91' M42 Won't Start, was running fine

[roadbiker_2]

All

I have been troubleshooting a 91' M42 for about two weeks on the weekends when I get a moment to do so.  The car was running perfectly fine, in fact the best it has run since we bought it.  I did all of the mess under the intake back around Father's Day so all of the vacuum lines and rubber have been replaced with either new BMW rubber or high quality silicone lines.  I will look to see if something came off, but I don't feel this is an issue.  I was driving the car and it backfired after accelerating off a stop light and then acted like it was just running out of gas.  I had just filled up with about 15 dollars worth of gas, but it had a little over a 1/4 when I filled the other gas. Once the car quit, I tried starting and it acted like it was not getting any gas or spark.

I have tested the CPS, it is ohm'd out at 530 ohms on 1&2 and infinite on 1&3, 2&3.  The Camshaft Position Sensor was checked this morning and is reading 1230 ohms on 1&2, 1&3 and 2&3 are reading infinite.  I have checked to see that the harmonic balancer has not shifter per some suggestions, and it all checks out to be at TDC when lined up with the mark on the HB and the arrow on the Oil Filter Cover and confirmed with a small screwdriver in the hole near the starter and also by visual inspection of number one piston being up and number two being down. 

I have verified the fuel pump is working and is at the right pressure, I am getting 46 psi and it is brand new as I suspected that this was the root cause of the problem.  It will pump up with the turning of the key, as it should.  I am also getting spark as confirmed by the spark test that I performed.  I was suspect of the injectors not getting fuel into the cylinders at this point, so I bypassed the white relay by jumpering 30 to 87 and 87b.  This caused the car to sputter, but that was it.  I received a follow up to this stating that I would also need to power the 86 terminal in order to potentially start the car.  If this is the case and I looking at just a failed White Main Relay?

It was suggested that I look at the AFM and possibly the temperature sensor as well.  Since I somewhat feel like I am chasing my tail with this, some common guidance is appreciated. I am a Instrumentation Guy by trade, I sell Industrial Temperature, Pressure and Flow instruments, but this is something else.  I don't farm too many things out with the cars as I generally just fix them myself. 

[Darky]

Hi

It's not your afm, these cars don't use that input till the car is warm.

injectors?

Cheers

[roadbiker_2]

I was suspect of the injectors, what would cause them to just quit like I suspected they did?  This sure seemed like a fuel pump failure when it went.  Where is the tail of the dog taking me next on this journey? 

[Froos]

Have a look at your fuel pressure regulator at the end of the fuel rail..

[roadbiker_2]

Froos,

Should I be looking for fuel in the vacuum line when I remove it?  Can the regulator be tested with a vacuum hand pump to see if the diaphragm is good since I am not running?  I assume that there is no way of really testing for a bad FPR since the car is not running as I cannot disconnect the vacuum line to see if the pressure will go up.  What else might suggest this is the culprit?  I had one other backfire after I put a new fuel filter in this car about a month ago, this is the second backfire but the car would not start after this one.  Car had been running fine, in fact very well after I replaced all of the  vacuum lines and water/coolant line connections under the intake.  I went back stock and did not delete the heater under the throttle body as I wanted to keep this car stock in appearance.  All boots and rubber were replaced along with new gaskets as well. 

[colin86325]

Sometimes a backfire can cause the AFM vane to get stuck or damaged.  Does the vane swing freely?

[doitover]

Have you checked compression? Is the timing chain okay?

[roadbiker_2]

All, the car is not with me as I am out of town.  The car had been running fine, so I don't think I have a compression issue.  I can feel the compression cycle when I was turning the motor over with a breaker bar on the crank nut.  I verified that the harmonic balancer had not slipped the other day.  The TDC mark lines up and number 1 was up and number 2 was down. 

I am planning on checking the flapper in the AFM and will clean it along with the ICV while I am cleaning things.  I will report back what I find, this could be that the flapper did get stuck with the backfire.  I think we are close . . . tomorrow I am off and will be checking all of the above.  If push becomes shove I am pulling the valve cover for a full confirmation on the Cam Timing, but I will also be looking at the Cam Position Sensor (CMP) to see if it dirty as well, I was not able to get it out the other morning, it has been PB Blasted. 

[Froos]

If uou suspect not enough fuel, and fuel pump is fine (tested) than the fpr mightbe out. My car could not start at 30 psi...i dont think the fpr cost that much

[roadbiker_2]

Ok, let's review everything that I just checked and also cleaned and inspected.  AFM checks out fine and was checked for resistance on the temperature element and also for the resistor change for the voltage change into computer.  ICV removed and cleaned, I did have a vacuum line that had slipped, but was not off.  I change the way that I had it connected to the ICV, I am using expensive silicone vacuum lines. 

While I had all of this off I inspected all of the other vacuum lines to make sure none had loosened or had come off. Checked the Coolant Temperature sensor for proper resistance, all good to go.  Pulled the Camshaft Position Sensor, I did not see anything out of the ordinary, cleaned it and reinstalled the sensor.  It had already checked out with its resistance test on 1&2 at 1280 ohms. 

Installed new main relay as it was only a few dollars.  I then tried starting and I am getting just some sputtering and no start.  I pulled number one and number two plug and they both have fuel on them.  I then checked for spark again and I am getting spark.  I decided to go ahead and check all of the coils as there are 4 and they are all within spec at 0.8 ohms. 

This is really wearing on me and I am a pretty patient guy.  The fuel pressure test was done back at the pump with bypass of the fuel pump relay to allow me to run it without the car running, is this the correct place to test this or did I need to have it mounted in another location?  I am willing to test this again as perhaps the FPR is not working properly.  Am I even going to be able to see this if I cannot start the car? 

If this test proves out that the pressure is fine and FPR is fine, I guess I am going to pull the valve cover to verify that all of the timing marks are lined up when I am at TDC.  Could any of this be related to the Turner Motorsport chip that was installed?  Could it corrupt itself? 

I am the point where this thing will just get a carburetor, a mechanical fuel pump, and a distributor with hall effect electronic ignition!  Maybe the Kohler out of the lawnmower would suffice. 

[roadbiker_2]

All, I have spoken with a ASE Mechanic and he suggested that I might have gas wash on the rings, which would cause a loss of compression, thus no start.  I added the oil and left the plugs out to turn the motor over, would I feel a resistance at some point that might be caused by the steering pump by chance?  I am going to do a compression check now to check and see how the cylinders are doing and to see if perhaps a valve or vales are bent.  I am trying to prevent pulling the valve cover as I do not have a valve cover gasket set handy to put it back together right now, but that would be the next step  There is some concern the the chain may have slack in it or perhaps jumped.  Comments on the resistance I am feeling would be appreciated. 

[roadbiker_2]

All, this is very much looking like this car jumped time as I have compression of 170-185 on cylinder 1, no compression cylinder 2, 3 and 4.  My question for everyone is why would this happen when the car has a chain and I was not hearing any noise from the tensioner, which was referenced as something that would make noise?

[Froos]

Did you downshift a bit to rough when you last ran your car? Cant inmagine an engine running with bent valves but does sound a bit like it. When i rebuilt my engine 3 exhaust valves were bent a little bit.