Fmi 157 spn 18

[JimT]

(08-21-2020 )SquareOne Wrote:  

(08-21-2020 )Hallmanhauling Wrote:  How bout if I replaced just the fuel pump head and not the rollers as well with it?

Hmm, that may be an issue. I wrote about this topic on here awhile back with my curiosity into the pump failures on these engines. Basically I wanted to know which came first...the chewed up cam/rollers or the plunger issue?

Unilevers ( like Mr. Hagg, another very knowledgable/respected member here ) had mentioned that the updated rollers come with a DLC coating on the pins which secure the rollers and allow them to rotate. The pins IMO seem to be the issue. From the limited pics I had seen of failures, it looked as if the roller pins would wear and cause the rollers to 'skip' along the lobes of the cam shaft thus causing major chewing of those components.

My original question (when the ceramic plungers were the supposed issue) was this -----> Was the erratic behavior of the failed roller and condition of the cam lobe the REAL cause of the ceramic plunger debacle?? In that instance, the real culprit would be the (now updated) pins which secure the rollers.

Now you got me thinking...

What if the fuel lubricated plungers, new and old, are the ultimate cause? Newer diesel is less suited for lubrication and air in the system, even just a tiny bit, could be enough to cause the plunger to hang up slightly. With the older ceramic plungers that might lead to plunger damage. But with both styles this could cause excess stress on the tappets and rollers. It's possible that, given enough time and possibly repeated hangups such as this, enough wear and stress could lead to significant damage to the tappets/rollers. This would explain why failures continue to occur even after they updated the plungers. If someone had access to enough data they might also be able to find a correlation between the average number of fuel filter changes and the average time to failure of a fuel pump, largely due to air trapped in the system (and contaminants) from filter changes.

Of course this is all speculation. I don't think anyone would be able to source enough data to test this hypothesis.

Anyway, I've let my mind wander enough for one day. As for the OP's dilemma, I'd venture to guess that no warranty coverage will be approved. They have way too many things they can blame you (or any shop) for doing wrong.