The relays internal coil can overheat on these cars and the relay will open. It is rare but I had one do that. It left me downtown and I had to open it up and tie it shut with a shoestring.

Can you tell if the engine wiring harness ever been reworked? They had bad insulation that just crumbled away inside the covering. Check the gray connector on the firewall behind the top of the engine for an open place.

Another connector is on the ICU out there under the hood. Never ever, do you want to disconnect that unit on the ICU! If you are suspicious that it looks tampered with then there is where the problem is can be.

Harness and connectors can be a pain on older cars but less wire or wireless systems are sneaking onto and off the invention table. The new cars are using coded signals down a central power wire (to save harness costs) to control several components.

That will be fun to troubleshoot for what is bad.
Phil

How do you know it's the in-tank pump? Most 240s will run on the main pump alone (although it's not good for the pump).

What can turn the pump relay off (besides the ignition switch) is Fuse 12. Corrosion or weak fuse contact terminals can act just like turning the Key OFF (except the dash warning lights won't come on).

The 25Amp blade fuse near the coil can have the same effect -- but the warning lights WILL come on when engine stalls, unlike with fuse 12. This includes fuse Holder contacts and wiring from battery + terminal.

Ignition failures will also shut down the Fuel system, if a loss of Coil 1 (negative) pulses is detected at the ECU (try cleaning the coil primary terminals 15 and 1).


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

First of all, the in-tank pump is just a lift or feed pump...the car will not run on it. The main pump is under the car on the driver side.

The fuel pump relay could very well be faulty again depending on the quality of the relay although this is unlikely. More likely is the connections to relay (often the holder will even melt from the resistance), a bad ground or you are losing spark...no spark, no fuel pump "on" signal from the ECU. It does NOT sound like a main pump failure.