Volvo: 1990 Volvo 240 keeps shutting off/loses signal to injectors, volvo specialist, crank sensor

Question
QUESTION: I have a 1990 volvo 240 that has sat for nearly 4 years due to a blown rear main seal. I took it to a mechanic to get it going again. They pulled the transmission and replaced the seal and stopped the leak. They also found that the crank sensor was bad (kind of melted)and replaced that as well. I just got the car back and when starting it, it will run (though kind of rough at first) then at some point, usually within 30 seconds it just shuts off. No sputter or anything just bam it quits. At the mechanic they showed me that they had one of the injectors disconnected and had a special little plug pushed into it that lites up when the juice is getting to it. You can see the light just turn off when the engine quits. They've checked practically everything from fuel pumps to fuel filters etc.. The fact that it runs pretty good after a couple of seconds then shuts off instantly tells me it is an electronic problem not a fuel problem. Some have suggested the ECU (brain) is bad. Any help would be appreciated as I have no other car and am up to $600 with this last mechanic and can't afford much more. I may have a mobile volvo specialist coming monday and bringing with him another ECU but he wants $90 just to diagnose it. Thanks in advance.

ANSWER: Jim,
Yes the ECM might be bad, wires sometimes fray. Look for a small relay that is called the radio supression relay black in color 1323592. That controls power to the injectors.

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QUESTION: Thanks so much for your help. It was the ECU. Put a new one in and she's running pretty smooth now. Engine sounds strong. Maybe you can help with a couple of other things? Got the check engine light still on. Getting a 213 code which points to the switch on the back of the throttle body. Pulled the throttle body off and it was all gunked up. The mechanic cleaned it thoroughly then re-adjusted everything involveing the linkage and the light went off for a few minutes then came back on. He's saying it's the 02 sensor. I'll change that and see if it works. Have no temp or fuel readings. The pegs don't move. Pulled the cluster and everything looks fine. Pulled the gas tank and the sender is shot. Completely corroded from sitting. I'll replace it as well. What could the no temp reading be? Thanks again. Jim

Answer
Jim,
I have seen the throttle switches that are all filled with oil fail. Replace the O2 see what happens.
The gauages most likely will be the wires at the cluster. Start shaking and testing them. The temp sender wire might be broken ground out the wire it should peg the gauge.