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1992 Buick Century 3300 V6 no start

Discussion in 'Non-Mopar Tech Support' started by AllanC, Aug 1, 2015.

  1. AllanC

    AllanC Well-Known Member

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    Car is a 1992 Buick Century sedan with 3300 V6 engine and automatic transmission. Engine has about 80,000 miles which is low for its age. Car was running several months ago but just quit while driving on the highway. My friend has replaced lots of parts with the "shotgun approach" in hopes of getting it to run. ECM (engine control module), ICM (ignition control module), crank position sensor have been replaced with used parts. Starter will spin the engine but no attempt to start. I do not know if the used replacement parts are good.

    Today I attempted to assist with a methodical approach. This engine has individual port fuel injection with a distributorless ignition. All 6 electrical connectors at the injectors were removed. I checked the resistance of the injectors and 5 had values of 12.5 - 12.8 ohms. Number 6 injector had a resistance of 10.5 ohms. Online research tells me that the proper resistance should be in the 12 - 15 ohm range. I don't know if that low injector resistance on #6 could be a problem?

    With all 6 fuel injectors electrically disconnected, I removed the air filter housing and sprayed starting fluid directly into the throttle body while the starter was engaged. Engine did not start. I removed the spark plugs on cylinders 1, 3, 5 which are closest to the radiator. I reattached the plugs to their respective wires and laid the plug body on a metal engine support and engaged the starter. All 3 plugs had spark jumping the plug gaps. Since this engine fires the plugs in pairs, 1 & 4, 2 & 5, 3 & 6, my spark plug test confirms that all 3 coils are good and all 6 plugs are receiving spark. I checked the routing of the spark plug wires against a known, running 3300 V6 engine and the plug wires are correct between coil and respective plugs.

    Since I am getting spark at the plugs, I am assuming that the crankshaft position sensor and ignition control module are functioning properly. Since I disabled the fuel delivery and used ample starting fluid in the intake, I will assume that the no start is NOT due to fuel delivery issue. When spark plugs 1, 3 and 5 were removed, I placed my thumb over the opening and had the engine cranked with the starter. There was noticeable compression but this is a crude way to check compression.

    I am wondering if the crankshaft pulley has somehow slipped on the crankshaft and is out of time? Since it is keyed to the crankshaft I would think that unlikely. What have I overlooked? I am open to suggestions.
     
  2. ImperialCrown

    Level III Supporter

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    When you pulled the plugs, did you notice any gasoline smell or were the plug tips wet with gas? Wet plug tips won't fire.
    Was it a nice blue-white spark? Orange spark may indicate low voltage.
    When it is cranking over, does compression sound present and even? Any sound like it is trying to start or any backfire out the tailpipe or out the throttle body?
    Otherwise it sounds like everything needed to start is there.
    #6 injector may need revisiting once it starts, but I doubt that it would cause a no-start.
    Does this engine have a MAF (mass air flow) sensor in the air intake hose?
    I do not know if the used parts are good or even compatible for the car. Can you install the old parts and start from the beginning?
     
  3. AllanC

    AllanC Well-Known Member

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    Disabling the fuel injectors and introducing starting fluid into the intake system was done with dry plugs. The engine has been unattended for many days so I know the plugs were dry. They were still dry after removal and after the starting fluid test.

    Spark was blue white so it seemed OK. I am wondering if the spark is strong enough. Seems that I have read some online posts that you can have spark but it not be sufficient to fire the air-fuel mixture on distributorless GM ignition systems.

    There is no attempt to backfire through the exhaust nor through the throttle body. To me the engine does not sound right when the starter is turning the engine. But my buddy thinks it is OK but I wonder about that. I know that when I had a 2.5 liter Chrysler 4 cylinder break timing belt teeth and get out of time, it had a funny sound / not normal when cranking which was due to camshaft timing not in sync with the cranshaft. I think a compression test with a spark plug adapter needs to be performed. Will a camshaft that is not in proper sync time with the crankshaft show up as low compression on all cylinders?

    Otherwise it sounds like everything needed to start is there.
    #6 injector may need revisiting once it starts, but I doubt that it would cause a no-start.

    There is a MAF in the intake beyond the air filter plenum box. I sprayed starting fluid directly into the wire mesh grid. I will disconnect it electrically and try another start. But I would think the MAF is used for setting the air - fuel mixture and would not be a trouble spot since I am bypassing any air - fuel mixture concerns with volatile starting fluid. But one should never make assumptions.

    I have concerns about a mismatch of parts. I found the original ECM on the car floorboard which can be reinstalled. I don't know if the original ICM is available. I was told the coil packs were exchanged recently and several years ago for a similar no start condition. At that time the no start was traced by trial and error to the crankshaft position sensor which was the culprit.

    Thanks for the ideas.
     
  4. ImperialCrown

    Level III Supporter

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    Can you see rocker arm movement in the oil filler hole?
    Know anyone with a scan tool that covers OBD1 GM cars? I would think they would be fairly common.
    We would want more than fault code capability. Reading real-time sensor values would be useful.
     
  5. AllanC

    AllanC Well-Known Member

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    Earlier today I was thinking about a broken camshaft but once I performed the thumb in the spark plug hole, engaged the starter and got some significant pressure at the plug opening, I moved away from that conclusion. Now I am thinking that maybe I should revisit this area and see if there is rocker arm movement. The front valve cover near the radiator is fairly accessible so I will probably remove it and verify that valves on cylinders #1, #3, #5 are opening and closing as expected.

    I grounded the A & B terminals on the diagnostic connector under the dash, driver side to interrogate for OBD I codes. This is similar to the key dance sequence Chrysler used with OBD I. I got no codes. But maybe seeing sensor values from the crankshaft position sensor might tell something. It is also possible that there is something amiss with the harmonic balancer pulley and the tone / pulse ring that activates the crank sensor. The engine does not have a cam position sensor so there is no easy way to determine if the camshaft is turning other than visual inspection of valves and rocker arms.
     
  6. AllanC

    AllanC Well-Known Member

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    Problem solved. The camshaft is broken. Removed the valve cover on cylinder bank closest to radiator. This covers cylinders #1, #3, #5. Engaged the starter and watched the rocker arms. Intake and exhaust oscillated on #1, only exhaust moved on #3, #5 rocker arms had no movement. So camshaft is broken in the middle of its length. In effect the engine has become a V2 with only proper valve action on #1 and #2 cylinders which are closest to crankshaft pulley end.

    I wonder if a broken camshaft would cause other internal damage. Next challenge will be to determine if camshaft can be removed with engine in the vehicle. Maybe removing the right front fender might give clearance to remove the camshaft. I don't know if my buddy wants to spend more money on it or junk the vehicle. Thanks I C for your input.
     

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