Hard start after sitting

[dave110]

Hello all! I have developed a hard start/ long crank after the truck sits for awhile, even if just over night. I thought the bat's where bad so I had them checked and they were good. They guy at the local shop that does just starters and alternators has a 2nd gen. Cummins and thought it cranked a little slow so I put in a rebuilt starter.( I took it apart when I got home just to see and they did put in oversized contacts like the ones from Larry B's  ). WOW! It cranks almost twice as fast now. Thought I solved my problem but the next morning it still cranked for 3-5 seconds til it started. Used to be it would roll over 1 time and light off and it is still that way when it is warm but let it sit a few hours and it cranks long. So I have decided I am losing fuel prime. Watching closer today I got a puff of white smoke at startup. I parked nose down but no change. I bumped the starter and let the LP run to try to purge the air out but no help. In researching I found some good suggestions but also have some ?? now. Some say the stock filter housing but that is already a high spot. How would air get from there down to the VP and up to the head? I'm assuming the return line in back of the head or the "T" fitting behind the stock LP but I have not even the smell of a fuel leak. If air is getting in, fuel should be getting out. If air is getting in it is displacing fuel that has to be going somewhere. Correct me if I'm wrong. I'm just trying to understand how this works to make it easier to diagnose.

Oh, I almost forgot. It seems the banjo washers and grommets for the return line must come from Cummins. I don't have a dealer close by. Do they have a website with a parts breakdown with part #'s or does anyone know the part #'s? Anything I am missing?

Thanks!

[mulcher812]

Well I know DAP sells a banjo bolt upgrade kit. The filter housing has a drain on it I would check and make sure it isn't slightly open. The other thing is have you done anything to the truck lately? I think I would start by priming the pump then injectors and see what it does. If it's the Tee behind the lift pump this will drain to the tank and you may or may not smell or see the venting. 

[dave110]

Have not done anything to the truck for a while. If it would be the filter housing wouldn't the air stay there because it is a high point in the system? I'm going to try tightening the return fittings today and see what I find.

[dave110]

I got the return line fittings tightened up. They sure made them easy to get to didn't they? I will run it today and try again tomorrow and see what happens. Where else could I be getting air into the system?

[mulcher812]

the filter is high but if it starts to siphon fuel it will just drain the level down about an inch an then you have a hard start.

[Mopar1973Man]

Air leaks are tough to find sometimes. Like crossover tube o-rings, maybe a mis-seated injector, bad lift pump suction line allowing the low pressure system to drain back. I typically suggest driving the truck to fill the fuel system with fuel and get all the air out. Then pressure the fuel tank with about 1-2 PSI at the filler neck. Have a friend crawl around under the truck looking for wet fittings or dripping fuel.

[dave110]

Thanks for the replies. I will keep trying and report back.

[dave110]

Just wanted to tell you all what I found so far. I checked tightened the return line fittings at the 'T' and in the back of head. Then I checked all the other fittings I could think of including the test ports on the filter housing. Came out the next day and I thought it was not going to start. Finally it did with a big puff of white smoke and I saw a fuel puddle on the drive. Checked it out and found the filter housing cracked around the test port. I did not tighten much so I think that may have been the original leak. That proves I was wrong about an air leak high in the system staying high in the system. Got a replacement put it on and now to bleed the system like I've done many times before. Crack the line at VP inlet and got pure air free fuel, no start, so I cracked 1,3,&4 at head and crank, crank, crank, (30 sec at a time), recharge bats. and finally got fuel at #1but nowhere else. Read the article on this procedure and it says crack 3,4,&5 so I tried that..... for 2 days. I was ready to give up and condemn the VP for a stuck rotor then I saw some fuel at 4. Closed it ,crank again, and fuel at 5, close it and it kicks a little after I pump the throttle. Tried again and it FINALLY started so I closed 3 and it cleared up and ran smooth shortly. Absolute worst priming experience I ever had and I'm wondering why. I never had trouble before. Does this mean my VP is going bad? No codes. Any other thoughts?

[rancherman]

whats your  FP  during cranking?

[TFaoro]

High FP while cranking can cause the VP to have a hard time starting... I'm sure Moparman could explain why (Hint hint)!

[dave110]

A mechanical gauge shows 20, and my electric gauge says 12 so somewhere in between there. I thought that high pressure was only a hot start issue though?

[mopartechnician]

Did you try wiring the trigger wire of your raptor to the wiper fuse. It has fixed many hard starts for me lately

[LiveOak]

If you have not do so, check for codes and check again if you have.  Read the VP44 Diagnostics for the entire page but it sounds like this section cut and pasted below and located here:

 

http://www.bluechipdiesel.com/vp44diagnostichelp.html

 

 

HARD START COLD, LONG CRANK TIMES, AND INSTANTLY RUNS SMOOTHLY

This is typically due to a cracked or broken diaphragm inside the Injection Pump. To test for this try disconnecting the electrical power from the Lift Pump BEFORE turning the key on, and see if it starts better. This happens because the electric lift pump pushes air which is always in the fuel chamber inside the VP44 pump, through the crack or break in the diaphragm, into the mechanical high pressure pump and it becomes air-bound until it rotates enough times to bleed out the air. If it starts better without an electric Lift Pump, it is because the electric Lift Pump hasn’t forced air into the mechanical high pressure pump through the crack or break in the diaphragm, which is what separates the fuel chamber from the high pressure pump. This failure requires a VP44 replacement to fix the problem.

[dave110]

Thanks for the replies Live oak & Mopar tech! I have not heard of the wiper fuse trick. My next thing was to disable the LP and try starting without it but this morning it started right up so I'm thinking I've found my problem..... I hope. I'll see what happens the next few days and post back. As far as the diaphram goes it all makes sense but I thought Mike proved that there is no such thing from reading another post from him. Or did I read that wrong?

[rancherman]

. As far as the diaphram goes it all makes sense but I thought Mike proved that there is no such thing from reading another post from him. Or did I read that wrong?

That's exactly what I was thinking too!

[mopartechnician]

Wire it to the wiper fuse and the pump shuts off during cranking getting rid of the hard starts

[dave110]

Well, on Friday it started like normal after sitting overnight so I thought I fixed it. On Saturday I had another long crank with a puff of white smoke so I guess I didn't fix. I'm thinking a cracked diaphragm from reading Blue Chips diagnostic page but I've also read there is no such thing as a diaphragm so now I'm confused. Is there a diaphragm in the VP 44 or not? I guess my next step is to disable the LP during startup but again I'm confused because I've read that is only during a HOT hard start and I have a COLD hard start problem. HOT starts are normal. After that I'll check injector tube O-Rings. Would I be able to see if they are leaking by pulling the valve cover? I'm not getting any fuel in the oil that I can tell.

[mopartechnician]

Wire the pump to the wiper fuse first. Eliminate an easy fix

[dave110]

OK, I'll try it but does that explain the white puff of smoke on a cold start? Just asking cause I don't know.

[dave110]

O.K. so I unplugged the LP this morning to test and it fired right off. I would like to wire the LP to the wiper fuse now. There are 2 wires on the original plug that trigger the relay. They both look white. Where do they go?