Hi Jones; It sounds to me as if your fuel regulator may be bad . But another thought is you may have a bad battery to engine block ground cable. Volvo had a recall a long time ago about this problem. Even though the hardware is tight, that does'nt mean the crimp connection is any good or has completely seperated from its contact. I know ,my ground cable bolt was tight, but when I touched it it literally came off in my hand . I replaced and re-routed it from the block going behind the power sterring hoses, up and over to the battery ground post. I also added a piece of wire to the pigtail ground wire that connects to the frame. After that no more problems. I checked it all out with my meter. good luck. Dan Metz , and please let me know what you found.
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Dan's 88 Volvo 740 GLE WAGON non-turbo