Hey,
I´m from Germany and i have a little Problem with my 1989 D250 with a 360 Engine.
When i turn the Key to Ignition on, the Fuel Pump doesn´t build up pressure. When i start the Truck with cold Engine it needs 5-6 seconds, but then it runs fine. When i press the Relais by hand for 2-3 seconds, the Truck starts right away.
I changed almost everything: Fuel Pump, Relais, Fuel Lines, SECM, Hall Effect Sensor... also checked the Wiring Harness from the Fuel Pump Relais to SECM.

When i check the voltage at the relais between pin 85 and 86, when i turn the ignition on, the 12V appears for only less than a second and then goes down to zero.

I don´t know where to look/check next ?! Is there another Sensor or something for the Fuel Pump Signal at Ignition on? Maybe the TPS ??

Thanks and sorry for my English

Dennis

 

Deos it have ASD(Auto Shut down) relay?
If so check that to make sure it is working properly.
The grounds for both relay's are controled by the computer.
Don't remember which pin(85 or 86) is the ground. I beleive it's 85
Try grounding that pin on the relay and see if the relay is working.
With the key in the run position the other pin should have 12 volts.
You could pull the relay and use a jumper to jump pins 30 and 87 and see if that works.
Pin 30 is fused power from the batttery and 87 goes to the device being powered, in this case the fuel pump.

Dave

 

Hey Dave,
thanks for your answer. No, there is no ASD Relais, just an AC-, Fuel Pump- and Starter Relais.
I will try your advices tomorrow.
Yes, Pin 85 is grounded by the computer. Thats why i thought it was bad and tried another one, but the same fault. I also tried three different relais. Now i think that there is a bad ground anywhere, but until now i couldn´t find it.

thanks
Dennis

 

Maybe there is an issue witht the relay getting power when the key is in the run position.
Try pulling the wire from starter relay that runs to the seloniod, so engine won't turnover.
Then check to see if you have power to pin 86 when the key is in the start and run positions.

Dave

 

I grounded pin 85 and the fuel pump works with ignition is on. Checked the pin 86 to Ground had 12V, but Pin 86 to Pin 85 just had 12V for half a second than shut down to zero. But the Relais klicks when i turn ignition on.
How get the SECM the Signal to ground Pin 85? Does it always turn the fuel pump on for the same time ( 3 seconds ) or does it get a signal when the Fuel pressure is reached?

Thanks, Dennis

 

Will engine run with pin 85 grounded?

Dave

 

Engine runs, also without pin 85 grounded. But it cranks to long till it starts, because the relay only works for half a second and doesn´t built up enough fuel pressure. I press the relay by hand for 2-3 seconds, than the engine starts right away, only cranks max 1 second.
I looked at the old SECM today, theres the Partnr: 4379 937. On moparparts it says thats for 318 Manual Trans, but on Rockauto (where i purchased my reman. SECM) it say that it will also work for the 360 TBI Auto Trans (mine). But i don´t think that this is a Problem..?!
I don´t know what to check next ?!

Dennis