KatKrazy

I guess it's never that easy......I just got done with a full rebuild on my 88 pickup. Had a few issues but after a new starter, she came back to life! Drove it a bit only to find that gear oil was spraying from the rear pinion attachment to the driveline. Got all that fixed with a new seal and was pretty proud of myself until today. Driving down the road, temp just into the normal range, and it sputters out and dies. Won't start. Trace out and find I am getting no fuel to the brand new filter. Pump was working great with good pressure a few days ago.

Have been researching here a little. I am going to check the EFI fuse and relay, the AFM wiring and operation. What else would you check? Like I said, it acted like it ran out of fuel with the sputtering and all that. I was doing a whoppin 5 MPH when it died.

What happened?

justin_4runner

does ur gas gauge work? could be out of gas? bypass the afm and see if it will turn on the fuel pump. if not and u already checked the fuse then i would say ur fuel pump went out.

KatKrazy

first thing i thought was a faulty gauge. Put about 3 gallons in and the gauge went up from where it was so ruled that out. I am going to bypass the AFM like you say and check the fuse when i get back to where the truck stalled. I will post results.

Any other ideas guys?

KatKrazy

And if after the AFM bypass, the fuel pump works? Then what?

rworegon

Might be a faulty Circuit Opening Relay (COR) if your rig has one. The COR sends the signal to the fuel pump when the ignition is on.

KatKrazy

Someone please clue me in

Name the different components in this pic please. Specifically the 3 clear-top fuses and the red top relay at the top of the pic. Does that 30 amp link look broken?



And these two items mounted on the fender


Is the greasy looking stuff normal inside the diagnosis cover?


Let's go from there.

Jarhead2147

The greasy stuff is normal. Autozone trys to sell it to you when you buy light bulds.

KatKrazy

I am fully frustrated now. Please help guys. I was simply driving around gettin a feel for the truck and all of the sudden, it acted like it had no fuel and died.
It has a brand new fuel filter.
It ran awesome when I was driving it
Now I am getting zero fuel on the "IN" side of the filter
I did the jumper trick to bypass the AFM and turned the key on.......nothing. And the COR didn't doesn't click when I turn the key either.

Does the COR not clicking mean anything?
All the fuses are ok. Not sure how to test my relays with a multimeter but read that the COR should click when the key is turned on and the AFM bypass is in place.

Anyone that can tell me what happened I would be grateful.

4Crawler

iTrader: (3)

I'll answer your question in two parts. First with some general tips on how a relay works and how to test one, then I'll follow up with some specific testing tips for the relay you are referring to. Relays usually do one of two basic functions. One is to amplify a small current to control a higher current, such as using a small switch to turn the headlights on and off. The other use is as a logic switch, such as turning on some device, like the fuel pump, when some other conditions are present, such as when the engine is being started or is running.

First off, to understand a relay you need to know what is inside one. Basically a relay is just a coil of wire (or winding) that is an electro-magnet and a piece of iron (or steel) with some electrical contacts attached to it that are pulled closed by the magnetic field made by the relay coil. Relays can have one or more coils or windings and one or more contacts and those contacts can be "normally open" (NO) or "normally closed" "NC" which refers to what state the contacts are "normally" in when the relay is off. Below is an image of a typical relay, the copper wire making up the coil windings is on the left side and at the upper right, you can see the small contacts attached to a piece of iron.



With these two basic components to a relay, testing one reduces to those two parts. To test the coil, use an ohm meter across the coil (typically makes no difference on which terminal is + and which is -) and measure the resistance. Sometimes, you'll have a specified resistance range for the test (see below) and sometimes not. As you can see in the image below, I have the meter set to "ohms" and it is on the 2Kohm range, which is the lowest range that I would anticipate to cover the typical resistance of the relay coil. With this headlight relay, I have the meter probes on the 85 and 86 terminals as those terminals connect to the relay coil. As you can see, the meter is reading 0.070 and on the 2K scale, you read that as 0.070K or 0.070 x 1000 or 70 ohms. Sometimes, folks think that you multiply the reading by the scale range (that is 2000) instead of 1000. But realize that the meter will read up to 1.999, which would equate to 1,999 (rounded off to 2000) ohms.



In the context of 12 volt automotive type relays, the coil resistance will typically be in the 50-100 ohm range, the exact value is really not that important. If you read much lower resistance (i.e. closer to 0 ohms), that indicates a short circuit in the relay coil and if you read much higher (i.e. closer to infinity) that indicates an open circuit in the relay coil. The open circuit condition is the most common failure mode in a relay, the coil windings are very fine wire that can easily burn out if too much current passes through it. Assuming you have normal continuity in the relay coil (resistance is within range), then when power is applied across the coil, the relay should make a click as the steel part gets pulled to the now magnetic relay coil. If that does not happen with the relay in its circuit, most likely something in that circuit has too much resistance to allow enough current to flow in the relay coil to magnetize it. Normal 12 volt relays usually pull around 0.1 amps (100 mA) and need a minimum of 8-9 volts across the coil to energize. So if something in the circuit it dropping enough voltage, the relay may not get enough current to turn on (or click).

Assuming you are getting the coil to pull in the contacts, you are almost there with testing the relay. The most common issue you may find with the contacts is that over time, they can get dirty or become "pitted" as arcing of current as the contacts close and open can result in the contact metal oxidizing and/or melting on one of both faces of the contact. Since the metal oxide is not as conductive as the bare contact metal; the contact may be physically closing but not allowing enough current to flow to make the relay's load turn on. Testing this with an ohm meter can be a little tricky, as the meter only uses a tiny (micro-amp) type of current to measure resistance and there may be enough conductivity in the pitted contact to read as a low resistance, but in use, with amps of current flowing, the resistance may be too high. So you are best off by trying to test the relay in its circuit and under load by voltage measurements. For example if you read 12 volts at the power input to the relay and a voltage that is much less than 12 volts (say less than 11.5 volts) on the output terminal, this means that voltage is being lost inside the relay due to contact resistance. If the relay tests out OK under load, but the circuit still is not working right, then most likely there is a wiring issue between the relay and its load. You would then want to try testing at various points between the relay and its load to find out where the problem lies.

There is some specific information on testing the Circuit Opening (CO) relay on the web page below:
http://www.4crawler.com/4x4/CheapTri...ORelayLocation

As noted, the CO relay is slightly different than the headlight relay I tested above in that it has two coils and one set of contacts. But testing it uses the same ideas as presented above, just test each coil by itself and then test the one set of contacts. As you can see in the table on the web page, the STA-E1 coil, which is turned on by the ECU during starting, is a rather low resistance winding in the 17-25 ohm range. And the B+-Fc winding, which is turned on by the Air Flow Meter, is a higher resistance (88-132 ohms) winding. These two windings make up the "logic" function of this relay, in that it turns on when the engine is being started or when it is running and when on, it supplies power to the fuel pump. Since the engine needs fuel to start or run, it is the CO relay that ensures the fuel pump is supplying fuel under those conditions.

Good luck in your testing and trouble shooting.

dropzone

iTrader: (6)

it is called dielectric grease, though the amounts the OP posted looks a bit excessive though hard to tell due to pic quality makes it look like peanut butter

Jarhead2147

I knew that. I just used his term. And yes, someone got a little liberal when applying it.

KatKrazy

Hey guys,

Question......I have a brand new battery in my pickup. I get a reading of a little over 12.5 volts when I test it just sitting there. About what should the voltage be at the battery when cranking but not running?