Engine/Transmission (1998.5 - 2002) fuel p.s.i with f.a.s.s

[KKunz]

what king of fuel pressure are you guys seeing with the f. a. s. s system I want to get one but a guy at the Cummins dealer told me any pressure over 18 p. s. i will make the injector pump fail

 

[snowracer69]

Personally I'd be looking at a mechanical system... .

 

[KKunz]

when you say a mechanical system do you mean a p-pump or a mechanical lift pump

 

[jgillott]

You can expect somewhere between 14-16 psi as a good baseline. Don't overly concern yourself with the statement from the Cummins shop. You are not going to give your VP-44 too much pressure.



There are many good LP alternatives out there. I've been running the FASS for quite a while now, and really can not give you anything but posative reviews. I'm sure others will add some comments on the other available options.



Justin

 

[snowracer69]

Don't overly concern yourself with the statement from the Cummins shop. You are not going to give your VP-44 too much pressure.

I disagree. I think you can give it too much pressure. Yes, there is an internal bypass setup on the VP-44 at 15 psi, or whatever it is, and yes it will probably bypass upwards of 30 psi. But how many people running 20 psi pumps do you hear of that have hard starting problems? Not necessarily right away, but down the line somewhere... I hear of a bunch. Now, by deductive and not scientific reasoning, I concluded that high-pressure at prime = hard start. Hard starting is usually the first sign of a problem and the downfall of a VP-44 (just ask GatorRam about his VP-44's).



The other theory on the bypass valve is this: The valve is there to take out pressure surges... ie, bouncing from 14. 9-15. 2 psi... stuff we can't see on a gage. If you are running the pressure at 20 psi, the valve is always open... it's not going to take out that small surge which would ensure a nice constant delivery of the same fuel pressure. Yes, you'll have good fp, but it won't be constant and steady.





I was talking about a mechanical LP solution too. Electrical pumps are just that, electrical! They have gremlins and they WILL die someday... it's just a matter of time... whether that time is 20k miles or 200,000 miles, is yet to be seen for most, but there have been several (many?) fass systems replaced already because of problems. I recommend looking into the RASP system. I finally got mine figured out and this thing is unreal. No hard starting (only primes to 8 psi), steady FP in cruise (14. 5-15 no matter how fast I'm going), the faster you turn the engine, the more fuel it supplys... what could be better? There isn't anything to wear out. The pump has no seals, no electronics, no wear parts whatsoever. Finally, it runs in conjunction with and parallel to the stock system... blow a belt and your stock LP will automatically take over and get you where you're going. You might only get there at 10 psi, but you're not stranded. And you're only trying to get to the local Napa anyway, so you can replace the lost belt. If you're paranoid, buy a second belt and throw it under the seat... belts literally take 5 minutes to change.



Post is getting long.



Josh

 

[KKunz]

what is the RASP system and where do i get information on it



kris kunz

 

[Moose Truck]

Rasp

RASP is from an outfit that calls them self K O Engineering, and the system is disturbed by DTT Transmissions.



http://www.dieseltrans.com/dodge/whats_new.htm



Hope this helps, Moose

 

[snowracer69]

i think moose means it's "distributed" rather than disturbed... although sometimes one has to wonder about Bill... .

 

[jgillott]

Josh,



I should have clarified my origional statement by saying that you are not going to over pressure a VP-44 with a FASS (or similar product) running at 14-16 psi, which is where most of the ones that I have delt with operate. I didn't mean to give the impression that you should be running at an extreme psi (20-30). If that is the way it sounded, sorry.



Your theory on running over the VP's internal bypass pressure is an interesting one. I've never considered that variable in the failure rate of the VP. Something to think about I guess...



The RASP sounds like a quite capable product. But unfortunately, I have no knowledge base on which to compare it to the FASS. I'm not here trying to promote the FASS system specifically, but since it was the origional topic, I would like to elaborate a little further. Believe me when I say that there are many excellent products out there in this catagory, and the RASP sounds like it fits the bill.



In my experience, the FASS does not prime to full pressure at start up. As the ecm cycles the supply pump (in this case the FASS), the pressure at start up levels off at 8psi or so. The pressure then builds within 30 seconds or so up to the opperating pressure, which is 14 at the VP inlet in my case. The overall operating pressure is easily adjustable through changes in the spring within the FASS system. Just my thoughts. .



Justin

 

[tractorface]

slowly builds pressure

jgillet,

If your pressure really takes 30 seconds to build you may have a problem. There is no reason it should take more than a second or two. My Fass did the slow build up deal before it stopped working on me. FYI, it was a fluke and I am a happy Fass customer.

 

[SpicyJam]

My FASS primes up right away. The only concern I have found out to having a hard start, is if the fuel pressure to the VP at start up is too high it can lift the three plungers off the ecentric in the VP. This can cause a hard start since you would need to crank the engine over for awhile to equal out the line pressure to seat the plungers back down. I thought this was the case with my hard start and after talking with Brad about his FASS and doing what he recomened there is no way the FASS is causing my hard start. I just have a leak that I have yet to find, since I can see a fuel puddle under my truck but can not find the source anywhere. Yes I have checked the return line many times out the back of the head, and the "T" fitting, and nothing.

Anyway, I don't belive the 16 to 18 psi of pressure is hurting my VP at all. My stock lift pump, check my gallery, would spike 20 to 22 psi at start up, and sit at 18 to 20 psi going down the road. So you tell me, 100,000+ and on the same VP, if pressure is killing the pump.

Just remember, fuel pressure is created by a restriction in the line. Run all your banjos and small fuel line you will get more psi out of it with a high volume pump. Simplest way I can think to say this is a garden hose, flows nice with an open end, screw on a nozzle and wal-la instant pressure with the same flow. The only reason we use a fuel pressure gauge is to make sure there is something going to the VP and for me reading a flow meter is a little tougher to read in the cab than my psi gauge.

 

[tractorface]

Fuel Leak

Spicy,

Another member had a fuel leak at an injector due to a bad o-ring. I believe It only leaked when the truck was running and gave him a hard start condition. He had a puddle under the truck as well.

Just a thought

 

[SpicyJam]

I thought of that, I did install new delivery tubes as well as new O-rings. Again who is to say that I didn't wreck it cranking on 6 again. cause I can't turn it no more. Follwed torque on the injector lines after the fire ring and new injector install, but I still seem to every once in while have a wet number 5 and 6, so what do I do?, crank it tighter, so I may have wrecked something. I need to pull the lines again and look at them closer.

After all that work I had no hard start for a week, then back to the same ole crap. I am not that worked up over it yet. Too much other stuff going on right now. Like getting twin turbo set up done for custmers and swap meets with the snowmobile stuff. Hopefully we get to set our diesel shop up in a new building soon. So with all that, customers come first before my own little hard start thing, I will get it. Then let you guys know what I find out. I can tell ya though working with Brad on this FASS has been intresting, hell of a guy. Later dudes.

 

[JDW]

Well I was runninng a pe pump at it messed up and ran 38 psi caused a hard to start situation. Ran a fass system running 20 psi no problem, have 120 hp injectors and superchip, doesn't drop and fuel pressure under a load.



Jason Wiseman

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