help me make the picnic

[5Toes]

so with the fuel return line clamped off in the engine bay the pressure is holding steady for over 10 minutes now at 42psi.

In my Bentley manual it says that if the pressure is maintained with the line clamped off then the most likely culprit is the fuel pump check valve. My car builds pressure super fast and never takes longer than 3-4 seconds to crank and fire, so not sure why its losing pressure. maybe a leak near the fuel filter area. I think this problem is not part of why the car wont run. the system lost pressure with two different fuel pumps (one fairly new from PO, one brand new last night) so Im not sure if the leak is somewhere else in the fuel system or not.

the car had the mess under the intake done when I first got it and last night I checked everything with a flashlight the best I could. the gaskets still all look new and nothing is unplugged. smoke test would be cool except I cant drive the car to a shop and dont have the equipment at home. Im about to go pull upper intake manifold now.

EDIT: also after a DME reset last night the car wont even idle now. hooray! atleast it always starts up and tries to idle

[5Toes]

I just removed the clamp and bled off the fuel pressure and repeated the test a few a times and now the car holds pressure just fine at same psi, no clamps or anything. lol wtf this car has a mind of its own

[RainRider]

the car had the mess under the intake done when I first got it and last night I checked everything with a flashlight the best I could. the gaskets still all look new and nothing is unplugged. smoke test would be cool except I cant drive the car to a shop and dont have the equipment at home. Im about to go pull upper intake manifold now.

http://www.bimmerfest.com/forums/sho...1372&highlight=

I made one a few years ago and posted it.

[TobyB]

Try unplugging the MAF and see if it gets better.

Likewise, check the throttle position switch just to make sure it's working.

fwiw,
t

[5Toes]

thanks Rainrider. Pulled the upper intake off and theres no signs of vac leaks at all. the m42 with the mess under intake done has only a limited number of potential vacuum leak areas. all rubber hoses are good shape with no cracks, intake manifold seal is great and injector seals are good as well. the injectors spray evenly and do not leak either.

I pulled the DME connector and had my pinout sheet ready but the small pins on the connector are limiting me from using my multimeter probes... any idea how to get around this?

Im pretty sure Im not gonna make the picnic... Im leaning towards a bad DME or bad engine harness at the moment.

unplugging the o2 sensor, or afm, or TPS sensor makes small differences but nothing major - car still barely idles and dies after a few seconds. the TPS tests good at the connector and has no dead spots throughout its range of motion, and the engine runs the best with TPS unplugged, o2 unplugged and AFM left good.

[Matt-B]

the m42 will run with every sensor unplugged but crank, badly but it will continue to run.

I had issues with my m42 when i had it, turned out to be grounding issues in engine bay

[5Toes]

Tried pinning out the ECU but could not get continuity on the pins I needed... not sure why. tried with ignition on and off with zero luck.

I have basically ruled out the fuel system, it holds pressure good now and the injectors dont leak at all and spray nice.

Im thinking bad grounds and weak spark at this point...

[AndrewBird]

Pressure bleeding off the rail sounds like a bad fuel pressure regulator. If it wasn't holding pressure, the injectors wouldn't be spraying like they should and cause a lean condition, much like how a vacuum leak would.

A bad check valve would only cause hard starting. Once the pump is running it does nothing.

I'd try a new FPR.

[5Toes]

it holds pressure fine good now. 42psi at idle and then it raises when giving it throttle. Not sure what happened or if it bled itself or what after the initial return line clamping. But it holds pressure now and thats whats important. I have observed the fuel injectors spray pattern firsthand.

going to check for how hot of spark when its a little darker outside. also going to go over all grounds tomorrow. my engine harness has some weird issues, somebody has been in it before and replaced some of the wiring to the relays (I noticed today)

I found this thread - http://www.m42club.com/forum/index.php?topic=13505.0 - his problem was bad grounds. kind of same issue as my car, however mine is obviously worse.

[5Toes]

confirmed that the car has weak spark. in the dark it shows as orange/yellow. all ignition coils show the same condition when grounded to strut tower. I order new ground cables from BAVREST just for good measure since mine are so tired looking. Gonna clean all grounds tomorrow and see if spark improves. my intake manifold gasket broke upon removal so Ill just be coming to the picnic in brothers car most likely

[BraveUlysses]

i think i have a spare upper and lower gaskets if you are willing to pick up

[5Toes]

thatd be awesome but I have no way to come get them in time LOL

So I just pinned out the DME and got these numbers - they are all not exact cause my memory isnt perfect

about 2800ohms for coolant temp sensor stone cold engine - thats good
crank sensor 550ohms or so
cam sensor 1250 ohms or so
TPS reads 1.6kohm up to 4.4kohm or so. all good. no flat spots or dead areas throughout range of motion

so it looks like my engine harness is OK

I got 12.58volts exactly acrossed the battery terminals and the same voltage from the + distribution block in engine bay grounding to engine and G103 on battery tray. seems good... but not sure how it performs under load. Need to test that next but need a helper.

[robert1700]

I have a spare M42 motor you can have