2nd Gen Non-Engine/Transmission Low Boost??

[EBottema]

Hey guys-



Last week or so my truck has felt different. Runs smooth as ever but boost seems to feel different. In 3rd and 4th gear around 1700 rpm is comes into play and but the max boost in 3rd gear is 15psi. 4th i can get it to 25psi, same with 5th gear...



However, in 2nd gear, i cant get boost unless im over 2100 rpm and i can barley get 10 psi...



4th and 5th seem normal to me but i feel im getting low boost in 2nd and 3rd gear...



Stock engine plus afe stage 2, 370 marine injectors... .



Am i just losing my memory or does this seem out of the ordinary?



thanks

erik

 

[bmoeller]

Something isn't right. I was seeing 20#, bone stock.



Are you having low power problems as well? Sounds like you either have low fuel pressure/flow, boost leak, or maybe a pinched/cut boost line to the AFC housing. If that line isn't getting enough boost, it will reduce the amount of power you can make. Or, maybe there is a problem with the diaphram in the AFC.

 

[EBottema]

Something isn't right. I was seeing 20#, bone stock.



Are you having low power problems as well? Sounds like you either have low fuel pressure/flow, boost leak, or maybe a pinched/cut boost line to the AFC housing. If that line isn't getting enough boost, it will reduce the amount of power you can make. Or, maybe there is a problem with the diaphram in the AFC.

20 pounds in 2nd gear??



No, power seems normal... . 6 months ago i replaced the rubber fuel lines and new lift pump. Truck starts up perfect too.



I'm leaning towards boost leak if anything. Where are the best places to look?



Erik

 

[RDelissen]

I'm leaning towards boost leak if anything. Where are the best places to look?



Erik

check where the connections are (with the hose clamps and such).

They might look tight, but are not always as tight as they look :-laf

 

[RBratby]

take a look on the passenger side intercooler boot. they are close to the fender and rub sometimes. i had that happen on my 97. new boot and a little trimming all is well.

 

[Dave M]

take a look on the passenger side intercooler boot. they are close to the fender and rub sometimes. i had that happen on my 97. new boot and a little trimming all is well.

I also had a leak there at passenger side intercooler boot where it attaches to the intercooler. At first I just looked at it from top and bottom where it runs against the inner fender and it looked ok. When I took the boot off I had a 3 inch split where it had rubbed agaist the innner fender lip. Don't just look but remove it if you haven't already. I replaced mine with Piers intercooler boots.



I had 7 psi max booost (major leak). Since your leak is not as bad it must be a smaller pinhole leak. Intake gasket could be leaking?... maybe the wastegate at turbo?



Good luck.



Dave

 

[cromptrj]

check all the intercooler rubber boots the one at the turbo gets loose first it seams like on alot of my friendsdodges and mine has before .

 

[EBottema]

How do you check the wastegate?



erik

 

[Dave M]

How do you check the wastegate?



erik

You could plug the wastegate line from the AFC to the wastegate with a bolt on the rubber hose going to the wastegate and see if boost increases. If boost goes up it would tell you that the wastegate is opening too early.

The line connected to the wastegate is basically manifold pressure putting pressure on a diaphram and spring, which moves the actuator arm that opens the wastegate. If no change than the wastegate is not the problem.



But I think you have to be carefull not to exceed 30 psi boost or you will damage your stock turbo and maybe blow a head gasket. Do not exceed 30-35 PSI is what I've heard. Might replace that boost line. Check the boost line from the intake manifold to the AFC where it connects to a "T" fitting that also has the line going to the wastegate. You could try plugging it also, but don't exceed 35 psi boost. But since you can reach 26 psi boost, I would doubt it is opening early, maybe just a small leak in the line. I would suspect a fuel problem or the AFC/governor or timing.



Intercooler could have a leak and is harder to troubleshoot. Do you have a catalyic converter that is plugged causing low power? Try disconnecting it?



What about that screen in the lift pump? Might need to verify fuel pressure from the new lift pump... . I know its new. . But!



Replace the fuel and air filter (edit: Ooops!. . Never mind replacing the air filter. . I see you have AFE so maybe clean it) if its been awhile.



Do you have an EGR valve? Another source of trouble sometimes.



Could pump timing have slipped? Are EGT's higher than normal?



As said before the AFC could be a problem. Is the govenor fuel lever hittting the cam plate correctly? There is a good pic of this and procedure on Piers site here: http://www.piersdiesel.com/TechLeverAdj.htm



Have you slid the AFC housing toward the front or messed with the "fuel plate"? If you slid the plate toward the front of engine (scribe its current location first) you will get more fuel... or so I'm told. You can remove the AFC I'm told and remove it as a source of problem, but someone else should chime in and explain that to you. The AFC basically controls the rack travel for fueling at low RPMs when boost is low until the boost builds up and takes over takes ... . thats just my understandiing of it. Sliding the AFC housing forward gives more fueling at low boost. But I believe after 8-10 psi boost the finger in the AFC housing is out of the picture and the plate takes over.



Hope that helps some.



dave

 

[bmoeller]

But I think you have to be carefull not to exceed 30 psi boost or you will damage your stock turbo and maybe blow a head gasket. Do not exceed 30-35 PSI is what I've heard.

The stock turbo can take more boost, but it is out of its map, at, or over 35#. 35# won't hurt a headgasket as long as it was OK to begin with. I'm making 40# with the PDR 40.

20 pounds in 2nd gear??

No. O/D, with the TC locked up. The stock convertor was to "loose" to get near that in a lower gear. Couldn't load the engine very well.



I'm saying that with the 370s and 215 pump, you would've gained more than 5# adding them.