[T3] Question about D jet idle issues 73 T3

William J catnine09 at dslextreme.com
Wed Jan 27 10:41:28 PST 2016

Jim :

 I'll answer what I can right below each suggestion you have offered. Here I 
will just say the fly cutting they did was just a slight amount to clean up 
the step no more than .001" . Now this was in 97 I'm sure at that time the 
fuel was much better.
----- Original Message ----- 
From: "Jim Adney" <jadney at VWType3.org>
To: <type3 at vwtype3.org>
Sent: Wednesday, January 27, 2016 7:47 AM
Subject: Re: [T3] Question about D jet idle issues 73 T3

> On 26 Jan 2016 at 16:05, William J wrote:
>>  I used a 72 case and heads I had here and it was the same exact auto 
>> trans
>> 1600 as the 73 the case and heads down to the PCV breather were the same 
>> .
>> However the stock pistons on both had the dished drop and the new set 
>> which
>> were Mahle were flat top yet at that time it ran perfect. I did used the
>> dist from the 72 and the vacuum advance from the 73 because the 72 auto 
>> dist
>> looked in better shape yet even timed at 5 BTDC I didn't have these 
>> issues.
>> I checked the timing and it does not jump around and is steady .
> I don't think you've mentioned how the car runs on the road. That's
> probably more important than how it idles. Cold idle is especially
> unimportant, although being in SoCal, cold really isn't very cold.
> Let us know how the car drives.
> Here are a few things you should check:
> 1) Make sure the mech advance is working. You can do this with a
> timing light while the engine is running; watch the timing marks move
> to the left as the rpms go up, and fall back when the rpms drop. Or,
> grab the rotor and twist it CW. It should move ~15 deg against spring
> pressure and then drop back smartly when you let it go.

    I have checked the mech advance both ways . The rotor snaps back fully 
and with the timing light it does advance smoothly no jumping and returns to 
5 BTDC at idle. I should also mention the vacuum adavnce unit does not hold 
vacuum , I noticed this in 2009 . I ground off the cans lip and found the 
diaphram was black and torn 1/3rd of the way around where the rod is 
riveted. I only screwed it back together to be able to hold the advance 
plate from moving . I have not been able to locate one.

> You're setting the timing to 5 BTDC, right? On a '72-3, that would be
> the 3rd mark from the left.
> Looks like this:   |    |    |  |
> Not like this:  |      | | |
> Right?

    Yes that's correct 3rd mark from the left the second mark is 0 degrees 
or TDC. Both the 72 pulley and the 73  pulley have the same marks.
> 2) Check the fuel pressure to make SURE it is staying constant while
> driving. Get a friend to watch your gauge while you're driving, or
> use a long hose so you can watch it yourself. If there's dirt in the
> tank, it can clog up the filter, allowing only enough fuel thru to
> maintain pressure at idle, but the pressure can drop as the engine
> demands more gas. I make kits to repair the overflow hose which is
> always broken by now. Driving with that hose broken allows water and
> dirt into the gas tank, which will cause all kinds of problems. The
> kits for a '73 are $33.

     I've only checked the fuel pressure at the engine with the RPM's high 
and at idle so I will figure a way to do it while driving . I understand the 
more load would only be while driving.
     Also I have driven it on the freeway last March and with the IAD temp 
connected up some hills and it never felt once that it was starving for 
fuel. I do want the kit we talked about this before. Just need the funds to 
do so .

> 3) Consider letting me rebuild your '73 distributor. The FI trigger
> points can wear to the point that they trigger erratically. I will
> check and adjust these in the course of a rebuild. Then you can
> return the '73 (505) vacuum can to that distributor. This costs $50
> plus the price of any major parts, if needed, but major parts are
> seldom needed.

    I took the 73 AH dist apart and replaced one slightly worn shim this was 
above the drive dog  and all the fiber washers since they were cracked . The 
weights and shafts and bushing had no wear and I cleaned it completely and 
lubed the advace weights and oiled the shaft and lubed the trigger cam. The 
Trigger points were NOS in 2000 and didn't show any wear . I was going to 
install the 73 AH dist but didn't soley because the braided ground strap on 
the AH is shorter than the 72 AF and the pertronix ign would set right on 
that ground and not seat . Also there is a small plastic ring on the shaft 
upper that the weights stop against on the AH that was cracked and fell 
apart I made a new one out of delrin the same exact size. I'm not certain of 
it's function, I assume it keeps the weights from contacting the metal shaft 
or it only allows the weight to move at rest to a certain point. Everything 
else in the AH looked like new. As I said can't locate the 505 vacuum can.
> 4) Check the resistance of each spark plug wire from dist to end. The
> resistive SP connectors occasionally open up and give poor running.
> Each should measure ~1000 Ohms. Replace any SP connector that
> measures infinity.

   I replaced all the plug wires and cap and rotor with all Bosch parts , 
grey 7mm high temp wires 90 degree cap boot's .
> 5) Pull off one SP wire from the dist at a time. Does the engine slow
> down the same amount from each one? If you find one that doesn't slow
> the engine down, there's a problem there.

  They all drop the same amount . I don't find a miss on any one cylinder 
even under load where it would really show up.
> 6) Check the coil nose, the inside of the dist cap, the rotor, and
> the SP connectors for spark tracks. Replace anything that's tracked.

  Coil nose has no tracks and is clean .

> 7) Check the condition of the SP wires. If it is hard and brittle,
> replace it. If you still have your OE wireset, don't throw it away:
> Almost everything there is reusable and better than anything you can
> buy new. I have good quality bulk wire which you can use to replace
> old hard wire.

 Have all new wires that came with the red resister ends , wires a braided 
metal core with red ends all measure 1K ohm. The coil wire is carbon fiber 
and the old one read quite higher in resistance than the new one.
> 8) If you get really determined, open up the brain and check
> resistances of all the components via the FI wiring harness. This is
> a lot of work unless you have one of the Bosch D-jet testers. One
> thing to look for is the fact that Bosch reduced the thickness of the
> pins on injectors at some point. It's only a couple of thousandths,
> but it makes for bad connections at the injectors. The solution is to
> CAREFULLY remove the female pins from the injector connectors and
> squeeze them down slightly so they grip the injector pins soundly
> again. This is difficult, frustrating, and time consuming, so you
> don't want to do it unless you actually have this problem. You should
> not have this problem if you still have the original injectors.

 I  have changed the injectors in 99 with NOS had the crimped braided german 
short hoses , Changed the fuel lines in 2009 and cut the stock crimps and 
used very expensive FI line I got from Bus Depot. . Also at that time I 
tightened all the injector plug terminals .
> Keith is a smart guy, but he's gone OCD on gas for the past couple of
> years. He may be right, but he's the only one in our group who seems
> to have any problems with modern gas. It's possible that there's
> something especially bad about the gas in upstate NY, but I doubt if
> that's the cause of your current problem.
> -- 
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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