fuel filter, or fuel pump?
02-20-2014, 08:22 PM
#1
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fuel filter, or fuel pump?
While driving my '93 corvette, I gave it some throttle to go around a truck and about the time I got even with him the car sputtered and stalled. I slowed down and it re-fired. I followed along at 65-70mph using slight acceleration and car ran fine. Later, I went to mash on it and it did the same thing and died, now it won't start. It does like it wants to, but just for a second, than nothing. I am suspecting a clogged fuel filter, or do you think it may be the pump? Where would be a good spot to break the fuel line loose, down stream of the fuel pump, to check? And where is the fuel pump located? I bought this car yesterday and have put about 650 miles on it since I got it. I haven't mashed on it until this afternoon when this happened.
02-21-2014, 01:37 AM
#2
Race Director
There is a Schrader valve on the fuel rails that you attach a fuel pressure gauge to so that you can monitor the fuel pressure.
The ECM will turn on the fuel pump for 2 seconds when the key is first turned on to pressurize the fuel rails for starting. If the engine is not started the ECM will turn off the fuel pump so it won't run continuously if the ignition is turned on but the engine is not started. The ECM turns on the fuel pump when it sees DRPs (Distributor Reference Pulses) from the ignition module. DRPs are produced whenever the engine is rotating, whether cranking or running.
The fuel pressure is partially controlled by the vacuum the engine produces. Higher vacuum means lower fuel pressure. When you go to WOT the vacuum drops so the fuel pressure regulator raises the fuel pressure.
What all this means is that there are several things to look at when monitoring the fuel pressure:
1 - Turn on the ignition but don't start the car. This checks the pressure at zero vacuum. Depending on your situation, it might be necessary to turn off the ignition and then turn it back on again to make the fuel pump run for another 2 seconds.
2 - Start the engine and let it idle. This checks the pressure at high vacuum.
3 - Drive at a fairly high speed (like 65 MPH). The pressure should stay relatively steady. This checks the ability of the pump to supply enough volume at speed.
4 - Turn off the ignition and monitor the pressure. It should stay relatively steady for at least 15 minutes. If it drops it could be a leaky injector, leaky fuel pump check valve or bad fuel pressure regulator diaphragm.
On the subject of fuel pressure regulator diaphragms, remove the vacuum line from the fuel pressure regulator and turn on the ignition without starting the engine. No fuel should come out of the vacuum port on the fuel pressure regulator. If fuel does come out the diaphragm is ruptured. Get it fixed immediately. A ruptured diaphragm caused a fire in my car:
The ECM will turn on the fuel pump for 2 seconds when the key is first turned on to pressurize the fuel rails for starting. If the engine is not started the ECM will turn off the fuel pump so it won't run continuously if the ignition is turned on but the engine is not started. The ECM turns on the fuel pump when it sees DRPs (Distributor Reference Pulses) from the ignition module. DRPs are produced whenever the engine is rotating, whether cranking or running.
The fuel pressure is partially controlled by the vacuum the engine produces. Higher vacuum means lower fuel pressure. When you go to WOT the vacuum drops so the fuel pressure regulator raises the fuel pressure.
What all this means is that there are several things to look at when monitoring the fuel pressure:
1 - Turn on the ignition but don't start the car. This checks the pressure at zero vacuum. Depending on your situation, it might be necessary to turn off the ignition and then turn it back on again to make the fuel pump run for another 2 seconds.
2 - Start the engine and let it idle. This checks the pressure at high vacuum.
3 - Drive at a fairly high speed (like 65 MPH). The pressure should stay relatively steady. This checks the ability of the pump to supply enough volume at speed.
4 - Turn off the ignition and monitor the pressure. It should stay relatively steady for at least 15 minutes. If it drops it could be a leaky injector, leaky fuel pump check valve or bad fuel pressure regulator diaphragm.
On the subject of fuel pressure regulator diaphragms, remove the vacuum line from the fuel pressure regulator and turn on the ignition without starting the engine. No fuel should come out of the vacuum port on the fuel pressure regulator. If fuel does come out the diaphragm is ruptured. Get it fixed immediately. A ruptured diaphragm caused a fire in my car:
02-21-2014, 02:41 PM
#3
Racer
Fuel pump is actually in the tank. If you lift up the gas lid, its sitting on top of the tank in a sense. It should be a not too bad install. Other issue though would be the age of the gas lines?
02-21-2014, 08:20 PM
#4
02-21-2014, 08:40 PM
#5
Racer