2K rpm max-water in fuel? - Chevy and GMC Duramax Diesel Forum
06-07 LBZ & LLY Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 39 (permalink) Old 07-02-2019, 06:15 AM Thread Starter
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2K rpm max-water in fuel?

I think I have some water in fuel. Here's the situation. LBZ, no mods, 200k miles, great engine

up to now no problems.
In tow mode. Replaced FF 2 weeks ago. Towing 10K lb TT. After driving for about 70miles I stop
for hwy construction. I take off again but now all I can get is 2K rpm and about 30mph. I limp
into town. Mech looks and says prime pump is leaking so he replaces it. I hook back up and take
off. All is good. About 20miles out I stop again. Start going, same thing. I go back to mech,
he changes fuel filter. Seems great. This time 50 miles out. Same thing. I go about 30 miles
to next town. I reset engine codes with elm327 and Torque pro. I'm good again. 20 miles out I
start up a hill and rpm cuts back to 2k and ck engine again. I finally get to flat coastal
plains and reset codes again, all is good. Besides resetting code I can pull over cool down and
turn off motor. Start back up and all is good again. TT is in place so I will go home today
unloaded. I suspect that there will be no problem however, I suspect that there is water in the
fuel. I'm thinking of putting HEAT alcohol in there and try running out fuel. Any other ideas?
I think what is happening is that sensors are reporting water in fuel and computer is putting me
into limp mode.

Torque pro with elm327 no longer reports codes, it did before. Something changed. That's another thread.

Don - WA5NGP

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post #2 of 39 (permalink) Old 07-02-2019, 06:20 AM
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Do you have a lift pump?

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post #3 of 39 (permalink) Old 07-02-2019, 06:26 AM Thread Starter
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No I don't, I understand why a lift pump would help but I've towed thru mountains before no problem so I was not inclined to add a lift pump. One odd thing that is happening, the ac cold line runs over top of FF and water drips off of line onto top of FF prime pump, even puddles. Doesn't seem like water would get sucked in but it looks odd to see water puddling there. Truck is total oem stock condition, except for radio.

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post #4 of 39 (permalink) Old 07-02-2019, 06:32 AM
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Quote:
Doesn't seem like water would get sucked in but it looks odd to see water puddling there.
You're sure it's water?
And not Diesel fuel?

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post #5 of 39 (permalink) Old 07-02-2019, 06:35 AM
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Quote:
Originally Posted by wa5ngp View Post
No I don't, I understand why a lift pump would help but I've towed thru mountains before no problem so I was not inclined to add a lift pump. One odd thing that is happening, the ac cold line runs over top of FF and water drips off of line onto top of FF prime pump, even puddles. Doesn't seem like water would get sucked in but it looks odd to see water puddling there. Truck is total oem stock condition, except for radio.
I asked about the lift pump because I had a similar issue due to my wiring shorting on my lift pump...

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post #6 of 39 (permalink) Old 07-02-2019, 09:08 AM Thread Starter
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Originally Posted by Hook'em_Horns! View Post
You're sure it's water?
And not Diesel fuel?
Now I am yes, its water. At first I thought it was diesel since I had recently changed the filter and replaced that plug. So that and the fact that mech said those prime pumps are prone to fail I had him go ahead and replace it. However, later when I pulled off the road I checked again after replacing pump and filter there was that water puddling again and I could see that the low pressure ac line dripping with water. You know how it is in Austin now, 99% humidity after all the rain. I even tasted it and it is water. However, I got to wondering if somehow that water was somehow getting into that prime pump. Seems unlikely but I'm going to wrap that pipe with foam so the water won't drain down onto the primer top. there is a little rectangular indentation where the water collects like in a tiny swimming pool.

I wish I could make Torque pro report the fails. Before it reported the glow plugs but won't do that now. It will clear the check light and that gets me going again. I'm going home later, not towing, I'm betting it won't limit at 2k any more. I assume HEAT won't hurt anything and might absorb the some water?

I can see how a lift pump can cover some of the sins of such a fine grained fuel filter. The mech said they sometimes collapse inside.

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post #7 of 39 (permalink) Old 07-02-2019, 09:53 AM
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Quote:
mech said those prime pumps are prone to fail I had him go ahead and replace it.
You had him replace the complete filter head with a new assembly?

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post #8 of 39 (permalink) Old 07-02-2019, 10:27 AM
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Quote:
Originally Posted by wa5ngp View Post
No I don't, I understand why a lift pump would help but I've towed thru mountains before no problem so I was not inclined to add a lift pump. One odd thing that is happening, the ac cold line runs over top of FF and water drips off of line onto top of FF prime pump, even puddles. Doesn't seem like water would get sucked in but it looks odd to see water puddling there. Truck is total oem stock condition, except for radio.
The lift pump would help if the fuel lines were collapsing on the truck cutting fuel supply to the vacuum pump. The lift pump would push the lines open again restoring fuel flow, its a bandaid to the problem. If that is your issue the fuel lines need to be replaced. Your symptoms do align with this issue, typically this will cause the truck to go into limp mode under heavy load as the engine becomes fuel starved. once the codes are reset, the truck runs fine until the next low fuel flow event when the code comes back and the truck is again put into limp mode. As the truck heats the fuel in the tank up, the lines get softer and eventually squish down and choke the fuel flow off.

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post #9 of 39 (permalink) Old 07-02-2019, 11:17 AM Thread Starter
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Quote:
Originally Posted by Hook'em_Horns! View Post
You had him replace the complete filter head with a new assembly?
Yeah, that's what he recommended and I was ok with it. I was in a bind driving between Austin and POC practically stranded in Gonzalez. Weird thing is I got 20miles away and same problem came back so I circled back and he replaced FF no charge. He seemed to have experience with dmaxes. They have dmax wrecker trucks, he says that they keep spare FFs in them, I guess they callapse frequently which I suppose is the reason people install lift pumps.

Very odd thing, this morning I drove around POC and now ck engine light has gone out and analyzers have said that I've got 3 bad glow plugs. Maybe at these daily temps it knows there's no need for glow plugs.

edit. it was a rebuild kit not a total new replacement of the top portion where the FF is mounted.

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Last edited by wa5ngp; 07-02-2019 at 11:49 AM.
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post #10 of 39 (permalink) Old 07-02-2019, 08:23 PM Thread Starter
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Quote:
Originally Posted by J83 View Post
The lift pump would help if the fuel lines were collapsing on the truck cutting fuel supply to the vacuum pump. The lift pump would push the lines open again restoring fuel flow, its a bandaid to the problem. If that is your issue the fuel lines need to be replaced. Your symptoms do align with this issue, typically this will cause the truck to go into limp mode under heavy load as the engine becomes fuel starved. once the codes are reset, the truck runs fine until the next low fuel flow event when the code comes back and the truck is again put into limp mode. As the truck heats the fuel in the tank up, the lines get softer and eventually squish down and choke the fuel flow off.
I need to take a look at those lines. These are the lines that lead from the tank to the filter right? Are they a braided flex or rubber fuel line that deteriorates with age?

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