Gas in Engine Oil - HPFP or Injectors to Blame?

SnakNest · February 15, 2022

I have a 2017 Silverado with the 5.3 EcoTec, approximately 81,500 miles. I'll be dropping it off at the dealership soon for diagnostics (which I don't expect much of a result from), but wanted to get some opinions from other owners as well.

The truck has never displayed any CEL codes, no starting / drivability issues or anything of the sort. But I noticed when checking my oil the last few weeks before my most recent oil change that the level on the dipstick appeared to be going up. Hard to quantify how much as it's generally a little above full after adding 8 quarts at the oil change. No milky appearance to the oil and no coolant loss, and I thought the oil looked thin and had a gasoline smell when I changed it a week or two ago. Plus my gas mileage seems to be a little worse than it normally is for this time of year. So based that layman's diagnosis and lack of an oil sample analysis, I'm pretty sure I've got gasoline getting into the crankcase.

I purposely added less oil at this last oil change to make sure that the level was in the cross-hatch section of the dipstick (even after sitting for an entire day), roughly 1/4" to 3/8" below the full mark. After putting only a few hundred miles on, the oil level is already back up around 1/4" above full.

Assuming I'm right about there being gas in the oil, I'm guessing it's either the HPFP or injector(s) to blame; most likely the HPFP since I'm not having any issues with the engine starting or running rough, and it's not throwing any codes. Is my line of thinking correct? Has anyone else had a similar experience, and if so, how did you diagnose and/or solve the problem?

I expect the dealership to tell me nothing more initially than they want to pull a sample to verify that I have fuel in the oil (and most likely to first charge me to change the oil themselves and make me drive it for a period of time before I schedule another service visit to have a sample taken). Aside from that, my bigger problem is that I just don't have much faith that they're going to be able to diagnose the issue if/when they DO verify fuel in the oil, since it's not throwing codes or having drivability issues otherwise. I have never had any luck taking things in to a dealership when there's not a CEL / code for them to diagnose. If they can't tell me with any degree of certainty, I'd rather throw parts at the problem myself than pay the dealership to do it since I'm out of warranty. Hopefully this forum can point me in the right direction if it comes to that.

rlcole321 · February 15, 2022

Sounds pretty cut and dry, but most dealers think of us as "Don't no nutten", which we know is not the truth. Now if you have a good repour with a service manager, you might convey the scenario to them as you described it, and might take it from there. outside of that, you just have to tell them the details and if they don't receive it go somewhere else, but it does sound like the HPFP is leaking (if you do not have a leaking injector which would set off a misfire code). Well good luck, I'd like to hear the final fix on this.

SnakNest · February 15, 2022

Thanks. I dropped my truck off this morning with specific instructions for them to call me with a diagnosis or prior to starting any work that would incur costs beyond diagnostics, and I still haven't heard anything yet. Only a few hours left before the service department closes, so I should be hearing something soon unless they just forgot to look at my truck

SnakNest · February 15, 2022

Well, within a few minutes of my last reply the dealer called. I was told that the tech said my fuel pressure was checked and is running high, so they feel that the HPFP is the cause of the issue and recommend replacement. I'm not sure how exactly that explanation makes sense, but I guess I'll go with it. They're saying $600-$700 in parts, likely upwards of $900-$1000 including labor.

I had already checked into parts elsewhere to do the job, and $600 is about what I had come up with on my own. So now I just have to decide whether I want to make this a weekend project for myself, or have the dealer fix it.

Grumpy Bear · February 15, 2022

The pump is no where near that expensive. Does require a new HP pipe however. Gouge!!!

SnakNest · February 15, 2022

I haven't looked anywhere else yet, but the local NAPA was listing the pump at $350-$450 depending on the model, $45 for the high pressure pipe, and $25 for the intake manifold gasket set. I believe that's all I would need (?). I'll have to do some more research online to see if I can come up with better prices.

newdude · February 15, 2022

5 minutes ago, SnakNest said:

I haven't looked anywhere else yet, but the local NAPA was listing the pump at $350-$450 depending on the model, $45 for the high pressure pipe, and $25 for the intake manifold gasket set. I believe that's all I would need (?). I'll have to do some more research online to see if I can come up with better prices.

12697966 pump and 12677004 pipe for 5.3 and 6 speed trans.

12691963 pump and 12677006 pipe for 5.3 and 8 speed trans.

diyer2 · February 15, 2022

I figure I can do my repairs for 50 - 60% less than paying for it. I paid myself $100 or more an hour and know it's done right and I picked the parts. Now I'm getting older and it's a factor.

Good Luck

SnakNest · February 15, 2022

Thanks to newdude for the part #s!

I always prefer to do my own repairs as well, as long as it's something I can do without special tools (that I can't fake or make with relative ease) or diagnostics equipment. I actually enjoy working on vehicles, but I enjoy knowing that things are fixed correctly even more.

I don't have time to type (and nobody else wants to take the time to read) the horror stories I've experienced having my vehicles serviced at dealerships. It's been almost exclusively for warranty work. But those stories definitely weigh into my decision to do my own work, too.

TJay74 · February 19, 2022

Intake manifold has to come off to replace the HPFP, with that it only takes maybe an hour to replace it. You will need the high pressure pipe and the high pressure cross over pipe and of course the pump.

The intake manifold gaskets are reusable, but they also arent that expensive to replace either.

SnakNest · February 19, 2022

I got the pump changed. Delphi pump, high pressure pipe, and Fel-Pro intake manifold gasket set, all from NAPA - about $400 plus tax altogether. Took me about 3.5 hours from start to finish, but mostly because I was being extra careful to not break any weatherpack plugs or wire mounting clips, and I also spent a good bit of time making sure I found TDC on #1 cylinder before removing / installing the pump. I could likely cut it down to 2 hours or less if I had to do it again.

The wire loom retainers attached to the back of the intake cover are a motherf***** to get out, and closer to impossible to get back in; if I had it to do over again, I would consider leaving the cover attached to the wire loom retainers, but I don't know if that would allow access to the pump itself. I only got 1/4 reconnected (the one furthest on the passenger side) when putting the intake back in, because I was mostly concerned with making sure I didn't knock anything into the engine intake or get any foreign material on the new manifold gaskets. If I ever have the occasion to take it back off (hopefully not), I'll try to get the other retainers back in the cover. I think the only practical way to do it is to attach all of the retainers to the cover prior to putting the manifold in, due to the amount of twisting and turning you have to do to the cover.

One more note to anyone who does this: if you do remove the intake manifold cover, MAKE SURE YOU PUT IT BACK IN PLACE EITHER BEFORE OR WITH THE INTAKE MANIFOLD, AND DON'T PUT THE MANIFOLD BACK ON FIRST. You can't get the cover off or on while the intake manifold is in place. Ask me how I know .

Also, I referenced the following videos on YouTube to help me:

https://youtu.be/JxYxj6CRuls

https://youtu.be/XNh_A43V268

I drained a few quarts of oil out of the crankcase and filled it back in the crosshatched range on the dipstick so that I can monitor the oil level over the next few days / weeks and see if my problem is solved. I'll post back later once I know for sure. Thanks to all who responded for your opinions and advice!

JONBLARC7 · March 3, 2022

They say the high pressure pipe needs to be replaced but it doesn't. I replaced it the frist time I took it off. Then read on the corvette forums that most of those guys aren't replacing them. I've have mine off aleast two more times with failing HPFP's becasue TSP said I needed a certin size lash cap and I didn't measure I just trusted them. So I failed two pumps before found a thread on the corvette forums on how to measure for a lash cap. I have never bought a new one sense that first one. Now my motor is getting forged pistons and I'll use the line I already have.

SnakNest · March 8, 2022

I wanted to post an update in the event that anyone else comes across this thread in the future with the same issue as me.

I've now put over 600 miles on my truck since I replaced the HPFP, and the engine oil level hasn't moved at all on the dipstick since then. So I'd definitely call that a successful fix in this case.

Thanks again to all who offered input with this issue!