1985-1998 [Subscribe to Daily Digest] |
 | [Main 9000 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: Fuel Pressure Regulator - how to R&R Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 2 Apr 2009 02:50:55
In Reply to: Fuel Pressure Regulator - how to R&R, bmacb  [Profile/Gallery]
, Wed, 1 Apr 2009 17:28:31
Members do not see ads below this line. - Help Keep This Site Online - Signup
|
How fast an engine starts depends on a lot of things. The Fuel Pressure Regulator probably isn't one of them.
The FPR adjusts the fuel pressure as intake manifold pressure changes, so the pressure drop across the injector is always the same. If your FPR was bad, the car would run poorly - either too rich or too lean. Starting? Probably not an issue.
Yes, there is a check valve to keep fuel pressure up after you shut the car off. But that's only temporary. Fuel pressure leaks down over time with any valve, given enough time.
So what does influence starting? Fuel pressure, compression, air flow. What controls fuel pressure? The state of the fuel filter, and battery voltage. The fuel pump is electrical, and motors spin faster with more voltage. So if you have a low cranking voltage, say due to a tired battery, the fuel pump doesn't spin as fast when cranking. Obviously a clogged fuel filter produces more resistance to a fuel pump that isn't running at full power.
Compression - low compression makes for harder starting. This would be due to bad rings, or just general leaks. And battery voltage - the faster the engine spins, the quicker you get the compression up.
Air flow - the engine is an air pump. Not very efficient at the slow speeds of cranking. If your air filter is clogged, it's hard getting air at slow cranking speeds. At higher speeds, (like idle and above), the clogging is somewhat overcome.
So, if the engine is cranking slowly, think about a fresh battery.
Second - try this trick: Before starting the car, turn the key to ON, but don't start the car. Spend 2-3 seconds looking at the dash lights. This is the Light Test time, when all the idiot lights come on so you know they work. Spend 3 seconds looking at them. Then turn the key to START. The fuel pump will run for about 2-3 seconds when you first turn the key to ON; this allows the system to build up pressure.
As noted, there are a lot of things that can cause 'long' cranking time. I put 'long' in quotes because every car is different. I've had cars that started right up - never seemed to crank - and others that cranked for a bit. Now, if you've just started seeing this issue, that is one thing. But if this is a new-to-you car, this just might be the way this car is.
Leave the FPR alone. Look for vacuum leaks (a larger percentage of airflow at low speed), slow cranking, clogged filters, and low cranking voltage indicative of a tired battery or grunged-up battery cables/connections.
posted by 76.234.102...
, Wed, 1 Apr 2009 17:28:31, Thu, 2 Apr 2009 02:50:55 <-- Viewing This Message, Fri, 3 Apr 2009 16:56:12, Sat, 4 Apr 2009 04:44:36, Sat, 4 Apr 2009 15:53:03
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
