Help with fuel system diagnostics

[PLohr]

Hello, guys.

I almost posted this in the 911 section. We are about 6 hours from home. But the truck is running, although not very well.

We topped off (8 gallons) with diesel fuel near Pinehurst, GA then the truck lost power. Wouldn’t exceed 60 MPH. Stopped at a rest stop to check things out. Took a 1/2 cup fuel sample from the filter housing drain to check for water with the engine still running. The diesel proceeded very slowly out of the valve. Eventually the injectors started sounding very erratic then the truck died while I had the drain valve open. I didn’t think opening the drain valve caused it to die but maybe that’s possible. After the engine quit, I primed the filter housing by cycling the key. It didn’t restart right away but eventually it did restart. Anyways, more of the concern is the loss of power.

The low pressure electric pump is working. I checked that.

Does the CP3 pump fail in this manner? It’s not totally dead yet.

Is it possible to get water in the fuel and never see the light come on?

2003 3500 2wd manual transmission. 180,000 miles.

Thank you for any help,
Paul Lohr

 

[AH64ID]

It sounds like the lift pump is failing.

What did you do to verify it works?

With the engine on the fuel should shoot out of the WIF drain with 8-10 psi behind it. With it barely flowing that tells me the CP3 is sucking fuel and it probably died from lack of fuel/air ingestion.

 

[BigPapa]

John, is the CP3 not just a simple pump, no electronics to fail, no intricate internals, either it works or it doesn’t? It has an integral “lift pump” on it. Our buses don’t run a lift pump.

Could he not have gotten a bad load of fuel that’s stopped up his fuel filter?

Just asking, as most times I try to help with these CR’s I don’t know what I’m talking about....

 

[AH64ID]

John, is the CP3 not just a simple pump, no electronics to fail, no intricate internals, either it works or it doesn’t? It has an integral “lift pump” on it. Our buses don’t run a lift pump.

Could he not have gotten a bad load of fuel that’s stopped up his fuel filter?

Just asking, as most times I try to help with these CR’s I don’t know what I’m talking about....

It is a simpleish pump. It does have the FCA on it, but that won't have an effect on the lack of fuel pressure at the WIF drain.

Same thing with a clogged filter as the WIF drain is on the input side of the filter.

There are CP3's that don't use a lift pump, such as the busses you mentioned or the Duramax. The are minor differences in the pumps thou, but the CP3 in a Dodge/Ram will suck fuel and run without a lift pump if the fuel line isn't blocked by a clogged filter or a failed pump (the LP is designed to fail as flow-thru failure but that doesn't always happen, thou it sounds like that might be the OP's issue).

 

[BigPapa]

Like I said, just asking. Trying to think of simple things before jumping to a bad HP pump. He stated his lift pump was functioning.

 

[AH64ID]

He stated his lift pump was functioning.

He did, but his lack of pressurized flow from the WIF drain indicates otherwise. That's why I asked him how he verified it's working.

 

[Darkbloodmon]

Could he not have gotten a bad load of fuel that’s stopped up his fuel filter?

I'd check the filter, simple stuff first.

 

[Ozymandias]

Drain valve is prior to filter as mentioned, if there is no flow then the pump is bad.
From what I know, but tell me if I'm wrong, the in-tank pump is not a free flowing pump if it locks up.

Ipening the drain the fuel should really spray out with quite some pressure and not just a trickle.

 

[AH64ID]

@Darkbloodmon a plugged filter won’t block the WIF drain.

@Ozymandias I’ve read a failed pump will allow fuel to be sucked thru it, but many report that doesn’t happen. It probably depends on how it fails.


Lots of possibilities, but the red flag is the lack of fuel coming out the WIF drain with the engine on.

 

[Darkbloodmon]

Drain valve is prior to filter as mentioned, if there is no flow then the pump is bad.
From what I know, but tell me if I'm wrong, the in-tank pump is not a free flowing pump if it locks up.

Ipening the drain the fuel should really spray out with quite some pressure and not just a trickle.

Took a 1/2 cup fuel sample from the filter housing drain to check for water with the engine still running. The diesel proceeded very slowly out of the valve.

Filter housing has the drain on it, this is a stock filter setup. This is an 03 truck there shouldn't be an in-tank pump. It should be a block mounted one. I can take a pic of my old filter housing with its drain valve, I use as a wall mount holder for picks and wire brushes in my garage.

 

[Darkbloodmon]

@Darkbloodmon a plugged filter won’t block the WIF drain.

Correct. At this time OP hasn't stated that they opened up the filter housing and checked the filter or drain. It's standard procedure to wipe out the bottom of the housing for heavy debris when changing the filter.

 

[Ozymandias]

Very rarely we still see these unreliable block mounted pumps after almost twenty years.
But yes, it could be possible that someone refused to move on to better solution and the pump is still there, but sure not the first one.

 

[AH64ID]

Very rarely we still see these unreliable block mounted pumps after almost twenty years.
But yes, it could be possible that someone refused to move on to better solution and the pump is still there, but sure not the first one.

Exactly, id be surprised if it was still filter mounted at 180K miles.

 

[PLohr]

Thanks for your help, guys.

Thanks to the Lord we are home safe.

Lesson learned: keep a socket on trips to check the fuel filter as well as a spare filter. Thank you.

We still have the old style low pressure pump on the filter housing. Long story made short, I change the low pressure pump every 80k miles or so. I agree they are not as durable when out of the fuel tank.

I had my wife turn the key to the run position while I held my hand on the low pressure pump. It at least initially functions with the key in the run position. That was the extent of my testing of the low pressure pump.

The truck is supposed to be back at our house on Sunday.

 

[AH64ID]

Glad you made it home.

Im still think the lift pump has failed. Even the canister style pump provides positive pressure to the fuel filter, which means it should shoot out the WIF drain if it’s working properly.

 

[PLohr]

It turned out to be a nearly plugged suction side fuel filter causing the issue. I was able to diagnose this by adapting a fuel pressure gauge to the fuel filter drain, opening the drain valve, then running the truck. With the plugged filter, the pressure was zero (but the engine still ran). I replaced the filter, started the truck then the pressure was 16 PSI.

I added the suction side fuel filter within the past year or so. Geno’s Garage recommended the suction side filter. It is a simple universal 3/8” fuel filter that is installed between the suction side of the pump and the tank.

Now the question is: what should be done with the fuel that’s in the tank? There could be a considerable amount of contaminants in the tank.

 

[AH64ID]

Could it be a filter that didn’t like trace amounts of water, or possibly failed internally?

Maybe pump some fuel into a clean bucket and see how it looks.

 

[BigPapa]

I’m guessing you’re referring to this filter from Geno’s. I found the description below on Glacier’s website. It looks to be a strainer that the aftermarket fuel system manufacturers recommend to protect their pumps from a bad tank of fuel. From the sound of it, it did it’s job. How long had it been on the truck?

From Glacier’s website:

 

[PLohr]

BigPapa,
Thanks for your help with this. I used a standard fuel filter rather than the strainer that was mentioned above. That could be part of the problem. I looked through my maintenance records and found that the filter was installed within the past 6 months (I don't have information more precise than that). The truck doesn't get driven much so the filter hasn't seen a lot of miles.

 

[BigPapa]

Well, at least we know what the problem was. As I said, sounds like your little filter did it’s job keeping trash out of your lift pump. With it happening after your top off, I’d suspect the fuel in the tank is contaminated. I’d pump, siphon, or somehow remove the fuel into something you can see into and see if it has trash or water in it. If it does, I’d drop the tank or lift the bed and completely clean the tank out. I’d also replace your OE filter if you haven’t already.