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Duramax Diesel Performance Shop What's it take to make big power? From a little to a lot, find out what it takes. Post a question or offer your advice.

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  #1  
Old 05-30-2008, 08:27 AM
flaptop flaptop is offline
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Default LB7 engine dies after cold startup

Have had all updates on Edge. When I start up in the morning it dies in say, 30 seconds, and won't start for 3 to 5 minutes and works fine after that. I have not tried unplugging edge to see if that is the cause. Was wondering if anyone else has experienced this?
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  #2  
Old 06-05-2008, 05:48 AM
flaptop flaptop is offline
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Anybody got a clue as to what is going on here? In my effort to figure this out I have unhooked both the edge and the scan gauge II The same thing happens. It dies a few seconds after startup and seems like it lost it's fuel prime. I pumped up the pressure with primer on filter housing and then it started. No obvious leak in the fuel system that I can see.
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  #3  
Old 06-05-2008, 09:00 AM
DmaxMaverick DmaxMaverick is offline
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Unless you've installed an aftermarket fuel lift pump, you won't usually "see" a leak. They system is suction all the way to the HP pump on the engine. If you've recently replaced the fuel filter, it's the likely suspect (still, if it's been on there a while). Try R/R it and ensure both O-rings are sealing well. Also, use some grease (dielectric "tune up" grease works well) or heavy lube on them to help them seat. Check your water drain valve and the WIF sensor module (thing at the bottom of the filter) closely for cracks or damage. A bad fuel filler cap can exaggerate an air leak, and they're cheap. If you replace it, be sure to get a "Diesel fuel only" cap, not a gasser cap (they vent differently).
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Old 06-09-2008, 03:14 PM
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Duraswede Duraswede is offline
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Hi, my LB7 was hard to start and had a rough idle, then i saw that there was a wet spot of fresh diesel around the drain valve on the right side of the alternator, there's a schrader valve inside that was not sealing compleatly, and this line (and any other fuel line on the feed-side) is a suction line and it was drawing air through the drain valve. it's worth a check.

Edit: sorry DmaxMaverick that i didn't saw that you already had mentioned the valve in your reply.. i was a bit too fast..
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Old 06-09-2008, 03:41 PM
DmaxMaverick DmaxMaverick is offline
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Quote:
Originally Posted by Duraswede View Post
Hi, my LB7 was hard to start and had a rough idle, then i saw that there was a wet spot of fresh diesel around the drain valve on the right side of the alternator, there's a schrader valve inside that was not sealing compleatly, and this line (and any other fuel line on the feed-side) is a suction line and it was drawing air through the drain valve. it's worth a check.

Edit: sorry DmaxMaverick that i didn't saw that you already had mentioned the valve in your reply.. i was a bit too fast..
Different valve, but good advice just the same. The cap on the schrader valve should prevent a low pressure/vac leak. However, it could leak just the same.
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Old 06-10-2008, 02:43 PM
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Duraswede Duraswede is offline
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Quote:
Originally Posted by DmaxMaverick View Post
Different valve, but good advice just the same. The cap on the schrader valve should prevent a low pressure/vac leak. However, it could leak just the same.
my cap havn't any seal in it (like the ones on the AC-valves)
so i found an O-ring that fitted perfectly.
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Old 06-10-2008, 03:09 PM
DmaxMaverick DmaxMaverick is offline
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The cap should have a cone shape inside the end (deepest part) of it. The cone should plug the valve hole. Very similar to an A/C valve cap. It isn't rocket science, so if the O-ring works, just as well.
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  #8  
Old 06-10-2008, 04:18 PM
chrisgrier chrisgrier is offline
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Default Oil Pressure Problems

I have a '03 4x4 lb7, the other day on the way home about a 1/4 mile the information center went nuts stating low oil pressure or low oil I am not sure which. I looked at the oil gauge and it was on 0. I reved it up and it did not move. I drove it on to the house. I call gmc for them to come and get it. I went and cranked it and the hand came off of 0 and jerked around up and down. I reved it up and the same it jerk up and down. The dealer says they cannot duplicate the problem, I picked it up today and I cranked it and it was twiching a little and showed it to the Service writer. He say unles it was constant they could not do nothing with it. I has warranty. 6.6L. I am going to change the oil and filter even it not due. It is full of oil btw, black but full. It don't float around like gas guages do sometimes it jerks/twiches but has not went back to 0 and sat there.
Can someone tell me where it is at and if there is any way to check it.
Sincerely
Chris
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Old 06-10-2008, 04:22 PM
chrisgrier chrisgrier is offline
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Default A/C Operations

I have the climate control unit on my lb7. I want to run it on inside a/c air reculation all the time because I have bad alergies to especilly gas and diesel fumes as well as life. I found the wire that open and close the door. and with the door open I cut the wire. Will the door stay open or is there a spring on it that will eventually pull it shut/open?
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  #10  
Old 06-11-2008, 10:10 AM
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Wow, a double hijacking!
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