This is my '94 850. Car was running great yesterday with no problems.

I went to start my car this morning and it started up, but was running really rough and was making some noises. I shut it off and tried to start it again, but did not start. It almost sounds like no compression when turning over. I checked for spark and it has it. I tried to get a fuel pressure gauge on it, but the throttle cable bracket is in the way. It does seem to have pressure after each time of turning the key on, so I am assuming the pump is running. I tried cranking it over more, but the battery died and I can't seem to get it charged by jumping it. I checked out the timing marks and they still look lined up. The belt is in tact and still has good tension, so I don't think the timing belt jumped. I looked through the spark plug hole and could not see anything abnormal like damage, coolant, etc. I do not see any coolant in the oil and the coolant level is fine.

I did a compression test and here are the results.
#1-130 psi
#2-180 psi
#3-180 psi
#4-170 psi
#5-180 psi

I know #1 cylinder is quite a bit off, but shouldn't the car still run?

I am going to get the throttle cable bracket off so I can get a fuel pressure gauge on it.

 

Have fuel pressure. Is at 40 psi when cranking over. Can feel injectors pulsing.

 

Turbo or no turbo?

 

If it did run, it would run very badly with that much of a compression difference in cyl #1.

 

Non-turbo

What would all of the sudden cause that kind of compression loss? It has been running fine before this.

I noticed that the tach is doing nothing.

I got some codes from A3 and they were 213,214, and 442. There was no stored codes in A2 or A6. A7 had 122 and 132.

I guess the code in A7 would explain nothing on the tach, but would it cause a no start?

 

I tested the rpm sensor and it is working fine. I am going to replace the battery because it does not seem to be taking a charge. I know some cars are very sensitive to battery voltage, so I hope this is the problem.

 

130 PSI wouldn't cause an outright misfire. You should notice a bit of instability at idle, but that's it. I'd start with the RPM sensor code. The sensor itself is fine... that's no surprise, magnetic sensors rarely go bad- they're a magnet, a coil or wire. Nothing more. But wiring can go bad. So check the wiring between the ECM and sensor for continuity as a first step. Keep in mind- codes don't tell you what is wrong with the vehicle, they merely tell you where it "hurts." They can help you to make a diagnosis, they aren't, in themselves, a diagnosis. Good luck!

 

I know there is a problem with the battery and that is why I am going to change that before I go any farther. It's 5 years old anyways, so it should get changed before winter. If that does not fix the problem, I will move on to checking the wiring. I was also talking to a mechanic friend of mine and he was saying there is a TSB for a ground that goes bad and can cause hard starting or a no start. I will get that cleaned like the TSB says to do.

Will have updates tomorrow!

 

New battery, still not running. The old one was bad though. I am looking through the service manual about testing all the sensors and it is saying I need a breakout box to do all of the tests. Do I really need that to test everything?

I tried to see if the injectors were pulsing while cranking the engine over with a test light and both wires have power even while cranking. They do not seem to be pulsing.

This cars electrical system seems to be much different than any other cars I have worked on. I don't seem to know where to start with this!

 

Just checked the coolant temp sensor. It is at around 7 ohms. The temp here is around 60-70 deg. The service manual says it should be at 2800 ohms for 68 deg. If the sensor was bad, I would think the temp gauge would be pegged with this low resistance, but it is not.

 

Engine seized up, problem solved.