Hard starting after Walbro fuel pump install - Diesel Bombers



5.9L Rotary Performance Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with Rotary Injection Pumps Related To Performance And Longevity

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Old 07-13-2010, 06:16 PM
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Default Hard starting after Walbro fuel pump install

Thanks to RSWORDS for the cool walbro fuel pump install write up. I followed his example, put a draw straw in the tank, installed the pump, Mallory fuel pressure regulator mounted near injection pump with the boost attached, ran it all to a newly rebuilt injection pump with a fuel pressure gauge plumed in right at the fuel inlet to the pump. The problem I've run into is after the truck sits overnight, or even as long as 8 hours, it's hard to start. It has to crank over 8 to 10 revolutions before it will start. After it's started i can shut it off and the truck will fire right back up before it even cranks over. I have 13psi at the injection pump, and no leaks. Whats the deal with the hard start? Is the fuel pressure to the injectors bleeding off overnight or are my injectors bad? I replaced the entire fuel system, including the injection pump, lines and all. Cant figure it out!
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Old 07-13-2010, 06:27 PM
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seems you have a leak somewhere.The pump is a known runner?
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Old 07-13-2010, 06:32 PM
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Yeah, the injection pump was just rebuilt by a local bosch shop about 2000 miles ago, and the walbro pump is new. The only line I reused was the return line from the injectors. But I dont see any fuel leaks.
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Old 07-13-2010, 06:37 PM
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Question after you start it and shut it off does it start right back up or crank over and over again? Try somthing crank it over and hit the loud pedal and if it fires right away it might need timing advanced and it sounds like it might be leaking off to but where i dont know
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Old 07-13-2010, 07:21 PM
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After I get it running the first time, it will fire right back up with no hesitation unless I leave it sitting for several hours...like 4 or more hours.

---AutoMerged DoublePost---

come to think of it, I had this same problem before I replaced the injection pump...but I just thought it was due to a bad lift pump. Now that I've replaced and bypassed all that it must be that return line from the injectors. Is it possible to have an air leak without seeing fuel? If I cant get to it real soon, will it hurt anything to continue running like this for a while?

Last edited by butcherman; 07-13-2010 at 07:21 PM. Reason: Automerged Doublepost
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Old 07-13-2010, 07:37 PM
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Sounds like you have a leak at 1 of the fittings, might not be leaking fuel might be just letting air in and losing the prime.
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Old 07-13-2010, 09:48 PM
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Did you ditch the whole fatory fuel filter and lines?
As others have said it sounds like you have air getting into the lines and it's draining back. Go over everything you have put in and make sure it's tight.
And yes you can suck air with out leaking fuel.
If you still have the factory filter setup I'd start at the fuel heater gasket.
Good Luck these problems can be a PITA
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Old 07-13-2010, 11:23 PM
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sounds like a fitting or clamp is sucking air. and yes they let air come in without leaking. double check all clamps and fittings im sure youll find something loose
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Old 07-14-2010, 12:35 AM
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how many PSI is the regulator set at? I wonder if the VE pumps are like the VP pumps in the sence that at startup if the fuel pressure is too high they are hard to start
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Old 07-14-2010, 12:51 AM
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it wont crank that long i had my psi on my ve pump at 15 with my airdog and not the slightest hesitation. when i did my p pump swap my truck did the same thing yours is doing, until i found the return line leaking a little bit. tightened it up and never did it again
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