Bad Relay Board?, testing...how? Options

[BMartin914]

I suspect that I may have a bad relay board that is preventing my car from starting. I have not yet tested for fuel at the injectors or spark but would like to know how to test the relay board to determine if it is indeed bad.

The bottom of the board is covered in some black goo-like crap whick looks like a poor PO fix - if that.

I probably won't be able to get around to doing anything more with the car 'til Tuesday or so, but am seeking some suggestions in the interim.

TIA

[bperry]

The extremely quick way is to swap the relay board out with a known
good one for a quick test to see if it makes any difference.

Beyond that, it starts to get pretty sticky if you aren't very
comfortable reading wiring diagrams.

What can help is to isolate the problem down a bit more
before messing with relay board.
Is the fuel pump getting power and running? Any spark?, etc...
If you have a 12 volt buzzer, you can temporarily hook
it up to the fuel pump wires and see if the fuel pump is getting
power.


As far as actually testing the actual relay board,
the method that I've used is to "yellow line" the board.
Start by making a zerox copy of the relay board wiring diagram
from something like the Haynes manual page 147 or 161.

Then get a ohm meter that beeps when continuity is zero.
I have a small digital unit from radio shack that has a continutity
setting.

Then "ohm out" each wire connection one at a time and as you
test the continutity between each point.
As each trace check out, use a yellow highlighter to mark each
trace on your zerox copy.

NOTE: this will only find "hard" failures and will not find intermitant
failures which can be quite common where the rivets attach
connectors to the traces.

If you want to visually inspect all the copper traces you will have to
remove all the factory tar from the board.
I found that this can be done fairly easily with a dental pick and
a small screwdriver. It helps if the tar is cold, so if its not cold
from your garage, put it in the freezer for a while to chill the tar
which makes it alot easier to chip away from the board.

Once most of the tar is removed you can visually inspect the traces.
To solder the rivets to the traces to make things really secure,
you'll have to clean the traces/rivets really well.

For a quick check, you may want to check the rivets/traces directly
under the fuse holders or those that were exposed to the air from
chipped away tar first.
Those seem to fail first because the heat
from the fuses heats up the tar which causes it to fall off and exposes
the rivets to the air which then causes them to oxidize and stop
carrying full current load to things like the fuel pump.

Good luck.

--- bill