuel rails. If it still bleeds, it's an in tank problem.

I doubt the 2.8 pump couldn't supply enough gas to at least get it to start and idle fine.
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phonedawgz
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Report this Post03-05-2014 07:45 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
What is the fuel pressure during cranking?

The fuel pump relay should get +12v on the Dk. Green/White wire during the "prime" two seconds. It should also get it for two more seconds if you bump the starter and the engine cranks just slightly. The other wire of the fuel pump relay coil is black and should be connected to ground.

When you turn the key to on, or you bump the starter you can't hear the relay click on usually since there are other noises happening at the same time however you should hear the relay contacts drop two seconds later. Are you hearing this? If so then the relay is getting the signal from the PCM, and your fuel pump problems are either on the contacts of the relay or the wiring to the fuel pump. Did you reuse the crappy Fiero relay? Many times they have corroded contacts in the relay base.

[This message has been edited by phonedawgz (edited 03-05-2014).]

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Lou6t4gto
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Report this Post03-05-2014 07:52 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Fuel Pressure key ON, cranking is "0", UNLESS I "hot wire" the pump, then it goes to 55 as long as power is supplied, disconnect power, drops to 20 in 5 seconds !
I Obviously have something screwed up. With KEY ON, On the plug is a Orange/black Wire with 12 volts, a Blue/white Wire with 12 volts, a Tan wire and a Light Orange wire with "0", and a Black wire with white stripe with 12 volts !? *Should a black/white wire have 12 volts ??* If I "jump" the fuel pump to "run", the car will start. So close, yet so far !
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cmechmann
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Report this Post03-05-2014 08:16 PM Click Here to See the Profile for cmechmannClick Here to Email cmechmannSend a Private Message to cmechmannEdit/Delete MessageReply w/QuoteDirect Link to This Post
What year is your car and are you using all the stock harness at the relay? I'm using a diagram for an 85 GT. It shows orange, changing to orange/black in harness going to fuel pump fuse, green/white(relay control), tan/white(120), C at ALDL connector then to fuel pump( shows it tied to the orange/black at oil sending unit after pressure comes up) and black/white(ground).
The black/white should be at ground unless it is not grounded and you are seeing 12v from across the relay coil. Check that terminal with it disconnected from the relay. It should be ground.
Be a little careful here, and this is slightly confusing. With the original 2.8 ECM, the way the schematic shows, the ECM supplies the relay coil(coil only,green white) 12v and the relay coil is grounded to the body. Then the oil pressure switch takes over that job once started. However, on most later PCMs(3800) handles all of the fuel pump relay function.
Sorry this also confused me some, that is one of the few circuits that the ECM/PCM would control the 12v side.

[This message has been edited by cmechmann (edited 03-05-2014).]

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phonedawgz
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Report this Post03-05-2014 08:58 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
No the Black/White wire should read 0v.

That is your problem. I assume you are making the checks with the relay in place and backprobing.

It sounds like the other end of the Black/White wire is not attached to engine ground, like it needs to be.

The stock Fiero harness spliced the Black/White wire to a large nest of ground wires. You can just run that one to ground since your harness is already done. Make it a good one since if you loose the ground, the relay will again stop working.
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phonedawgz
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Report this Post03-05-2014 09:04 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by cmechmann:

What year is your car and are you using all the stock harness at the relay? I'm using a diagram for an 85 GT. It shows orange, changing to orange/black in harness going to fuel pump fuse, green/white(relay control), tan/white(120), C at ALDL connector then to fuel pump( shows it tied to the orange/black at oil sending unit after pressure comes up) and black/white(ground).
The black/white should be at ground unless it is not grounded and you are seeing 12v from across the relay coil. Check that terminal with it disconnected from the relay. It should be ground.
Be a little careful here, and this is slightly confusing. With the original 2.8 ECM, the way the schematic shows, the ECM supplies the relay coil(coil only,green white) 12v and the relay coil is grounded to the body. Then the oil pressure switch takes over that job once started. However, on most later PCMs(3800) handles all of the fuel pump relay function.
Sorry this also confused me some, that is one of the few circuits that the ECM/PCM would control the 12v side.



Every GM ECM/PCM I have seen puts out 12v to the relay. I have never seen one that grounds it. They are all also pretty much wired with a Dk. Green/White to the relay also. The 3800 works exactly the same as far as the PCM as the stock Fiero ECM re sending out the voltage.

The oil pressure switch ALSO (rather than takes over) closes the power circuit to the fuel pump. Consider it a back up to the relay. In face many times when the relay fails the driver doesn't know it other than it takes longer for the engine to start since he has to crank it long enough to build up oil pressure.

Yes many later PCMs do drop the back up secondary oil pressure switch, however most 3800s do not. Look at the sender. If it is one or two pins in a verticle manner (with the clip at top) then the sender is oil light or oil pressure only. If the sender has 3 or 4 pins, then the sender also has the fuel pump back up switch included.
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cmechmann
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Report this Post03-05-2014 09:19 PM Click Here to See the Profile for cmechmannClick Here to Email cmechmannSend a Private Message to cmechmannEdit/Delete MessageReply w/QuoteDirect Link to This Post
Sorry for the mix up. Most ECM/PCM controls are done on the ground side. A/c relays, solenoid controls, injectors etc. To keep the load of the driver/transistor.
Makes me wonder why that circuit doesn't fail more often. In other systems stuff that is controlled by the hot side goes often.
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Lou6t4gto
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Report this Post03-06-2014 02:02 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
It "Dawned on me" in the "middle of the night", that I had put "ground wires" from the engine to the cradle, but not from the cradle to the car. I Haven't gotten out there yet, but COULD that cause the problems I'm experiencing with the pump ?? ( The cradle has urethane bushings)
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Lou6t4gto
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Report this Post03-06-2014 04:29 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
well, that had nothing to do with it.
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Darth Fiero
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Report this Post03-07-2014 08:37 PM Click Here to See the Profile for Darth FieroClick Here to visit Darth Fiero's HomePageClick Here to Email Darth FieroSend a Private Message to Darth FieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
The cradle is not a good ground.

The PCM harness should ONLY be grounded to the engine block or cylinder head.

The battery should ground to the engine block and also to the chassis.

You should have two separate ground straps that ground the engine block to different points on the chassis.

The cradle does not need to have a ground strap attaching to it since you shouldn't be using it to ground anything to anyway.

-ryan

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Lou6t4gto
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Report this Post03-07-2014 11:38 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Good point ! well, all seems to be working now. Thanks
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