Author Topic: New to this engine, have a few questions to ask  (Read 2772 times)

Uniquestrain

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New to this engine, have a few questions to ask
« on: April 27, 2013, 04:43:08 AM »
Ok so first off
I did a engine swap in my recently purchased 91 318 and i put a 94 m42 in it
So i got to connecting all the heater hoses, sensors and wiring i kinda knew (not really but did my best) and my car ran fine for a few hours and then it just started getting worse and worse
Started to bogg, wouldnt idle right, would shut off.
Questions i have
Does the 91 m42 have knock sensors? I dont remember seeing any when i took it out and this new engine has one and i just left the wire hanging there...not sure if that can be the problem and not sure where it would connect to :[
2 my cam positioning sensor has a crack on the wire housing....i pressure washes my engine bay and i think might have had something to do with it not turning on at all now but still started after that (poorly)
3 when i try to start it now there are no signs of fuel going into the cylinders. No type of gasoline smell at all, would the fuel pump not turn on for a bad cam sensor?

I just need help getting my car running great since i know very little on these engines.
I love my car and have already done so much to it and plan on keeping it for a very long time

DesktopDave

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Re: New to this engine, have a few questions to ask
« Reply #1 on: April 27, 2013, 10:11:49 AM »
No knock sensors on the E30.

Cam sensor is a problem, but not critical.  Fix it later.

No fuel usually means a bad crank sensor or a bad pump relay.  There are three relays on the firewall, separate from the relay box on the wheel well.  From left (passenger side) to right (driver's side) they're the O2 heater relay, fuel pump relay and main relay.

First off - to test the crank sensor, pull the plug out and put a multi-meter on it.  You want to test the sensor, not the chassis wiring.  Don't test the harness side (goes to the DME).  Test the sensor side.  The sensor must have 640 ohms between pins 1&2.    Pins 1&3 and 2&3 should have very high resistance...100Kohms or so.  PM me if you don't understand what I'm saying.  This is important!  If the DME doesn't get an excellent signal from the crank sensor, it never turns on the fuel pump.  I'd also unbolt the sensor and carefully clean it up.  It should be very close to the trigger wheel, like credit card thickness.  If it's too far away clean up the mount socket and check the mounting plate.

Next, test the fuel pump and relay:
Cut a short 4-6" bit of good 14 gauge wire...strip a bit off the ends to make a jumper wire.  If you want to get really fancy, crimp a pair of male spade plugs on the ends.  Use that jumper wire to short FP relay socket pins 30 & 87.   Turn the ignition switch to position II, the pump should run continuously.  If the pump doesn't turn on find out why.  Pull the rear seat & inspection cover and directly jump the pump connectors with 12vdc off a charger or car battery.  Check the harness as well - I've seen wires pull out from the connector plug.

If the pump works, test or swap the relay.  It's a standard four-pin relay...easy to replace.  In a pinch, the windshield wiper relay is the same, swap them out.  You can test the relay by putting 12v on pins 30&87.  You should feel the relay snap shut...and you should see zero ohms resistance (continuity) on pins 85&86.
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Uniquestrain

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Re: New to this engine, have a few questions to ask
« Reply #2 on: April 27, 2013, 01:24:26 PM »
Ok ill try that today and ill let you know how it goes
Thanks for all the help, i really appreciate it

colin86325

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Re: New to this engine, have a few questions to ask
« Reply #3 on: April 27, 2013, 09:51:43 PM »
You might see if there are any stored "stomp codes" in the ECU to help you troubleshoot.  A google search will provide the procedure if you are unfamiliar with the procedure or the meaning of the errors.

Uniquestrain

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Re: New to this engine, have a few questions to ask
« Reply #4 on: April 28, 2013, 04:33:04 AM »
You might see if there are any stored "stomp codes" in the ECU to help you troubleshoot.  A google search will provide the procedure if you are unfamiliar with the procedure or the meaning of the errors.

Well i switched out my cam sensor and crank sensor
Seems to be a little bit better, spark got a lot better
My guess is the fuel pump or a bad relay
Gonna test them out later on today!!! Wish me luck

One thing i didnt mention before
When my car was beginning to get really bad, i had to kinda pump the gas pedal to keep it from dying or to even try and get my rpm up
Dont know if that means anything but every little bit of info helps right?