i have come a cross a truck that the relays have stopped working . ( the main and the fuel pump)
87d21 z24 engine 5 sp trans.

with the key out of the igniton and the realys jumped the ecm lights arel on but when you start the truck (by virtue of the relay by pass)
the ecm light goes out..


i was hoping some one could shed some light on this...



thanks

Don't you have some relays that you can swap in?
Power getting through all of the fusible links?
Voltage at and beyond the fuses?

Does the truck start before it runs out of fuel?

i did put in fresh relays.

there is power going to the relays but when you put in the relays the do not send the power through..

that is why i put a jumper on them .

the jumpers allow power to go to the fuel pump and allow through to the main relay ..

this will allow the truck to start and run but the fuel pump is on all the time. the indicator lights on the ecm are on when the key is not in the ignition and off when the truck is running..

the fusible inks seem to be working.


thanks

what is the voltage from your battery w/ engine off?. Should be 12.5volts if you have a good battery. Do you have a charger? if not then get one and try charging it or swap in a known good battery.

Battery might not even take a charge.

SOunds like relays aren't getting enough Voltage, and the fact that you swapped in fresh relays makes me think the battery is at fault- which is highly likely given how cold it is in your neck of the woods.

COld brings out the weak batt's.

the batt is new and test good.

i am getting power to all the realys involved
but the relays once pluggled in do not transfer the power to the rest of the system

this was solved by replacing the ecm and the fuel pump relay..


thanks for your help..