Injector pump, HPCA, timing...

[NH2112]

Friday night I put a new (good used) IP in my truck. Saturday I bled the lines and got it running, which took all day. Come to find out the HPCA solenoid's plunger had a bent tip and was sticking in the seat, not letting fuel out the return line and keeping the engine from starting. So, I just took the plunger out since the HPCA system isn't hooked up anyway, and it started right up. However, the timing is WAY advanced, both by sound and according to my pulse detector - when I put the new pump on I aligned its line with where the old pump's line was and injection timing was something like 18* BTDC. The old pump was set at 11*B, I think. Now, the new pump doesn't have enough movement to retard it far enough, and while the Cummins sound at idle is pretty darn cool, it makes for a pretty noticeable loss of power once I take off. Does my "free-flowing" fuel return fitting have anything to do with my drastically changed timing?

I've been thinking of replacing the timing set due to there being about 280-290K or so on the original set, and the difference between valve and injection timing has to be causing some problems, but I'm going to be getting rid of the truck in a few weeks and I'd just as soon not spend any more money on it (I do have a low-miles 99 6.5l that will be getting a gear drive, so conceivably I could use its timing set.) But I'm wondering if anyone has just retarded the pump drive gear 1 tooth to make up for an otherwise out-of-range IP? Is the drive gear even loose enough to do this? Or am I just asking for trouble, and would I be better off biting the bullet and putting the new timing set in, finding TCD for the IP, and making a new "0" mark on the boss and flange? I suppose that before I do anything like this, I should come up with a lumy probe adapter and check where combustion is taking place, as well as injection.

[arveetek]

I would repair the faulty HPCA system. That should take care of the timing issues. Most of the time, a worn injection pump and/or a worn timing chain will give you the opposite problem: you won't be able to advance the pump far enough to get it timed right. That's the way my engine was before rebuild. I had the pump hard over towards the driver's side, and it still wasn't advanced enough.

The injection pump relies on housing pressure to control the timing, though I don't entirely understand the system myself. With the mod you made, I can see why the timing would be out of whack.

Casey

[NH2112]

Thanks, Casey, I guess I'll check and see if I have a good top cover and put it on. The nerd in me wants to get an adjustable needle valve to thread in the top cover and experiment with how restricting the fuel return affects timing LOL

[dieseldummy]

What you have done by removing the obstruction in the return line is the exact thing that the HPCA does to advance timing. The lower the housing pressure, the higher the timng value. If you block off the return line enough the engine will fail to start or run, as you found out. If the return line is free flowing the timing will advance as much as possible. I would recomend fixing the HPCA you have or swaping around or something of that nature.

Justin

[NH2112]

I was under the impression that the HPCA solenoid pulled the plunger in when activated, preventing fuel from flowing out to the return line, and that the higher fuel pressure advanced the timing slightly. However, what you say does sort of make sense given what I'm seeing on mine. I got a good top cover off one of my junk pumps today but never had the time to put it on and mess with the timing after work. Hopefully 1 more day of driving it won't blow holes in my pistons :eek:

[dieseldummy]

During fuel economy experiments my rig I had ran with the HPCA activated for miles at a time. Might have hurt it, might have not...

[NH2112]

Well, I swapped a good top cover on tonight, retarded the injection timing to 14BTDC, and....it runs like doo-doo, doesn't want to start, you name it. So, sometime soon I'm starting over and checking all the stupid, basic things because I just know the problems are being caused by something minor that has a domino effect. This is where it'd be nice if you could do like you would with a gasser, get the crank & cam aligned at #1 TDC on the compression stroke, then make sure the rotor's pointing to the #1 plug (I don't trust the stamped lines 100%.) Hopefully it'll be a cheap fix!

[dieseldummy]

I hope ya get it figured out. I've never had a timing meter on mine, just set it at the factory lines and advance from there. That's cool you can establish a scientific baseline.

[britannic]

Is that 4* BTDC or 14*BTDC?


Originally posted by NH2112:
Well, I swapped a good top cover on tonight, retarded the injection timing to 14BTDC, and....it runs like doo-doo, doesn't want to start, you name it. So, sometime soon I'm starting over and checking all the stupid, basic things because I just know the problems are being caused by something minor that has a domino effect. This is where it'd be nice if you could do like you would with a gasser, get the crank & cam aligned at #1 TDC on the compression stroke, then make sure the rotor's pointing to the #1 plug (I don't trust the stamped lines 100%.) Hopefully it'll be a cheap fix!

[NH2112]

Originally posted by britannic:
Is that 4* BTDC or 14*BTDC?

14*BTDC, measured with my pulse meter. 280-290K of slop in the timing chain does have effects LOL

[NH2112]

Well, Sat morning I attacked the problem and the first thing I noticed was a nice puffing out the #5 intake port while cranking :mad: "Great," says I. "A cracked valve seat, bent valve, etc." If it hadn't been for several of the washers on the exhaust flange being seized to the studs I'd have both heads off now, but I didn't have pliers big enough to work them off so the heads are held in with 2 bolts each till I can bring some good pliers home from work tomorrow. I'm also going to replace the timing set, it's not that much extra work since I have it stripped this far anyway and at 280-290K it's definitely due. So hopefully I'll have it all put back together this coming weekend and it'll be running like it always has, or better since valve timing will now be in sync with injection timing.

[dieseldummy]

Sorry to hear of your misfortune. Hope ya get it all taken care of, almost 300K is a heap of miles for anything. I'd most certainly be happy with that. My old '89 gasser made it to 275K before it died...