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Re: [T3] fuel injection poser

On 21 Nov 2003 at 6:23, pete schutza wrote:

> I've been working on a nagging problem with my '69 fastback relating to cold
> starts and running rich in general. It has been carbon fouling plugs and
> gets about 12 mpg. On cold start, engine lopes as if missing on one hole.
> THEN idle "hunts" between 1000 - 2000 rpm, THEN calms to the higher idle
> once fully warmed.

The first thing to check would be the charging system regulating voltage. Low 
system voltage will make the D-Jetronic FI run rich, which would produce all 
the symptoms you describe. Measure this voltage at the battery with the engine 
warmed up after a drive and still runnning at medium RPM. The voltage across 
the battery should measure 14.1-14.4V; if it measures below 13.5V replace the 
voltage regulator with a genuine Bosch 30-019.

This is a very common, and poorly understood, D-Jetronic FI system problem. 
Fortunately, it has a cheap and simple solution. I have VRs if you can't find 
one locally.

> To further compound my situation, I've learned that my 69 engine was
> replaced with a 70 engine that used a fresh air temp sensor instead of
> crankcase (oil) temperature sensor. The net effect is that I've got a wiring
> pigtail dangling where there should be a crankcase sensor (at the aux. air
> switch atop the crankcase).

It's probably important to verify that you have a consistent set of FI parts. 
In particular, you should have a matching brain and pressure sensor. You'll 
probably have to remove these to get the part numbers off them and record them.

> The following info that Dave Johnson offered has raised some questions:
> "The thermo switch does nothing until the engine temp reaches "a high
> activating temperature (+50 degrees F and 32 degrees F)"

Actually, the temp switch only turns on when it gets DOWN to a temp which 
varies depending on which temp switch you have.

> My 69 had a crankcase temp sensor and a clyinder head temp sensor.  Correct
> me if I'm wrong, both act to enrich fuel at cold start-ups, then leans the
> mixture as the engine warms to full operating temp.

Yes, that's right. They act together to give your engine the amount of fuel it 
needs depending on the engine and air temps. I think the different locations of 
the 70 temp sensors will not be a problem for you.  

> "The cold starting valve allows fuel enrichment - The valve only operates
> when the starter is operated with the temperature below that which the
> thermo switch operates".


>  " To avoid an over rich fuel/air mixture when starting a cold engine at
> temperature between + 50 F and + 23 F, it is important to hold the throttle
> valve fully open until the engine fires".
> My '69 has no cold start valve.  It starts very well without touching the
> throttle at all, but idles roughly until full warm-up. If I open the
> throttle it tends to flood easily. Has my footless starting been wrong all
> along? Should SOP be to put my foot into it?

No cold start valve was normal for 68-9, but the fact that your temp sensor is 
in the Intake air distributor means that you have a later ('70?) IAD. The later 
IADs have a cold start valve built into it; look at the lower right side. It 
may not be hooked up, however. That's probably fine.  

If it is hooked up, that may be part of the problem, if there's something wrong 
with the wiring. For now, just unplug the electrical connector and see if that 

Whatever way seems to work for you to start it will be fine. I usually give 
them a little bit of gas, but every car is different.

Jim Adney
Madison, WI 53711-3054

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