Guys, I have a friend who has intrusted in me to fix his truck.  It is a 2001 CTD.  This truck use to start when you turned the key right away, hardly would crank over a half an engine revolution and start.  Now it cranks two or three complete revolutions before it starts, usually after a hot restart.  He lost the factory lift pump years ago and had the dealer install an intank lift pump.  He had the injector pump fail shortly after that pump was replaced.   I'm wondering what the lift pump pressure should be when the key is turn to run but engine not started.  I have none at this time but it starts and has presure of about 7 to 8 psi when running.   Should there be initial fuel pressure and go off after a few seconds?  I know my FASS fuel pump on my truck initually gives fuel pressure then shuts off and starts up once engine starts.  I'm not sure about a factory system.

 

Thanks, wes.

The factory system does the same thing.  Any codes?  

I would suspect that he has low fuel pressure at start, an air leak bleeding down the fuel line a little, or a weak VP44 due to previous issues.  

There really isn't a number for initial start up that I am aware of.  If he isn't having issues anywhere else while driving, I would consider looking at the line for leaks.  If there isn't much evident, there aren't many options to troubleshoot air leaks other than start changing O rings and banjo seals.  

At key on the ECM bumps the lift pump for a second or so. The pressure bleeds off immediately and will stay that way until you turn the key. The ecm then pulses the lift pump until the engines fires off. My understanding is the VP does not like full pressure when starting. If you have or have installed an aftermarket pump and it is connected to the OE harness, that is how it should function. So key on 0 pressure except for the initial bump. Does the truck start normally on cold starts? Have you checked for any trouble codes?

 

If he is only seeing 7 to 8 psi while idleing, he is grinding another pump to failure. He needs a better fuel pump. The in tank pump is as bad as the stock carter pump or worse.

Edited October 13, 20159 yr by dripley

Thanks guys.  I didn't see any bump in pressure when the key was initially turned on so we my have a bleed back and or failing lift pump.  I also have no fault codes.  He doesn't have an aftermarket pump but does have a dealer installed in tank pump after the original one on the side of the engine block died.  He later had to put a new vp44 on it also, probalby because of the failing lift pump.  The truck runs fine after it starts.  I know when I installed my FASS system I had to wire in a relay that shut off power to the pump when cranking the engne because the vp44 didn't like all that pressure at start up.  I hate air leaks, they are so damn hard to locate.  Oh well at least its not my truck and I'm getting paid.

Edited October 13, 20159 yr by WesHawkins

Sounds to me like the electronics on the VP are on their way out. If it only does it when hot that would be my explanation.

Thanks guys.  I didn't see any bump in pressure when the key was initially turned on so we my have a bleed back and or failing lift pump.  I also have no fault codes.  He doesn't have an aftermarket pump but does have a dealer installed in tank pump after the original one on the side of the engine block died.  He later had to put a new vp44 on it also, probalby because of the failing lift pump.  The truck runs fine after it starts.  I know when I installed my FASS system I had to wire in a relay that shut off power to the pump when cranking the engne because the vp44 didn't like all that pressure at start up.  I hate air leaks, they are so damn hard to locate.  Oh well at least its not my truck and I'm getting paid.

The Fass and the AD both use the relay. It's purpose is to take the power load for the pump off of the the ECM and use the oe harness as a trigger for the relay. If the pump is weak you might not see the pressure bump, but it should bump power to it. Dodge gave me on of those when mine went, for a $1000 anyway. A lot of monery for a piece of crap. Anyway when starting the engine the ECM should switrch the pump on and of rapidly to produce about half pressure for cranking. Hard to see that since the engine should fire right off. 

 Weak lift pump pressure can take out the VP in two ways. Lack of lube for the pump's internals and no cooling for the pump and the electronics that run it. Good chance that is what is going on like Ghostman says above.

I can't believe people still using factory lift pumps on vp44 trucks, even the ones that were upgrade from dodge to intake units were garbage too. Tell him if his planning on keeping the truck to get a fass and chase all the leaks at minimum, a fuel gauge will pay for it self in short time too. 

When my original VP went out I took it to dealer and they installed the in tank pump, along with a new VP. It only lasted through the summer and was doing the same thing, started fine when cold but after it warmed up if I shut it off some times it would crank for 10 seconds or more before it fired up. I ended up just taking it as a loss and redone the whole system with the draw straw and AD frame mount along with another VP, and of course a fuel pressure gauge along with an idiot light. If I had to do it over I think there is better options out their than the draw straw, because my truck will drop fuel pressure considerably with less than 1/4 tank of fuel. Ideally you should have about 18 psi. at idle and no less than 12 under heavy load.

I can't believe people still using factory lift pumps on vp44 trucks

Well this truck actually has two problems.  One is the starter is dragging on the initial turn of the key causing very slow initial cranking hot and cold.  With that repaired and checking his fuel pressures, are only 8lbs at idle and only 6.5 to 7 going down the road at light throttle.  According to the factory manual pressure should be at least 10psi.  I hope the injector pump isn't damaged.  I have talked the owner into installing an aftermarket lift pump.  I have a FASS system in my truck and am putting the same in his.  His will be a little more work since he has already had the retrofitted in the tank pump replacement about 8 years ago.  Just waiting for the parts to arrive.

The lift pump isn't ideal but likely not the problem here. You'd be surprised how many guys are still running around on the OEM lift pumps. I know a guy with an 01 with original VP AND block mounted Carter lift pump. It's a dually with a dump body and a plow  and gets worked hard every time it gets fired up. Hes not the only guy i know with the OEM set up, either. Go figure. 

Did you correct the slow cranking issue? Diesels need cranking speed to light off. That definitely needs addressed.

Edited October 19, 20159 yr by diesel4life

 

Ya, changing out the starter with a new replacement took care of the starting problem.  Both he and I would better be safe than sorry when it comes to the fuel pressure.