M20 has spark and fuel, but just cranks?

[Jean]

M20 don't like me :(
I replaced the bad head with a good head on my 89 525i car, and it fired right up first for a few seconds but I didn't keep it running for long as the exhaust manifolds were not on it and I just wanted to hear it fire up. Timing was set per the marks on the head/crank... and it did fire in this configuration so .

So, then I finished everything else, manifolds with new gaskets and nuts (had to wait for the right ones to arrive) and now all it does is cranks.

Here is what I've tested

- it is getting spark at each spark plug wire
- i've replaced the spark plugs with new copper plugs
- it is getting fuel to the rail
- removed the fuel hose going to the rail and put it in a can, while cranking it sends fuel
- cps checks at about 500ohms (but the fact that it is sending fuel and spark probably only confirms cps is not faulty yes?)
- the 6th spark plug wire with it's cyl. id/wire sensor was toast, the sensor plug that goes to the engine harness was broken so i replaced it with another, made no difference. and i guess this sensor is not even critical to engine running since aftermarket spark plug wire sets don't even come with it?

- i've disconnected and reconnected the cps and that spark plug wire sensor wire to the main harness
- i've replaced all 3 relays near the dme
- car has plenty of gas (over half a tank)
- battery is charged
- it keeps cranking

- disconnected afm to see if it makes a difference, it did not

I have not replaced the following:
dme (although it DID fire up and run for a few seconds with this dme)
fpr (I think I have a spare and can try )
icv (it makes noises, and I do have a spare I can try as well)
afm (don't have a spare)


I bought some starter fluid today, so I'll give that a shot as well. Right now I don't know if the injectors are firing fuel into the cylinders or not ... if it's sending spark it should be also firing injectors yes?

Bentley says if there is spark then cps is fine. There is no relay between dme and injectors, so they must be wired directly to dme stage. If CPS is ok and there is spark, then injectors should fire yes?

Jlevie?

[lolcantturn]

Check your timing belt one more time. It coulda slipped off a tooth.

[lole30]

M20 don't like me :(
I replaced the bad head with a good head on my 89 525i car, and it fired right up first for a few seconds but I didn't keep it running for long as the exhaust manifolds were not on it and I just wanted to hear it fire up. Timing was set per the marks on the head/crank... and it did fire in this configuration so .

So, then I finished everything else, manifolds with new gaskets and nuts (had to wait for the right ones to arrive) and now all it does is cranks.

Here is what I've tested

- it is getting spark at each spark plug wire
- i've replaced the spark plugs with new copper plugs
- it is getting fuel to the rail
- removed the fuel hose going to the rail and put it in a can, while cranking it sends fuel
- cps checks at about 500ohms (but the fact that it is sending fuel and spark probably only confirms cps is not faulty yes?)
- the 6th spark plug wire with it's cyl. id/wire sensor was toast, the sensor plug that goes to the engine harness was broken so i replaced it with another, made no difference. and i guess this sensor is not even critical to engine running since aftermarket spark plug wire sets don't even come with it?

- i've disconnected and reconnected the cps and that spark plug wire sensor wire to the main harness
- i've replaced all 3 relays near the dme
- car has plenty of gas (over half a tank)
- battery is charged
- it keeps cranking

- disconnected afm to see if it makes a difference, it did not

I have not replaced the following:
dme (although it DID fire up and run for a few seconds with this dme)
fpr (I think I have a spare and can try )
icv (it makes noises, and I do have a spare I can try as well)
afm (don't have a spare)


I bought some starter fluid today, so I'll give that a shot as well. Right now I don't know if the injectors are firing fuel into the cylinders or not ... if it's sending spark it should be also firing injectors yes?

Bentley says if there is spark then cps is fine. There is no relay between dme and injectors, so they must be wired directly to dme stage. If CPS is ok and there is spark, then injectors should fire yes?

Jlevie?

not always. the signal could be going into the dme but not out of it. or the signal might not be getting to the injectors. get some noid lights and see if you have injector pulse at the connector.

If the injectors were not firing and you sprayed starting fluid in it should of started and your getting spark it should of started..

Just because the cps shows 500 ohms does not mean it is good. It just shows there is good continuity between the sensor. But the sensor could still be bad and sending out a distorted signal causing the car to not start.

Check to see if you have any codes would be a good place to start.

Check your timing belt one more time. It coulda slipped off a tooth.

even a tooth off it would be able to start.

[Jean]

I have not tried starter fluid, I'll do that tomorrow. I just read through the bentley and it seems that if there is SPARK then CPS is ok? AS otherwise there wouldn't be Ignition or Fuel pump won't be running either.

Could a possibly bad CPS cause SPARK but not FUEL?
IF there is spark AND fuel, then it has to timing correct?

Under what condition could it be a bad DME though?

[lole30]

there is no field test for a dme besides replacing with a know good dme.

Just because there is spark and fuel does not mean the cps is good. Yes it could be good in the sense that it is sending the signal for the fuel and spark to go off. But is the sending the signal at the correct time and sending the correct waveform that the dme wants to see is very important.

The cps is a magnetic based sensor working in conjuction with the teeth on the balancer ( one missing tooth to determine TDC). It produces a signal based on this. If you had an oscilloscope you could see the signal it produces it would look something like this.

http://fcc.orgfree.com/fcc/scope.jpg

now if that signal is obscured because of a failing sensor it could be firing injectors and spark at the wrong time like say on the exhaust stroke.

Spraying starter fluid in to see if it will start and pulling codes will be a good place to start diagnosis though.

[Jean]

Also I put all new gaskets and replaced most vacuum lines as well (except for the ones going from the tb to the booster).

[Bene]

how well did you clean the head-block surfaces before installing the head?

over the summer my dad changed the head on his Tacoma. When he got it back together, regardless of everything being in the right place, it wouldn't fire up. we tested the compression and each cylinder was only getting about half the required psi. I tore it back down, gave the block surface a good scrub down, and now the truck runs like new.

so test your compression. if you don't have a compression tester, parts stores will lend them out. if it's low you'll have to tear it back down and clean off all the old gasket material off of both surfaces. If you think it's clean enough, clean it again. I use a flathead screwdriver, steel wool, and paint thinner. make sure you plug the cylinders and coolant ports with paper towels or something and vacuum all the crap up as best you can before you put it back together.

[jlevie]

Spark when cranking the engine doesn't completely rule out the CPS or DME, but it does push them to the bottom of the list of suspects. Intake leaks or a fuel delivery problem are the likely causes at this point. A check of fuel pressure at the rail will cranking will tell if the filter, pump, or FPR is at fault and a noid light will tell if the injectors are firing. If you don't see firing pulses at the injectors, check C191 (under the intake) for damage.

[Jean]

Bene - block and head were cleaned, no old residue was left before installing new gaskets.

jlevie - installed a known good dme today and it fired up on first try and ran, i then shut it off and re-installed original dme and it wouldn't start. re-installed the replacement dme and it wouldn't start either. it seems that the car starts on the first try only but does not start again.

I then installed another CPS, same deal, just keeps cranking.
Installed replacement FPR (new), same deal, just keeps cranking.
Checked spark plug wires with ohm meter, they check the same as on my e30 car.
Checked distributor, checked rotor, everything aligned as it should.
Removed top cover and checked timing on the cam and the crank, everything is spot on.
Tried starter fluid down the intake boot, no firing (this makes no sense, since it has spark why wouldn't it start with starter fluid?)

Few hours went by and I then tried starting it again, and it fired up and I could hold it running at 2-4k rpm but it had really crapy partial throttle response and then died. So there is gotta be something else, not timing and obviously not injectors as when it fired up it ran on all 6 and pretty smoothly, minus the partial throttle response and hesitation to start again?!

I could not rent a fuel pressure gauge, so that is one thing still left to do.

Another thing is, under the knee pad I found a shock sensor thing, so it must have some kind of alarm, yet there are no presence of alarm under the hood of the car or near the starter either.

[Jean]

I am also thinking maybe coolant temp sensor is faulty or would it not cause these issues?

[Jean]

anybody have access to this - See S.I. 12 05 89 (1862) concerning E30, C191 (E34 x 1563) multiplug moisture.

I have ETM for 89 e34 and it does not e ven list X1563 or C191?

[jlevie]

I know for certain that a 90 525i has a C191, since I salvaged the engine side of C191 to repair the harness I have in my Spec E30. I suspect that an 89 also has C191.

While an aftermarket alarm might prevent the engine from firing, one tends to expect there to be no spark if an alarm is the cause of the no start. What you describe sounds more like a fuel problem or intake leaks.

[Jean]

Ok C191 = the round fuel injector harness plug? I'll check it.

http://forums.bimmerforums.com/forum/showthread.php?t=1597051

[gtdragon980]

The 89 should definitely have the c191. Mine was corroded so bad that the car would barely start and if it did, it ran like shit.

[hotballs]

Seems like a DME thing.

The only time something like this has happened to me was when I was swapping lots of chips and DMEs in an EWSII car. Sometimes it would start even with the incorrect EWS signal. But then not start other times.

Obviously your car doesn't have EWSII but what you're describing points to the brain not allowing things to run correctly, sounds DME related.

Can't remember, was there anything with the OBC which caused a lock out on the ignition?