Engine/Transmission (1998.5 - 2002) slow starting problem

[Aaron_A]

Ever since I installed my FASS system my truck cranks much longer before starting, but it only does this if the fuel tank is less than about 3/4 full. When I first turn the key to the on position the fuel pressure only goes up to about 4psi,but if the tank is full or close to full the psi goes up to about 14-16 and the truck starts fine. If I bump the starter pressure will go to normal levels and then will start just fine.

I thought this problem would dissapear after I installed the relay for the FASS but it still acts the same.

Anybody have any ideas.

 

[SteveE]

Hard start

Mine was the same, so I went back to a fuel filter in line to retain the low micron level and to keep the fuel heater.

Quick starts are back to normal.

Don't know why, just does.

Fuel filter should hold some fuel pressure on the VP.

Here is a picture of hook up.

Hope this helps,

Steve

https://www.turbodieselregister.com/user_gallery/sizeimage.php?&photoid=12829&width=3

 

[Aaron_A]

I also have my FASS tapped into the original fuel filter/heater.

Im not sure if the fuel is draining back to the tank,or its the low voltage to the relay powering the FASS at key on, or ?????

 

[Aaron_A]

After checking into this a little more,I think the fuel is running back to the fuel tank after the engine is turned off. The few seconds that the pump runs at key on is not sufficient to build pressure for the engine to start.

I just went outside and turned the key on and watched the fuel gauge,and it only went to 2psi,then I bumped the starter and watched the fuel gauge,and it went to 15-16psi after awhile.

After the FASS quit running I watched the semi transparent fuel gauge line that is tapped into my stock filter canister and watched the fuel travel back out very quickly.

I need to know what I need to do to keep the fuel from running back to the tank.

If anyone has experienced this and has a fix please please please let me know

Thanks Aaron

 

[UN-S1L3NT-24V]

..... Noooo I just installed the FASS yesterday and it has been hard to start too, My truck started up instantly before I installed it. I am not going to deal with hard starts I hate that more than anything. If anyone finds a fix let me know before I get rid of the FASS

 

[tractorface]

Some thoughts

My truck started great after the FASS install. I do have a hard start problem some month's later and am in the process of tracking it down now. Two things come to mind for those of you that just installed it and are having problems. When I installed my Fass I played Hell getting the supply line off the tank and ended up (unaware at the time) damaging the rusty POS supply return fitting in the fuel module. So it would be possible to damage this fitting and let air into the system quite easily. Bottom line is I would check for leaks before I removed my fass.

I have been giving my problem a lot of thought. The old cannister was mounted above the inlet to the VP44 so in theory any air trapped in the system after shutdown should travel to the highest spot, in this case your fuel cannister, where it would not be able to cause a problem. If on the other hand you installed your FAss as I did with the fuel line sloping downhill the entire way from the FASS any trapped air would end up in the VP and could cause hard starts. I am going to address this on my truck once I track down my current problem.

 

[Aaron_A]

I have been thinking about this a little more and I want to try checking my overflow valve on the vp-44. My old lift pump was lucky if it could make 12psi and the new FASS can easily peg a 15 psi gauge, so Im curious if the overflow valve could be staying open allowing the fuel to return to the tank after shut down.

It may not be the problem but its another thing to check.

 

[tractorface]

good idea

Another member pointed me in the same direction. Mine is bad and was jammed open when I took it off. Ordering a new one as soon as I get to the dealer to pre-pay

 

[CStewart]

Tried changing out the check valve on mine and it didn't help the hard start problem. I'm thinking my quick connect fitting at the fuel tank is leaking so I'm going to try and replace it with a compression fitting.



Chris

 

[tractorface]

I could be way off but I don't see how a small air leak on the supply line to the Fuel pump could cause a hard start problem, especially if you run the FASS. I would expect the air to be eliminated from the line by the time fuel was moved through two filters and a pump. I am starting to wonder if a check valve on the supply line close to the pump would solve it. I think it is a drain back problem as someone else stated earlier. For what it is worth I worked on a large genset install at a nuclear power plant last month and had many conversations with the Cummins fuel engineer about the fuel system on this genset. It was for a "critical start" application which basically means the genset is supposed to start as quickly as possible. What Cummins does in this case is install a fuel reservoir at least 6" above the inlet to the injector pump. This allows any air that might enter the system during shutdown to travel up into the reservoir and be eliminated before a hard start is noticed. Anyway I don't like to get ahead of myself so I won't pursue this unless my other options fail. Could be as simple as installing a Racor or even the stock filter back in the stock location. Problem is my truck worked fine for 4 months after the original FASS install. Anyway just thinking out loud.

 

[Lockard]

I have a similar problem, installed injectors and lift pump several months ago. Truck has never started the same since. It starts right up when cold but takes several seconds to turn over after it has been run to temperature. From what I have been able to read, it may be the overflow valve on the VP-44 but am not sure. Please post any successful fixes. I already checked the fittings to make sure they are all tight.

 

[RabidRam]

Another person with the exact same problem as Aaron_A.



Is it possible that the fuel drains out of the VP-44, then the FASS is so stinkin' strong that it foams the fuel when it's pushing it back up to the VP-44? In theory, the less fuel you've got, the faster it could get movin' up to the VP-44 (more foam). Maybe that's why the hard start condition doesn't appear 'til some of the fuel is gone. I know these pumps are so strong that you've got to shut the engine off when you're fueling up or else you'll get diesel spit back at ya.



Just a thought. And IF (big if) this theory is right, I wouldn't know how to go about fixin' it, anyways. Maybe "de-BOMB" the FASS?



Dave

 

[Aaron_A]

Last night I filled up my fuel tank,and the truck starts normal again. It cranks longer after its below about 3/4 tank,the lower the fuel level the longer it takes to start. If I cycle the key and then bump the starter to let the FASS run it eventially will build pressure.

I think this weekend I will lift the bed up and pull the fuel tank module to check for any leaks.

This is driving me crazy

 

[Aaron_A]

Looking at the other posts I noticed most of the trucks with this problem are 98. 5 or 99 models, Is this something to do with early 24v trucks?

Just a thought.

 

[tractorface]

Changed the overflow valve.

Nope I just changed the overflow valve and it did not solve my problem. The new one passes the test in the manual and the old one did not. Even with that said there was zero change. Looks like it is back to the drawing board. I can definetly say that air can enter the system through the return line, I know this because when I change the overflow valve zero fuel comes out but it makes the truck very hard to start, I assume this is because air that would not have otherwise been in the VP enters through the open return fitting on the VP. Maybe everyone with a Fass and this problem could get the facts together and post so we can try and come up with a solution.



OK Facts

-Fass installed in Dec. Truck ran and started flawlessly until April

-Mileage does seem to be down slightly some tankfulls other tanks get 19. 5 may not be related.

-Truck starts fine if started whithin one hour of shutdown even hot

-The longer it sits the more it cranks before firing.

-Fuel pressure on initial keystroke slowly rises to 7 psi before falling back to zero

-After starting pressure rises quickly but pauses at 12 psi for a second before pegging the meter around 16psi

-Tried cycling key to build pressure before starting am able to get 12psi but this does not change starting habits

-Fass uses stock liftpump wiring for control with power supplied from battery via relay.

-Have painstakingly checked all lines on system and am comfortable I have no leaks.

-Repaired fuel tank module without modifying supply and return lines in tank, this had no effect on starting habits

-I want more power and bigger injectors and am leaning towards using this problem as an excuse to get em.

 

[JimKing]

Changed the overflow valve.

After adding my FASS I experienced similar trouble.



After many hours, and several beers, I found the problem was the fuel pickup screen in the tank. I had a slime problem sometime back and had it cleaned, seems like they didn't get it all. I saw the same symptoms. lower the tank level, more effort it took to start. Replacing the whole assembly fixed it.



Even if you haven't been slimed, it bears looking at. Fact is the whole fuel sender/pickup tube assembly is (IMHO) not exactly a feat of modern engineering. It is, however, so flimsy it can be broken using a high flow fuel nozzle at a truck stop.



Finally, I just got back from 8000 miles through the southwest, from rain in Texas to 112 degrees in Yuma, and 65 in San Diego. truck ran flawlessly, (except for that boot blowing off the intercooler) Still have to wait 5-7 seconds for the pressure to bleed back after the pump light goes off, because mine won't start when fuel pressure exceeds 14-15 pounds. I'm thinking that i will lower mine a bit more to around 12-13 psi, see if it improves starting.