keeganeli

I have a 94 civic dx. So my problem started with my fuel pump taking a while to prime (Humid or rainy day) so i tried changing out my main relay with a new one but that didn't solve the problem. I didn't know what to do so i tried doing the paper clip trick to pull codes but instead of my CEL flashing codes at me the fuel pump turned on right away and haven't had a problem for months until two weeks ago when my car wouldn't driver faster than 30mph. There was oil on my spark plugs so my dads friend (mechanic) changed the plugs, gasket, wires, o-rings, distributor cap and rotor, and cv-axles since they needed to be replaced. He did all that work and the problem was still there because it was the CAT, so i just hallowed out the CAT instead of buying a new one. The problem of my fuel pump came back but would only delay for a couple seconds. I didn't think anything of it because it had rained so i figured it was just doing its thing. But a week later i was driving on the freeway and the car would stall out and start back up randomly and i could hear the main relay clicking on and off. So i got home called my grandpa who is an electrical engineer to take a look at my car. We tested the main relay and all the terminals and main relay is fine. When we connected terminal 2 to terminal 8 giving the ecu a ground the fuel pump turned on right away. We tried figuring out if it is was the ecu that was faulty or a gound or sensor that was bad. The problem was intermittent and effected by temperature. Which i thought was a humidity and moisture issue as i said before but it was really just cold and hot weather. Well i tried driving to school today because the temperature was average and i live less than a mile away from school. (i know why not walk but i pulled my groin this past Saturday at a track meet) So as I'm driving around the parking structure my fuel pump cuts out so i pull over pull out the wires my grandpa gave me to connect terminal 2 to terminal 8 on the main relay. The fuel pump turns on, awesome, crank the car over and the car won't start even though this has worked before. I sit there for about 15 minutes while i wait for my grandpa he gets there is puzzled. So say hell with it turn the key to ignition without the wires on terminal 2 and 8 and the fuel pump turns on car starts up and luckily a parking spot opened a few spots down. I give him my key limp to class and he tells me when he was checking it out he would connect terminal 2 to 8 and he could hear the fuel pump but the car wouldn't start. So after class i get the key from him turn it to ignition fuel pump turns on and i hurry home luckily making it with no problems. So now since I've told you my story I've read that it could be my crankshaft angle sensor. Does that sound about right? If not could you PLEASE help me i know its something simple that just needs testing until i/we can find the problem. Also this past week the car has been unreliable whether or not the fuel pump would turn but never had the problem of it not starting with the fuel pump on. Also everytime i go to pull codes nothing happens with the CEL or the fuel pump turns on.

If any one has any idea of what this can be id greatly appreciate the help

Former User

Holy wall of text --> Cliffs Notes?

keeganeli

Basically something is keeping the fuel pump from turning on and it's not the main relay and it's not the fuel pump itself. Some days it works some days it doesn't but it also depends on the weather outside.

Former User

Probably a bad ECU.

keeganeli

So thats why when it won't start and I see a check engine light it won't give me codes when I use the paperclip? If it is the ECU how can I go about testing to make sure it's the ECU?

paco_sinbad

Swap in a known good ECU?

Former User

How often does the problem occur?

keeganeli

Everyday for the past week and a half... The fuel pump will only prime at certain times of the day when it's not too hot or cold.

Former User

Here's a pretty reliable test if you don't have a known good ECU to swap.

1) Turn key off. Unplug ECU connector A.

2) Touch/connect one end of a wire to pin A7 (or A8 if it also has a wire) in ECU connector A and the other end to the metal frame under the dash.

3) Turn key to ON(II). Does the fuel pump stay running as long the key remains in ON(II)? Does the turn off when the key is switched off? Repeat this test numerous time by turn key off and then to ON(II). The pump should run every time the key is turn to ON(II).

If the pump reliably turns on after numerous tests, but intermittently does not after ECU connector A is plugged back in, then replace the ECU.

keeganeli

That is the same as connecting terminal 2 to terminal 8 on the main relay correct?

Former User

Yes, if you do the test with ECU connector A unplugged and connect main relay terminal 2 to A7 (or A8). The latter is critical because it removes the ECU from the loop.

keeganeli

Okay because when I connect the two terminals the the pump instantly turns on but starting Tuesday when I connect the two terminals I can hear the fuel pump but the car won't start it just keeps cranking like there is no fuel going through the injectors. Could this be from the ECU or another problem?

Former User

Test^ done with any connectors unplugged? Give all information and be precise. How exactly did you do the test?

keeganeli

I took the cover off the main relay and touched terminal 2 to terminal 8 with wire and I didn't disconnect anything. I'm going to do what you told me to do tomorrow because I'm not home right now and won't be till tomorrow.

Former User

I would avoid the test you're doing. The terminal 8 side of the circuit has a resistor that steps down the voltage, whereas the terminal 2 side does not.

keeganeli

I did the test and the fuel pump turned on right away every time. I know you said it could be the ECU but could the crank sensor or TDC sensor not be sending the correct information to the ECU?

Former User

The CKP sensor only affect the fuel pump when the engine is cranking or running, so if the pump doesn't prime in ON(II), then it's not a fit.

keeganeli

Okay because when the fuel pump does turn on and I drive the fuel pump will also cut in and out after about 10 min of driving.

Former User

Are you saying the fuel pump never fails to prime when key is turned to ON(II) [engine off]?

keeganeli

No the fuel pump does fail to prime at certain parts of the day when it's either too hot or cold but if I drive it when it does turn on (prime) then after about 10 minutes of driving the fuel pump with either turn off and stay off or will turn on and off then eventually stop working

Former User

Replace the ECU.

keeganeli

Okay thank you so much for your help!

keeganeli

Was not the ecu... I replaced it with a remanufactured one from cardone... Worked fine I had to wait a few extra seconds to wait for the fuel pump to prime which is a little unusual. But the problem is I went to go drive it right now and the fuel pump wouldn't prime at all I waited a few minutes and nothing. It rained today where I live and the inside of my car was pretty cold when I got in right now so it comes down to a temperature issue again.

Former User

Does the ECU have a warranty?

If you did the test exactly as I mentioned, it eliminates only the ECU from the fuel pump circuit. You said when you did the test, the pump always primed, but when you reconnected everything and used the key, the problem returned, thereby pointing to an ECU issue. Repeat the tests to see if you get the same or different results.

keeganeli

Yes a 1 year warranty and okay thanks!