Saturday, August 27, 2011

A tale of two Chryslers

I am called to a shop this day for a problem with a 1997 Chrysler Sebring with a 2.5 liter V-6 motor. The shop owner explains to me that this vehicle has been all over the place. Lots of replacement parts. It runs real poor. So poor that the catalytic converter glows red after only a few moments of operation. The shop owner has had enough of this car. He has spent a considerable amount of time and resources on it. The vehicle sets Cam/Crank error codes as well. It has had multiple crank sensors. After listening to the shop owner and hearing the vehicle run. I am pretty sure we have some cam and crank relationship issue. I have been down the road with these vehicles before. There are many things that can go wrong from improper timing belt replacement, broken camshaft dowel pins, worn crankshaft gears, wrong or damaged flywheels, wrong year PCM with wrong flywheel with wrong camshaft sprocket, etc. The first thing I do is scope camshaft sensor and crankshaft sensor to look at the signals and more importantly the relationship between the two.
There she is. The crankshaft sensor reads off the flywheel and the camshaft sensor is inside the distributor which is driven off the end of the camshaft. The relationship between the two looks great. Amplitude of signals and ground point are also excellent. However, I am seeing a very weird crankshaft sensor pattern.
I changed the timebase so we can see more detail. Here the crankshaft sensor signal (arrows) is not what it is supposed to be. There should be four equal pulses reflecting the slots in the flywheel. If you look at the pattern sometimes we have this more often we have this freaky pattern. Hmmm. Do we have a damaged flywheel? This car has been around the block. Who knows how many times the transmission or engine has been out of this. Remember, this car has had multiple new crankshaft sensors. Something tells me that the problem still is with the crankshaft sensor itself rather than the flywheel. I recommend to the shop owner to get an OE crankshaft sensor and to make sure it has the felt spacer on the end of it. This felt spacer is the air gap adjustment between the sensor and flywheel. When installed it will bottom out. The first start takes the felt spacer off and sets the air gap. Subsequent crankshaft sensor removals and replacements require this felt spacer to be reinstalled before sending the sensor back home. I have seen plenty of aftermarket crankshaft sensors that do not posess this spacer. Installing the sensor without the spacer will cause certain sensor damage. I inform the shop owner of my hunch. But, warn him that he may be taking this transmission out. I reason with him that I would rather gamble with the sensor than a transmission removal. He agrees.
A couple of days later he calls me. He goes on to tell me that the vehicles crankshaft sensor he removed had obvious contact damage. The new OE sensor fixed the car and the car runs well. I was happy for him.

The next Chrysler is a 1995 Chrysler Cirrus with a 2.5 liter V-6 motor. It is a crank no start. Also, the shop owner says it has no scantool communication. I crank the car over. It has a nice even cranking sound. I hook up my scantool and I indeed have communication. This is one of those vehicles that have the familiar OBD2 data link connector but are really not true blue OBD2. We used to call these cars OBD one and a half on the techline. I check certain key parameters on the scanner such as map voltage, vehicle theft status, and cranking inj pulse. All look good. I check spark quality and scope ASD (Automatic Shutdown) relay voltage and injector pulse right at an injector. I have great spark, good ASD voltage cranking, and proper injector pattern. What gives? I spritz a little carb spray into the throttle body and car cranks starts and stalls. I break out the propane and can run the car. Ok, I know I have no fuel. Hooking a fuel pressure gauge up on this vehicle is a pain in the a$#. So, I use ATM (Actuator Test Mode) to actuate the fuel pump relay. I hear the relay click but no fuel pump operation. I remove the relay to jump out and look at the pattern with my low amp probe.
I removed the relay next to it for comparison. Do you see what is missing?

The terminal that is the output of the relay out to the fuel pump is not there. It has sunk down below where the relay blade terminals will make contact. I am able to use a long duckbill terminal to make contact with it to get this fuel pump to run. I hear the fuel pump turn on. I try to start and we still have a no start. Huh? The fuel pump is wailing away. Ok, lets get the low amp probe on there.
So we have a nice pattern. But very low amperage. I typically see 4-5 amps on these vehicles. Even a cheap pump will give me 3 or so. This is very low at barely 2 amps. Ok, we have a good pattern but low amperage. What would cause that? I think we are out of gas. A quick rap on the tank confirms this. I advise the shop owner to remove the underhood fusebox and repair the terminal. Oh yeah, put some gas in it as well.