Community Forums

crawbob · 12-07-2013, 09:35 AM

I have had the low boost problem for 6 years. Cummins West now Cummins Pacific has been working on it the whole time with no results. They have replaced almost everything, Injectors, High Pressure pump, lift pump, turbo, boost sensor, and a few other things. I have replaced the CAC, fuel tank and filters. I am running about 5 to 6 lbs low on boost, 19 to 21 on my guage. It used to be about 26 inches. Cummins Pacific has given up saying it within parameters, but on the low side. I have lost 2 gears on any hill I go up. It starts good and there is no smoke. Very poor turbo response, lag. Exhaust temps run 800, which is low. Any suggestions?

McRvnut · 12-07-2013, 10:14 AM

Quote:

Originally Posted by crawbob

I have had the low boost problem for 6 years. Cummins West now Cummins Pacific has been working on it the whole time with no results. They have replaced almost everything, Injectors, High Pressure pump, lift pump, turbo, boost sensor, and a few other things. I have replaced the CAC, fuel tank and filters. I am running about 5 to 6 lbs low on boost, 19 to 21 on my guage. It used to be about 26 inches. Cummins Pacific has given up saying it within parameters, but on the low side. I have lost 2 gears on any hill I go up. It starts good and there is no smoke. Very poor turbo response, lag. Exhaust temps run 800, which is low. Any suggestions?

By the sounds of things you must have spent like 12K?? or more.Seems silly replacing things like main pump? CAC could be pressure check and repaired if it did leak? Injectors? not likely.What would replacing fuel tank have to do with turbo boost. a 350HP cummins should run 28-30 lbs boost
I had a 350HP and installed the Banks fuel management system and could get
as high as 38-9 lbs boost @ 1275 EGT. Is it possible your ECM is wrong in its programing?

palehorse89 · 12-07-2013, 10:17 AM

I assume you or they have tried another guage in it to verify your gauge is reading correct? It almost sounds like the turbo wastegate valve is open a bit....... not allowing proper boost? and that condition would cause the "lag" time to be even worse. Just a thought.....
Some reading here: http://www.irv2.com/forums/f123/turb...te-108946.html

crawbob · 12-07-2013, 10:29 AM

Replaced fuel tank for other reasons. They also replaced computer with a test computer with no change. Also reprogramed computer out of specs with out any change. Waste gate is OK.

crawbob · 12-07-2013, 10:33 AM

Had banks system on and it only gives 23 Lbs of boost. About 2 to 3 Lbs of boost more than stock. The boost shown on their computer is 44 to 46. Should be over 55.
they say 46 is with in margins, but on the low side.

Sammie · 12-07-2013, 10:35 AM

Bad boost gauge?

Sammie

crawbob · 12-07-2013, 10:49 AM

Not a bad boost gage. Cummins computers give the same results. Cummins can't figure it out. A bad boost gage would not cause me to loose 2 gears on a hill. Only low boost, HP, dose that.

McRvnut · 12-07-2013, 10:51 AM

Quote:

Originally Posted by crawbob

Had banks system on and it only gives 23 Lbs of boost. About 2 to 3 Lbs of boost more than stock. The boost shown on their computer is 44 to 46. Should be over 55.
they say 46 is with in margins, but on the low side.

iam not sure what your referring to but the ISC 350HP cummins DOES NOT
ever get 44-46 lbs of boost never mind 55??
I installed the Banks system on my 2002 350HP cummins which they claimed added 115HP and 200lbs boost.It was very good power but highest the gauge read was 38lbs which is about 8 lbs over max stock
I still cant understand installing a 4000$ fuel pump was supposed to do?
I do know that the stock 350HP cummins when loaded up and pulling toad was poor power on steeper passes and was the reason I turned to the bank system
I would down to 4th gear on lots of mountain passes before the banks system

palehorse89 · 12-07-2013, 10:56 AM

Well after 6 years and a whole bunch of $$$$$ thrown at the problem by you and what ever the Authorized Cummins dealer has done for you with no results......I am thinking you are going to get the same questions and answers that you have had listened to for 6 years on here, maybe...... Have you just taken it to the same Cummins shop or have you given another Cummins dealer a chance to look at your problem, a second opinion, or 3rd opinion on this matter?

McRvnut · 12-07-2013, 11:20 AM

could it be something as simple as the max fuel pressure setting on the fuel rail pressure switch is too low(wrong setting) as in bad switch etc

any possibility you have a exhaust muffler system problem?

exhaust brake not fully opening?

1985 Bounder · 12-07-2013, 11:27 AM

Crawbob, did you have anything done at the time you noticed your boost go down? Was it a sudden drop of boost or was it a gradual decline? Has the turbo itself been replaced or repaired? I used to run a fuel injection repair shop and we repaired turbos. With some answers maybe I can help.

McRvnut · 12-07-2013, 11:30 AM

Quote:

Originally Posted by 1985 Bounder

Crawbob, did you have anything done at the time you noticed your boost go down? Was it a sudden drop of boost or was it a gradual decline? Has the turbo itself been replaced or repaired? I used to run a fuel injection repair shop and we repaired turbos. With some answers maybe I can help.

Just read the op and u will see he says replaced turbo as also many other things

1985 Bounder · 12-07-2013, 11:41 AM

Fair enough McRVnut, but the other questions will still help to diagnose the problem. I did not go back and re-read the OP before offering my help. My bad.

crawbob · 12-07-2013, 12:12 PM

The 44 to 46 Lbs of boost is inside the intake manifold. You have to add the barametric pressure to you boost gage to get the same reading as the intake manifold pressure the Cummins diagnostic computer give you. This is where The Cummins computer takes its readings. Every thing reads normal, on the low side, according to Cummins. Full throttle, fuel pressure etc..