FASS DDRP Dely wiring help....

[Anthony_Schiro]

**** ^^DELAY^^*****I have figured out that the FASS DDRP is causing the hard starts with my truck (01 QCSB Auto). Now i have been searching all day for moparman's diagram to wire into a power on circut to no avail. I tried splicing in an add-a-circut by cutting the green wire going to the DDRP itself to the wiper relay and that seemed to work until the truck started sputtering going down the road so i figure i did it wrong. Do i need to splice the red wire going to the ddrp? so frustrated.... thanks in advance

[Mopar1973Man]

All right here...

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/25-fuel-system/49-fuel-pressure-specification-for-bosch-vp44-injection-pumps

[vineyardmh]

The schematic shown might not be completely correct, IIRC.Here is what I think might exist - original and modified.The ECM would provide power directly to the engine block mounted Lift Pump (original) ...the yellow line would go high (12V) when the ECM wanted the lift pump to run. The lift pump would also have a connection to ground.With the Dodge fix to put a new lift pump in the tank - the ECM line (yellow) - would draw too much current to power the new lift pump ...and could cause an internal to the ECM relay to fail prematurely ...so the ECM line would control a relay. The yellow line would go to the coil of the relay (85, and the other side of the coil - 86 - goes to ground. A source of 12V+ connects to 30 ...and when the relay is energized (ECM energizes relay)...the Normally Open (NO) heavy duty contacts close and switch power to the Lift Pump to cause it to run. In this way - the ECM still completely controls the Lift Pump - but the heavy current goes through the relay contacts instead of internal to the ECM.You can do a 'sanity check' by using a small Ohmmeter - the relay coil will have about 80 to 250 ohms resistance (depending on type/size/model). Typically - the relay coil contacts (blades) are a bit smaller. If there are 5 blades ...2 for coil, 3 for the Single Pole/Double Throw Switch ...and when de-energized - the resistance between 2 blades will be infinite (Open) and between 2 blades will be near zero (Closed). Then if you energize the coil ...the previously Open path will now be zero ohms, and the zero ohm path will be infinite (open).

[Mopar1973Man]

The schematic shown might not be completely correct, IIRC.

Yes. It's correct. This layout will CUT the power to the lift pump during cranking. This prevents the hypersevsitivity to cranking pressure after a torn diaphragm occurs in the VP44.