Fuel pump relay?

Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Something ir wrong with my reference source. I'm unable to download images right now. I'm going to ask one of my colleagues to lend a hand.
Was this
answer
helpful?
Yes
No
+1
Friday, September 11th, 2020 AT 1:11 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Its the fuel pump relay no.2 that powers the fuel pump when the computer grounds the coil side of the fuel pump relay no2 thru fuel pump relay no.1
Was this
answer
helpful?
Yes
No
+5
Friday, September 11th, 2020 AT 1:11 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
It sure is, dunno where I got that must be Mit1-lol-You have a nice day for me time to go to bed-its only 2150hrs 22 Dec
Was this
answer
helpful?
Yes
No
Friday, September 11th, 2020 AT 1:11 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
OK Buddy. Have a great holiday if I don't talk to you before that.
Was this
answer
helpful?
Yes
No
Friday, September 11th, 2020 AT 1:11 PM (Merged)
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Thanks guys.
Was this
answer
helpful?
Yes
No
Friday, September 11th, 2020 AT 1:11 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Merry Christmas to you guys too-thanks for all the help
Was this
answer
helpful?
Yes
No
Friday, September 11th, 2020 AT 1:11 PM (Merged)
Tiny
CINDY MARTIN GRIFFIN
  • MEMBER
  • 4 POSTS
  • 2003 MITSUBISHI GALANT
  • 130,000 MILES
I am not getting power to the fuel pump. We have replaced the pump and checked the relays.
Was this
answer
helpful?
Yes
No
Monday, September 14th, 2020 AT 12:56 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,870 POSTS
When are you checking? Have you checked for spark? Please list which engine you have.
Was this
answer
helpful?
Yes
No
+2
Monday, September 14th, 2020 AT 12:56 PM (Merged)
Tiny
CINDY MARTIN GRIFFIN
  • MEMBER
  • 4 POSTS
2.4 engine. We are getting power leaving the relays.
Was this
answer
helpful?
Yes
No
+1
Monday, September 14th, 2020 AT 12:56 PM (Merged)
Tiny
CINDY MARTIN GRIFFIN
  • MEMBER
  • 4 POSTS
Is there a kill switch?
Was this
answer
helpful?
Yes
No
+1
Monday, September 14th, 2020 AT 12:56 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,870 POSTS
You need to be specific. Are you testing at the fuel pump relay? The automatic shutdown, (ASD) relay? If you are testing for voltage at the connector for the fuel pump, you had better not have twelve volts there unless the engine is rotating, (cranking or running). The exception is you should see twelve volts there for one second when you turn on the ignition switch. If you are able to hear the hum of the pump for that one second when you turn on the ignition switch, the pump circuit is working.

About ninety five percent of crank/no-starts that involve a dead fuel pump also include no spark. That is why I asked if you have spark. Too many people get hung up on the first thing they find missing, and overlook the rest of the symptoms. You could have a problem in just the fuel pump circuit, but those account for perhaps one or two percent of no-starts.

There is no kill switch. "Inertia" switches are a troublesome Ford thing. Some other manufacturers might use them, but I am not aware of them. Other than that initial one-second burst, the Engine Computer turns on the ASD relay when it sees signal pulses coming from the crankshaft position sensor and camshaft position sensor. The ASD relay sends current to the ignition coil(s), injectors, oxygen sensor heaters, and fuel pump, or a separate fuel pump relay. This way, if a fuel line is ruptured in a crash, there will be no fuel pressure in that line. With no pressure, the engine cannot run. There will be no signal pulses from the two sensors when the engine is stalled. The computer turns the ASD relay off when there is no sensor pulses. That stops the fuel pump from dumping raw fuel onto the ground where it would be a fire hazard.
Was this
answer
helpful?
Yes
No
+1
Monday, September 14th, 2020 AT 12:56 PM (Merged)
Tiny
CINDY MARTIN GRIFFIN
  • MEMBER
  • 4 POSTS
What and where is the ASD located?
Was this
answer
helpful?
Yes
No
Monday, September 14th, 2020 AT 12:56 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,870 POSTS
Sorry for the confusion. Mitsubishi calls it the "multi-point fuel injection", (MFI) relay. The fastest way to test this circuit is to use a test light, and back-probe the red wire at any fuel injector, either of the two sensors, or at the mass air flow sensor. Digital voltmeters can work, but they respond too slowly to see the initial twelve volt pulse.

You should see the test light turn on for that first one second when you turn on the ignition switch. What is important is does it turn on again steady while you are cranking the engine.

The rest of the circuit is a little different than what I am used to seeing, so I am going to have to back up and study it. The ignition coils have their twelve volts switched on with the ignition switch, not any relay, so we cannot use them for any test procedure. There are two fuel pump relays. Fuel pump relay number one turns on any time the ignition switch is on. Fuel pump relay number two is the one that is turned on by the Engine Computer. They are in series, so both must turn on to have twelve volts to the pump. That will be on the white/black wire at the pump.
Was this
answer
helpful?
Yes
No
+3
Monday, September 14th, 2020 AT 12:56 PM (Merged)

Please login or register to post a reply.

Sponsored links