5.9 Ian throwing codes but running fine

[FAC]

I figured I might as well tell the story so, I just finished a drive from Wisconsin to San Antonio, about 1250mi in two days. The bus ran fine except for two long cranks after getting fuel. It usually starts before you can count to one. This was about 5-6 seconds of cranking. No odd idle or anything once it fired. It was 10* when I left and I would get a warning light at sustained high loads but it would go out when I let off and as I got further south and it warmed up above freezing I couldn’t get the light to come on at all even intentionally. So I figured I would finish the drive.

About an hour left and I got a stop and warning light, I checked gauges and everything was normal. So I shut it down on the shoulder and restarted all gauges were good so I got back on and no light after that.

Now we are at my in-laws and I got a code reader and found 51-11 low fuel pressure and 100-1 low oil pressure
I’m assuming the 51 was the warning light and 100 was shut down light.

For the 51 I’m thinking I’ve got a weak pump or dirty filter and it is exacerbated in the cold. Seems straight forward enough to me

The 100 code I am not sure about, my dash oil pressure was at 25psi normal for my engine at cruise rpm 2200 ish and the code didn’t come back the last 60 miles or so.

Essentially I would like to know if I can check anything else before throwing parts at it? I have a multimeter and basic tools
Thanks for reading the whole Thing!

[Bon Voyage]

I’d start with changing the fuel filters and inspect them, change oil and filter and double check the oil pressure gauge. Also take a sample of oil for analysis.

After that go for a spin and keep the live data for oil pressure on the scan gauge if it allows it.

[FAC]

Thanks for the reply, I think that is what I will do

[fo4imtippin]

Similar stuff happened to me on the maiden voyage home. These cummins were retrofitted with fuel pressure warning systems as part of a recall thing. I changed my water/separator filter and the racor one on the frame rails, and the lights stayed off.

[Booyah45828]

51-11 is for low fuel pressure. The pressure sensor was an afterthought after they had issues with lift pump failure causing wide spread injection pump failures. It's nice that your bus had that campaign performed, as some didn't.

Anyways, seeing that code says the fuel pressure dropped below 3 psi, and that triggered the warning light. Start by replacing the fuel filter and water separator. Inspect what the fuel you pour out for algae or anything else that's funky. If nothing is found, you can install a new lift pump. What year is your engine as 2003 puts you in the window where they changed a lot. Before that they had all the pumps back behind the filter on the side of the block. Around 03 they had a few models that had a rare pump that was up front near the timing cover, and 04 is when they went to rear gear train and common rail.

100-1 was your shut down alarm. It's a 1 wire switch that is supposed to see oil pressure any time the engine is running. Might be a bad switch or chafed wire. If it's not active, pull the connector and see if it's wet with oil. If it's active, see if the switch is grounded with the engine running.

[FAC]

I will be picking up filters this morning and changing them out and do some snooping in them.
I do have the old style right pump near the filter on the block. I think that makes it a 2002 build date?

I will look for an oil pressure switch too

[Booyah45828]

That'd be an 02 then. Go with the airtex style "upgrade" pump. Factory was a carter 4070 style and they were hardly sufficient when new with a perfect system. The airtex is a lot better then the carter. Go with genuine airtex or delphi branded, or at minimum purchase one from a chain store with a warranty. I've swapped a lot out in the past.

[FAC]

When I swapped out the engine side filter I swirled a little magnet down in the bowl and got some sparkly metal powder. I feel like I dodged a bullet!
I don’t have time to wait for a genuine Airtex to get here. Orielly had the standard ignition brand airtex style pump with a one year warranty so I went ahead and got that one. Thanks again to everyone that helped

[Booyah45828]

I believe the ones from the parts store for a dodge truck will have different fittings then what's used on your bus. You might have to get creative mounting it, but it is a much better pump then the carter.

[FAC]

The banjo fitting and bracket lined up perfectly, it had the same plug on it too. my bus Had a barb fitting and a hose clamp on the inlet side so that was the only difference. for now I just hose clamped the line onto the quick connect fitting, I need to replace the fuel line and I’ll get barb fitting on there when I get home.