Date: Sat, 20 Jan 2007 22:26:41 -0500
Reply-To: Bob Donalds <donalds1@VERIZON.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Bob Donalds <donalds1@VERIZON.NET>
Subject: Re: Ping/Knock/Detonation
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Its an interseting combinations of events. I guess an extented road
trip gives you the time to notice variations.
The 1.9 dist has both vac advance, retard plus centrifical advance. Most
check the timing at idle and asuume the rest
is ok but total advance is even more important to engine life, power and
ping than where it is at idle. You mentioned that you went with a rebuilt
dist, rebuilt distributors have a better chance of sticking centrifical
weights than the old fathful units that came out IMHO. Rebuilts have been
washed and lubed maybe once so they easly stick from lack of mantanance.
Mantanace? on a dist ? yes my friend right here in river city with the rotor
removed on the 1.9 dist you will see a felt pad inside the shaft it requires
a drop or two of 3 in 1 oil a couple of times a year to keep the weights
lubed and free just like the world famous 009 bug dist plus very other dist
installed in a bug from 1971 on.
To little advance can be just a leaking vac hose they do rot out and or fall
off. That reminds me that my 84 with a 2.1 thas a tee fitting that goes to
both the fuel pressure reg and the vac canister from the plentum. If it was
not 20 F and dark I might go check that on my own van.
The other possiblity that comes to mind is the fuel pump just like the
timing its most often checked at idle and pronounced healthy. The vaines in
the pump can wear over time 20 years in some cases and idle pressure is not
an indication of that the pump is doing under load with the injectors wide
open so to speak. Old weak pumps might only have 20 pds at 3K under load and
would show some loss just by reving the engine. lower fuel pressure sure
would cause a leaner mixture and ping.
I also seem to recall that when I first installed my 2.1 engine it ran very
lean untill I checked the continuity of the ground wire on the left head
from the coolant temp sensor the wire and connector looked just fine but
zero continuity.
As for timing the 2.1 engine I found 2 things 10 hp more power on a dyno
once you get to 3 or 4 BTDC. Number 2 problem you run into a higher idle
than desirable made worse by the fact that the engine speed screw will
bottom out long before the ilde comes down to a resonable 950 or so.
My conclusions
1) Check timing both at an idle and at 3K is best. When reved it should
total about 54 deg
2) TDC is a good place to set the timing on a 2.1 with the digijet system
3) Never trust a dyno reading to tell you where to set the timing (this from
the school of hard knocks)
4) check the fuel pump pressure at idle and at 2k
5) checking the exhaust gas with a 4 gas anilizer again at and above idle
can tell you lots about the injection system.
Another option would be a fuel air ratio meter with the wide band 02
sensor $300 ( how many hours labor is $300 at your local repair shop )
6) very few repair shops do the pin testing needed to see what the computer
is getting from the sensors threw the wiring harness AND blame the dam
rebuilder for a sh--ty job "must be the cam is in wrong send it back"
7) Ranting seeping in it is past the cocktail hour
8) my spell check does not work
9) Always carry a trash bag in your van and only you can prevent forest
fires
going faster miles an hour with the radio on
I remain
Bob Donalds
Boston Engine
all rights reserved
----- Original Message -----
From: "Michael Diehr" <md03@XOCHI.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Saturday, January 20, 2007 1:02 PM
Subject: Ping/Knock/Detonation
> I'm finishing up a long (3K miles) road trip and the van has been
> running like a champ (for the first time ever, wahoo!). However,
> I've noticed a problem with pinging (aka knock aka detonation).
> It's very particular -- it only happens at 1/2 throttle or higher at
> 3200 thru 3500 rpm, even on 91 or 92 octane gas. Happens most of
> the time -- only exception seems to be at temperatures of 30F and
> lower at 3000F altitude or higher, which seems very consistent with
> it being ping (heat & pressure related).
>
> As far as I know, the timing of the engine is good at idle, but I
> doubt that the advance has ever been tested.
>
> This is a 85 westy automatic with a newly rebuilt 2.1L block
> installed (about 5k miles post rebuild). It has the stock 1.9FI
> system, including a rebuilt computer & distributor & afm.
>
> It seems weird to me that the RPM range is so specific -- it really
> only does it at that particular RPM range. Any ideas? Bad
> distributor advance? Flat spot in the AFM? 1.9L FI system not
> well matched to a 2.1L block?
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