250 HPDI, bogging at high RPMs

[Neilslure]

My 250 HPDI is bogging/surging a little when it gets over about 5400-5500 RPMs. My initial thought was fuel filters as they were about due to be changed. I have changed them all, VST and strainer were spotless, clear bowl filter had a few specks but otherwise clean. The water seperator in the bilge had about 10 hours when this started so I doubt that is the cause. Bulb stays firm. It idles fine and runs perfect until it gets to 54-5500.

Any ideas of what it could be?

[Stratos21XL]

this is probably a dumb question but have you checked or changed the plugs lately? If so then I would check the low pressure fuel pumps, I think the HPDI's only have two of them on the side by the VST. they also have the small screens or commonly know as the "secret filters" that could be something to look into as well. I think there is a sticky posted at the top of the page about them.

This is the link for the filters/screens.
http://www.bbcboards.net/zerothread?id=630903

[Neilslure]

If it were plugs, wouldnt it perform poorly at all RPMs?

[Stratos21XL]

you would think it would. Here's what happened to me. I did a shock treatment with ring free on motor. The second time out my motor ran like crap on top end, very similar to what you had posted. I got back to the ramp, got the boat out of the water and pulled over in the shade and started pulling the plugs one at a time. There were tiny carbon fragment all over the tip and electrode of the plugs. I went and bought new plugs, put them in, and trouble was gone. I was back up to 5900 RPM's where it should be. just saying it might be worth a shot in checking them, there cheap to replace.

[Neilslure]

[Neilslure]

Gonna try some new plugs tomorrow, if that doent work, its going to a dealer.

A buddy of mine that is a tech at a major maine dealer suspects that it is something fuel related.

[Yatesville Junkie]

Not sure if the HPDI has an O2 sensor, but if it does, thats what it is. I have an OX66 and I changed everything before the O2, big mistake and costly too. Check the O2 sensor.

[Batman]

Follow the link posted by Stratos21XL. My 300 HPDI did something similar. I removed the 4 screens and soaked them in Sea Foam and reinstalled and it now runs great. Take your time and follow the instructions and in 1 1/2 hours you can be headed to the lake.

[Rich Z]

http://www.bbcboards.net/zerothread?id=630903

[Neilslure]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by Stratos21XL &raquo;</td></tr><tr><td class="quote">you would think it would. Here's what happened to me. I did a shock treatment with ring free on motor. The second time out my motor ran like crap on top end, very similar to what you had posted. I got back to the ramp, got the boat out of the water and pulled over in the shade and started pulling the plugs one at a time. There were tiny carbon fragment all over the tip and electrode of the plugs. I went and bought new plugs, put them in, and trouble was gone. I was back up to 5900 RPM's where it should be. just saying it might be worth a shot in checking them, there cheap to replace.</td></tr></table>

Stratos21XL is right on the money.

The day I first noticed this, I did add Sea Foam to my gas, it was a bottle I had laying around for a while so I poured it all in. Usually I use Ring free every few tanks. Yesterday I emptied my boat getting ready to haul it to a dealer. I had ordered plugs from the Auto part store Sunday and they were due in today so I didnt have a chance to run them. I talked to my dealer this morning and asked if he thought it may be the plugs, his answer was good enough to talk me into changing them and a quick lake test before making the 2 hour drive. I left work early, picked up my plugs, a quick change in the parking lot at the ramp and I was in the water. All the plugs had a little carbon with the 2 center ones being a bit heavier. I ran the donkey snot out of it, all seemed well, I just wish I would have carried a few rods with me since I no longer needed to drive to the dealer .

[Stratos21XL]

Sweet!!! I am glad that got you fixed up. It's amazing how well the de-carb products work to break up carbon, the drawback to that is not all of it makes it out of the engine through the exhaust.