Your fuel pump started acting up directly after washing the truck? Was it one of those automatic jobs that sprays the under carriage as you pull in? Regardless I'd probably be suspecting water got somewhere it shouldn't. Just sayin.

 

Fuel pumps do that. Here today, gone tomorrow. Most have to be towed from where they rolled to a stop.

 

unless you have a spare on board.

 

Yeah, there's that option. For myself I have to balance the fact that a good quality pump will go well beyond 100,00 miles and do I just replace it every 100k or roll the dice on that long trip that I have planned?
There is no wrong answer.

 

Not immediately after. I’d made it most of the way home before it lost power and started hicupping and blowing blue smoke real bad. I could hear the motor making a “knock-knock-knock” noise as I eased the clutch out in first to make a right hand turn which was my first “what was that” moment. I’d say it lost 2/3rds of its normal power at least but was technically still drivable. It was below freezing and wondered myself if I’d sprayed something I shouldn’t have. Never happened before but who knows. I might try to fire it up in the next day or two after it’s well above freezing and see if anything changes. At this point I’m hoping its just a bad pump that picked a somewhat convenient time to give up. Might be my imagination but it has seemed like the truck has been a little down on power and sluggish as of late. Fan clutch WAS bad and stuck on. Fixed that last week while doing the water pump and that made a noticeable improvement, but still seemed like it was down on power and the 6637 air filter isn’t THAT bad, although looking like it’s due also.

 

Hate to say it but that was a swing and a miss on that one. Swapping in a new pump didn't fix anything either. At that point I had no choice but to do what I should have done in the first place...run a gauge off the fuel bowl drain valve and see what the fuel pressure was doing. Leveled off at 62 psi idling. Curiouser and curiouser. I also pulled the tank sending unit since that's relatively easy on my truck. The shower head foot part had in fact broken off since the last time I'd taken it out way back in 2017, but it's plastic stem attaching to the bottom of the strainer housing was still holding on, so just the bottom round part is floating around in there somewhere. Unfortunately I'd filled the tank so there was no chance of fishing it out of there.

Now I am genuinely flummoxed. Nut on the IPR valve was on there tight. Jiggled the ICP sensor connector and "hello", something did in fact happen. It felt loose in the sensor and the idle spiked ever so slightly upon moving it around. Now I'm suspicious. Unplug it and find no oil in the connector. Don't think it was my imagination but it ran a little better and with less blue smoke with the sensor unplugged...tried low idle and a sustained 1000-1200 high idle both ways a few times, shutting it off and restarting each time and I do believe it ran worse with the sensor plugged in. Fortunately, I saved the original ICP sensor that I replaced with a new OEM one back again, around 2017 when I bought the truck. I noticed it didn't make the truck run better after replacing it back then with a new one, and realizing how much they cost and that there was likely nothing wrong with it, I threw it in my box of spare parts. We will see tomorrow what swapping the other sensor in does, but I ran out of daylight. I should note that it still did not run great with it unplugged, just noticeably better. This makes me a little concerned there might be other more complicated and less easy-to-fix problems going on with the high pressure oil system, and we might be back to theories about pumps being bad, just not the one I originally assumed. I also plugged in Forscan and got no PCM codes. With how bad it is running I would have assumed HPO/ICP problem would have tripped a code somewhere, which is was pointed me originally to it being a fuel pressure issue, since we all know there is no code that will get thrown for low fuel pressure since there is no sensor watching it.

Anyway, totally botched that diagnosis about the fuel pump. At 175k I assumed that was a slam dunk guess.

 

You at least got a code and CEL while the ICP was unplugged right?

 

Yeah, that tripped the CEL. It defaulted the ICP reading to 725 psi I noticed on my CTS2. Too bad I never added the fuel pressure PID to it way back when or I would have probably seen immediately the fuel pressure wasn't problem. It's a pretty worthless gauge IMO, until the truck starts acting up and you have to quickly start checking stuff off the list.

 

While doing the pressure test did you check for air also?

 

HMMMMM. Grounds for engine management and fuel supply pump corrosion free?

 

I think you might have nailed it.

Two things. I ran the tank low (like 1/8) which I usually don't do. Also, I pulled the sending unit from the tank and found the shower head broken off. Because the back of my truck looks like this, it's fairly easy for me to do this unlike with the pickup trucks. Yes, the tail lamp is upside down. That one broke and all I had was a spare passenger side one.



No idea when that happened but the working theory at this point is that it reached a critical low point and started sucking a bunch of air in. Today I swapped the other ICP sensor in, fired it up, and it didn't really fix anything. (I did however realize the yellow weatherproof grommet on the pigtail is gone, which explains why the pigtail jiggles around a little in the sensor) However I let it idle in the yard for an hour or so until it fully warmed up and went about some other business, and with the tank full again, it seemed to slowly smooth itself out and reduced the amount blue smoke. Took it for a 10 mile or so drive and while still not running fantastic and still getting a little bit of blue smoke, it was running almost normal again. Still stumbles a little and blows some blue smoke when the throttle is goosed in neutral. I think I need to figure out who sells that replacement pickup foot part and order one, but it appears it WAS a fuel related problem and running that tank too low can be a no-no and cause some real problems.

 

A lot of people just remove all that crap on the fuel pick up and install a tube union and short piece of SS tube to get to the bottom of the tank. then a piece of hose clamped on the return laid on the bottom and routed away from the pickup. That fuel pick up foot is way more trouble than it's worth, not to mention the filter screen and mixing chamber problems waiting to happen.

 

Yeah, it was like $40 for that stupid part on Diesel O rings. If I had a pickup truck where getting to the tank sending unit was a major ordeal, I could see doing the Hutch mods and adding a frame rail mounted filter setup so you never had to go back in there again. For me, I can have the sending unit out in 10 minutes so replacing the foot is easy enough. Getting that strainer housing apart without breaking it to clean the two little filters is a real pain the pecker though. 7 years and over 175k later there was not that much crud in them from the last time I'd looked at them.

 

The real trouble w/ the mixer is the mixing part. It dumps the return fuel there with the outgoing fuel and sends it back through the line. So any air bubbles it's picked up along it's journey, which with diesel fuel can be easy to do, goes right back to the front of the line for another ride. It's like that slow day at the amusement park when nobody shows up and you get to ride the roller coaster over and over and over. Sweet deal for riding roller coasters, not so much for air trapped in your fuel.