Excursion 12v/nv4500

[PToombs]

Check the screen in the inlet of the lppp, if you have no prescreen they can clog and starve the IP.

[Gots_a_sol]

For reference again:
Idles fine, but starts missing/stumbling when revved up.
Won't go past 2k rpm.
Billows white/white-ish gray smoke when revved up.
Fuel pressure sits at ~10 psi at idle, drops to 5 when revved up but will start creeping back up if you hold the rpms up for a bit. I was under the impression this would sit at 15 psi so that might be a clue (THD kit).

New low pressure piston lift pump, no change other than higher psi obviously.
New 5x12 fuel injectors, idles much smoother but it still had the stock injectors with 330k prior to this
LPPP pre screen is clear of debris.
Replaced the AN fitting on the lift pump with a hose barb with a hose going straight in a fuel can, no change.
Replaced filters for the hell of it, no change.
Fuel heater deleted
Checked the firing order just to sure and it is correct (had all the lines off when did injectors)
Pulled the nut off the timing gear and the woodruff key still appears intact.
Pulled the top off the afc housing and the little pin moves freely and the diaphragm was fine.

[PToombs]

Did you ever try changing the timing? Twist the pump towards or away from the head to see if it made a difference? I reread the last page and didn't see any mention of it. I wonder if the timing is way retarded and when you rev it up it's firing too late, after TDC?

[Gots_a_sol]

I have not or ever messed with the timing on this engine. I'll put that on my list of things to screw with next.

[spencerdiesel]

Did you check the IP gear when/if you killed the dowel pin?

[Gots_a_sol]

KDP was done years ago when the engine was in my dodge.

I removed the oil filler and removed the nut to check the woodruff key the other day and it appeared fine.

[spencerdiesel]

Shouldn't matter but what HG did you use?

[Gots_a_sol]

Felpro I believe.



I had the truck running today while messing with something and put pressure on the return line and it started running smoother. Hmm, grabbed some vice grips and clamped the line down a bit (not completely cut off). It raised the idle fuel pressure up to ~12 psi (could go higher if I clamped down on the line more) and wow, it runs normal again. Still hazes a bit, but it revs nice and cleanly now.

Also putting power to the ksb doesn't change anything


So the question is, is there something in the pump that is supposed to regulate the pressure some?

[PToombs]

Yes, the banjo bolt for the return line is an orifice that keeps the case full. It is possible it is bad, but it's more common on P-Pumps. If you have another pump or can borrow a friends bolt to try it do it and see if it helps. If there is a fuel shop nearby they may be able to test it, I've never had one done, or you can buy a new one.

[Gots_a_sol]

WELLLLLL


I pulled the banjo bolt out of the return and it is the banjo that is meant for the feed side (replaced that one with a tapped banjo for fp gauge). Apparently when I put it all back together I got the proper one mixed up. Now to find the stupid thing...

[Gots_a_sol]

Found proper banjo bolt and installed. Fuel pressure is a steady 15 psi and she seems to run nice and smooth. I let the tags run out last month so no test run yet.

[spencerdiesel]

Happy dance ?

[Gots_a_sol]

No pre mature happy dances here. I want to drive it first



I'm guessing I had the fuel injector or headgasket issue which I fixed then went and screwed myself up by mixing up the banjo bolts. Oh well, its not like I had just bought a replacement injection pump that shipped this morning, oh wait...

[spencerdiesel]

All that means is you put a 14mm H/R on this pump, run her till dead, and repeat

[Gots_a_sol]

Went and got tags back on it today. Annnnd...




Test drive was good. I have some tuning to do to compensate for the new injectors but alls good. Oh and I have no heat for some reason, I think the heater core is air locked.


I got the wastegate on the he351cw adjusted properly too (at rest it was sitting open about 3/16") and combined with the new injectors, wow, she feels a lot stronger than before. Me likey