Mechanical pump timing, am I missing something?

[Crocky125]

So I just installed a reman db2-4970 in my 1993 6.5. (30,000km on engine, put a cheap reman in it to get it running at first and clearly the head and rotor wasn't replaced and I was getting hot start issues so I had some spare time and swapped the pump this weekend)

So I got it running where it isn't making any white smoke, but sounds a little to far advanced and especially when I check the timing by pushing in on the advance arm it dosnt have much change to sound. And I played with it a little more tonight and when I had it set to where it would stumble like I've read the throttle response wasn't the best and it would blow white and sputter. So am I missing something or is the sweet spot just that fine? Might retard it a little from where it is Now. Starts better when it's hot now. But I either have to cycle my lift pump to start it or hold the throttle down to start when it's hot, is that just normal with mechanical 6.5's?

Thanks

[More Power]

An experienced 6.2/6.5 owner can most times set the injection timing by ear. If the rattle sounds too harsh, it likely is, and the pump timing should be retarded a bit. There is about 2 degrees of timing change per MM at the scribe line on the pump flange.

You can apply 12 volts to the green wire connection on top of the pump to activate the "Cold Advance" solenoid. The engine rattle should get noticeably more rattle-y.

Otherwise, I'd recommend visiting a diesel garage to have them set the timing. Shoot for 3-1/2 degrees BTDC at 700-rpm on a warm (at op temp) engine.

Some engines appear to be difficult to set the timing on, or a little/lot movement at the scribe line doesn't make much difference. These engines usually have sloppy timing chains.

[Crocky125]

So I got an absolute no start when it was hot today and haven't been able to get it to start yet, worse than with the old pump now, anything that could effect that? Thanks

[More Power]

After eliminating all the basic ancillary fuel supply stuff, a worn out head & rotor in the pump can produce hard starts when hot (i.e. close fitting tolerances in the head & rotor have opened to a point that injector POP pressures cannot be achieved at cranking speed when hot). If it starts when cool, you're on the road to eliminating possibilities and finding the cause.

[Crocky125]

After eliminating all the basic ancillary fuel supply stuff, a worn out head & rotor in the pump can produce hard starts when hot (i.e. close fitting tolerances in the head & rotor have opened to a point that injector POP pressures cannot be achieved at cranking speed when hot). If it starts when cool, you're on the road to eliminating possibilities and finding the cause.


Started up just like normal once it was cold, no spitting or sputtering and ran good. Once hot it wouldn't start again.

[trbankii]

Sounds like you have your answer.

[Crocky125]

Yep going with faulty ip. Put old one back in and it's already a little happier, although it wasn't nearly as hot when I tried today, but the new one wouldn't start after just being idled up for 15 minutes with a couple minute break. Rock auto already said I'll be able to get a refund once returned

[Robyn]

The issue on the IP is that the re-builders are using junk head/rotors

The best choice is to go to a local diesel pump shop that is affiliated with Stanadyne and have one built up for you.

There are just far too many re-builders that clean, wash and install new soft parts in these pumps and sell them as REBUILT

The issue is the head/rotor clearance is excessive, and once hot the already loose parts get looser and then can't make pop pressure resulting in the no hot start.

Be sure the injectors are set to proper specs for the DB2 pump

Injectors set up for the electronic DS4 are set to a higher pressure and are not suitable for use with a DB2 unless reset to the lower pop pressure.

Good luck

[DickWells]

Be sure the injectors are set to proper specs for the DB2 pump

Injectors set up for the electronic DS4 are set to a higher pressure and are not suitable for use with a DB2 unless reset to the lower pop pressure.

Good luck[/QUOTE]

Well, heck, Robyn. I don't recall seeing that comment before! I've run original (replacement) injectors in my Suburban for years, and they're for the electronic pump. IIRC, way back, I had them popped, and they were somewhere in the 1900 to 2100 psi area. Is this too high for a DB2?

I see from this thread that Jim said the cold-start solenoid should be hooked up to avoid white smoke at startup. Sounds like I'm gonna have to put that second wire into service after all.:o Indeed, white smoke on start-up, a lot of it, has been a big bugaboo ever since I went mechanical.