max boost pressure

what is the max boost pressure on a stock 99 cummins i should hit. just was wondering what the max boost i should try and stay under so i dont hurt anything. and my truck keeps putting out a code every once and a while then the tach will jump around and sit at zero then jump back up. all the vitals are fine and is still running fine. anybody know what might be the problem.

 

I wouldn't go over 40psi with a stock head gasket/bolt setup. You hit around 26 psi of boost and it then defuels. You need some sort of boost fooler, tuner, performance box to boost any higher. As far as the tach jumping around, it could be a few things. I tending to think your lift pump is not working very well and the truck is runnning out of fuel and then the fuel pressure catches up again. Start with a fresh fuel filter, I keep a spare in the truck. 98.5 -2002 trucks have the vp44 injection pump and the lack of fuel pressure will toast the vp44. Aprox 70% of the fuel going through the vp44 is for cooling purposes. A good reason not to run it low or out of fuel.

 

Those trucks in stock form (no programmer or boost fooler/elbow) should only hit about 17 to 21 psi boost. And Woods is correct, with aftermarket performance modifications with a stock head gasket you should try and stay below 40psi.

I will also stress that fuel pressure if of utmost importance with these trucks.

-Chuck

 

i have the edge with juice in it and i set it so it wont go over 30 psi. and my fuel pressure at idle is 14 to 15 psi. on level one at wide open throttle it get down to about 9 maybe 8. but when if i put it into level 5 the pressure can drope to 5 or 6. im about to take it to my local dealership to get services done on it and have them check out the warning light to see what code its putting out.

 

i forgot when i was sitting at a light the truck started rocking like some one rear ended me and then the tack dropped down to zero. it only did it a couple times then it was back to normal it had never done that befor.

 

5 or 6 psi is not good. you will start to harm the vp44 with those kinds of readings. i am at 17 idle and 12 at WOT on level 3 with my quad superchip stack. the fuel is what cools the vp44 from over heating the electronics and the pump itself. if fuel pressure/volume drop it will start to overheat and cause failure in the tune of 1200.00 plus.

Johnwaytogo

 

only when its on level 5 that its that low. i never use it. but the rest of the time its at idle between 15 to 16 psi. and when im in level one it never drops less that 10 psi. but im taking it in because its also starts reving wierd once and a while when i get off the peddle. then if i tap the gas it will be back to normal.

 

Folks I'm new here and I have a question related to this - would installing a FASS system help to prevent low fuel pressure problems and extend the life of the VP44? BTW stumo I installed a BD turbo boost builder and it increased my boost from 19lbs to 28lbs without throwing codes. Big difference in power and it helped bring the EGT down noticeably under load too!

 

Yes a FASS will help save the vp44 pump buy keeping the fuel supply constant and pressure up. but if your IP is already bad a fass wont fix it but it will help save the new one

Johnwaytogo

 

Thanks John.waytogo

 

I'm running the stock lift pump with an aux pump from jegs and hitting about 21 psi at idle. Do you think that set up is ok?

 

I read recently from an article in dp that the max boost for an ISB(stock) is 60 ....were the earlier engines less? do you disagree with the 60?

 

Since I've installed my Edge box,I've discovered that my fuel pressure at idle is 11 or 12.Driving down the road it jumps between 7 to 9.I'm getting a new lift pump for it soon.My question is have I hurt my injector pump? I dont turn the tuner up and there's not gonna be any towing until I get another pump on it. Thanks

 

I also have 02 and with a comp box. I get about 14 psi at idle and between 9 and 10 while cruising. When I really get on it It will run down to about 5psi. I never worried about it until I read an old article in dp where they mentioned that dodge had a warehouse full of old pumps that were burnt up from guys running chipped trucks and never upgraded their lift pumps. ( that's about all the detail the article gave ) So what new pump you going with?

 

The ISB's have NEVER hit 60psi in stock form. That had to have been a typo.

 

For the aftermarket fuel delivery pumps I highly recommend the FASS.

 

Sorry, I wasn't clear, I meant with the stock head bolts and gaskets. In other words what they were saying is as long as you stay below 60 on the boost no need to up grade to a head stud bolt kit.

 

>>>>>>>>>>>>>>>>> I'm going with stock for right now.Just dropped 3 grand on it in mods so moneys tight.I will upgrade to the FAAS system when I can

 

45-50 is where I have seen head bolts streach.

I won't even start to tell you the headgasket issues I've seen.....
I am the master of desaster when it comes to headgaskets.
I'll put it this way... Head studs and a factory gasket lasted me 2300 miles. I blew it BETWEEN Cylinders.

With headbolts I can have a head off a 12v Cummins in 30 min. Stud 45min.

 

ok, from what I've read people talk about going to a head stud bolt kit but never really mention the gasket issue. Do you think to do one it's necessary to do both? Or do we need to worry about bolts at a certain boost level and gaskets are good to a different level? Do you think your situation was a freak deal? What kind of boost were you running when that happened?
Is ARP the recommended stud kit?