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Discussion Starter #1
I'm not sure what kind of issues I'm having, so I'll start by just describing what its doing: (FYI - bone stock 4bta)

-The starts and cruises just fine. Low end power seems exactly the same as always and I can still here the turbo whistling. However, where (in the powerband) it used to really seem to spool up and give me a ton of power, that's not there anymore.

It acts as if it does in the winter before it warms up. I drove on the highway the other day and couldn't even pass a semi, where as before I could put it in 5th and run 90 all day long. Driving in some hills the other day that I've never had to downshift for... had to drop it into third from fourth.

I can't accurately comment on mileage because of a speedo issue, but it doesn't seem like it's gotten bad enough to notice. Everything sounds and smells normal so I don't even know where to start.

Could I have a waste gate issue? Having stock spring and turbo, could I damage anything running it with the waste gate J-hooked? The turbo is still compressing air because I can hear it after I shut it down and it whistles like it always did. But I'm wondering if the air isn't just getting dumped out the exhaust and killing my boost. I have a homemade boost gauge I'm going to try out.

Other than the 2500rpm govnr, I was completely happy with the power I was getting with the stock setup. Now it feels like I'm driving a 4.0 again...

Any other thoughts or advice?
 

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Have you tried....

My first suggestion would be to change the fuel filter. It's been my experience that about 95% of the problems that you run into with a diesel are either bad fuel or the fuel filter needing changed. Plus it's probably the cheapest possible solution to try first.
 

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Discussion Starter #3
Yeah, I agree... however, I just changed it about 6 weeks ago. This is my first diesel, but it doesn't feel like it starves for fuel (possible Napa gave me a more restrictive filter??)The problem is, that I can't really remember when I really noticed the power drop since I didn't drive it a lot this winter. At one point, I just attributed it to wintermix.

I did find a loose fitting on my compression side of my after cooler plumbing (the elbow coming off the turbo that one of my boots is clamped to was loose at the turbo) a few weeks ago and thought would fix it, but it didn't change a thing. Meaning, I'm not feeling any of the boost that the turbo (sounds) to be producing.

I know, I know... I need gauges... getting there.
 

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Discussion Starter #5
The fuel pressure was fine... I'm almost completely convinced that it has something to do with the wastegate.
 

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If you think the waste gate is the problem remove the hose fron the line and plug the line off and see what it does from there /

Scott
 

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Discussion Starter #7
boost

Hey Scott,

Finally hooked up a boost Gage at lunch today. I was surprised to see that I do have boost, although I'm not sure if it is normal or not. Under full throttle in first, second and third gear, I was able to get to 14-16 pounds before the govn took over (2500rpm) and knocked it down to 10-12. Cruising around 60mph I'm maintaining about 10-11psi.

Does this tell me anything? If this is normal boost, I'm going to change the fuel filter again just to verify that I'm not running a restrictive filter. Any P/N's for the recommended p7100's filter??? Maybe I don't have the fuel pressure that I think I do.

Thanks again for the input..
 

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Hey Scott,

Finally hooked up a boost Gage at lunch today. I was surprised to see that I do have boost, although I'm not sure if it is normal or not. Under full throttle in first, second and third gear, I was able to get to 14-16 pounds before the govn took over (2500rpm) and knocked it down to 10-12. Cruising around 60mph I'm maintaining about 10-11psi.

Does this tell me anything? If this is normal boost, I'm going to change the fuel filter again just to verify that I'm not running a restrictive filter. Any P/N's for the recommended p7100's filter??? Maybe I don't have the fuel pressure that I think I do.

Thanks again for the input..
With stock gov springs and fuel setting that's about right if you turn your fuel up the boost will be around 20 psi or so .I always use Fleetguard FS 1251 on all the 4b .

Scott
 

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Discussion Starter #9
Ditched my unnessecary check valve on my fuel supply line, changed the filter to a napa 3777 (10 micron filter.. Didn't have access to the FS1251 yet). Took it out and ran it and it felt a bit better, but I still don't have any spooling power at higher speeds/RPMs. My boost floored at 60mph and about 2000rpm's was between 10-12 psi.

I have yet to put a fuel pressure guage on it and I know that I need to do that before anything else, so I'll update after that. Are there any screens between the two pumps on this engine? I've had problems in the past on other vehicles where there was significant blockage at screens on either a carb or before a fuel rail. I've already verified that the screen in the tank is good.
 

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Your lift pump has a screen . Your about where it should be on boost ,to get more boost the fuel needs turned up and GSK spring set .

Scott
 

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Just a vague possibility here, but I had some of these same problems. Watch your temp gauge when crusing under a slight load on a long stretch, see if it 'walks' back & forth? If so, inches up, then drops a few degrees, inches back up, drops, it can indicate a blown head gasket.

You can fab adapters to use a standard compression gauge through your injector holes [with all injectors removed] to be sure of gasket condition.

Pain in the butt to change but not all that bad for a strong healthy guy. I used a hoist to lift the head ;)
 

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Discussion Starter #12
My temps stay nice, cool and constant... My fans don't even kick on in town unless I'm stopping and going in the heat for more than 30 minutes. I hope I don't have to do a head gasket anytime soon on this thing!
 

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Discussion Starter #13
Ok - Been a while, but I hate to admit that I haven't even had time to check my fuel pressure yet. Now that I'm driving the Jeep more (Finally nice out!), I'm ready to fix this [email protected] issue! I spoke to a very knowledgeable 6B guy and he said that even if I am showing lower fuel pressure at high RPM's, that I should first check the regulator spring on the P-pump that is in that banjo fitting on the return line. He said that many times they will get old and not be able to hold up against high pressure as well, letting too much fuel by too early... causing my problem (if I do in fact have a fuel pressure problem).

He recommended pulling the spring out, stretching it to a resting length of 1/2", reinstalling it and trying it out. If that does work, I'll replace it. I'll let you all know if that's the case. Once that's all done, I'll finally start doing some other upgrades..
 

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Ok - Been a while, but I hate to admit that I haven't even had time to check my fuel pressure yet. Now that I'm driving the Jeep more (Finally nice out!), I'm ready to fix this [email protected] issue! I spoke to a very knowledgeable 6B guy and he said that even if I am showing lower fuel pressure at high RPM's, that I should first check the regulator spring on the P-pump that is in that banjo fitting on the return line. He said that many times they will get old and not be able to hold up against high pressure as well, letting too much fuel by too early... causing my problem (if I do in fact have a fuel pressure problem).

He recommended pulling the spring out, stretching it to a resting length of 1/2", reinstalling it and trying it out. If that does work, I'll replace it. I'll let you all know if that's the case. Once that's all done, I'll finally start doing some other upgrades..
If you have low pressure just replace it , no need to take the time and try to mess with a weak spring.

Scott
 

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Discussion Starter #15
Ok-shoot me a price on the kit:) the engine is a 1995..

So for a sanity check- low rpm pressure should be around 10-12psi and high 20-25??
 
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