Check connections. Your probably sucking air somewhere

 

If your fass is running during startup then your pressure will be too high. It should be below 5 psi. Mopar1973man has a thread on wiring in a relay so the Lp cuts off.

 

the connection on the top of the fuel filter has diesel on it so ima go tighten it and see how it does

 

High fuel pressure at startup shouldnt cause a no start. I have had a few not start because they were only pushing 12-15psi at key off.

 

It unbelievable to me how many people dont know by now that this is even an issue, or understand this issue, or why its an issue. Its not like its not talked about almost every week or more. :confused013: Especially with more and more guys installing a FASS, Airdog, Raptor, etc. Search hard hot start and you should find loads of similar threads with guys having the same problem.....and I'm probably subscribed to every thread too saying the same thing. I gotta learn to be like Moparman and copy and paste my posts.

So..........when you are experiencing the hard hot start, simply unplug the FASS fuse and try starting again. If it starts like normal (which it probably will) then immediately replace the fuse and follow this diagram. :thumbsup:

 

Hua. Must be because of the volume of the aftermarket lift pumps, and the return not being able to keep up. I have had 2 fass pumps (hpfp and 150/150) and never had this problem. I have even bumped the starter, waited a few sec, then hit the key. Fired right up like normal.

I have seen the exact oposite on vp44 engines at work (stock lift pump). 12-15psi they wont start, 18-20psi they fire right up. This has happened several times.

 

Wow!!! i wish i had purchased a FASS LP so that I could get to do additional wiring in order to drive my truck, then wait on a FEDEX driver to show up when I have a warranty issue, then post up questions of why my FASS, airdog, or rapter pump died and I am stranded in podunk USA.S:

 

thanks guys it does it off and on now im gonna have the guy who does everyting to my truck chec it out

 

If you have or know someone knowledgeable about the 2nd gen Cummins ISB fuel system then great.:thumbsup: But.....IF.....that person isnt completely knowledgeable about the 2nd gen Cummins ISB fuel system then then you will more than likely be spinning your wheels looking for fixes and possibly spending unnecessary money. Thats the advantages of these forums. So if you or your friend need more help just explain exactly what your truck is doing and someone here can point you in the right direction.:thumbsup:

 

some times itll fire off just like normal other times itll crank and crank and crank then fire right up like i just changed the filter i checked all my lines no leaks it does it the worst when i just get in and turn the key

 

If your hard start issue is ONLY after its been sitting for awhile like during work or overnight then try parking it during one of those times with the nose of the truck pointing downhill. If that helps then you have a leak somewhere in the return fuel line. That leak can be very hard to find. It may be any on of the fittings in the line or the banjo on the back of the head or the T fitting just below that or a leaking injector o-ring. Sometimes baby powder can help in finding a leak.

If your hard start issue is ONLY when the engine is at full operating temp and you shut if off for a very short time like at the gas station or store then you have either an overly aggressive fuel pump placing to much pressure on the VP during engine cranking or your VP's computer is getting old and showing its age of hot start cycles. Two ways to determine which one it is:
If it starts normal after you remove the fuel pumps fuse then its the fuel pump. (just replace the fuse immediately) If that doesnt work then pouring a cool gallon of water directly on the VP will cool the computer enough to allow a normal start. If that works then its the computer. An old computer will sometimes also do things like puff some white smoke upon that hard start up or have dead pedal while driving. Its rare to ever generate a code from a failing computer.:thumbsup:

 

i park down hill every night its still the same it did it the same all day today when i start it i let my gauge do its test and it always says about 4 pounds ill try the fuse tomorrow ... do i put it back in while the truck is running or turn it off and put the new one in

 

Explain in detail EXACTLY when it hard starts for you. My previous post gives the most common examples.:thumbsup:

 

if i just jump in and start the truck just get in and turn the key on

 

i am interested in this cuz it sound like a powerstroke with a HPOP failing. i wana c were this goes

 

so far no were man i cant find any leaks nothin it still does it very very annoying

 

So you have or have not tried pointing the nose of the truck downhill overnight?:confused013:

 

Trying to keep this thread alive! I have had my airdog 165 in for 3 days now and in the morning when the motor is cold fires right up at a blip of the key. When the truck is at 185-190 warm it seems to crank for a few seconds then fire up.......Only when the engine is warmed up though. Its kinda embarrassing to sit there at the gas station or the bank and have a sweet truck that sits there and cranks and cranks and cranks then fires......Whats the deal? Never happened last week with my stock lift pump.....

 

You're describing a clear cut situation where your new higher volume / higher pressure aftermarket fuel pump is placing to much pressure on the VP while the engine is cranking. Even though the ECM oscillates the fuel pumps power during engine cranking, in order to reduce fuel pressure, many aftermarket fuel pumps are simply to aggressive and will still place to much fuel pressure. One easy way to fix this hard hot start problem is to follow the diagram pictured by adding another relay to the fuel system wiring loom. That new relay, when setup correctly, will completely interrupt all power to the fuel pump during engine cranking but yet still allow the fuel pump to run completely normal at all other times. If you're not completely sure thats your problem then next time it hard hot starts, simply remove the Airdogs fuse and try starting again. I'm betting it will start like normal. And when it does, just dont forget to shut it off quickly or quickly put the fuse back so the fuel pump is running.:thumbsup:

 

Is there any harm with cranking it for a few seconds before it fires in the long term.....?

 

Not really, except more wear and tear on your starter and batteries. If you're concerned about the diagram, dont be. Its very easy and the diagram makes it look far more complex than it is. You just go down to your local parts store or electrical store and ask for a 5 pin relay that has the exact pattern show in the little box in the diagram. Then wire it as shown. The only wire you have to touch thats already existing is the yellow wire which is the fuel pump power wire. The relay splits that wire. The rest of the wires are just running to a source or tapping into.

Also, just for knowledge, there is another factor which can cause this hard hot start. The ISB is fully electronically controlled. Because of this any improper voltage or amperage will cause weird problems which will have you chasing your tail looking for the reason. The most common place for this to be an issue is your batteries. If one of the two is not perfect then it will go undetected unless you unhook both batteries from each other and the truck and load test them. You may find one of them has a bad cell but together they still start and run the truck. Bad batteries are trouble.
The other place to look is all major electrical connections and grounds (including battery and battery cables). Make sure any and all connections on the engine are tight and not corroded. This can more of a problem in high corrosive areas where they treat the roads with salt or calcium chloride.

Saying all this, I'm sure its still your fuel pump. Try unhooking that fuse like I said and see what happens.:thumbsup:

 

KATOOM, thank you for all the helpfull hints. Guys like you make forums like this a great thing for all of us!

 

i took the inline fuel filter out and put a splice in it cranks longer now so im going to order some 3/8 line ... some people were talkin on mine crankin and thought they knew every thing about diesels so after i beat them then my buddy with a common rail beat them and they asked what was done we both told them our fuel plates were out and they could do it with a screw driver and they popped the hood and were like cows at new gates it was great guess you woulda had to been there but it is still embarrissing

 

Mine does the hard start after sitting for a while (an hour or more). Facing downhill doesn't really seem to help. I just replaced the washer seal to the feed the of my vp44. I didn't even think about doing my return lines. Does anyone know the size of the washers I need for the return lines? Are they 12mm like the feed?

 

Your injector o-rings could be cracked. Not something you'd see but it would cause a starting problem. Were they replaced with your injectors?:thumbsup:

 

I originally had a shop put my injectors in but when I did the head gasket I had to reassemble the head myself when Igot it back from the machine shop. I did use the old orings but the hard start didn't happen until my vp44 was replaced again. I didn't know if they used the old seals again and they were just getting old.

 

Just after replacing the VP or after replacing the VP and the fuel pump? And the banjo at the back of the head and the T fitting just below it, both can leak. Try some baby powder. I understand it really helps finding leaks.:thumbsup:

 

I did the air dog first. It started doing it after the vp was installed. Thanks a ton though I'll check for those leaks. Do you happen to know if those banjo bolts are 12mm as well?

 

My setup has not changed when mine started the hard start

I run a fass hpfp I believe a 95 through 2 fleetguard filter heads first is a fs1000 second is a 2 micron ff 5320 then 3/8 push-loc line directly to the pump full flow 90 sweep at the pump

Setup has been on the truck for awhile I left it parked for ancouple
Months and ever since it
Has had a hard start warm or cold sit for long periods or short downhill or uphill but some times it just starts right away

So I changed the line out from the hpfp to vp with 1/2pm push-loc and still the same I am goin to replace the line from the tank to the hpfp but have not gotten around to it yet

I will try your diagram thou and see if that helps cold weather comming and with only one battery (optima) little nervous bout starting at work

 

Remember guys.....batteries play a huge role in proper function of the ISB. If you dont have enough of the right voltage/amperage then it could cause starting issues. The first thing everyone looks to when they experience a hard start is leaks but there is threads where someone replaced the batteries and the problems went away.

Sorry but I dont remember the exact size of the head banjo either. And also leaks on the return side are harder to find because the return line is low pressure so for air to enter a hole or crack is more common than for fuel to escape. With the supply side (post fuel pump), a leak will or could more likely leak fuel since its under more pressure.:thumbsup:

 

Thanks again katoom I'll let you know what I come up with.

 

Going back to what Katoom said about batteries, I put a Fass on mine this summer and was having hard start issues. Turns out one of my batteries was shot so I replaced them and no more problems. Might be a cheaper, easier idea to check out....