Help, no power to fuel pump!
 

Car doesn't start. Fuel pump works but there is no power going to it. What could be the problem? A cut wire? IF its a cut wire, what possible places can the cut be at?

Thanks!

Re: Help, no power to fuel pump! (BG Boost)
 

did you check the fuse?

Re: Help, no power to fuel pump!
 

I have the very same problem, the fuse is good, i changed the main relay it is also good,
but there is no power to the pump
i do now what it is may be a bad wire i also checked them everthing looked ok.
so i think it is the ECU but not sure
thanks

Re: Help, no power to fuel pump!
 

Check for power at the fuse (touch the little exposed metal pins on top of the fuse with a test light....both of the pins) then check for power on the wire that carries power to the fuel pump at all connectors all the way to the pump. It could also be that the pump is getting a bad electrical ground connection.

Re: Help, no power to fuel pump!
 

It's most likely your Main Fuel Relay. On hot days, the solder inside the unit tends to crack and expands thus not giving piwer to the pump.

Unplug that sucker and open it up and drip fresh solder on all the connects and you should be good to go.

Re: Help, no power to fuel pump!
 

the main relay is brand new and it clicks
so i think it is either wiring or ecu
does anyone have the wiring diagram
thanks

Re: Help, no power to fuel pump!
 

I checked the fuel pump fuse on both ends there is voltage.
can you tell me from the battery what is first then what comes next? is it like battery, fuse, relay and fuel pump? does ECU or ignition switch get involved in anywhere?
Thanks

Re: Help, no power to fuel pump!
 

MM&Y of car would help.

The PGM-FI Main Relay has 3 fuses, a 12V+ constant, [hot at all times], a 12V+ switched, [hot in run and start] a 2nd 12V+ switched, [hot during cranking to start only].

There are number of things that would prevent the fuel pump from running.

I need the MM&Y to help.94

Re: Help, no power to fuel pump!
 

It is 1998 Honda Prelude
the relay has 7 prongs

Re: Help, no power to fuel pump!
 

any ideas if it could be the ECU

Re: Help, no power to fuel pump!
 

It could be the ECU/ECM as it provides the ground for the fuel pump relays coil, the other side of coil gets it's power from the output of the fuel injector relay.

Sorry I do not have a wiring diagram for a 98 Prelude.

If you have a 12V test light you can do some tests that do not require the wiring diagram.

Unplug the PGM-FI Main Relay...

With the ign. switch off, test the leads in the plug, there should be a 12V+, [hot at all times], if so, what color is it?

Turn ign. switch on to run position, there will now be another lead with 12V+ on it, [hot in run and start] turn ign. key to start to make sure the lead still has 12V+ on it, if so, what color is it?

Now turn ign. switch to start, there should now be a 3rd lead with 12V+ on it, [hot during cranking to start only] if so, what color is it?

There will also be a black lead in the plug, it is ground for the injector relays coil, the lead that is hot in run and start is on the other side of injector relays coil, that lead is also power for the fuel pump, [through fuel pump relay]

That is 4 of the leads the other 3 leads are...
1- The fuel pump power lead, [most likely a yellow/green or yellow/black].

2- the injector power lead, [it may also be yellow/green or yellow/black].

3- the ECU/ECM fuel pump relay control lead, [possibly a green/black or green/blue]

Give me the colors of the 3 leads with 12V+ on them and the colors of the other 3 leads, and I will give you some other tests to try. 94

Re: Help, no power to fuel pump!
 

Thank you for your help.
I will get those to you most probably on Monday.
Thanks

Re: Help, no power to fuel pump!
 

Hello back.
Here are the answers to your questions:
With the ign. switch off, test the leads in the plug, there should be a 12V+, [hot at all times], if so, what color is it?----NO VOLTAGE IN ANY LEAD

Turn ign. switch on to run position, there will now be another lead with 12V+ on it, [hot in run and start] turn ign. key to start to make sure the lead still has 12V+ on it, if so, what color is it?----ONLY NUMBER 6 LEAD HAS VOLTAGE. THE COLOR OF WIRE IS BLUE WITH RED STRIPE

Now turn ign. switch to start, there should now be a 3rd lead with 12V+ on it, [hot during cranking to start only] if so, what color is it?---NUMBER 6 AND NUMBER 5 LEADS HAVE VOLTAGE.. THE COLOR OF WIRE TO LEAD 6 IS BLUE WITH RED STRIPE....THE COLOR OF WIRE TO LEAD 5 IS RED WITH ORANGE STRIPE.

Thanks for your help in advance. Please let me know what you think
Sincerely

Re: Help, no power to fuel pump!
 

Your problem is no constant power, [is there a yellow/white lead] check the fuses in the engine bay fuse box, most likely a 15A fuse.

With no constant power there is no fuel injector relay output, so no power to injectors, no signal to ECU/ECM, [IPG1 & 2] no power to fuel pump relays coil, [unless cranking to start] and no power to a few engine solenoid/valves.

With no signal the ECU/ECM there will be no fuel pump relay control output or injector pulse from ECU/ECM. 94

Re: Help, no power to fuel pump!
 

Hello I checked all the fuses there is non that don't work.
there is also no yellow and white lead...

one thing though, ABS fuse is not broken but there is no voltage in either end of the fuse.
Is it because the car is not starting and running
or is it something else?

The other thing is that I scanned the car unfortunately it did not give me any code instead it said "error" even though my check engine was on due to catalytic converter.
Let me know what you think please thanks

Re: Help, no power to fuel pump!
 

Then there is a connection problem between the fuse and the PGM-FI Main Relay. 94

What are the other wire colors in the PGM-FI Main Relay plug? 94

Re: Help, no power to fuel pump!
 

Hi just an update and i need more advice

I just replaced the ECU now I got the power to fuel pump.
On the relay I have now 1,5,6, and 8 powered up.
I also have fuel and sparks.
but it still does not start please let me know what i should check now
thanks.
i scanned it it gave me 0.
check engine light when key is on comes on and turns off as it should..

Re: Help, no power to fuel pump!
 

Where is the ecu located?

Re: Help, no power to fuel pump!
 

Wondering if there’s any follow up to this post. I’m having the exact same problems and don’t know where to go from here.