How to check relays. And no spark trouble shooting | Ford Explorer - Ford Ranger Forums - Serious Explorations

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How to check relays. And no spark trouble shooting

SlaminFool

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Title....I tried this guide on here
1. Does "THEFT" blink rapidly with ignition key in Off, On or Start?
Yes: Verify key validity
Check Passive Anti-Theft System (PATS)
No: Go to next numbered step
No it does not
2. Check fuel tank gauge reading. If fuel possibly contains water or condensation from cold add treatment to the tank.
Haven't checked fuel, not getting spark
3. Turn ignition key to On
Does "CHECK ENGINE" illuminate?
Yes: Go to next numbered step
No: Perform the PCM Power Procedure
It does illuminate
4. Turn ignition key to Start
Does starter motor crank engine?
Yes: Go to next numbered step
No: Perform Starter No crank procedure
It cranks fine
5. Does "CHECK ENGINE" illuminate while engine cranks?
Yes: Check crankshaft position (CKP) sensor
No: Go to next numbered step
It did at first, but i replaced the CKP and it doesnt now
6. Does fuel pump run?
Yes: Go to next numbered step
No: Perform Fuel Pump Electrical Procedure
Haven't checked yet
7. Check battery voltage
I did, 12.6
8. Perform TPS Test Procedure
I checked if there was power going to it and there was, i didn't check the voltage though
How do you test to make sure relays are working??, I have a 1992 2wd v6
I would really like to get this explorer started. PLEASE HELP anything you can think of I'll try
 
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MrShorty

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Relays are nothing more than electrically actuated switches. They consist of two electrical circuits: What I call the coil side of the relay which is the actuating circuit (and is really little more than an electromagnet), and the switch side of the relay, which is the circuit being controlled.

Using the PCM relay as an example. When you turn the ignition switch on, that completes the circuit for the coil side of the PCM relay. As current flows through that side, the magent should force the contacts of the relay closed, allowing current to go to the PCM and the rest of the engine management system. In testing, you want to verify that current is flowing through the coil side of the relay. Once that is verified, see if the switch side closes.
 
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SlaminFool

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Is there anything else you can think of that would cause me not to get spark?
 
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MrShorty

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No spark only, or no spark and no fuel?

My firsth thought with a no spark only is some fault in the ICM, which usually starts with the ICM power and ground. ICM, as part of the engine management system, gets power from the EEC relay, so, if the EEC relay is working correctly, then I would start by checking for power at the ICM.
 
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SlaminFool

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Today i unhooked the connector and took the ICM off of the fender. There was some whitish looking grease on the pins that go into the connector. how can I check the ICM to make sure it is working? It is 12 pin if I'm correct. And i don't hear the fuel pump coming on either when i turn the key to on
Also is there an easy way to test the relay???
 
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MrShorty

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Some auto parts stores can test some ICM's, if you think it is the ICM itself. More often than the ICM itself are faults in the power and ground circuits to the ICM. As it also sounds like the fuel pump is not coming on, and the fuel pump relay gets power from the EEC relay like the ICM, I would be inclined to check the EEC relay.

As I said, relays aren't difficult to test with a wiring diagram and a voltmeter and some basic DC electricity. Is there power to the coil side of the relay? Is there continuity through the coil? Is there power to the switch side (coming from the EEC fuse, in this case)? Is the switch closing?
 
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BigRondo

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Here is a basic automotive relay:

RelayWiringGuide.jpg


With no power on the coil there is a connection between pins 30 & 87a (closed), and no connection between pins 30 & 87 (open), as shown in the picture.

When power is applied to the coil (pins 86 & 85), there is a connection between pins 30 & 87 (closed), and no connection between pins 30 & 87a (open).

To test the relay, disconnect all wiring or remove it from it's socket. For the tests listed below, the meter will be set on Continuity/Resistance.

ContinuityResistance.jpg


Step 1 is to test the Coil:

  • Set the meter on Continuity/Resistance
  • Test the continuity between terminals 85 & 86
    • If meter measures Continuity/Resistance, the Coil should be good
    • If the meter measures No Continuity/Resistance, the Coil is bad and the relay should be replaced

Step 2 is to test the Normally Closed Terminals :

  • Set the meter on Continuity/Resistance
  • Test the continuity between terminals 30 & 87a
    • If meter measures Continuity, the Normally Closed Function of the relay should be good
    • If the meter measures No Continuity, the Normally Closed Function of the relay is bad and the relay should be replaced

Step 3 is to test the Normally Open Terminals :

  • Set the meter on Continuity/Resistance
  • Test the continuity between terminals 30 & 87
    • If meter measures No Continuity, the Normally Open Function of the relay should be good
    • If the meter measures Continuity, the Normally Open Function of the relay is bad and the relay should be replaced

If at this point the relay has proven to be good, The next step is to test that it functions properly when the coil is energized.

Step 4 is to test the Actual Function of the Relay :

  • Set the meter on Continuity/Resistance
  • Connect one probe from the meter to Terminal 30 on the relay
  • Connect the other probe to Terminal 87 on the relay
    • At this point the meter is reading No Continuity
  • Connect Terminal 85 to the Negative on the Battery
  • Connect Terminal 86 to the Positive on the battery
    • At this point the Coil is energized
    • The meter should be reading Continuity
      • If the meter is reading Continuity, the relay is good!
      • If the meter is reading No Continuity, the relay is bad and should be replaced

Hope this helps out and didn't confuse you too much! :D:thumbsup:
 
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SlaminFool

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Thanks for the info BigRondo and MrShorty. I'll check the relays RIGHT now.
 
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BigRondo

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You're welcome. Good luck!
 
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SlaminFool

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Ok, i took out all 3 relays, i have a brown one with 4 pins coming out, a black one with 5 pins: and it looks like one of the pins was broke off about a quarter of the way. And a white/grey relay with 5 pins. The diagram you posted didnt match the relays.... But i checked continuity and there were 2 different points of continuity on the black and the white one. There was absolutely no continuity between any of the pins on the brown relay. I'll take a picture and upload it if I can to specify. If they aren't too expensive, im just gonna go to auto zone this Saturday and get 3 new ones.
 
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MrShorty

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bigRondo, that is a nice write-up. If any moderators are reading, I think that post would be nice as a sticky or into a useful threads place for anyone who wants details on testing relays to find.
 
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BigRondo

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Thank you sir. I thought about making a "how to test a relay" thread so it could be used as a sticky. Might just do that tonight when I get home.
 
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SlaminFool

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Thank yall so MUCH!! I replaced the ignition and the ecm relay. The car will start for a few seconds with ether sprayed into it. Now i KNOW I have a fuel problem. Any ideas of things to check to get fuel
 
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MrShorty

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Is the pump running? If the pump is not running, then you check the fuel pump circuit for breaks/shorts. If the pump is running, then put a fuel pressure gauge on it and see what kind of pressure you are getting.
 
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SlaminFool

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No, the fuel pump doesn't come on. Is there a way to trace the wires? All i see is that it goes into the tank, then comes out and goes into that machine on the side rail under the car. Where else do the wires go through to get to the inertia switch? Through the car interior?????
 
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MrShorty

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I prefer not to start by tracing every inch of wire. The way I would do this would be to get a wiring diagram and a voltmeter. Then ground the fuel pump test lead (so the fuel pump circuit should have power). Check for power at the pump connector (behind the tank near the rear axle). If there's power there, then check the ground connection for the pump. If there's no power there, then work backwards through the circuit to the next convenient component (the inertia switch). If there's still no power at the inertia switch, then move up to the next convenient place (the relay). And so on. Once I know which section of the circuit contains the break, then I can worry about tracing every inch of wire.
 
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SlaminFool

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How do i ground the fuel pump test lead???????
 
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SlaminFool

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Ok, I have figured, either the fuel pump is bad or the injectors are clogged? How to find out which?
 
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MrShorty

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Fuel pressure test. If the fuel pump can generate sufficient pressure (spec is 40 psi) and holds that pressure while trying to start, it is likely that the injectors are not opening. If the fuel pump runs but fails to generate sufficient pressure, then the pump is at fault (or there is something restricting flow upstream of the fuel rail, like a clogged filter).
 
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SlaminFool

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Ok, the fuel pump was not coming on at all. I made an access panel behind the driver side back seat. It was a huge PITA! I got to the wires for the fuel pump, and i hooked a battery up to it and it's still not running. So, I'm going to replace it next weekend when i get paid.
 
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