Mike Perez

I have been trying to figure out this surging and power loss for over a week. Bought a Low fuel pressure sensor and found my FP has been dropping below 5 psi intermitently.

obtained a new lift pump; checked fuel line to the tank for leaks; cleaned sending unit microfilter in the tank and put it all back together.

when priming the the motor I found that it took a couple of times to get the lift pump to begin pulling fuel ( by quick Keying the starter) after the fourth try the lift pump started and I was able to bleed the system.

Truck started, no low pressure signal, drove 3/4 mile and the low pressure signal came on then off a couple times, so I pulled into a fueling station and put 5 gallons of diesel; re-started the truck; low pressre light came on then dead (Towed Home & this is a new lift pump).

Next day primed the system again put a FP gauge on the truck and started up with 15 psi. Test drove in neighborhood FP gauge fluctuated to 9psi then 5psi than 0 psi and I pulled back in front of my house and parked the truck.

I now unplugged the lift pump and placed a volt meter on the connections, my truck is receiving 1 volt than 4 volts, randomly, but never more than that.

Any ideas for a fix or by-pass?


Thanks Mike

99 Dodge Diesel Fass DDRP Lift pump

BigIron70

What year is your truck?

Mike Perez

Of course, 1999 5.9 diesel stock except for lift pump Fass DDRP.

nickg

at least for testing purposes and bypassing the PCM, you could wire the LP with its own fuse and relay, power up the relay from any run circuit in the fuze box. or just run a fused circuit from the battery, doing this will help you determine if the PCM/wiring or the pump is faulty

I believe there is a fuel pump relay, it could be faulty as well, which may not allow full voltage to the LP, so thats something else you could check

I believe the PCM cuts fuel pump voltage during cranking (not 100% sure) but it does limit the pumps output to 7psi during cranking

forwardho

Mike,
I just went through the same thing. Low voltage at the lift pump on mine went to 7 or 8 volts to zero. The truck would just die. Found the cause to be Diesel fuel leaking from the pump to the conecting wires. There must a gasket that leaks. I replaced the fuel lift pump and no more problems. It just might be that your new lift pump is also bad. Let us know what you find out. GOOD LUCK

BigIron70

You might have wiring problem. Power for pump comes directly from ECM. Check voltage at ECM and grounds.
OPERATION

Normal current flow to the pump is 12 amperes.

With the engine running, the pump has 2 modes of operation: Mode 1: 100 percent duty-cycle with a minimum pressure of 10 psi except when the engine is cranking. Mode 2: 25 percent duty-cycle with minimum pressure of 7 psi with the engine cranking

The 25 percent duty-cycle is used to limit injection pump inlet pressure until the engine is running.

The transfer pump is self-priming: When the key is first turned on (without cranking engine), the pump will operate for approximately 2 seconds and then shut off. The pump will also operate for up to 25 seconds after the starter is engaged, and then disengaged and the engine is not running. The pump shuts off immediately if the key is on and the engine stops running.


ENGINE CONTROL MODULE (DIESEL) - 50 WAY CAV CIRCUIT FUNCTION
1 H104 18BR/OR IDLE VALIDATION SWITCH NO. 1
2 K244 20YL/DB CUMMINS BUS (+)
3 K6 18VT/WT 5V SUPPLY
4 K14 18BK/DB SENSOR GROUND
5 F18 18LG/BK FUSED IGNITION SWITCH OUTPUT (ST-RUN)
6 G60 18GY/BK ENGINE OIL PRESSURE SENSOR SIGNAL
7 K21 18BK/RD INTAKE AIR TEMPERATURE SENSOR SIGNAL
8 G12 18GY/RD MANIFOLD ABSOLUTE PRESSURE SENSOR SIGNAL
9 K46 18TN/YL CAMSHAFT POSITION SENSOR SIGNAL
10 K7 18OR 5V SUPPLY
11 K104 18BK/LB B(+)
12 K246 20YL/DG CUMMINS BUS (-)
13 K242 20WT DATA LINK (+) FUEL INJECTION PUMP
14 K2 18TN/BK ENGINE COOLANT TEMPERATURE SENSOR SIGNAL
15 K135 18YL/WT TRANSFER PUMP POWER SUPPLY
16 H105 18LG/DB IDLE VALIDATION SWITCH NO. 2
17 K124 18GY CRANKSHAFT POSITION SENSOR SIGNAL
18 K48 18DG FAULT SIGNAL
19 - -
20 - -
21 K1 18DG/RD WATER IN FUEL SENSOR SIGNAL
22 - -
23 K240 20BK DATA LINK (-) FUEL INJECTOR PUMP
24 - -
25 H102 18LB/BK ACCELERATOR PEDAL POSITION SENSOR SIGNAL
26 G113 18OR PTO SWITCH SENSE
27 - -
28 K22 18OR/DB THROTTLE POSITION SENSOR SIGNAL
29 S21 18YL/BK AIR INTAKE HEATER RELAY CONTROL NO. 1
30 Z12 18BK/TN GROUND
31 H101 18DB/WT ACCELERATOR PEDAL POSITION SENSOR SUPPLY
32 H103 18BK/YL ACCELERATOR PEDAL POSITION SENSOR GROUND
33 K45 18LB/RD KNOCK SENSOR RETURN
34 K44 18VT/OR CAMSHAFT POSITION SENSOR SIGNAL
35 K135 18YL/WT TRANSFER PUMP POWER SUPPLY
36 K131 18BR/WT FUEL INJECTOR PUMP RELAY CONTROL
37 G85 18OR/BK WAIT-TO-START WARNING INDICATOR DRIVER
38 D21 18PK/DB SCI TRANSMIT
39 D20 18DG SCI RECEIVE
40 D2 18WT/BK CCD BUS (-)
41 D1 18VT/BR CCD BUS (+)
42 K247 20LB/RD CUMMINS BUS SHIELD
43 - -
44 K243 20OR/BR DATA LINK SHIELD FUEL INJECTOR PUMP
45 K24 20GY/BK CRANKSHAFT POSITION SENSOR SIGNAL
46 - -
47 S22 18OR/BK AIR INTAKE HEATER RELAY CONTROL NO. 2
48 A14 18RD/WT FUSED B(+)
49 Z12 18BK/TN GROUND
50 A14 18RD/WT FUSED B(+)



FUEL TRANSFER PUMP (DIESEL) - 2 WAY CAV CIRCUIT FUNCTION
1 K135 18YL/WT TRANSFER PUMP POWER SUPPLY
2 Z11 18BK/WT GROUND

Mike Perez

Thanks for the advise Nickg & Forwardho, I will start with exchanging relays...then running power strait from battery to check Lift Pump; also clean the ground connections.

I will also buy all the banjo bolt washers and replace them...

I'll reply as soon as I finish trying these ideas,

Thanks, Mike

Would diesel fuel block coductivity?

Mike Perez

Bigiron70 Just got your info thanks for the download.

I'll get started, Mike

Mike Perez

well so far the lift pump works, I replaced two banjo bolt washers on the intake side of the lift-pump and wired the lift-pump strait to the battery.

I do not have continuity in the ground wire and need to take the filter system off to get to the ECM. I'll try to trace the wires from the lift-pump to the ECM

on Tuesday morning when I get back from work to continue trouble shooting.

I'll keep in touch, Mike

nitrousn

The is not a transfer pump relay. The pump is powered direct from the ECM.

nickg

I stand corrected, thanks
Nick

Mike Perez

As I was physically checking the ground wire right off I could see about a 1/8 inch of movement from the ground wire entering the female connector, so I placed the volt meter in the female connection ( quick cranked the starter) and manipulated the female connection towards and away from the ground wire.

I read 0 volts when I pulled away and 12volts when I pushed toward the connector.

When I let the connector rest ( without me holding it) 9 volts.

I wil finish splicing a new solid female connection tomorrow and see if this is the fix.

Mike

BigIron70

Sounds like you found the problem, that good news. Use rosin core soldier and heat shrink tubing for best electrical connections. Do not use crimp connectors, they will always corrode and cause problems later.

Mike Perez

I hope so, I will solder and heat shrink, thanks for the down loaded information.

Tomorrow we will know if it solves the problem,

Mike

Mike Perez

I just came home from a 100 mile test drive; FP never dropped below 9 psi. Soldered new wires and was able to salvage the stock connector by taking it apart and putting back togeather with 3 " wires to solder and heat shrink to the cut section.

I thank everyone on this thread for all the help, I hope this is the fix,

Mike