fuel pump relay

[Mitsu_dude]

lemme start off by saying what my car is doing. it feels like its sputtering and i found out that it was from lack of fuel. obd1 reader came in handy. so now i will give you the in depth story...

well a couple days ago my fuel pump went out so i threw in a walbro 190. got the cel checked before hand and all it said was fuel pump. so i crank the car thinking the problem is fixed but no. its still not getting fuel, i can tell because the car is still sputtering from lack of it. so i replace the fuel filter thinking okay, the filter could be clogged. crank it, and problem is still there, but now, the cel says fuel pump circuit?????? WTF why would the code change if all i did was put in the new pump and filter? im so confused. and i dont even know where the fuel pump relay is to check it. i did some searching and i think i read something about it being behind the radio and something about it being under the center console. so my question is, does it sound like the relay went out? if so, where is it and how do i go about fixing it?

 

[steve]

Yes, if you measure with the relay plugged in and you see voltage on pin 7, the ecu is bad.

If he sees voltage there with the relay plugged in and the key is off then it shows that the coil on the MPI side of the relay is good. With the key on and everything plugged in your correct that he should see close to 0v on pin 7 since the ECU should be pulling it low.

 

[yokotabrat]

If he sees voltage there with the relay plugged in and the key is off then it shows that the coil on the MPI side of the relay is good. With the key on and everything plugged in your correct that he should see close to 0v on pin 7 since the ECU should be pulling it low.

Thanks for clarifying that Steve. I meant to be more specific, but was in a rush.

so in theory, with the cover pulled off the relay, if i start the car then the fuel pump relay should click once and the little contact thingy should be down the entire time???? and also i was reading somewhere that a kinked fuel line from the fuel pump might throw a code as well. is this true?

Yes, the contact should remain closed if the car is running and started. If you hear it click and then the car dies a few seconds after it's started, that's probably the relay shutting off when it isn't supposed to. Checking the voltage at pin 7 when you're trying to start the car will tell you for sure.

I don't think a kinked line would throw a code. The ecu is simply looking for a voltage. A kinked line probably won't cause the voltage to not be present unless it blew the fuel pump.

 

[steve]

I don't think a kinked line would throw a code. The ecu is simply looking for a voltage. A kinked line probably won't cause the voltage to not be present unless it blew the fuel pump.

Correct, the fuel pump CEL is just checking for voltage to the pump after it turns the relay on.

 

[Mitsu_dude]

i checked it again with teh cover off the relay and the 4 pronged side didnt click, or make contact or anything with the key in either position, and when i cranked it, it took like 2 or 3 tried to get it to turn over and it still didnt do anything and the car died in seconds.

 

[yokotabrat]

The 4 prong side of the mpi relay is to power the ecu. If that isn't working, your boost gauge won't go to zero and you won't see the check engine light flash when you first turn the car to ON. That side of the relay is also controlled by the ecu. Do you see the CE light and boost gauge move when you first turn the car on?

 

[Mitsu_dude]

yea. when i try to crank it the cel is always on and the boost gauge moves to positive boost

 

[yokotabrat]

Sounds like that side should be working then. You can check by seeing if there is 12V on pins 4 & 5 of the relay.

With the cover off on the relay, you might be able to probe with the multimeter to measure voltages without having to mess with how to measure it with the connector in the way.

 

[Mitsu_dude]

i would have to go borrow it again to measure it. my buddy is gonna get annoyed. is there anyway to test it without the meter? i read something about sticking something thin in between the contact and the relay, like where it should go down, and testing it that way. some guy did it with paper or something, and some guy used a penny. could i stick a penny in there and test it?

 

[yokotabrat]

Yep, jam a wire (or paperclip) into pin 7 or where ever it goes to inside the relay and connect the other end of the wire to ground (somewhere on the chassis nearby should work). That should turn your fuel pump on until you disconnect the wire. Then start the car and see if it stays running.

Make sure it's that pin and not something else or you might blow a fuse.

 

[steve]

+1 I'm so glad there are still people on the site that pay attention. It warms my heart to see my words come out of other people fingers.

 

[Mitsu_dude]

+1 I'm so glad there are still people on the site that pay attention. It warms my heart to see my words come out of other people fingers.

lets just say in my down time ive had a lot of free time. i think i even memorized a flow chart for a 16g. nah, but i have been reading a lot. seems im not the only person that you have helped with similar problems

Yep, jam a wire (or paperclip) into pin 7 or where ever it goes to inside the relay and connect the other end of the wire to ground (somewhere on the chassis nearby should work). That should turn your fuel pump on until you disconnect the wire. Then start the car and see if it stays running.

Make sure it's that pin and not something else or you might blow a fuse.

so i just leave it plugged in and shove a paper clip into it in pin 7, then ground the other end?

 

[yokotabrat]

+1 I'm so glad there are still people on the site that pay attention. It warms my heart to see my words come out of other people fingers.

We've had a good teacher. That and I like electronics. I have to, it's what I do for a living.

so i just leave it plugged in and shove a paper clip into it in pin 7, then ground the other end?

Yep. That simple.

 

[Mitsu_dude]

i was about to do the paper clip thing when i double checked my old results where i just looked at the relay with the cover off. the 4 prong side actually does make contact and stays down the entire time. the 5 prong side still clicks and makes contact every time i turn the key. does that help, or do i still need to try the paper clip?

 

[yokotabrat]

Does the 5 prong side only click when you are trying to start the car? If so, does it stay down after the car is started? Everything I've been assuming is that it will click when you first start the car, then release (instead of staying contacted) a few seconds after the car has started. If that's the case (it's releasing when it shouldn't be) then still try the paperclip thing.

 

[Rob10_99]

If you did paperclip it, that would narrow it down to the MPI being intermittent possibly, I took my MPI apart and cleaned up the contacts and that solved my problem.

 

[Mitsu_dude]

ok. heres exactly what it does. the 4 prong side makes contact and stays down even if the car is running. the 5 prong side makes contact when i turn the key and also stays down with the car running.

 

[yokotabrat]

If the 5 prong side stays down then that sounds like the ecu is controlling it properly, but still might not be sensing the voltage. They're seperate circuits in the ecu. Try the paperclip thing anyway and see if that changes anything or gets rid of the CEL. You might have to do some work with a multimeter to see if voltage is going to the fuel pump sense wire to the ecu, then. Let us know what you find by grounding the wire.

 

[Mitsu_dude]

it sounds like its getting voltage ### when i turn the key that wally sounds like a lochness monster growling at me. but, i had to redo some wiring to my fuel pump to make it work. could that be the problem? the stock pump has a positive and negative screw thing that u run ## wire to and tighten the nut on. my walbro 190 didnt have that. it had 2 silver circles there, but no thread bolt thingy coming out of it. instead, it had a plug in like the fuse box does. so i got 2 sound sytem attachments, like my drawing. sorry, i tried to be creative. they have square openings that fit snug onto each of the pumps little fuse teeth. could be causing my problem because maybe its not getting proper voltage? ok, nm. my drawing is messing up and wont show right.

 

[yokotabrat]

It's possible the wiring is the problem. The only way to know for sure is to measure the voltage on pin 13 of the ecu. This is what generates the CEL if there's no voltage there when the fuel pump is supposed to be on. Did you try the paperclip/wire grounding? Can you still hear the pump turned on when the car dies?

 

[Mitsu_dude]

sorry ive been busy these past few days with work. i havnt done the paper clip thing, and im not sure about being able to hear the pump after the car dies, but i can go check right now.