512 BBi ignition problems

>>It idles near perfectly, at around 1750 rpm<<

WAY TO HIGH...

Idle speed has to be 1000-1050

Check Timing again...wouldn't hurt to check advance curve either.

However if one bank in particular is back firing this may indicate a Fuel System Pressure Issue on that side. Ot would be helpful to know the Fuel Pressure readings from both banks .

JRV

Coach,

Sorry for the questions with questions, but...

When she backfires, do you mean through the exhaust or intake?

Does she backfire or one side, or both?

What are the CO/HC readings at idle and at high RPM when the backfire occurs?


Regards,
David

David, it backfires from the 1-6 bank, which is the driver's side exhaust. It actually backfires from the exhaust, not the intake...I am almost certain. CO reading is about 1.2 to 1.6, but the idle is 1750 on my optimistic tachometer. The diel screws are in as far as I can push them in without closing them completely. Next I guess fuel pressure measurements...

JRV what would cause the idle to be so high?

>>The idle screws are in as far as I can push them in without closing them completely<<

Crap !!

One of two things seems likely..Timing is too far advanced...this must be checked and reset if necc. first.

First check and reset timing, then we can go from there to the only other possibilty besides a throttle cable holding throttles open..you can easily check cable for slack.

Regards, JRV

(James Here). JRV, do you have the specs for checking/adjust the timing? We have a timing light, but we do not have the proceedure for doing so.

I guess it is possible that it has jumped a tooth, would anything else cause the timing to be that out of whack?

James

Hi James, (have to move this thread and start a new one in Tech Section..it's taking too long to load.)

no timing doesn't jump a tooth it migrates higher.

On the right side Bell Housing there is a cover plate that exposes the Flywheel and timing marks. Pul the little cover, hook TL pickup to #1 plug wire, hook other leads to 12V+ and Ground. In the hole you will see a pointer and the flywheel, set Timing to 10 degrees before PMS by loosening at then rotateing Distrib. As you near correct timin the idle will fall and may need to be reset (will need).

JRV

[coachimi]

just saw this thread from 2003. I dont remember if I had posted the solution to the whole problem was that the two alternators needed to be rebuilt. Once rebuilt, the car has run very nicely and nary a single backfire. Go figure. I spent a fortune and several shops tried to fix it, to no avail. I finally got a tip from another Boxer owner about the alternators.