installed 2.7L engine brand new wont fire up

so i just recently been overhauling a barely used m20 motor for my 87 325e ( blew up the old one).. ive been steadily bying parts very pay check to build the engine to completet .. okay so the motors in and eveything in it, on it, and around it , is brand new except the alternator.. so its all in and i was hopeing the fire it up yesterday and it would not start.. it has no spark, and the fuel pump is not turning on.. so theres no fuel i hot wired the fuel pump and it works so thats not the problem so im wondering if the the computer has some part in this i dont know.. all my fuses are good the battery and starter both work it just doest go VROOM after i turn the key.. it just cranks over but no fire .. any suggestions on what i might need to check ..

Is the crank sensor new? Is it installed correctly? My guess is the ECU isn't "seeing" then crank move, so it never sends injector pulses or spark to the engine. It will also prevent the fuel pump from running unless it senses the engine is turning.

Also, why were you overhauling a barely used engine?

Yeah i'd check the cps. Are you running the same one from your old motor?

Just a question but why put the 2.7 back in? My 2.7 is on its way out.. I'd atleast put a 2.5 in it if I weren't doing my 3.5 swap already. I've had the 2.5 and I'm currently driving the 2.7. IMO 2.5 all day long over the 2.7.

Is your coil getting any voltage when in the ON position?

Originally Posted by Newman271

Just a question but why put the 2.7 back in? My 2.7 is on its way out.. I'd atleast put a 2.5 in it if I weren't doing my 3.5 swap already. I've had the 2.5 and I'm currently driving the 2.7. IMO 2.5 all day long over the 2.7.

Turbo man!!! Lol a 2.5 you can turbo but low boost a 2.7 you can run mads amount of boost

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Yup I'm boosting mine once I get the I top end

Originally Posted by BmwMan92

Yup I'm boosting mine once I get the I top end

You need more then the i top end if you have a 325 with the 2.7 bottom end youll need the i intake

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Originally Posted by hornhospital

Is the crank sensor new? Is it installed correctly? My guess is the ECU isn't "seeing" then crank move, so it never sends injector pulses or spark to the engine. It will also prevent the fuel pump from running unless it senses the engine is turning.

Also, why were you overhauling a barely used engine?

its been a few years since ive played with an M20, but from memory, the ECU doesnt control the spark like it does on the M50 and later engines, on the M20 its only the injectors and runs off the CPS which would explain why no fuel but not why there is no spark.

of course, there could be two issues at the same time

please correct me if im wrong.

Originally Posted by damalex

You need more then the i top end if you have a 325 with the 2.7 bottom end youll need the i intake

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I know what I need to do the build

The Bentley manual points to these things as possible reasons for no spark:
1. distributor
2. spark plug wires
3. coil
4. spark plugs
5. CPS
6. DME/ECU

I'd strongly recommend getting the Bentley manual. It has saved my ass a few times.

my reason for overhauling is kuz i blew up my original motor so i got a used one from a wrecking yard out of an automatic.. but to be sure i was putting in a good motor i bought all new parts for the engine.. timing belt n tensioner,, gaskets spark plugs oil pump radiator, but kept the same wiring harness!

yes im running the same cps as the old motor and same computer inside the glove compartment
all the same wiring and electronics. but new mechanics..lol

heres the deal.. when I blew up my last motor I was driving about 90mph (in 5th gear) .. and i wanted to go faster so i was making a shift down to 4th gear.. in the proccess of shifting i made a misjudged shift into 2nd gear blowing up the motor.. so the car dies on the highway and will no longer start .. by the way i did not break the timing belt. i found a valve in the bottom of my oil pan with alot of shattered metal.. anyways by makeing the bad shift from 5th to 2nd .. could that result in a surge signal or some type of backfire to the computer and ruin it or possible that being a way to ruin the CPS?? i have no idea but worst case scenario i buy new CPS and
new computer.. but before i don that i need to figure out wats happening and why it will not fire up ??

Originally Posted by BmwMan92

Yeah i'd check the cps. Are you running the same one from your old motor?

Yes I am. But not sure if theres damage to it from blowing up the old motor

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Originally Posted by alpinewhiteE30

Yes I am. But not sure if theres damage to it from blowing up the old motor

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Does that engine have the pulse sensor to? I've seen to many times people plug those in backwards

Originally Posted by BmwMan92

Does that engine have the pulse sensor to? I've seen to many times people plug those in backwards

pulse sensor.. wouldnt it be those two sensors on the side of thebell housing/or tranny? ya there the same ones because i kept all the original wiring from the old motor just swapped em on to the new motor! i checked them being mixed up .. still doesnt fire.. i wonder if the ecm is damaged from the last motor .. do thos commonly go out in e30's? if so does buying a new ecm require me to restes signals n all kinds of crapp or can i buy a new one, plug it in and its done? does it all bye itself? how do those work

Plug and play. Nothing to replacing a DME.

I hope you don't mean a "new" DME but rather a different DME. These don't go bad all that often and you'll lots of people selling these on online forums for fairly cheap.

Those cps on the bell housing go bad all the time on older motors. Chech with a multi-meter. 3 wires - one pair should show the resistance of the little coil and the other open (infinate). The 'open' teminal is the shroud round the wires. If you have open on all pairs of terminals the coil is the problem and you need new units. I use Pelican Parts for stuff like that.

One of the the two sensors counts ringgear teeth and the other gets a pulse at 20deg BTDC (? - working from memory). If they are the wrong way round the ecu gets very confused!