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Old 06-15-2018, 01:35 PM   #11
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Can you test fuel pressure?


I'd say fpr issue or lift pump. If its lift pump related, would be a good time to upgrade to a FASS or Airdog system.
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Old 07-06-2018, 11:21 AM   #12
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Fuel hose replacement

I had some time this morning while it was cool to work on the fuel lines. I've done some research and I'm hoping my P0087 low fuel rail pressure is due to the collapsing/kinking rubber fuel hose sections on the 1/2" supply line. I decided to go with the Trident marine fuel hose from Larry B's for replacement. The line from the sending unit (at the tank) to the back of the fuel filter/water separator has two rubber sections. My steel portion of the line is very rusty. So I decided to replace the whole thing with hose. ( many people do this with the 2nd gen 12valve cummins engines) (I used this same hose on my Cummins with good results).

I removed the line, then used a dremel to carefully cut the outer clamp. Then you can pry the clamp apart and pull it away and slide the hose off. Be careful not to cut through the metal portion. Of the end/barb (it will be reused.)
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Old 07-06-2018, 11:26 AM   #13
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Forgot to mention this is an LMM Duramax (07)

I used approximately 56" of hose from the tank to the fuel filter/water separator. I used a good hose clamp to attach the new hose on each end.

Make sure your new hose won't rub anywhere. I had to tweak the fuel line from the sending unit down a little so the hose wouldn't rub on the edge of the frame. You could also pad the frame or the hose to prevent rubbing through.

I still plan to replace the other two sections of rubber hose. One by the trans and one by the fuel rail on the left side of the engine. More to come. I hope this cures my fuel rail pressure problems.
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Old 07-06-2018, 11:27 AM   #14
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Sorry for the upside down pictures...
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Old 07-06-2018, 11:50 AM   #15
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Quote:
Originally Posted by Mr4btTahoe View Post
Can you test fuel pressure?


I'd say fpr issue or lift pump. If its lift pump related, would be a good time to upgrade to a FASS or Airdog system.
I just noticed your reply... I haven't tested fuel pressure yet. I was told this fuel line replacement is the most common issue on the Duramax. It only does it when it's hot out and when I get on the gas pretty hard. So makes me think the hoses are collapsing under acceleration.
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Old 07-06-2018, 04:00 PM   #16
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I changed out the other section of hose on the fuel line. It goes from the other side of fuel filter up to the fuel rail.

I got everything changed and took it for test drive with eventually the same results: low pressure fuel rail bank 1.

Ugh.

I watched data stream on my scanner and fuel pressure is 4500psi or so at idle and would peak aroubd 25-27k psi. One thing I did notice is throttle position stayed at 14.1%. So I'm not sure if that is part of my issue?
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Old 07-09-2018, 10:16 PM   #17
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Duramax bottle test

I did the "bottle test" yesterday. The LMM Duramax has a fuel pressure relieve valve on the driver side of the fuel rail at the rear. Many people say this will cause the P0087 low fuel rail pressure code to come on. The spring gets weak and let's fuel bypass and temporarily causes low fuel pressure. (This is my understanding). So you do a bottle test to redirect that fuel into a bottle to test if the FPRV is holding tight or letting fuel by. (It seems my FPRV is OK)

I let the engine heat up to operating temp and went and drove on the highway. Turned around and mashed on the pedal to take off and around 55-60mph it went into limp mode. Checked bottle and no fuel. Checked and same code I've been having. Ugh... what's my next step? Lol

NOTE: pictures are from van so looking at rear of engine inside van with engine cover removed. I had to remove glow plug module and heat shield to access the hose.

I also wondered if the fuel pressure sensor is reading right. I read that key on e fine off the sensor should read 1-1.8mpa which is 145-261psi. (Mine flashes between 71-107psi) so this could be another potential issue... more to come on this later.

Sorry to bore you all! I hope by documenting my troubles will help someone else in the future. The duramax Chevy Express vans are different animals than the trucks and harder to find info on...
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Old 07-10-2018, 01:18 AM   #18
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testing

do you have an in tank pump? if you do, install tee fitting in the line just after the fuel tank, make the line go all the way to the windshield.. install fuel pressure gage in the line and tape the gage to the outside of the window.. record pressure at idle, record pressure at failure .

go from there...

if you do not have an in tank pump, go the output side of the booster pump if you can, install tee fitting..........

william

that scanner only gives some insight at to what could be wrong, you have to use the 15pound computer ontop of your shoulders to find what is wrong. and it could be more than one thing.

william
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Old 07-10-2018, 06:53 AM   #19
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Nice job on the fuel lines. If your fuel lines collapse then the inside pressure must be lower then the outside so the engine sucks harder then the tank can deliver. I do not know anything about Duramax and if they have a lift pump in the tank or on the engine but I would check tank screen filter and if a pump is in the tank then also the pump.



Good luck, J
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Old 07-10-2018, 07:19 AM   #20
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From my understanding this is a common duramax problem. The trucks have only the high pressure pump at the engine (called cp3). The vans have the same system with the addition to a lift pump in the tank that only runs for first 30 seconds or so. So essentially the pump at the engine always "sucks" the fuel to the engine. The collapsing fuel lines have actually been a technical service bulletin that GM put out. That is why I started there replacing those areas.

I do appreciate the ideas. I think I might think about pulling the tank and sending unit next to see if the screen or pick up is plugged.

Yesterday I drove the bus in town to get a weight on it at the coop. (Scale wasn't available). I didn't have any problems with the code or limp mode yesterday and it was high 90's. I drove it normally without mashing the pedal or accelerating hard.

I drove the bus to work this morning to try stopping by the coop to get a weight today. I need an empty weight for the rv conversion tag...
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