I appreciate anyone's thoughts on a problem I have been troubleshooting for the past week. My head has no more ideas.

My 90 740 Turbo Wgn stopped running. Here's what I have tested...

1. Engine gets spark
2. Ran the Fuel Diagnostic Test (plug 2 option 3). All the devices tested but didn't hear the fuel pump come on.
3. Replaced Main pump (external) and filter (no improvement - still won't start).
4. Placed lead from 30 to 87/2 on the Fuel Relay socket (both pumps come on - Main & Tank Pump)
- After putting the relay back in, I was able to start the car with the fuel pressure in the system, but it eventually dies.
5. Opened the Relay and didn't see any bad connections or burnt solderings.
6. Replaced with New Relay anyways (still no start).

For some reason, I think I might have a bad Fuel Control Unit because it is not tripping the left side of the relay when the engine turns over. I was able to test that the right side of the relay and it worked (I believe that side controls the stop valve..not sure though).

Thanks in advance for any suggestions.

Duke from CA

 

Do you have injector pulse?

You might have a bad engine speed sensor.

 

During the diagnostic, I hear and feel the injectors open up. If I manually run the fuel pumps (place a lead on the relay sockets), the car will run until the fuel pressure in the line is used up. The problem is that the pumps won't run while the relay is in place to continue feeding the engine. It seems some other sensor is not engaging the relay to run the pumps. I don't even hear the (tank pump) prime the fuel lines when the key is turned to accessory.

I am not a mechanic by trade, so I hope I answered your question correctly. Thanks for the quick response.

Duke

 

Do you have 2 black relays by your coolant bottle?

If you can check with some kind of light if you get injector pulse.It only lets out about 3 to 6 volts.But you have to use the power and ground from the injector plug.The pulse fro the injectors work by ground pulse.