fuel pump power RTH

[icurunnin]

some of you may know I am trying to have 662 together to get to pinks all out and rep. the board. well along with all the other crap I have to throw on the car, I installed my TRE fuel pump today. Everything went smooth after breaking the soft line and hard line apart FINALLY. went to crank it over and no fuel pressure.
Check my power signal to the fuel pump and nothing. check the MPI fuse under the hood and its good. checked a relay (assuming fuel pump relay) next to the ecu and it clicks with the key. I cant seem to come up with anything and its driving me nuckin futs. working on it now so any immediate help would be greatly appreciated fella's. /ubbthreads/images/graemlins/wink.gif

 

[Terry Posten]

Did you rewire it?

There is a dual power circuit that the MPI relay feeds. It feeds power to the pump for a few seconds on the "start-up" circuit until the ECU sees the CAS signal and then it switches over to the primary circuit.

Maybe something shorted out when you were swapping things.

Try to jump 12v directly from the battery to the positive pump wire to make sure the pump works. It the pump works, try to start it with the jumper in place.

If that works, you may want to just run a power wire with an in-car switch to get you to the event. But if you do, disconnect the stock power wiring so you don't back-feed power.

 

[icurunnin]

its not getting any power at the wire stock hot wire.
I do have a fuel pump rewire and the relay works great and is getting hot power, good ground, but no signal to the accesory switch. I even did away with the relay and just went to the stock plug and it was not getting power.
I am getting good ground at the harness, and my gas gauge is reading correctly. anyone know where the stock hot side leads to or feeds from?

 

[Terry Posten]

Can you just run a new 12v wire from a switched ignition source to turn your relay on and off?

The reason that the car has a dual power source that monitors the CAS signal is in case you have an accident and your motor stalls, you don't pump gas over the ground if the fuel line ruptures.

 

[cOmpressor]

You might as well run the 12v like Terry is suggesting. It's not hard and will clear this problem along with other future problems with the stock wiring.

 

[icurunnin]

Quoting Terry Posten:
Can you just run a new 12v wire from a switched ignition source to turn your relay on and off?

The reason that the car has a dual power source that monitors the CAS signal is in case you have an accident and your motor stalls, you don't pump gas over the ground if the fuel line ruptures.


I just thought of something..... Is it possible that my ecu could have leaky capps and it was just the timing of the car sitting for over a month and me working on it? I may just have to tap a ignition source like you say.
Only reason I am trying to avoid that is to keep from having anything hacked/rigged on the car. if something is wrong I would like to fix it. but I guess sometimes you have to take a walk to the dark side /ubbthreads/images/graemlins/mad.gif
The scenario was
pull car into shop (running fine)
put 3" exhaust on
O2 housing wouldnt come off so I pulled the turbo, manifold, and O2 as one piece
car sits as I wait for parts and while I do the port work
now no power to the fuel pump

 

[toybreaker]

Check engine light work?

That's the same feed from the key the mfi relay uses. If it lights up when the key is turned on, it's a good sign power is getting to the relay.

After that, it gets more complicated. There's more than one black and white wire at the mfi relay, (ones an inny, and ones an outty.)

The one at terminal three is the power in from the key, and is live 24/7 the key is in the run position.

The other one at terminal 2 is the switched output out to the fuel pump.

The relay has two coils for the pump circuit.

Check for power at the pump on the black and white wire while cranking the engine over on the starter.
That's the starter authorised coil inside the mfi relay, and its live 24/7 the starter is cranking. No power at the pump while cranking will eliminate the ecu as a player.

The other coil is energised by a ground signal from the ecu on the white/red wire, and is used to run the pump while the engine is running. As Terry said, the ecu uses the cas signal as an indication the engine needs fuel. (No cas signal = no fuel )

If you need anything let me know, I've got a few spares I could send your way.

Good luck at Pinks!!! /ubbthreads/images/graemlins/worthy.gif

 

[icurunnin]

so is the big silver relay next to the ecm the fuel pump relay you speak of? I have not tried cranking it over since it has no turbo manifold or coolant in it.
I will try cranking it over to see if I get any luck with it. I know once the rail has enough pressure the fuel pump will not kick on. I dont know if the galant falls into that crowd of cars or not.
I am hoping cranking it over does the trick some how and gets everything back on par. nothing has changed to make this problem arrise.
I will try it tonight when I get home. in the mean while if anyone else has anything else to look for or try, please post away.

oh and I am going to pinks just to show the car. The qualifying was the past two weekends. I just want the car to be out there to rep for gvr4's and hope there are some out there.

 

[toybreaker]

Quote:

I will try cranking it over to see if I get any luck with it.



Oooops, didn't know the car was apart.

You can unplug the yellow/black wire in the starter harness, (so the engine doesn't crank) and test it that way, but it's probably best to have another approach.

Does the check engine light illuminate when you key the car up?

You can energise the fuel pump check connector (yellow/green wire at the firewall) and if the pump lights up, that indicates you'll be spending some time troubleshooting the mfi relay and ecu.

If it doesn't energise the pump, you'll be looking for a harness or pump ground issue.

 

[icurunnin]

ok I do have a check engine light while cranking and I am getting power to the black/white while cranking. what next? also I never got a yes on the big silver relay next to the ecu being the fuel pump relay?

 

[icurunnin]

also ran power to the yellow/blue wire and I am getting power

 

Quoting icurunnin:
also I never got a yes on the big silver relay next to the ecu being the fuel pump relay?



Yes the big silver relay is the fuel pump relay, technically called the "MPI control relay." It switches power to the fuel pump either when the ecu activates the relay or when the starter circuit activates the relay.

 

[icurunnin]

just checked the ecm and it looks brand new with no leakage, burnt smell or anything suspect.
whats next?

 

[icurunnin]

I pulled the MPI relay apart and didnt find anything out of the ordinary.

 

Hopefully this will help:



While cranking or running the ECU grounds pin #56, which pulls in the righthand half of the MFI relay, which connects +12 volts to the fuelpump.
Its very common for acid damage from a leaky 47uF cap in the ECU to spill over to IC110, which is what drives pin #56.

 

[icurunnin]

thanks jeff and I will check that when I get back to the house today.

 

[icurunnin]

went to the house and checked that portion of the ecm and didnt see anything that looked suspect. I took some pics but cant load them up till I get back to the house.

 

You can always try grounding that ECU pin manually to see if that fixes the problem. Or, read the voltage on it. If it shows +12 volts then the relay isn't being activated by the ECU.

 

[icurunnin]

well with all the crap that happened last night putting it back together, its safe to say its just gonna sit. here are the pics and Terry the ecm will be heading your way.

 

I doubt that is necessary. That appears to be a new factory replacement ECU, so it has no acid damage. /ubbthreads/images/graemlins/applause.gif
You need to keep looking. As I said, the ECU simply grounds pin #56, pulling in the MFI section that connects the +12 volts to the fuelpump. It should be easy to find with a voltmeter and a jumper wire.