im about to smack this car

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forrestinmississippi

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#1
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mississippi
#1
hey yall,
i got this E30 that im working on for a lady and im hoping somebody can help me. we're a mercedes shop but i like bmws and my boss gives them all to me. unfortunatley when i get in a bind, im stuck. so this one came in dead. the lady turned it off at the gas station and went to re-crank it and it was completely dead like the battery was disconnected. when i got it, it was theh same thing but jiggling the battery cables got me power. now it wont crank. it spins over, but i cant get any fire out of the coil. i threw a new coil at it, a crankshaft sensor and a junkyard motec computer but still got nothing. the computer's powering up it seems, but its just not doing. its a 91 model 325 4 door. no alarm, manual trans. the customer installled a timing belt recently tho i dont know that has anything to do with anything. im about to start back to college and this has not been an awesome last week of summer. help me please! thanks
forrest
 
mjbst111

mjbst111

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#2
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Pittsburgh, PA
#2
i'd check the fuel pump. Pull up the back seat and see if the pump (passenger side panel) is getting voltage while someone turns the key. If it is bang on the tank (fist or wratchet or something) while someone turns the key. Sometimes you get a few more minutes of love from the pump by doing this. If that works, get a new pump.
 
Kirby

Kirby

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#6
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#6
If I read correctly, he says:

"but i cant get any fire out of the coil. i threw a new coil at it, a crankshaft sensor and a junkyard motec computer but still got nothing. the computer's powering up it seems, but its just not doing."
Click to expand...
So checking the fuel pump isn't going to solve his problem.

Do you see solid voltage swings (10 - 12 volts) on the PRIMARY of the coil? I haven't worked on an E30, but I am VERY familiar with Volvos of the same age and Bosch ignition.

If no solid voltage swing on the primary, look for a "POWER MODULE" (transistor, lol) that sits between the computer and the coil. It takes the 5 volt pulse from the computer and switches 12v directly from the battery to the coil.

These modules need a good ground and are heat-sinked to the body/firewall/fender. The heat sink rusts, loses thermal conductivity and burns up the transistor.
 
B

Big Daddy

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#8
Yes I saw it, but assumed that since he "threw a new coil at it" and did not say it did not work that it must have. If he still has no voltage from the coil than yes the fuel pump is a waste of time.
 
Kirby

Kirby

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#9
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#9
I agree Dan, it's a bit of interpretation. It's not real clear as to whether the new coil gave him spark or not. Maybe he did get spark and I am reading it wrong.
 
E

epj3

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#11
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Lancaster, PA
#11
Check that the crank position sensor isn't too far away from the harmonic balancer's teeth. You should, as a general rule, be able to squeeze a penny in and out of the gap.

Also check the DME and fuel pump relays (i think someone else said this too). I'm not positive where they are, but I do belive they are in the fuse box. There is another box with relays in it on the strut tower (if I remember correctly...), but I believe those are for other things (like the aux electric fan). I could (definitely) be wrong, but if the car has a bad ignition switch, it wont allow the fuel pump relay to turn to on.

I can pull out my bently a little later and see if it says anything...
 
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