Hard starting '96 Seville STS - Advice sought
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Northstar Engines and System Technical Discussion Discussion, Hard starting '96 Seville STS - Advice sought in Cadillac Engine Technical Discussion; My STS is becoming exceedingly hard to start. We first replaced the engine temperature control gauge, then the fuel pressure ...
  1. #1
    larryntripp is offline Cadillac Owners Member
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    Hard starting '96 Seville STS - Advice sought

    My STS is becoming exceedingly hard to start. We first replaced the engine temperature control gauge, then the fuel pressure control valve. After replacing the fuel pressure control valve the problem seemed to be fixed for about two days. They it became even harder to start. We now speculate the check valve in the fuel pump is what has gone bad, as it becomes somewhat harder to start the longer it sits. The car runs fine, once started. Any other ideas or suggestions?

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    akaz87 is offline Cadillac Owners Fanatic
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    Re: Hard starting '96 Seville STS - Advice sought

    Quote Originally Posted by larryntripp
    My STS is becoming exceedingly hard to start. We first replaced the engine temperature control gauge, then the fuel pressure control valve. After replacing the fuel pressure control valve the problem seemed to be fixed for about two days. They it became even harder to start. We now speculate the check valve in the fuel pump is what has gone bad, as it becomes somewhat harder to start the longer it sits. The car runs fine, once started. Any other ideas or suggestions?
    Ok, let think about this. 3 problems that it could be and you elimiated one. The fuel pressure regulator was changed out correct? If so, which would be my first guess, then its proably your fuel pump. I am thinking maybe not though. Do you have a pressure gauge at your house? If so, pull your whole fuel rail up and hook your guage up to it. The fuel rail takes maybe 20 minutes to pull. Next turn your ingition on so you get a full 50lbs in your guage. Next shut it off and watch the injectors on the fuel rail. If one of them is leaking you will definitly see it. Keep watching with a flash light. There is about a cup that will leak out. The fuel rail has a cup to 2 cups at most. Anyhow,if you dont see any leaks at all and your pressure is still falling its your fuel pump. Sorry for so long, this is just the best way to check, without waisting any money. Another thing is the Fuel pressure regulator could possibly be bad. I could start the car and pull the pressure hose off the FPR valve. Let it idle for about 10 mintues and see if there is any gas coming from the nipple of the FRP, the top little spout. If not, and the injectors are leaking, you have an almost definit its the Fuel pump. It is worth check all this out just incase since the fuel pump is around $300.00. While your at it I will change the fuel filter, and all plugs and wires. Might as well get everything out of the way and done with. USE ONLY AC DELCO for the plugs and wires. The other plugs are just not made for cadillacs. If it does end up being the fuel pump, I could order it online at Autorock.com. They have really good prices on all cadillac parts. If you can get all AC delco parts, even the pump. Haha, I sound like a rep for them. Anyhow, if you have any questions at all go ahead and post and i'll get back to you as soon as I can.

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    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
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    Re: Hard starting '96 Seville STS - Advice sought

    Quote Originally Posted by larryntripp
    My STS is becoming exceedingly hard to start. We first replaced the engine temperature control gauge, then the fuel pressure control valve. After replacing the fuel pressure control valve the problem seemed to be fixed for about two days. They it became even harder to start. We now speculate the check valve in the fuel pump is what has gone bad, as it becomes somewhat harder to start the longer it sits. The car runs fine, once started. Any other ideas or suggestions?
    Get a fuel pressure gauge on the fuel rail (there is a screw on schraeder valve fitting on the rail just for this...) and watch the fuel pressure when cranking. It should come up immediately. The engine will still start immediately without the check valve at the fuel pump so it is not likely just the check valve. If the fuel pump is starting to fail it may build pressure slowly.

    The other thing to check is the fuel pump relay. Make sure it is pulling in correctly (touch it when the key is turned on to feel the "click") and check for voltage at the fuel pump relay feed. It may be a faulty or tired relay.

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