Xoutpost.com - View Single Post - Tricky crank no-start problem

DonaldFoss · #42 05-23-2024, 12:24 PM

I agree with the beer break or asking the Captain to come by for a visit...

I installed an analog fuel gauge inline under the hood and have a pressure tester that connects to the Schrader valve on the fuel rail. My fuel pressure is 51 PSI on both gauges when cranking, 40 PSI in the line before the fuel rail when not cranking, 45 PSI on the Schrader valve on the fuel rail when not cranking, and 30 PSI in the line the next morning the couple of times I looked. It takes several days for the fuel pressure to go to near 0 by itself.

Since these are NGK 4-strap spark plugs for BMW, they're supposed to be pre-gapped. I haven't measured them, but I have feeler gauges, so that's not hard to do. What should the gap be? I can easily measure the voltage going into the coil, but isn't the voltage at the plug really high? My O-scope only goes to 475 volts, but a regular multimeter goes to 1,000, I think; I will have to look. I've never tried to measure the voltage at the end of a spark plug before. I have been using a recessed inline spark plug tester, basically, a light that goes in line with the spark plug. I've also taken a video of the spark plug out of the engine and grounded while cranking to ensure it lit since I can't see that from inside the car. (The wife is ok with me working on it but wants nothing to do with it, and the kids all have their own places now. Have a Son-in-law who is a Toyota mechanic but hates German cars...)

I can certainly check compression again. I normally do 10 seconds with the check, throttle open, fuel off, etc. When you say 4 strokes, do you mean listening for 4 repeats of the sound? It's cranking at 140 RPM, so 4 strokes or 8 RPM a little more than 1/20th of a second, kinda hard to hit--or am I overthinking this, i.e. need some Captain, and you mean something completely different?

On the valve timing, I can check the timing mark on the crank and timing cover when cylinder 1 is at TDC. It was correct before I installed the engine; something could have happened during installation, which took 4 tries to get right. Timing would certainly explain a few things, including why I got fire out the intake with starter fluid. On the flip side, it can't be that far off or it would be kissing the piston heads and making all kinds of terrible noise, bending valves, etc.

Once I understand your compression check test, I'll do that and check the timing mark, then report back.

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