99 Buick Regal LS doesn't start when below 32 degrees


StumpedGMowner1
03-22-2017, 12:34 PM
I have been working on this car for way too long. The problem first started with a long start condition that progressively got worse and eventually became a crank but no start condition. Then one day when it was warmer than 32 outside it started and ran fine. After the temp dropped back below freezing the car wont start it just cranks. No misfire no backfire.

With no obd codes set i went at it head first. So far i have replaced the following: IAT, Cam sensor, Crank sensor, Coolant temp sensor/sender, ICM, All 3 coil packs, fuel filter, and the ECM.

I am stumped. Vehicle still wont start below freezing. Any ideas would be great. Just a reminder that at 33 this car runs and drives great.

brcidd
03-22-2017, 08:19 PM
Does it try to fire when you spray carb cleaner in intake breather? Is fuel pump running? does fuel pump generate adequate pressure?

If it fires when sprayed with carb cleaner, then you have a fuel delivery issue- most likely low or no fuel pressure.

When ignition turned on for 2 seconds, can you hear fuel pump running? if not pound on the fuel tank and see if pump comes on during ignition on 2 second interval- if it does, you have just analyzed your issue, and need a FP.

Tech II
03-22-2017, 11:48 PM
Simple diagnostics would have saved you a lot of money......spark, fuel pressure, injector pulse when it won't start?

StumpedGMowner1
03-23-2017, 10:52 AM
Lol sorry i forgot to mention the diagnostics i have already done. Did node test of all injectors. Did spark gap test on all plugs and fuel pressure was at 41 psi but i didnt have time to do a leak down test. Didn't do compression test because car runs great when it decides to start. I dont have a high pressure fuel relay in this model nor do i have a resistor in the wiring to the fuel pump. I have been a mechanic for 12 years. I have fixed countless cars over the years both foreign and domestic. This little bugger has me stump. Nothing shows up out of spec on the scanning equipment other than an O2 sensor heater and a bad wheel speed sensor.

Tech II
03-23-2017, 08:50 PM
But did you check for spark and injector pulse on ALL cylinders, when it didn't start? And fuel pressure when it didn't start?

Also, did you check coolant data, compared to ambient air?

StumpedGMowner1
03-24-2017, 08:19 AM
Ok so i finally figured this nightmare out. When it didnt start i was still getting spark and fuel within spec. What i wasnt getting was enough volume of fuel. Pressure was fine until the engine was cycled. It would drop off to 18psi when cranked. Ended up being a collapsed fuel line up the firewall. Thanks to all. Glade to be done with that one.

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