740 no won't start

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  #21  
Old 01-04-2012, 08:20 AM
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Originally Posted by lambo
Something else I noticed is that there's no pressure at fuel rail when I crack it open after sittn a day from cranking on it, maybe main fuel pump is bad not pressurizing system enuff. Just asking, because my rover holds about 37 psi for days. Also what's the easiest way to install a permanent gauge at rail, just a tee and gauge , just trying to do some diagnostics to get this thing running again
As you can see it is difficult to diagnose problems on the net. I would suggest you find out what engine and FI system you have. There are no big secrets to these cars so you'll need to keep on plugging. As mentioned the key areas are fuel and spark. How many fuel pumps do you have ? Unless you have the Regina system you should have one in the gas tank and one under the car (main pump) below the back passenger door. As starters when you turn on the key you could hear both of these pumps work.I would as a normal maintenance item replace both the fuel pump relay and the radio suppression relay in the engine compartment attached to the cooling system bottle. The only other main sensor to consider is the crank sensor located in the back of the engine below the dizzy . This past summer I did some preventative maintenance on my wife's 89 740 with 315K miles. 2 new pumps , fuel filter , both relays and new crank sensor. Cleaned TB and IAC and reset TPS. Then timing belt , plugs , wires , cap and rotor. If it weren't for the ridiculous cost of fuel injectors I would have replaced them too. So work one at a time and see and let us know how you are doing.
 
  #22  
Old 01-04-2012, 11:23 AM
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Ok, yes 2 fuel pumps. With new pump relay installed I hear NO pumps working. Also no gas at rail. BUT when I jump the socket for relay, I hear both pumps and get lots of gas at rail. Just got noid lite to check injector pulse. Got spark and suppression relay test good
 
  #23  
Old 01-04-2012, 12:14 PM
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Originally Posted by lambo
Ok, yes 2 fuel pumps. With new pump relay installed I hear NO pumps working. Also no gas at rail. BUT when I jump the socket for relay, I hear both pumps and get lots of gas at rail. Just got noid lite to check injector pulse. Got spark and suppression relay test good
That would tell me the new relay is bad or the connections under the relay panel are a problem. Is the new relay a "new" relay or one from a salvage yard. Do you have the correct relay. Here is some more info Volvo Relays
 
  #24  
Old 01-04-2012, 02:28 PM
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He'll yeah, it's purring like a kitten. Contacts for relay needed cleaning for one. 2nd was terminals at coil needed cleaning also, wasn't allowing enuff juice to power it. All is well now. Thanks to all. I'll be back for sure
 
  #25  
Old 01-04-2012, 09:06 PM
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Yay! Apparently I need 5 characters or more to post, so that what this is about.
 
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