A few weeks ago I was having a hard time starting my truck and with all of your help we narrowed it down to a leaking hose that connects the rigid line from the fuel filter to the rigid line on the VP-44. This was done by replacing the hose with a loop of clear vinyl tubing and checking for bubbles. I replaced the line and was fine for 2 weeks. Then the hard starting came back, especially on the driveway parked uphill (everytime when left overnight.) and 2-3 times out of about 40 starts parked flat. So yestarday I put the clear vinyl tubing in to check for air leaks somewhere else and after leaving it parked uphill overnight it fired right up.

I haven't checked FP but lift pump is only 3 weeks old. No codes are being thrown.

My question really is, how long can I leave the vinyl tubing in there? I just want to keep an eye on the potetial leak problem. Will it deteriorate and mess anything up? Is there something magical about a looped piece of fuel line? Hmm?


I guess it is possible that I could have developed a leak in the same place again, maybe I didn't get the clamps tight enough???

Thanks for the input

 

As long as you take good care that it doesn't rub anywhere you can leave it in.
The disadvantage is that it isn't nearly as stable as the stock line, and it's routed in some risky places.
To determine whether your problems are caused by air in the line you should take a look at the loop during startup.
I'd also suggest getting an FP gauge ASAP

AlpineRAM

 

Today again no problems starting. Do you all think there may be something to a loop in that small piece of hose that prevents air from entering the system, other than the obviously tight connection. The bottom of the loop is below the connections, about 3 inches.

 

Finally this intermittant problem showed up again, on my uphill driveway and flat ground. I have seen no entrained air in the system witht he looped fuel line. Does this mean my VP is shot? Am ordering FP guage as we speak. The truck still runs great after it starts.

 

As far as the clear polyvinyl lines. My Massey-Ferguson diesel tractor came stock with them both supply and return. Still the original lines after 14 years...

 

when you have the no start issue try unplugging the lp electrical connector ant try to start the truck. if it starts then there is the possibility of the vp44 is bad.

 

How would unplugging the lift pump connector diagnose a bad VP44? If anything, it's going to do more damage than what's already done. If the truck even runs long enough to diagnose anything.

 

That was the procedure STAR had the mechanic use on my truck when i had problems starting after lift pump replacement. No codes would show.... but truck started fine when the lp was unplugged.

 

If the VP44 develops timing issues this can be diagnosed by switching off the LP- simply because the VP44 uses a solenoid that bleeds off fuel pressure in the timing element to adjust the timing. If this part is defect it won't be able to set a correct timing for startup. No fuel pressure-startup. Too high fuel pressure during start (like aftermarket LPs do provide sometimes)-hard start to no start condition. The VP44 sports a rotary vane lift pump internally that is sufficcient to provide enough flow for low cylinder loads per revolution (see smaller European diesels where the VP44 is running without an external LP for hundred thousands of miles without problems- where the displacement per cylinder is about half of the ISB) This pump will flow a certain amount of fuel per revolution. A part of it is bled off directly into the return, another part is used for lube and injection. As you step up the load more fuel is injected and less remains for lubing and cooling the pump.
As long as there is no or minimal load on the engine the internal pump will be easily sufficient, but if there is a high torque demand all the fuel will be injected and the pump will be starved for coolant and lube.
This is just about the flow inside the VP44- an external LP has to cope with the total demand per second of the VP44.

desertram- the loop should go up from the connectors to make tha air go up and get trapped, and therefore visible. If it faces down the air will go up and easily enter the pump before you can see it.

HTH

AlpineRAM

 

Alpine,

Your are correct about the up loop, why didn't I think of that? When I have the problem, to get it to start I have to pump the throttle of just put my foot to the floor. Does this have anything to do with what you're saying about the defective timing in the VP-44. When I step on the throttle is the computer telling the VP more fuel which overides the defective startup sequence or something???? I may be talking gibberish here I don't know?

 

desertram: I don't think that pumping the go pedal makes much difference- but I don't know about the 02s programming. For startup the VP44 will give very much fuel with almost no timing. I don't know whether they put in some programming to give you influence over the startup behaviour.
Maybe you can use this loop to make fuel visible on the windshield (very temporary only, very careful) so you can see whether there are bubbles or not for any situation.
Did you try one of those diesel additives that say that they clean and lube?

AlpineRAM

 

Sorry to hear the prob is back. I'm still a bit suspicious of that VP though.

 

Well I turned the loop up, duhhh! and I can't get the problem to repeat itself. It starts fine. I put a FP gauge on it, just a mechanical test guage at the schrader valve and I have 12-13 lbs at idle and drops down to 8-9 at 2800rpm (no load). I changed the filter too. My dad's 01' has 15lbs at idle and we couldn't get it below 10 at 2800rpm. His is stock, 79000 miles on original LP an VP. Put his scanner on it no codes as well.

I don't know?? This is crazy.

 

Hmm- makes me think what your fuel pressure would look like under load.

Did you see any bubbles in the loop? (That would indicate some leak somewhere)- According to your pressure readings (and also the ones of your dads truck) the LP sounds a bit fishy to me. (Shouldn't drop below 10 psi under full load any RPM- revving up in idle isn't putting a torque demand on the engine)

AlpineRAM

 

I know, I am a little worried about that too. It was parked uphill, I don't know if that may have an affect on the readings or not, my dad's was parked flat. The guage I used was from a local parts store, kind of cheap but pretty close I'm sure. I have gauges on the way just haven't recieved them yet. No air in the lines at all, nothing. Has started fine for a week, parked uphill, downhill, flat doesn't matter. The last thing I did was flip the loop up and haven't had a problem since. Lift Pump has 1200 miles on it. I have been fighting this since January, when the dealer put in a lift pump to correct the starting problem that lasted 3 miles and died. So they put in a new one, that didn't fix the starting problem and here we are.
I know it sounds crazy but it has warmed here quite a bit recently, single digits and teens at night to above freezing and near 70 during the day. I think some of the rubber hoses get a memory during the winter and may leak a little air until they soften under warm conditions and take the shape of the line they are connected to. Just a thought.