Tried to start the e30 today. (electrical troubleshooting)

[Jordan]

Checked and double checked everything, finished topping off with fluids, connected the battery and gave it a crank.

It cranked for maybe 2 seconds before the battery died... dammit, forgot to charge it up

Backed the M3 up to me, and connected jumper cables

Cranked it again. No start. And again.. no start.. well it cranks like a champ, thats about it.

After a quick check on the fuse box I noted fuse #10 had blown, I replaced it, and went for another crank. This time I saw it blow

Before checking what it was I took the fuel line off the fuel rail, bone dry. Had my stepfather try to start it while I listened to the fuel pump... not pumping.

ARG!! well I looked up what fuse #10 did in the Bentley, and it does say "fuel delivery" amoung many other items. So I suppose fuse #10 is my arch enemy now.

I have the battery on the charger, gonna leave it on over night. I shall try to track down the problem in the morning, until then does anyone have any ideas?

[boom-monkey]

Fuse 10 generally blows when the wire for the backup lights shorts out, at least thats what it was doing in my car. I'd see if for some reason or another your wire is frayed and if so replace it (duh)

[UNHCLL]

Does it pop when you crank, or when you turn the key to the "on" position?

You have the pump wired up correctly, yes?
All your chassis grounds are good?

[M-technik-3]

How old is the fuel pump? They are weak units, it could have died while sitting around.

So grab the multimeter and start ohm out the fuel pump loop.

[Jordan]

Fuse 10 generally blows when the wire for the backup lights shorts out, at least thats what it was doing in my car. I'd see if for some reason or another your wire is frayed and if so replace it (duh)

I made a brand new reverse light harness from scratch for my car (much improved over the stock design, thick plastic shielding over the wires etc)

This is not the problem, that I can say with certainty

[Jordan]

Does it pop when you crank, or when you turn the key to the "on" position?

You have the pump wired up correctly, yes?
All your chassis grounds are good?

Pops as soon as the key is turned to the first position forward

Yes, the pump is wired correctly, the 2 terminals are of different sizes, so it is impossible to mess that up.

I would assume all chasis grounds are tip-top. All of them were hit with a diegrinder to bring to metal (where paint was sprayed) then bolted down.

[Jordan]

How old is the fuel pump? They are weak units, it could have died while sitting around.

So grab the multimeter and start ohm out the fuel pump loop.

The pump came out of my parts car, it has been dry and in storage for about a year. It did work fine prior to removal. I will test it tomorrow as I need to fix my multimeter (one of the probes fell off.. ghetto)

[UNHCLL]

Pops as soon as the key is turned to the first position forward

You have a bad ground somewhere if this is the case.
What is listed for components on Fuse 10?

Also, just to cover all base's you are running the proper amp fuse?

[Jordan]

Pops as soon as the key is turned to the first position forward

You have a bad ground somewhere if this is the case.
What is listed for components on Fuse 10?

Also, just to cover all base's you are running the proper amp fuse?

What makes you think a bad ground, rather then something shorting out?

Yes I am running the proper 7.5amp fuse

Fuse #10:

Seat belt warning system
SI Indicator
Tach/fuel eco gauge
Instrument gauges and indicators
Brake warning system
Backup lights
OBC
Fuel delivery
Idle Speed
Check Control
Stop lights/cruise control

[UNHCLL]

Fuse #10:

Seat belt warning system
You have these still plugged in?

SI Indicator
All connections are tight and correct on back of cluster?

Tach/fuel eco gauge
Same as Above

Instrument gauges and indicators
Again

Brake warning system
Cluster?

[b]Backup lights[b/b]
Check tranny switch and connections to rear lights

OBC
THESE WIRES!!!! - you removed your OBC correct? The wires that should plug into this, all are capped/crimped/sealed etc? I'd be wary of this part....

Fuel delivery
Check the Pump to make sure its not siezed

Idle Speed
Shouldnt matter since its not starting

Check Control
Plugged in?

Stop lights/cruise control
Check the bulbs, connections in tail lights, and cruise control wires under dash on column... You removed CC correct?

A bad ground can cause a fuse to pop, for example if a hot wire goes directly to a ground, the fuse will act like a light bulb filament.

Keep us posted

[randomtask37]

[AdamF 88iS]

You ditched your OBC? Are you sure you bypassed the old OBC relay for the CODE function properly?

[Jordan]

You ditched your OBC? Are you sure you bypassed the old OBC relay for the CODE function properly?

Adam, I have no idea what you are talking about, so talk some more about it.

Chris, tomorrow I will pull the check control, and the intrument cluster out of the car, then try to start it. This is eliminate alot of variables (about half the damn list) I will also disconnect the backup light harness (even tho i know its good)

CC, and the OBC have been removed, I want to say that a hot wire going to ground is very likely (duh) but finding which one....

I will inspect that block of wires I asked for pictures of a couple weeks ago, I still dont feel right about that area.

And yah, I actually had my stepfather turn the key while i watched the fuse. The wire glows quite nicely (instantly) and then pops maybe 0.5 sec later.

[UNHCLL]

Chris, tomorrow I will pull the check control, and the intrument cluster out of the car, then try to start it. This is eliminate alot of variables (about half the damn list) I will also disconnect the backup light harness (even tho i know its good).

Kill two birds with one stone here... go to the local auto store and buy a big box of 7.5amp fuses.

Remove each of the above listed components 1 by 1 and try to start the car after each removal. If you finally start it after removing component X, you know where you're problem lies.

As for Adams OBC idea, I do not think this hold water, that is just a memory/ignition cancel inside the OBC. it wouldnt cause the fuse to short/burn up.

Given your description of glowing then poping, bad ground/reversed wires are a certainty in my mind.

Good luck tomorrow!!

[rs4pro3]

There are wires on the stock Harness which must be pluged intogether after removal of the OBC to get the car to work. I'd ahve to go look to see where the wires are but they basically the OBC relay box plugs in between the wires. But this shouldn't cuase the fuse to blow.