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SC400 takes longer to start up after fuel pump replacement

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Old 10-15-14, 01:55 AM   #1
blake96
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Default SC400 takes longer to start up after fuel pump replacement

So i just replaced my fuel pump as preventative maintenance on my 92 sc400 and now it takes double the time to start. Airtex OEM fit). What could it be?
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Old 10-16-14, 05:35 PM   #2
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Just put a new Airtex in my 93, and did the fuel pump ecu bypass and it starts in 80% less time. Aside from the bypass, tune-up and ECU is about all thats left.
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Old 10-16-14, 06:40 PM   #3
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I've tried pretty much everything to address the long-crank starts on mine. Plugs, wires, caps & rotors, checked coils, fuel filter, swapped in a used fuel pump, fuel injectors, fuel pressure regulator, charcoal canister, ECU capacitors, vacuum lines... None of it has consistently helped. For some reason, fuel pressure drops when the car is shut off, but every hunch has proven to be a dead end.

The two things that have worked consistently are:

1) A quick bump of the starter, wait a second, then turn the key again.

2) Fuel pump ECU bypass. Wait a couple seconds with key in the "On" position, then crank it. I've only done it by jumpering the pins in the diagnostics box at this point, not the permanent bypass.

Both methods bring the fuel pressure back up to where it should be. It may just be an unsolvable mystery what's allowing it to drop... I've exhausted all the likely culprits.
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Old 10-21-14, 06:14 PM   #4
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Do you have air pressure blowing out the gas cap when you refill at the gas station?
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Old 10-21-14, 06:34 PM   #5
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Quote:
Originally Posted by bigwhite View Post
Do you have air pressure blowing out the gas cap when you refill at the gas station?
Me or the OP?

Yes, I have what seems like excessive pressure (but no consensus that I could find about how much pressure is ideal) when opening the gas cap, to the point that gas will pour up and out of the spout when fairly full. That's why I looked into the charcoal canister, in case the venting system wasn't working properly. I haven't figured out how to disconnect that line at the tank end, though, and see if air will blow through.
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Old 10-21-14, 06:52 PM   #6
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The OP seems to have a worse case.
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Old 10-21-14, 08:06 PM   #7
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Quote:
Originally Posted by bigwhite View Post
The OP seems to have a worse case.
I doubt that. If I don't employ one of the two workarounds, mine will crank for 3-4 seconds before starting. That's definitely more than double normal, which is what the OP stated.
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Old 10-22-14, 05:58 PM   #8
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So do either one of you have pressure blowing out of the gas cap when you refill?
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Old 10-22-14, 08:24 PM   #9
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Quote:
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So do either one of you have pressure blowing out of the gas cap when you refill?
I can't speak for blake96, but I already answered that in post #5.
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Old 10-23-14, 07:51 PM   #10
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Must have overlooked #5, just wanted to make sure you had pressure on the system. I know there were some faulty gas caps.
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Old 10-23-14, 07:51 PM
 
 
 
 
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