Poor running / hard start on fresh m20 build.

[82eye]

post of shame ... groan .... think i know what's up but any guidance and or experience is helpful.

details :

fresh build, everything has been touched.

new rings / bearings on stock bore, rebalanced bottom.
lightweight flywheel, fresh clutch kit and new starter.
long tube IE header, custom mid and stromung catback.
mild 272 regrind cam, hd rockers, valves freshened with a grind but original.
173 ecu sssquid chip stage 1.5.

symptoms - the good :

car does start and run but struggles to fire.
it can achieve an idle(ish).
compression check shows 150+ dead even across all 6 cylinders. they are all about 2 pound over the 150.
had a fuel issue, it's clearly getting fuel now, i replaced the pump, but have not t'd a gauge to check the fpr.
fpr is original to me but was replaced by previous owner.


symptoms - the bad :

horrible over all running condition. misfires and backfires.
will buck on idle accompanied by random knock.
no knock on throttle but misfire and backfire present.

pulled plugs : only 2 and 6 looked healthy to me for a fresh start.

plug 1 looks brand new, like it wasn't firing at all, was not wet but i could smell fuel on the plug.
2 - healthy with a little white build up.
3/4/5 - looked rich to me with black build up. number 4 being the worst.
6 was healthy like 2

plug build up could just be crap burning off from the build, but i'd expect them all showing the same and number 1 is too clean.

what happened so far :

car was started and brought up to 2500 rpm for a couple minutes to seat the rings. achieved poor idle for about another 2 minutes and was shut off to avoid possible damage.
compression checked after start.

so far my first guess is the timing belt. belt was installed with engine on a stand and was checked multiple times over. i just can't figure how it would be out. my pops is convinced it's the new chip. not sure i could even get a start on the old one and the new will start and the car does achieve an idle even if bad. he wants me to put the old chip in cause he's convinced it controls timing no matter what i say.

at present i guess i will tee a gauge on the rail just for educational purposes, and if the pressure is good the only thing i can think to do next is start pulling it apart to get at the belt.

any other ideas would be welcome.

[tomstin]

Time to back up and take a breath. Its always difficult to check your own work. Start with the simple stuff. Check the firing order. Is the rotor on correctly under the cap? (not long ago someone had it on wrong, not impossible). Are the injectors wired correctly? Are they all firing? The timing belt being on correctly is always a suspect after installing and then having problems. A pain to verify, but with backfiring, something is firing at the wrong time.

Good luck!

[82eye]

Time to back up and take a breath. Its always difficult to check your own work. Start with the simple stuff. Check the firing order. Is the rotor on correctly under the cap? (not long ago someone had it on wrong, not impossible). Are the injectors wired correctly? Are they all firing? The timing belt being on correctly is always a suspect after installing and then having problems. A pain to verify, but with backfiring, something is firing at the wrong time.

Good luck!

backfire is definitely timing. gonna start tearing into it today. plan is to check the simple first as i tear it back to the belt. i have to wait for a fan clutch tool and wrench so i'm starting with the simpler diagnostics today. dist wiring will be one of the first to check.

truth is i'm still in denial lol

engine was torn down and rebuilt on a stand with multiple checks during the process. we can't figure out how we screwed the timing but it's clear the car is telling us it isn't firing anywhere close to what it should be.

[digger]

put the standard ecu chip and injectors in it (mnimise variables) as its basically a stock engine and get a fuel pressure gauge they are cheap

[TobyB]

+1- minimize your variables.

Use an inductive timing light on each plug to see if each cylinder's getting spark, and when (mark the harmonic balancer at 120's)
Use a simple light on each injector to make sure all 6 are getting pulsed voltage.
Dear Gott in Himmel, get a fuel pressure gauge on it.
Make sure you haven't left a big air leak in the manifold, like the mounting bolts for the intake support or the brake booster. Smoke testing tells all, but is often overkill.
(A friend and I once discovered that #2 had 2 intake manifold gaskets on it, and #4 had none. Yes, that was a bit of a vacuum leak)

Get a friend over to look at things. It's humbling, but a fresh set of eyes looking in different places can find what's only obvious AFTER you see it.

t

[82eye]

put the standard ecu chip and injectors in it (mnimise variables) as its basically a stock engine and get a fuel pressure gauge they are cheap

gonna try a 525 ecu that will run it. it's an ix unit but i've had the car run it previous to see if it worked. aside from a slightly warmer cam and exhaust it's fairly stock. the chip is only a half stage over what a complete stock set up would upgrade to.

edit: the chip is a sssquid and doubt it is the root cause, but it could help going back to stock. i have new injectors as well.

[82eye]

+1- minimize your variables.

Use an inductive timing light on each plug to see if each cylinder's getting spark, and when (mark the harmonic balancer at 120's)
Use a simple light on each injector to make sure all 6 are getting pulsed voltage.
Dear Gott in Himmel, get a fuel pressure gauge on it.
Make sure you haven't left a big air leak in the manifold, like the mounting bolts for the intake support or the brake booster. Smoke testing tells all, but is often overkill.
(A friend and I once discovered that #2 had 2 intake manifold gaskets on it, and #4 had none. Yes, that was a bit of a vacuum leak)

Get a friend over to look at things. It's humbling, but a fresh set of eyes looking in different places can find what's only obvious AFTER you see it.

no air leaks on a smoke test, but the smoke maker was cheese. think i'm gonna diy a better one and try again. also have a vacuum gauge but it's not a definitive test. pressure gauge on the rail is gonna happen this wkend before our next attempt.

we been all over the car and found a few minor leaks and double checked wiring. i pulled the plug wires from the dist and tested them, then labelled them and re-installed. local mechanic is coming over to take a look, he's a bmw fanatic and has been asking about the car, e30's are near unicorn status here. he suggested making sure the plug wire set was tested and installed properly. his first question was whether we had switched one or two around.

edit: if there is no difference on our next attempt i'm gonna tear it down to the belt and make sure it's in correct. the outside timing mark on the crank damper seems correct when checking tdc but i know it's not the final answer on it.

[82eye]

yay .... post of not so much shame. it runs and strong.

one injector connector was not on properly on number 1 cyl, and we retraced all the electrical and found the main ground loose from the oil pan to frame. then tested the dist wires, labeled and replugged them. fired and ran happy instantly.


also didn't like how the rad sat so we removed and re sat the lower plastic holders and reinstalled the rad. all the hoses seemed a little less stressed.

edit: i'm positive i messed up the dist wires. i can't see another reason it was so far out. we're bleeding the rad and it's happy and running well. maybe a bit loud.

[TobyB]

Well, yay! Sounds like pretty normal things that happen when you pull it all apart.

t

[82eye]

Well, yay! Sounds like pretty normal things that happen when you pull it all apart.

t

i've fired a couple new builds but never an m20 or any other bmw engine.
pretty sure i got lucky on this. its a happy engine now so far. probably need to re-adjust valves a touch but these things are kind of typewriters normally.

gotta bleed the cooling system proper and check for other leaks over the next few days. then toss a plate on and give a bit of a road test.

[jbontke]

I was going to suggest the ground! Glad you caught that. I always check and clean grounds, especially when an engine was removed. The DME works on such small voltages, a good ground is key to complete the circuit.

[82eye]

I was going to suggest the ground! Glad you caught that. I always check and clean grounds, especially when an engine was removed. The DME works on such small voltages, a good ground is key to complete the circuit.

pretty sure i had two dist wires switched but it wouldn't settle until i checked all the grounds and redid the main from engine to frame. now i'm fighting to get it to bleed proper. it's been 3 days and i still can't get the heater box to loosen up an airlock. probably gonna have to start another thread.

other than that it fires and runs strong.

[jbontke]

Now i'm fighting to get it to bleed proper. it's been 3 days and i still can't get the heater box to loosen up an airlock. probably gonna have to start another thread.

other than that it fires and runs strong.

Have you tried jacking up the nose of the car to help bleed the cooling system? I have read about that working for other e30 owners.

[82eye]

Have you tried jacking up the nose of the car to help bleed the cooling system? I have read about that working for other e30 owners.

yes. i started another thread in general discussion. front is 3 ft in the air, getting no heat in the cabin, no real bleed at the therm housing bleed screw either. getting super frustrated. been 3 days at it.