Hard Start, Question on lift pump, 2004.5

[DBarfield]

Hi guys, I have a 2004.5 with 85,000 miles on it. It has started having a long crank before it would start issue. Reading the forums, I have seen that injectors or connector tubes leaking and not building up enough pressure to tell the ECM to start is a leading cause. I was getting ready to buy the tools to troubleshoot until I saw something that was odd. I have a pressure gage on top of the Filter which measures 5-6 psi when the pump is running. The lift pump was replaced with the OEM unit about 20k miles ago. When the truck starts, the pressure will slowly drop to around 3 psi and the truck will quit. The lift pump is not running. If I cycle the key and wait on the lift pump to run through a cycle, it will crank from 5 to 15 seconds and try to start again and repeat the run for a couple of seconds and die. The question that I have is what is telling the lift pump to operate? Shouldn't it be running almost continuous after the engine starts? Is there a sensor or other device that might be having an issue? One more symptom, the engine will occasionally stumble while driving for up to 5 seconds. If the engine is idling, it will die but if you are driving or giving it fuel, it will just stumble and then pick up again.

Fuel filters have been replace a couple of times. Diesel kleanz has been run through the tank when it was low on fuel and fresh fuel has been added to tank. I unplugged the FCA and the noise around the injectors immediately changed. It did not help the truck start better and it immediately through High fuel pressure codes which cleared when I reconnected FCA. Originally, there was not any CEL but there were two codes, P0107 - Map Sensor Voltage too low, and P0073 - Inlet air temp sensor voltage too high. cleared those codes and I have not seen them again.

The truck has sat a lot for the last 5 months but was used to pull a 10 to 12K triler about 50 miles when it was used. When it is running, it is strong and smooth. Any help would be appreciated.

David.

 

[MLee]

looks like you have a process of elimination to go through, pump pressure,pressure regulator valve, battery voltage. The newer ones have a lot of ticks to check out.

 

[SOOT]

Do you have anyway to check the rail pressure? The pressure relief spring might be weak and not allowing enough fuel pressure at idle. Or there is a restriction somewhere in the fuel line between the tank and filter.

 

[PDM]

The lift pump is not running.

David.

David, if you have the fuel filter mounted lift pump it is supposed to run while your engine runs, and if that pump quits the engine dies. As you probably know that OEM fuel filter mounted pump has a high failure rate, so that might be your problem. Carter P76110 fuel pump is an improved "brushless" direct replacement that is supposed to be more reliable.

 

[Prairie Dog]

If you just run the key on It will run continuously if you have the latest SW. Otherwise it will shut off after about 15 seconds.

 

[DBarfield]

Thanks guys, I know that this can be several things and I really hope that I do not have to go into the injectors now. I replaced the lift pump 20,000 miles ago probably in 2010 from the unit in Genos. I am assuming that the unit was not the new "brushless" style. I did not see anything in the factory service manual of a sensor or feed to keep the lift pump running so I will check with Smarty on the latest SW. At least that will take one item off the checklist.

 

[cerberusiam]

If it the pressure will not hold at 5-7 psi with the engine idling you have a bad pump, not much else it can be. That will definitely cause a hard start if it is blocking flow so make sure you have good LP pressure all the time when the engine is running before doing any more. Depending on how good your fuel is even at 85k you could have injector problems. They do NOT like contaminated fuel, short runs, and minimal usage.

 

[DBarfield]

If you just run the key on It will run continuously if you have the latest SW. Otherwise it will shut off after about 15 seconds.

I upgraded the Smarty and downloaded onto the truck last night. It cranked in 5 to 10 seconds and ran steady with fuel pressure staying 5-6. Tried again this morning and again started in a little over 5 seconds. It was a bit cold around 32 and again ran steady. At least one issue seems to be resolved, I still need to check the rest of the issues on long crank times. Thanks for your help.

David.

 

[cerberusiam]

Sounds like the LP problem is fixed and now you have injector issues. If the engine is not firing in at least a slow 2 count it is not building rail pressure correctly. That coud be injectors, PRV, FCA, or even the CP-3. PRV is going to be the easiest to check and replace if needed. FCA is a replacement thing as you cannot check them. If that doesn't do it it is time for an injector return flow test and a CP-3 return flow test.

 

[DBarfield]

Hopefully final answer to this issue that has bugged me for a couple of months. It seems that my fuel pre-filter was the culprit that I installed when I replaced the OEM fuel pump on the Filter case. I replaced the main filter a couple of times but not the pre-filter. I found a couple of other issues that I resolved at the time that lead me down the wrong paths. I moved my fuel pump pressure port from the top of the Fuel filter canister to the inlet banjo bolt of the CP3 pump. I found the hose for my fuel pressure gauge was old and slightly dry rotted and in certain positions could open up holes. Now, my fuel pressure is running 8 psig +/- except when I load the engine, and it drops towards 0. Oh well, at least I know that I can not push it too hard.

Moral of the story, is that I know a little bit more about this truck/Cummins. I now have the tools to troubleshoot the fuel system and I have a base line for what needs to be done in the future. I have seen that the lift pump pressure gauge is not needed in the 3rd Gen trucks but in my case, I wish that I had had one and will consider installing a permanent gauge. And lastly, as was mentioned earlier, check the little things as an $8 item has caused me a lot of grieve that could have got very expensive very quickly. Thanks for everyone's help. David.