Replaced VP44 because truck would start hard when warm. Im sure it was the injection pump that was bad because I would run cold water from a hose on it when the engine was hot and it would fire right up afterwards. So I put a new vp44 on and the truck runs and starts great for a day or two. Then the truck wouldn't start. After cranking on it for 2 30 second cycles, I let it sit for a few minutes, the truck fired right up. Truck would start hard occasionaly for a few more days so I took all the fuel lines back off and put them back on and made sure they were all tight. Truck started good 4 times when it was hot and cold. Then, Truck wouldn't start. I tried bleeding the injector lines and barely got much fuel out of them at first then finally did and had to crank the truck forever to get it to fire. There doesn't seem to be air in the lines, and I can't find any visible fuel leaks. I have a fass and am running 20 psi into the injection pump. It seems like the 12 valves had a fuel shutoff solenoid problem but what about 24v? Sorry for the long post but am am stuck! Please help, Im close to burning the truck to the ground and getting a 12 valve.

 

I suspect you may have a dud injection pump. Where did you get it?

 

Diesel Care and Performance Inc. In Memphis TN.

 

If you are getting a good fuel supply tot he VP, I suspect your injection pump is about done.

If you are sure there is no air in the supply side, not much else it can be if you have pressure.

Dave

 

I'd call them up and get some help from the guys who built it! Just a thought, double check the fuse for the fass. if it is blown the injection pump will have to pull fuel from the tank and cause problems

 

check all your return line fittings...if there is a slight air leak on them but not enough for fuel to get out then you could be losing prime whent he truck sits for any length of time between starts

 

Im sure the fuse isn't blown to the fass, (I can hear it running) . I'm gonna call Diesel Car and Performance today and see what they have to say. The pump has a one year warranty so I should be safe. I haven't tapped the wire yet either. Well thanks for the input guys.

 

does it just start hard do you have fuel pressure when trying to start or a small buzz when you turn the key then when it starts you get fuel pressure. to much pressure when trying to start can cause hard starts.

 

Check with the FASS people on this and/or look in the install manual if you still have it . This happens on some 24V units when a FASS is installed. There is an easy fix. HTH

 

Would it start hard because of the new inj. pump having too much pressure going to it (ive had the FASS on it for 60k miles and started fine with 2 other vp 44s) or does it have to do with the ecm?

 

Try parking you truck facing down a slope. The slope doen't have to be that great, just enough to get the back a little higher than the front. I had this stupid hard start for OVER a year, but if I park it facing down a hill it cranks fine. I've replaced the injection pump, a holley blue pump, carter pump, all my 1/2" fuel lines and I installed an AirDog 150 along with new fuel lines again a few months ago and I still have a hard start. I guess the next thing I'll be replacing is my return line and injector tube orings.....soo much fun....

 

Does this happen only when warm now with the new VP? If so, you may try to swap relays in the main fusebox under the hood. There is a relay for fuel pump or something like that. Switch it with another one, like for fogs, etc.

Mine would have a hard-start condition when hot. Like when towing during the summer for a few hours, then shut down. I would have to crank for awhile, stop and try again and it would finally fire up.

I swapped the relays under the hood and it hasn't happened since. Someone here told me to check that out. It could have been a fluke, but give it a shot if it's not a bad VP44.

 

Truck wont start at all now. New Pump is on the way, I'll let you guys know how it works out.

 

Normally we don’t see this until later in the year. BUT what happens is the VP likes to have low pressure when cranking. The ECM trys to do this by pulsing the pump when cranking. This works for a centrifical style pump like the stock unit, but ours is a gerotor style pump. Meaning when the gear spins, it makes pressure. SO pulsing the pump may not work.....its a hit and miss deal with some trucks. Mine has been fine for over 3 years without an issue.

BUT anyway......we have a fix to relocate the trigger wire for the relay on the FASS/HPFP harness to the power window fuse. This fuse is dead when cranking and should fix the hard start issue if this is the problem. If it doesn’t....you may have some other issues going on. Check your VP electrical connection.....i have seen this not be on 100% tight and cause issue before. OR even dirty connection.

See below for a schematic for the “hard start fix when hot” with a FASS.

 

I had the relay in the PDC go out on me and it was intermittant. I changed injection pump twice, they test ran pump for 6 hour with out a hiccup. Would die on road and would restart after key off. I decided to swap relays with another in PDC since they have same part number. I haven't had any problem since doing this. Relay must have been causing the problem since it power ups the injection pump
FUEL INJECTION PUMP RELAY - ECM OUTPUT
The Engine Control Module (ECM) energizes the electric fuel injection pump through the fuel injection pump relay. Battery voltage is applied to the fuel injection pump relay at all times. When the key is turned ON, the relay is energized when a 12 - volt signal is provided by the ECM. When energized, 12 - volts is supplied to the Fuel Pump Control Module. The Fuel Pump Control Module is located on the top of the fuel injection pump and is non-servicable.

The fuel injection pump relay is located in the Power Distribution Center (PDC) Refer to label under PDC cover for relay location.


Good Luck