Engine Check Light came on

[CAT Lover]

Originally Posted by kketterling

Today we put a pressure gauge on the fuel line and got about 68 psi but when I put it under a load it dropped to 62 and then would bounce back to 68 and it did this a number of times. So tomorrow we are going to test to see if I possibly have a slight blockage in the fuel line way back at the 90 by the tank or elsewhere. Then next we'll see if there is air in the line. This is very frustrating to say the least.

That sounds like the rock filter. I'm not sure about RV's but, some trucks that used CAT 3126, C7, C8 and C9 motors had an inline filter that ran between the fuel tank and fuel filter. Not many people outside of the factory or service center knew this. It would clog up and people would experience power loss and could not figure out why. Most people removed them.

[kketterling]

Update: Today we disconnected the fuel line at the primary filter and blew back to the tank with the intent of clearing any obstruction in the line. We then primed the fuel line and started the coach to ensure there was no air in the line. We noticed this time when the engine was off and priming via the hand pump that the pressure guage would register some pressure with each pump. It didn't do that before.

Right now we've run a line to the drivers seat so I can read the fuel pump pressure while driving down the road. If it still stutters while driving I can observe if fuel pump pressure is fluctuating. Pressure idling right now is around 68psi. Heading to the mountains Wednesday so will be a good test to see if stuttering still exists.

[2016RoadglideCVO]

Hi guys,
Just found your thread about the dreaded check engine light. I have the same coach with a C9 and on out trip south to the Baja have been getting the code SPN 157 FMI 17.

Everything seems to be running fine though. Each time I get the code I pull over, shut down the engine, restart it after 5-10 minutes and the code is gone. It seems I get the code on a long haul uphill or on an extremely rough part of highway like I5. I had the oil changed in April this year.

By reading your posts, you guys know a helluvalot more about mechanics than me. I don't know if I should go to the Kenworth shop in La Paz and have them change the filters or what?

Mr. Kettering, did you find a solution to the check engine light? Sounds like I have the same issue with the C9.

Could you let me know?
Thx

[kketterling]

Newintown: For the most part the engine check code was resolved when Cat replaced a weak injector. Code only reappeared once after that and Cat replaced some more sensors which I don't think it did anything but we did it anyway.

What I've been plagued with since the injector change is a stutter in the engine when under a hard load but no code appears. I think I've resolved this by blowing back in the fuel line to the tank via the hose right before the primary filter. The thought was that maybe a few flecks of dirt collected at the elbow coming out of the tank. That seemed to be reinforced by the fuel line pressure when we tested that. I did some hard pulls with the coach this week and did not get any stuttering so I have my fingers crossed that was it. I also wonder if the fuel restriction might have had anything to do with the injector demise.

You can start with the filters as a first step, but from what I've read, dirty filters typically will not throw codes. Let them run diagnostics on it and see what it says.

Engine needs fuel, air and compression but a lot of things to check. Good luck and keep me posted. May need your findings to help me resolve mine if issue persists.

[Captjake1]

Glad it seems to be resolved thus far!

[2016RoadglideCVO]

Thx Ken, I checked my log book, both filters were replaced 10,000 miles ago by the previous owner. I am doing several short runs in the next few days. I am going to contact my CAT dealer at home and have a yak at them again.

Will let u know if anything develops.