Re: 1981 XJ-S ECU Repair?

[Mike Morrin <mike_morrin@tait.co.nz>]

jnuttall@julian.uwo.ca wrote:
> 
> Three months ago I asked the list for suggestions on curing the poor
> cold start syndrome on Paul's 1981 XJ-S. This is a somewhat uncommon
> car. It is one of probably only a few hundred pre-HE vehicles to have Digital P
> Jetronic fuel injection. Apparently this type of car had European specifications
> and was not sold in the US, but this one ended up in Canada.

I would like to know if the Pre-HE vehicles with Digital P performed any
differently to vehicles with D Jetronic.  In particular, how did the
fuel consumption compare?

Does this vehicle have oxygen sensors (if european spec, I expect not)

> 
> Thanks to Matthias, Dick, Greg and Michael who responded with
> suggestions on the cause of Paul's trouble. Paul has now found time
> to investigate, and it seems that Michael, who suggested a dud ECU,
> was probably correct. Paul has tried replacing the ECU with one from
> a 1986 XJ-S HE. The cold start problem goes away but, not
> surprisingly, the car does not run well in other respects.
> 
> Paul therefore wants to repair or replace his 1981 ECU. It is
> possible to buy a new one or get the old one rebuilt, but the expense
> is significant. Quite possibly only one or two components in the ECU
> are defective. Is it possible to obtain a circuit diagram and/or
> other information for the ECU which would enable an electronics
> technician to diagnose and repair the defective ECU?
> 
The repair (and testing) of electronics boxes like ECUs is very
specialised, and I would only trust a technician who is very familiar
with the things in general, and preferably this box.

I spent several years doing similar work on electronic ignition systems,
mainly on Japanese and European motorcylcles, and I know how easy it is
to destroy a box you are not familiar with.

regards,

Mike Morrin

1975 XJ-S
1968 XK150 FHC
> John Nuttall
> 
> jnuttall@julian.uwo.ca
> 
> 1977 XJ-S
> 1979 XJ-S - parts

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References:

• 1981 XJ-S ECU Repair?
• From: jnuttall@julian.uwo.ca

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