WTAllstar

Before I start, here's some links that I've been using so far.

https://www.yotatech.com/forums/f116...wiring-235292/
http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml
http://www.4crawler.com/4x4/CheapTri...ORelayLocation

So here's the issue. I have an 88' 4runner 22re. Recently did some extensive maintenance, but have been driving it almost daily for the last 4 weeks without problems. (Only problem is that after putting it back together, the temp gauge cuts off after about 10 minutes).

Anyway, drove it about 40 miles on Sunday, stopped for maybe 20 minutes, went to crank it up and it only turns over... no fuel to the EFI. I determined this because I'm getting spark, and when I spray some starting fluid in the TB it cranks for a second.

Removed fuel pump and jumped it with some wire right to the battery and it sounds like it's functioning just fine.

With a multi meter I'm showing 2-3 volts going into the COR (testing B+/blk and a ground) I'm showing the same voltage at the pump also.

I've tested the AFM and everything checks out except that I do not have increasing ohms on dynamic test #2 (http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml) Omhs stay consistent at about 300.This may keep it from performing it's best, but should not affect the voltage going to the fuel pump right?

The main relay seems fine (am I correct in assuming I would be having other issues too if this was bad?)

With the +B and Fp jumped, I get power to the COR with the ignition turned on, but it is still only 2-3 volts. So I guess I need to figure out where that power goes in between the battery and the COR? Any suggestions? I'm not good with wiring diagrams (or electronics in general) but I only see the EFI fuse and the main relay, both of which seem ok so far. This may be a dumb question, but how do I test voltage at these points in order to further narrow down where the power loss occurs?

Thanks in advance for your time and expertise. Last but not least, what are the pros and cons of just installing a toggle switch at the dash and running power straight to the fuel pump if i can't figure out how to get juice back there?

rustypigeon

I'll try to help you narrow down the problem...

First, turn the ignition on and check the voltage between the +B terminal in the DLC and a good chassis ground. (don't stick the black wire of the multimeter into any terminal of the DLC, make sure it is on a chassis ground) You should be reading battery voltage, around 12.5 volts or whatever you battery is charged to. If you do not have battery voltage at the +B terminal of the DLC with the ignition on, you have a bad EFI main relay, or a problem in the wiring.

Check this out and let us know what you find.

Also, where did you have the multimeter probes when you were checking the COR? To determine the voltage at the the +B terminal of the COR, you should have the red probe at the +B terminal of the COR of course, and the black probe of the multimeter should go to a good chassis ground. If you had the black probe on the wrong terminal of the COR, you could get an erronous reading from the resistance of the COR. That is why it is best to have the black probe on a known good chassis ground.

You mentioned something about powering the COR by jumping +B and FP terminals of the DLC. This does not power COR in any way, it just bypasses the COR and the AFM to test the fuel pump.

WTAllstar

Thanks for the input Rusty, I just checked the B+ terminal and I'm getting the same low voltage reading there. So I guess I got to find the EFI main relay. I'll let you know what I find, thanks again.

WTAllstar

I think I found the EFI main relay. I pulled out the relay and tested voltage at all four terminals with ignition turned and found the following: The top two terminals showed 12v. Bottom left nothing, bottom right 2v (same as pump, DLC, COR) So how do I determine if the Relay is good, am I even going about it the right way? Thanks again

rustypigeon

Sounds like your EFI Main Relay might be bad. You have 12volts going to two of the terminals just like you are supposed to. That tells us that your voltage is good up to that point in the circuit.

http://personal.utulsa.edu/~nathan-b...95efimainr.pdf

The EFI relay is easily tested when removed from the truck with your multimeter. The above link shows you how.

CAUTION: when applying battery voltage to the relay terminals as shown in the link above, be sure to put a fuse inline with the jumper wire. This will insure you don't fry your jumper wires, start a fire, injure yourself or explode your battery if you accidentaly short the wires together!