Author Topic: How do I know if it's too advanced? Runs ok. (Read 5054 times)

rallydiesel · « **on:** October 16, 2007, 09:36:29 pm »

I just put a replacement pump on and after timing it to 1.05ish, it smoked like a mofo and sputtered. It ran WAY better with the cold start pulled out than pushed in. So, I tried timing the pump advanced. Well, after much trial and error. the pump is set to 1.27 mm and seems to run much better.

My question is, assuming the dial gauge is correct, what other things would I be seeing if the timing was this advanced? Wouldn't I be hearing strange sounds? If those numbers are real, is the pump worn to crap?

QuickTD · « **Reply #1 on:** October 16, 2007, 10:34:03 pm »

That much static timing on a properly functioning pump would probably be pretty noisy.

The numbers could well be real. Low housing pressure due to stuck vanes or wear in the transfer pump will cause retarded dynamic (running) timing. Using an ordinary banjo bolt in place of a proper "OUT" bolt on the return fitting will cause similar problems. Housing pressure is used to actuate the hydraulic advance in the pump, anything that causes a loss of housing pressure will also cause a loss of timing advance, particularly at higher engine speeds.

A very worn plunger/head might also cause retarded timing at low engine speeds but would probably manifest itself as very poor hot starting long before the loss of advance was noticed.

fatmobile · « **Reply #2 on:** October 17, 2007, 12:27:35 am »

Yeah, too advanced makes it noisy.

rallydiesel · « **Reply #3 on:** October 17, 2007, 07:47:10 am »

Hmmm. I put in new nozzles when I switched pumps. I never had the injectors recalibrated before putting them in. Is it possible the new nozzles have increased the pop pressure such that the pump timing needs to be way advanced? I am going to have the injectors tested today to make sure.

jtanguay · « **Reply #4 on:** October 17, 2007, 11:59:49 am »

Quote from: "rallydiesel"

Hmmm. I put in new nozzles when I switched pumps. I never had the injectors recalibrated before putting them in. Is it possible the new nozzles have increased the pop pressure such that the pump timing needs to be way advanced? I am going to have the injectors tested today to make sure.

i wouldn't think that a worn injector spring would ever give a higher pop pressure. you'd expect the spring to become weaker over time, and thus inject fuel a little earlier. what could happen, is that one or two injectors may wear differently, giving uneven injection, which could make the engine run pretty rough.

rallydiesel · « **Reply #5 on:** October 17, 2007, 07:47:47 pm »

OK, I talked to a Bosch tech that tested my injectors. They popped a little low, so that blows up my theory. He said I most likely have a problem with my cold start advance mechanism. The pump is not exactly the same as the old one in that it doesn't seem to have the two stage cold start advance the original pump does. When I first pulled the cold start after attaching the cable, I think I pulled it too far and may have broken or over-rotated something in the pump.

I am going to take apart the cold start advance mechanisms in both the pumps and compare them and hopefully be able to fix the new pump using the old one as a guide. I really don't feel like paying the $900 to have the pump overhauled and recalibrated (although it almost, ALMOST! seems inevitable).

:cry:

rallydiesel · « **Reply #6 on:** October 22, 2007, 10:47:24 am »

Got her running! Sounds nasty with no exhaust or resonator :oops: The problem was just that I had turned out the fuel screw too much.

:twisted:

rallydiesel · « **Reply #7 on:** November 03, 2007, 07:26:03 pm »

OK, I replaced the head on the IP and cam plate with parts from the original pump. The original pump ran well at 1.00mm. Even with these parts the pump has to be set unusually advanced to run well. Only other thing pump wise could be the transfer assembly, but then I would think the pump would run like crap no matter how it was timed.

Only other thing I can think of is that I had the block decked and the cylinder head machined and the cylinder walls are slightly overbored (still in spec though), so maybe something is weird there?

Anywho, I will continue running it advanced as it actually runs quite well the way it is now. No loud clacking, minimal smoke and decent power.

:?

rallydiesel · « **Reply #8 on:** November 04, 2007, 12:46:10 pm »

I am beginning to think the TDC mark on the flywheel may have moved. :oops: In that, I mean I put on a new pressure plate and never checked if the dowels and bolt holes are in exactly the same place as on the OEM. I am definitely going to check TDC when I pull the pan and install the new oil pump.

Anyone ever heard of new pressure plates requiring punching a new timing mark on the flywheel?

bigblockchev · « **Reply #9 on:** November 04, 2007, 04:06:36 pm »

To be absolutely sure you have TDC you may need to pull an injector and use some kind of coathanger extension on a dial guage to fit beside the glowplug and touch the top of the piston, you can rock the crank back and forth to get TDC. Not real simple but definitive. Cheers Dan