Cranking but not starting.. fuel pump relay?
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Northstar Engines and System Technical Discussion Discussion, Cranking but not starting.. fuel pump relay? in Cadillac Engine Technical Discussion; I've got the dreaded "it cranks but wont start" problem. It always eventually starts, and it doesn't matter whether the ...
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    99esteees's Avatar
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    Cranking but not starting.. fuel pump relay?

    I've got the dreaded "it cranks but wont start" problem. It always eventually starts, and it doesn't matter whether the car is cold or hot. The engine doesn't miss out, nor does it ever stall. I checked the FPR and it checked out good, but I went ahead and replaced it. I'm doubting it's the fuel pump, and I am starting to wonder if it could be a bad fuel pump relay. Is this a possibility? Can anyone help me locate this sucker so I can get it replaced? Thanks

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    weister42 is offline Cadillac Owners Enthusiast
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    Re: Cranking but not starting.. fuel pump relay?

    The relay is in the relay box in the engine compartment.

    Does it start easier when you press on the gas pedal? If so then you probably have the same exact problem as me - seeping fuel injectors. I start having the crank but not start thing and I don't have a faulty FPR but I replaced it anyway just like you . Problem didn't go away and I replaced the fuel pump relay like you did . Problem didn't go away and I had a mechanic cleaned my fuel injectors. Problem didn't go away and replaced a leaking fuel pressure release button. Problem got a little better but it's still there. Took it to another mechanic and he told me all 8 of my injectors are seeping gas, so if I let it warm up then park for more than 30 minutes she starts in a rich fuel condition. Depress the gas pedal(opening the throttle body) would help clearing out excess fuel. If I park for 4 hours or so she'll start fine.

    My mechanic told me he has never seen such a thing, but he told me all 8 injectors are bad.

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    Re: Cranking but not starting.. fuel pump relay?

    Quote Originally Posted by weister42
    The relay is in the relay box in the engine compartment.

    Does it start easier when you press on the gas pedal? If so then you probably have the same exact problem as me - seeping fuel injectors. I start having the crank but not start thing and I don't have a faulty FPR but I replaced it anyway just like you . Problem didn't go away and I replaced the fuel pump relay like you did . Problem didn't go away and I had a mechanic cleaned my fuel injectors. Problem didn't go away and replaced a leaking fuel pressure release button. Problem got a little better but it's still there. Took it to another mechanic and he told me all 8 of my injectors are seeping gas, so if I let it warm up then park for more than 30 minutes she starts in a rich fuel condition. Depress the gas pedal(opening the throttle body) would help clearing out excess fuel. If I park for 4 hours or so she'll start fine.

    My mechanic told me he has never seen such a thing, but he told me all 8 injectors are bad.
    Wow, thats a big mess right there. The likely hood of all 8 injectors being bad sounds absurd, but who knows. My problem is not helped my pressing on the gas pedal. It does it whether the car has sat 5 minutes from a 3 hour trip, or 8 hours in the freezing cold. I've yet to change the fuel pump relay actually. I was looking at the relays, and I seen a STRT1 and and STRT2, but nothing about Fuel Pump under the hood.

    My fuel pressure tested fine. I'm going to test it while cranking tomorrow. I'm hoping the fuel pump relay might just be the problem.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Cranking but not starting.. fuel pump relay?

    Quote Originally Posted by weister42
    My mechanic told me he has never seen such a thing, but he told me all 8 injectors are bad.
    I've had several injectors leak on me, causing a backfire on startup. I think the northstar injectors are just prone to leaks. Mine didn't even have 70k on them.

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    Re: Cranking but not starting.. fuel pump relay?

    I believe and someone correct me if I'm wrong, but if you have a faulty oil pressue sending unit, it could cause you the same problems.

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    Re: Cranking but not starting.. fuel pump relay?

    Quote Originally Posted by Pjs
    I believe and someone correct me if I'm wrong, but if you have a faulty oil pressue sending unit, it could cause you the same problems.
    That would be nice to know. I have replaced the fuel pump relay, and FPR with no luck. I am getting no fuel pressure with the key in the ON position, but I get 40psi with the car running, once it finally starts. This is VERY aggravating.

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    Re: Cranking but not starting.. fuel pump relay?

    No fuel pressure with key on means that the pump is not being energized during the crank cycle (key on), so you have to build oil pressure to activate the pump. Look at the relay again. Is it the right one? Are the contacts lean? Check the circuit. I think you have the gremlin cornered. A FSM will be invaluable at this point.

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    Re: Cranking but not starting.. fuel pump relay?

    Quote Originally Posted by Ranger
    No fuel pressure with key on means that the pump is not being energized during the crank cycle (key on), so you have to build oil pressure to activate the pump. Look at the relay again. Is it the right one? Are the contacts lean? Check the circuit. I think you have the gremlin cornered. A FSM will be invaluable at this point.
    Got the relay from the dealer, and it had no effect. I tried changing it with other relays, which are all the same part number. Contacts are clean. I'm narrowing it down to either a bad fuel pump, or bad connection somewhere between the fuse box and the fuel pump. It's definitely a gremlin somewhere.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Cranking but not starting.. fuel pump relay?

    Didn't you say it eventually ran when cranked enough? That has to be the relay circuit. When oil pressure builds, it clicks the oil pressure switch on, which bypasses everything and turns the fuel pump on. If it runs, the fuel pump is fine, and the wiring to the fuel pump is fine. It's the circuit that controls the relay that's giving you problems...

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    Re: Cranking but not starting.. fuel pump relay?

    Yes it always eventually fires over. The relay must be fine. How can I further diagnose the circuit myself? Is it possible?

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    Re: Cranking but not starting.. fuel pump relay?

    Sounds like the check valve in the fuel sender isn't doing it's job. It's there to keep fuel from pooring back into the tank after shut off, and maintain residual pressure in the lines until the engine is started again. If this checkball is bad, it will effectively drain the fuel lines dry, and you'll have to wait for fuel to be pumped back up though the lines all the way up to the injectors. Just a thought. I' haven't seen that too much on these cars, but it is possible.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Cranking but not starting.. fuel pump relay?

    Quote Originally Posted by 99esteees
    Yes it always eventually fires over. The relay must be fine. How can I further diagnose the circuit myself? Is it possible?
    When you first get in your car to start it.... and you turn the key to run (NOT start), do you hear the fuel pump turn on for a couple seconds? Listen closely.

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    Re: Cranking but not starting.. fuel pump relay?

    Thanks danbuc I will keep that in mind. Eldo, very rarely do I hear it. Although it does run from time to time. It's hit and miss.

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    Re: Cranking but not starting.. fuel pump relay?

    99 seville I assume?

    Fuel pump relay is in the "rear junction block". The relay is grounded through a black wire to a place called "behind right side of rear seat". Fuel pump relay signal from ECM comes to it from a dark green/white wire from pin 36 of the ecm, connector C2 (? if that makes sense?).

    Now what you can do is make sure the wiring at the fuel pump relay connector is working fine. Make sure it has ground and power. Check to see if the signal from the ECM is arriving there (on the dark green/white wire) when the key is put into run for the first time. You'll only see it for 2 seconds.

    If you're feeling daring, you can try connecting the "power" pin to the "output to fuel pump" pin to see if it turns the fuel pump on. If you do this, be extremely careful. Use a length of wire and just touch the two contacts. Expect a spark. If you short the wrong things, you'll blow the fuel pump fuse. No biggie.

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    Re: Cranking but not starting.. fuel pump relay?

    Sounds like a task that I'm not able to get into with the bad weather coming in. Might just let Cadillac take a look at it Monday unless the weather clears. I put a new relay in to no avail. Thanks for the diagram though.

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