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Discussion Starter #1
Hey all, I've had no luck searching, so need to ask.

My '91 75TS 'misses' when hitting sharp bumps. I've tried the obvious things like ground and ignition connections, about to go deeper and look at the trigger pickup and fuel pump wiring. Problem seems worse when hot. It also has an original 90's vintage after-market immobiliser/alarm fitted (how do you sort that out??)

I heard there was a factory mod for the fuel pump wiring due to incorrect small wire size being used in manufacture - is this true?

Been to Craig's page, but wiring diagram is no longer available?

Any hints would be greatly appreciated.
 

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I have basically just rewired my '89 75 TS's fuel pumps because I thought I had a problem there. My wiring was exactly as per the wiring diagrams in the workshop manual and seemed very undersized for the job but almost certainly original.

In my case it turned out that the wire that went from the ignition switch (the green/black that is attached to the brown) to the starting relays had been cooked over time. Once I replaced that my problem finally disappeared.

I also removed the 'factory' alarm/immobiliser recently. It was not as hard as I thought as most of the connections were not actually solid connections. The installer had just bared the main wire and wrapped the alarm wire around it then finish off with tape! Start by pulling the horn wiring (with horn removed) through the firewall. Disconnect the few wires that tap into the ARC wiring and pull through to the drivers side. From there you can sort the connections to the fuse box and ignition etc. Don't forget the couple of connections in the engine bay just behind the intake plenum. They attached to fuel pump wiring and something else.

I had removed the steering column (was also replacing clutch m/c...) which made the job much easier.
 

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Discussion Starter #3
Thanks PtP, I think getting rid of the old immobiliser (Cobra?) would be a good idea. I'll check the ignition switch first though. Where are the fuel pump relays etc located that aren't in the fuse box?

thanks again.
 

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In the engine bay not far from the battery is four relays in a row. They are for;
1) Motronic (original part number ends in 113)
2) Fuel Pump (has a diode in it) (ends in 112)
3) VVT (113)
4) Aux Motronic (113)

Relays 1,3 and 4 are the same and very common but relay 2 is quite special. I was only able to source it in Perth direct from Bosch. That said, you can run the car with just the same relay as the other three and it will work but there is a reason the diode is there so I wouldn't recommend going without for long periods of time.

Also, try this site for the manuals;
Index of /alfa/75
 

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Discussion Starter #5
great, thanks. I cleaned the contacts on those the other day, wasn't sure what they did.
 

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Discussion Starter #6
Update: May finally have found the problem. The first plug/connector (rubber booted EFI-type) that attaches the trigger pickup to the wiring loom was intermittent. One of the three pins had been pushed back in the housing. Once re-seated all was good again. I've secured the connector as well as the large loom going to the adjacent four EFI/FP/VVT/EFI relays to prevent movement, as it also caused the engine to cut if wobbled aggressively.

Hopefully one more niggling issue resolved. Thankyou all for the assistance. :)
 
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