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View Full Version : What can cause no power to fuel pump other than relay?


ladybugaz7
Apr 6, 2010, 02:10 PM
We have a 92 civic that just all of a sudden will not start. Went to take hubby to work did great. After setting for just a few hours I went out to leave to work and it wouldn't start. It is trying to start and has spark. Took fuel filter line off and no fuel coming out. Went to fuel pump in gas tank and tested connections to fuel pump and no power getting to fuel pump all of a sudden. Looked at what we believe is the relay and tested and it seems to be good. What would possibly be the issue as to why it won't start? PLEASE help!!

TxGreaseMonkey
Apr 6, 2010, 02:34 PM
Does the Check Engine Light stay on, when the ignition switch is turned to ON (Position II)?

ladybugaz7
Apr 6, 2010, 02:43 PM
The check engine light stays on but was told that is because the idol sensor needs to be replaced and is unplugged because when plugged in it idols VERY rough up and down... But light is on rather sensor is plugged in or not... We just purchased this car last week and we are finding out all the quirks... Please advise...

TxGreaseMonkey
Apr 6, 2010, 02:46 PM
The ECM has likely failed. Perform the K-Test on the ECM:

The K-Test: Remove the MAP Sensor connector and turn the ignition switch to ON (Position II). Using a multimeter, check for 5 volts going between the MAP Sensor connector's reference wire (+) and ground. As you look at the connector, this is the socket on the right. Really press the black test lead into a cleaned main ECM ground on the thermostat housing. If the voltage is low, it's probably indicating ECM failure. Most failed ECMs will record a fraction of a volt. To me, the K-Test is simple, elegant, and accurate.

TxGreaseMonkey
Apr 6, 2010, 02:52 PM
If the ECM is bad, the main relay, which controls the fuel pump, won't work. Let me know the results of the K-Test and we'll go from there.

ladybugaz7
Apr 6, 2010, 02:55 PM
ECM? Would that only affect the fuel pump. Excuse my lack of knowledge I am trying to learn!! My hubby probably knows just what that part is but I would like to know also what it is... We get off today at 5 home by 6 and will have him try this test to see what it does... Will let you know once test is complete.. Thank you...

TxGreaseMonkey
Apr 6, 2010, 02:59 PM
ECM = Engine Control Module (computer)

If the CEL does not go out, most Civics will not spark and the fuel pump will not run. That's why we begin our diagnosis here. Remember, the Main Relay actually contains two individual relays. One relay is energized whenever the ignition is on, which supplies battery voltage to the ECM, power to the fuel injectors, and power for the second relay. The second relay is energized for 2 seconds when the ignition is switched on, and when the engine is running which supplies power to the fuel pump.

The Manifold Absolute Pressure (MAP) Sensor is the “key” sensor on Hondas. It controls timing (similar to the old vacuum advance on distributors) and air/fuel mixture, depending upon manifold pressure changes. Like any transducer, it converts energy from one form to another. Here, it converts throttle body vacuum pressure changes into fluctuating electrical current signals to the ECM. If this sensor does not receive the proper voltage from the ECM, you will experience catastrophic ignition and fuel system failure.

ladybugaz7
Apr 6, 2010, 03:08 PM
Ok that makes some sense to me... We did however have the sparkplug spark when we unplugged the top of one to see if it was getting spark when we turned it over... The MAP sensor we are going to test is located?? My husband may know this but I am asking so I know for sure when we go to test...

TxGreaseMonkey
Apr 6, 2010, 03:33 PM
The MAP Sensor is along the firewall, just to the right of the battery and fuel filter.

You are not testing the MAP Sensor, however. You are testing that it's getting the proper reference voltage from the computer. The ECM (computer) is what's being tested.

ladybugaz7
Apr 6, 2010, 03:48 PM
Correct... The K - Test... Ok will let my hubby see what he comes up with and will let you know...