Okay, so my truck started out losing prime after it sat say overnight without being started. I had a FASS installed hoping to fix it, and although it didn't I was able to take the time to prime down from 30 secs to 1 min to about 5 seconds. I've looked my tank and fuel lines over as best I can and just can not find any leaks, but the truck is getting worse. Less and less time has to pass in order for it to lose prime, I'll have to reprime after about an hour now, and it's getting harder and harder to start. My 5 sec prime time is now back to around a minute.

Now the really confusing (to me) part is this. I don't claim to really know anything about anything, but if I crack an injector and bump the starter I should be getting fuel from the injector right? I cracked my #1, 3 and 4 and don't get anything from them. I can hear the pump running and my gauge shows pressure, but nothing at the injectors. I can seal em back up, start the truck (1 min prime plus I have to pump the gas pedal) and of course if I crack injectors with the truck running I get fuel. I shut the truck back off, I can bump the starter again but the pump doesn't run at all. The truck will fire right back up like normal at that point though.

I tried parking on a slight incline facing downhill, and still had the hard start issue. I'm at a loss. Could it be the injectors or injection pump? Both are new, injectors are stock installed at a dealer and IP is industrial injection. Block is new also. If I remember correctly the hard start issue seemed to arise (although not this bad) after the injectors were replaced, but I was having lots of problems then (hence the new block) so it's hard to tell.

Anybody have any idea? I'm all ears.

 

Sounds kind of like it could be related to your fuel cap. Might not be venting and when it sits it's possible it might be pilling the fuel backwards through the line. ???? just a guess.

 

Pumping the pedal does absolutely nothing on these trucks other than wear out the APPS. If you want to see fuel at the injectors, just hold the pedal to the floor while you crank. You should see plenty of it then. Check the top of your fuel tank and make sure there is not a cap on the vent. Sometimes they forget to take it off at the factory.

 

I have worked on lots of gas & diesels over the yrs , but haven't done much with the VP pump engines , I say that to say its some what of a guess .
1st , the electric pump [ lift pump ] is putting lower pressure to the main , VP , so you not necessarily see fuel come out of the injectors , unless you either are turning over the engine , it takes high pressure from the main pump to pop open an injector .
From you description , if everything els is OK , it sound like the return to the tank [ in my truck , its called the overflow valve ] , [ in others fuel injection cars & trucks , its called the pressure regulator ] , is weak , this is how the pressure to the main pump is controlled , by restricting the return to tank .
With your truck I do not know what name it goes by , it would be easy if the parts that always did the same thing , always had the same name .

 

I had a tiny hole rusted in the return line from the Vp44 to the tank. Had the same problems your having. Couldn't even tell it was leaking fuel.

 

Replace the check valve banjo at the output of your vp 44. This thing is not seating well everytime and allowing fuel to drain back out of the pump. I had the exact same problem and this was the fix. It's an inexpensive part anyhow..

 

Where did you get it from? I think I might need one.

 

A leak in the return line will cause this issue as well. You may not even know it is leaking. Crawl under the truck and you may see fuel all over the frame on the left side as it gets blown rearward when traveling.

The rubber fuel lines they used in the second gens were notorious for this happening.

 

<---- bone dry frame and hoses. Gonna take a peek at the banjo this afternoon. How could you tell if its bad? Where do you buy new ones? Cummins?

 

I got mine from a cummins shop in Phoenix. If someone has a part number handy, it would help you find one..

 

Cummins part number 3941156

 

Thanks

But it looks like all the symptoms I have point to the circuit board in the VP.

 

Try checking the injector seals, one might be leaking causing you to loose prime.

 

When I installed my first set of injectors I had hard starting as well! Looked everything over, had the computer reflashed and finally pulled out the injectors and had them tested and the pop pressure on them was set too high so we readjusted the pressure and she started perfect every time! Who's injectors do you have?

 

They were changed back with stock injectors at a dealer. I'm starting to think that an o-ring is leaking or something. The only thing that the ticket says about the new injectors they put in was "Injector 14099006". I really wanted to go with aftermarket injectors but was in a time crunch and thought that would fix my truck. These were $175.00 a piece so I could have came out cheaper with aftermarket