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Re: Need Advice: Fuel Pump or Computer? Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 30 Mar 2001 11:06:40
In Reply to: Need Advice: Fuel Pump or Computer?, Floyd Russak, Thu, 29 Mar 2001 02:17:11 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Pumping the pedal in a fuel-injected car does basically nothing. All the pedal does is open the throttle plate to let air in; the computer decides how much fuel to stuff in. This worked in carbureted cars because pumping the pedal would actually inject extra fuel (accelerator pump).
The manual in every FI-equipped car states for you to start the car with your foot off the gas pedal. However, sometimes in hard starting situations, I will hold the pedal about half-way open (no pumping, just hold it) as I crank the engine. The engine is just an air pump, and cranking an engine with the throttle closed takes a lot of energy. If your battery is tired and/or very cold, or the connections poor, the engine may not turn very fast and not want to catch. If you hold the throttle partially open, it will crank faster, and will usually catch faster. I use this trick when I'm trying to limp a few extra weeks out of an old battery, or if it's really cold out.
Hard starting is usually due to one of three things - ignition timing, cranking speed, and fuel pressure. Since you've got a DI car, your timing is fixed. Does the engine crank fast, or just barely turn over? If it's cranking slowly, have the battery checked, and clean up the battery cable contacts. Not the outsides of the clamps, but actually pull the clamps off and polish up the inside parts where they meet the battery post. Slow cranking can also be due to old cables, and bad connections between the cables and chassis (ground).
Low fuel pressure can be due to a bad or weak fuel pump. Is the problem worse with half a tank or less? The car has a two-stage fuel pump (actually, two pumps), one for scavenging below a half tank. If you see the problem more with a half-tank or less (and the parked on a hill points to that), you many need a new scavenge pump. Also, don't ignore your fuel filter - if you don't know the last time it was replaced, replace it. If it's clogged, you'll hurt fuel pressure.
If you suspect low fuel pressure, try this trick - Open the fuse panel, and with a piece of wire, jumper between fuses 14 and 22. You don't even need the key on. You'll hear the fuel pump run. Let it run for about 10 seconds, then remove the jumper. Then try and start the car. If the car starts right up, you probably have a fuel pressure problem. By running the pump for a few seconds, you pressurize the system.
Good luck!
, Fri, 30 Mar 2001 11:06:40 <-- Viewing This Message
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