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Post by DiverProg on Jan 1, 2005 17:35:53 GMT -5
Continuing my posts from the TrustMyMechanic.com board (see: trustmymechanic.com/forum/viewtopic.php?t=4905)I tested the resistance on both the injectors. The value for both of them was 1.7 ohms. According to my Hanes manual, this is within the acceptable range. While I had the injectors free to where I could see them, I started it up. It ran for a little while and then the injectors stopped spraying and then it died. I did notice that the pump relay was still engaged (I heard the pump continue it's whinning) until it stopped. Could this be the fuel pressure regulator?
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Post by DanD on Jan 2, 2005 9:24:44 GMT -5
Here are a couple of service bulletins I've found. Hope something their helps. I would still like to know what the fuel pressure is though. In the second bulletin they talk about the pulsator being ruptured, I think they mean internally and blocking off the flow of fuel. If so you would not of seen this during the pump replacement. It would be like a little flap of torn rubber inside that would intermittently block the line.
Dan.
VEHICLE DOES NOT START READILY UPON CRANKING #56-63-05A - (Jan 1, 1996) Subject: Vehicle Does Not Start Readily Upon Cranking (Replace Fuel Pump Relay) --------------------------------------------------------------------
Models: 1993-94 Chevrolet and GMC Truck M/L Vans 1994 Chevrolet and GMC Truck S/T Utility 1994 Oldsmobile Bravada with 4.3L Engine (VIN W, Z - RPOs L35, LB4) ---------------------------------------------
This bulletin is being revised to change the correction procedure and parts information and to add the L Van and artwork. Please discard Corporate Bulletin Number 56-63-05 (Section 6E - Engine Fuel & Emission).
CONDITION
Some owners may experience extended engine crank times on cold start and may set diagnostic trouble code 54 and activate the MIL (Check Engine light).
CAUSE
This condition may be due to failure of the fuel pump relay.
CORRECTION
Verify condition using the normal diagnostic procedure in the service manual. Replace the Fuel Pump Relay (P/N 12077867) following the service manual procedure. Replace the connector (Kit P/N 12166225) following the instructions in Figures 3 and 4. Note that each of the four cavities of the old connector are lettered. The new connector is numbered and it should be wired according to Figure 3 and not the instructions contained within the connector kit.
Parts Information
P/N Description Qty --- ------------ ---
12077867 Fuel Pump Relay 1 12166225 Connector 1 12129073 Bracket (S/T Only) 1
Parts are currently available from GM
ENGINE HARD START OR NO START (REPL. FUEL PUMP PULSATOR) #66-63-09 - (Mar 24, 1997) SUBJECT: ENGINE HARD START OR NO START (REPLACE FUEL PUMP PULSATOR)
MODELS: 1992-96 CHEVROLET AND GMC TRUCKS 1992-96 OLDSMOBILE BRAVADA WITH GASOLINE ENGINES
CONDITION:
SOME OWNERS MAY REPORT THEIR ENGINE IS HARD TO START OR WILL NOT START.
CAUSE:
THE FUEL DELIVERY SYSTEM MAY HAVE LOW OR NO PRESSURE DUE TO A RUPTURED FUEL PUMP PULSATOR. THE PULSATOR IS THE FLEXIBLE CONNECTOR BETWEEN THE FUEL PUMP AND THE METAL FUEL LINE IN THE TANK. THIS RUPTURE APPEARS AS A TEAR IN THE PULSATOR OPENINGS AND IS THE RESULT OF EXPOSURE TO GASOLINE CONTAINING A HIGH PERCENTAGE OF ETHANOL.
CORRECTION:
FOLLOW THE STRATEGY BASED DIAGNOSTIC STEPS FOR THE REPORTED SYMPTOMS. IF DIAGNOSIS REVEALS LOW OR NO FUEL SYSTEM PRESSURE, AND THE FUEL PUMP IS IDENTIFIED AS A POSSIBLE CAUSE, FOLLOW THE SERVICE PROCEDURE FOR, ON-VEHICLE SERVICE, FUEL PUMP, IN THE APPROPRIATE TRUCK SERVICE MANUAL. BEFORE REPLACING THE FUEL PUMP, INSPECT THE PULSATOR FOR SIGNS OF TEARS OR LEAKS. IF THE PULSATOR IS DAMAGED, REPLACE IT WITH P/N 25175836 AND RE-TEST THE FUEL SYSTEM FOR NORMAL PRESSURE. THIS PULSATOR IS MADE OF VITON WHICH IS RESISTANT TO ETHANOL CONTENT FUELS. P/N 25175836 REPLACES P/N 25094266 FOR TRUCKS. THIS CHANGE WILL APPEAR IN GMSPO PARTS CATALOGS AS THEY ARE REVISED.
PART INFORMATION:
P/N DESCRIPTION QTY 25175836 DAMPER ASM - FUEL PULSATOR 1
PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.
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Post by Venturi on Jan 3, 2005 16:56:57 GMT -5
Welcome to the forum Eric.
Just to clarify which engine you have, is the 8th digit of the VIN number a Z or a W?
Since you’ve have spark when it wont start there are two things that you will have to check in order to get pointed in the right direction to getting this thing fixed. The first is to check the fuel pressure with a fuel pressure gauge during the times the engine will not start. If the fuel pressure is within specs and the fuel pressure holds after the pump stops running you can assume that the fuel pump and the fuel pressure regulator are doing their jobs.
The second thing to check for when the engine won’t start is injector pulse. The computer controls the ground circuit to the injectors. If the computer is not grounding the injectors or there is an intermittent open in the circuit, the injectors will not allow fuel into the engine. You will need a noid light to check for injector pulse.
Checking the fuel pressure and testing for injector pulse have both been suggested before, you MUST check these items and let us know what you find before we can be of any help. As it stands right now we simply don’t have enough information to help you.
Let us know what you find out.
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Post by DiverProg on Jan 3, 2005 21:16:58 GMT -5
The VIN is a 'Z'.
My only problem is this. I can't seem to find a noid light. Every auto parts store around here (Auto Zone, Advanced Auto, NAPA, Pep Boys) don't seem to know what I'm talking about and don't know where to purchase one. Do you know who might carry such an item or where I can get one relatively inexpensively?
I am going to get a fuel pressure tester and get those figures for ya. That piece of equipment costs around $40 at Auto Zone.
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Post by DiverProg on Jan 3, 2005 22:16:01 GMT -5
Well, I FINALLY got a hold of a guy who knew what he was talking about at Auto Zone. He found the pressure tester and noid light. Go figure.
So, I'm out to get some testing done and I'll let you know the figures in a few.
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Post by DiverProg on Jan 4, 2005 1:25:29 GMT -5
Hooked up the noid light to the injectors. Lol and behold, the injectors stopped firing right before it dies.
Could this be either the computer or a ground issue?
BTW -- I didn't hook up the fuel pressure gauge since the injectors weren't operating normally.
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Post by Venturi on Jan 4, 2005 12:55:01 GMT -5
Ok, now we’re getting somewhere.
At one point you said the check engine light would not illuminate when the engine would not start, is this still true? If so this could indicate a power or ground supply problem to the computer or a problem with the computer itself. Double check to see if the check engine light does or does not illuminate with the key on when the engine wont start. This could be an important clue to the problem if the check engine light only illuminates when the engine will start so let us know what you find.
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Post by DiverProg on Jan 4, 2005 14:51:59 GMT -5
When I first start it up, the check engine light illuminates. As soon as it dies, with the ignition still in the run position, the light does not illimuminate (this is immediately after it dies with no changes in the key position). When I key the ignition to the off position and then try to restart it, the light illimunates.
I believe this to be accurate but I will double-check it this evening, just to be sure.
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Post by DiverProg on Jan 4, 2005 18:54:22 GMT -5
Yep, I was right. Right after it dies, the check engine light does NOT illuminate.
After I switch the ignition off and then try to restart, it does illuminate.
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Post by way2old on Jan 4, 2005 20:52:51 GMT -5
I'm not really sure, but didn't these series of GM vehicles have a problem with ignition switch? Have read other places where the switch is faulty and causes wierd problems. I don't have access to GM TSB's but maybe Dand or Venturi can research this. Reading and learning. And welcome to the little site that will Driverprog!!
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Post by Venturi on Jan 4, 2005 22:00:23 GMT -5
Yea, the ignition switch is a possibility but we should be able to find that quickly if it is the problem. Also let’s forget about the check engine light for the time being, I was under the impression it was behaving differently. You’re going to have to make some voltage tests. I’m assuming from your previous posts that you have a digital volt/ohm meter and a service manual. Let me know if you don’t have both of these. Also keep in mind these tests must be done ONLY when the engine wont start or they will be invalid. After you lose injector pulse, check for battery voltage to the injectors. With the key on you should have battery voltage on one terminal of each injector connector. Check your repair manual for the injector power supply wiring colors. The colors changed from year to year and I don’t have access to a wiring schematic at the moment but I think one is white and the other is red. If you don’t have battery voltage at the connectors trace the wiring back to the #1 ECM fuse while looking for any open circuits. Also check the injector wiring under the air cleaner, the wiring tends to get pinched between the throttle body and the air cleaner. If you still have battery voltage to the injectors when the engine dies you’re going to have to find out why the injectors aren’t being pulsed. With the key off dismount the computer (ECM) and remove the connectors at the computer, check all terminals for any misaligned pins or corrosion. Repair as needed. If you find no problem with the connectors reconnect them and try to restart the van or watch the noid light for injector pulse while you wiggle, push and pull on each of the connectors. I’ve found a lot of poor connections in the connectors themselves and on the computer circuit board by doing this. If you have an intermittent injector pulse while wiggling the connectors try to isolate the intermittent connection to one connector. If wiggling the connectors gets you nowhere, you will need to check all of the power supplies and grounds to the computer. The best way to do this is by back probing the connectors with a voltmeter while still attached to the computer. The connectors may have plastic shields on the back where the wires go in, these can be removed to gain access to the rear of the terminals in the connectors. If you look closely at the back of the connectors you will see that each row of wires corresponds to a letter and each wire in that row corresponds to a number. This is how you will identify which wire terminals to back probe with the voltmeter. Check your wiring schematic in the repair manual for the terminal numbers of the ECM power supply wires. (I will try to post the power supply terminal numbers later tonight if I can locate a schematic.) Connect the negative lead of your voltmeter to a good engine ground such as an unpainted bolt or bracket. With ignition on, slide the positive probe of your voltmeter into the back of the ECM connector until it touches the metal terminal of the desired wire and take a voltage reading. You should have battery voltage at each power supply wire to the computer. If you find one with low or no voltage check the wiring schematic and trace it back to its power source. If you find no problems with the power supplies you have to do some voltage drop tests on the ECM ground circuits. I’m not going to get into that procedure at the moment because I need to locate a decent wiring schematic on this vehicle and I don’t want to get too far ahead at this point. Besides you should have enough to keep busy for a little while at least. I kinda rushed through the tests here so if you don’t understand something or feel I omitted some information please let me know.
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Post by Venturi on Jan 4, 2005 22:49:14 GMT -5
Ok DiverProg, you should have battery voltage on ECM connector terminals E15, E16 and F15. You should also have battery voltage on terminals A9 and A16, these are the ground controlled side of the injectors.
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Post by DiverProg on Feb 5, 2005 18:06:45 GMT -5
All right. I know it's taken me a while to perform these tests but it's been cold and snowy here. I have checked the voltage on both of the injectors after it dies. There is voltage (12.8 V) on both injectors. I went ahead and pulled the PCM, checked the connections (no corrosion) and every connection looked good. I started back probing all of the stated connections (A9, A16, E15, E16, and F15); they all had voltage to them (12+ V). You mentioned earlier to do some voltage drop tests on the ECM ground circuits. Is this where we want to go next?
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Post by DiverProg on Feb 16, 2005 11:43:17 GMT -5
Wanted to give an update and close this issue.
I put in a new computer module and everything seems to be working fine.
Thanks guys for all your help! It's much appreciated.
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Post by DanD on Feb 16, 2005 15:24:41 GMT -5
Thanks for posting the fix. Dan.
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