Northstar Engines and System Technical Discussion Discussion, 7 seconds before start., in Cadillac Engine Technical Discussion; Hi there. I was fortunate to get a 96 STS at a great price but ever since I got it ...
Hi there. I was fortunate to get a 96 STS at a great price but ever since I got it it will crank over about 7 seconds before a stumbling start. How would one correct this and how? And is this a Normal problem? Thanks in advance.
Sounds like a leaking fuel pressure regulator... most common cause of a rich condition at startup that will cause those symptoms.
With the engine idling pull the vacuum hose off the fuel pressure regulator and watch the vacuum nipple on the fuel pressure regulator for any sign of gasoline...there should not be any. The fuel pressure regulator is that small canister shaped device on the fuel rail with a vacuum line attached to it and the fuel return line exiting from it below... If the vacuum diaphragm starts to seep fuel it leaks down the vacuum line creating a rich condition in the intake manifold at startup that can cause a long crank and a stumbling start like you describe.
One other way to diagnose if it is a rich condition causing the problem is to hold the throttle wide open just before you begin to crank. Depress the throttle completely and hold it during the crank. This will put the PCM into a "clear flood" mode that turns off the injectors and stops the fuel delivery for a moment. If the engine starts instantly (or quicker) doing this then it is likely a rich problem caused by the FPR or a dripping injector.
If the FPR looks OK then unclip the fuel rail and lift the injectors up out of their pockets in the intake manifold so that you can see the tips of the injectors. Turn on the key to energize the fuel pump and watch the injectors for drips to see if one is leaking when turned of.
i recently had the same problem, thanks to the info on this forum and the helpful people,it was the fpr, when i unpluged the vacuum line i did not see any leaking fuel, it took about 5 mins for the fuel to show leaking but it came out eventually, once i changed it, it starts every time right away also no more black smoke when you jump on it
Fix the FPR and get the start to where it is clean. Then run the motor hard...several WOT accels to redline upshifts....to clean the carbon out...then evaluate the start up puff. If it is not using much oil I wouldn't worry about it at all. Sounds like a car that has really been babied and has a lot of residual oil and carbon in the chambers....needs to be "exercised" frequently to keep it clean the rings loosened up and mobil.