Low Boost

[Bad340fish]

Ok first off I have already checked the IC hoses, The air cleaner is all good, and the gaskets look ok on the intake horn.



I used to get about 26psi out of my truck. I changed to a straight through muffler and lost a few lbs no biggie. Well for the hell of it I pulled my wastegate line off the other day and didn't get any more boost. Well I had to take my truck into the dealer today so I de-bombed it stock air cleaner and all. I can muster up a whole 15psi of boost in stock form which is wrong. So what gives? The turbo is not screaming like there is a leak somewhere or anything. Doesn't sound like its over speeding or working to hard at all. My EGTs are normal. My boost guage fittings are tight. Can the wastegate be bad or stuck open?? Kinda makes me feel weak lol... my old Conquest Gasser would pull 15psi(at the cost of a set of spark plugs lol). TIA for replies



Oh yeah to Top it all off the Diesel Mechanic is no longer at my formerly awsome dealer. All they have is a guy that can run the Valves... sad

 

[Steve St.Laurent]

When my last lift pump went bad I lost approximately 2 psi of boost. Other things to check are the bolts holding the intake down (the whole intake, not the horn). You could also have a hole or a split in the intercooler, you can get plugs for either end of the intercooler and pressurize it to check for leaks there.

 

[Diesel Junkie]

I found out about a bad lift pump a couple of weeks ago. I had always had a solid 30# boost and I started seeing a spike of 30# then a drop to24# at full throttle.

As it turns out the lift pump was studdering. It had good pressure with no load at all throttle levels, but when you would bump the starter it would vibrate between 0-15lbs for about 6 seconds then shut down. You could actually hear it!

Replaced lift pump and all is well. Holding 31lbs boost now and eating gassers again!



Scott

 

[DarrellB]

Might want to check the boost/map sensor. I have had 2 go bad and you will realy notice it. When the first one went bad the truck would not build boost till it hit about 2,200rpms and then it would only run about 22lbs instead of 32lbs. Thesensor is right behind the fuel filter housing and you will need an 1 1/4'' deep barrel socket to take it out.



Big D

 

[Bad340fish]

Update

Could my wastegate just be shot?? I got the truck back today and re-BOMBed it(so slow stock. . still slow not stock but better lol). Well with the EZ on and the stock boost elbow I get 16psi TOPS. It was the same without the EZ which leads me to believe that the wastegate is leaking maybe?? I pull the line to the actuator off and get 20PSI which well sucks . How do you check the wastegate?? The diesel tech got fired at the dealer I really trust around here so not sure what to do from that standpoint. It still spools up quick which IMO rules out a leak of any kind. TIA

Clark

 

[DarrellB]

Bad340fish, sounds just like what happend when my boost/map sensor went out. I would spend the $26 and replace the map sensor.



When mine went out I thought it was the lift pump so I replaced it and the problem was still there. So I then thought it was the waste gate sticking open and didn't want to cut out the waste gate in fear of over boost and defueling the truck. I took the truck to Cummins of Cumberland and they said they had never seen a waste gate fail on the B series motors. I left them the truck and they replaced the boost/map sensor and the truck ran great. The service manager told my that the boost sensor will defuel the truck in case of over boost. So when the sensor goes bad it is telling the truck that there is too much manifold presure and the truck defuels to prevent the over boost.



The only down side was the bill was almost $300, I took the bill to my dealer and they cut me a check to cover it. I have another sensor going out again and this time I will replace it myself. (only takes about 20 minutes)



Try the boost sensor and let me know what happens.

If you need the part# for Cummins I can give it to you.



Later

Big D

 

[Lurch]

But with the EZ plugged in the ECM shouldn't ever see an overboost code. Puzzling.



Lurch

 

[DarrellB]

Thats kind of what I thought cause I have a PowerMax but evidentaly it doesn't mater if the sensor is completely shot.



Big D