Dk2685

Hey y'all first time posting!

Ive had a crank/no start situation on my 89 3.0 v6 that I jus can't fix. It initially died when I was driving in the rain when the truck died. The efi fuse had blown and when I replaced it it shortly blew again after starting. I towed the car home and since found what was likely shorting the system, a melted o2sensor wire up against the front exhaust. I feel like something else got damaged in the process because now the car I don't have power to the fuel pump or distributor and jumpering the fuel pump is not working. I'm not getting spark though the truck does crank. Help!

scope103

Start by checking for 12v to ground at B+ with key-on. If you don't have it, jumpering will not start the pump. B+ is powered by the EFI relay (powered by the EFI fuse), so if you're missing B+ pull the EFI relay. Test the relay, and test for voltage at the right pins of the socket. (Note that this requires a multimeter.)

Dk2685

Thanks for the quick reply!

I have 11v at the b+ socket but .34v at the efi socket. Also I already tried replacing the relay to no avail.

scope103

11v? Why don't you check your battery (voltage to ground from +, voltage from + to -). If you get 11v there your battery is VERY discharged, and may not be enough to run the pump.

If you get around 12.6 at the battery, you need to find where the extra volts are going before they get to B+.

Dk2685

The battery is at 12v. And just to confirm. Is the correct way to test voltage at the b+ to go from the terminal to the + side of the battery?

wyoming9

iTrader: (1)

Voltage is measured across the circuit from positive to ground

So B+ at the check connector to the engine block or the negative battery terminal

Dk2685

Thanks! This is my first time trying to ID electrical issues and I'm confusing myself a bit. I get no voltage reading when going from the b+ terminal to the engine block.

wyoming9

iTrader: (1)

Either you are not getting a good ground or B+ at the check connector has a open circuit from the ECU

You do have the ignition switch in the run position ??

Always start with your Battery Voltage

Dk2685

the battery is putting out 12v and yes I had they key in the in position. Other electrical components like the stereo, lights etc are working fine. I think I got confused because so many components (fuel pump, distributor, Ignition coil and sparking system) were not giving me any sort of reading.

Is it possible there's a problem in my ecu?

scope103

Yes, it SOUNDS like you're confusing yourself.

Before you said you got 11v at B+. Did you measure that to the + terminal of the battery? If so, B+ (which connects to the output of the EFI relay) is somehow grounded. That's the same line as to the O2 sensor Heater, so you MIGHT be just measuring resistance to ground through the O2 sensor.

You should get 12v from B+ to the engine block, but perhaps you didn't get a good connection. To be sure, measure B+ to the - terminal of the battery. If you get 0v with key-on, you have a problem with the EFI circuit. You say you got 0.34v at the EFI relay socket. That relay has four pins; you should have 12v (w/key-on) on pins 1 and 5.

Last, you CANNOT get "no" reading with a multimeter. You can get 0 volts or 0.001volts or infinite ohms, or all sorts of other readings, but NONE of them are "no" reading. We can guess that "no" reading on a voltmeter is 0v, but once you get to measuring resistance, what is "no" reading? 0 ohms? infinite ohms?

Charchee

Get a charger on that battery while you think about it and get a good 12.5 volts or so before you get too carried away with your testing. Like Wyoming said, always start with your battery voltage. Don't let all of the things that aren't working rattle you. It's tougher to diagnose why any one of those components aren't working than it is when they all aren't working. Measure the B+ by placing your red lead on B+ and the black lead on the negative battery terminal. They are plenty close together to accomplish that. I think Scope is right about pin 1 and 5 of the EFI relay having 12V with the key on but if it makes it less confusing, measure the voltage at all of the pins and see what you fine. Keep your black lead on the battery's negative post for all of your voltage tests in this area to insure you have a good ground. You have wires from your battery going into this fuse/relay box and ground wires that run from the box to the fender well. Check all of your connections there and make sure there isn't a broken wire or loose connection that you can see.

Just take a deep breath and take notes on your multimeter readings. Test everything you can put your lead on and write them down. Then go sit in the shade and look over your notes and just think about it. It's actually a pretty simple circuit. Also check your EFI fuse every so often. You don't want to do tests in the engine compartment for two hours only to find out that your fuse has blown at some point without you knowing.

Post the results of your tests and we'll help you get it figured out.

Dk2685

Ok an update: my battery is now putting out 11.94 v. I don't have a charger but will try to give it some juice sometime soon.

From b+ to battery negative in getting .19v and from b+ to batt pos. It's 11.60 v.

the efi relay terminal 5 to btttery is .34 and from terminal 3 to 5 is The same.

all the fuses are good

thanks y'all!

Charchee

Looks like we have a solid short on the wire to B+. Measure that voltage again with EFI relay pulled out. B+ to battery +. I'm just curious. I didn't see your reading on pin 1 of the EFI relay socket. What did you read there?

scope103

Actually, that might not be a "solid short," Dk2685 may be just reading "through" the o2 sensor heater to ground. So don't bother reading voltages "to" the + terminal on the battery; you just ending up getting results that don't mean much.

I assume those measurements were with key-on. Key-on should close the EFI relay, which powers B+. With the relay out, pin 5 goes to the EFI fuse which is "always on." So if you get 0.34v to ground on that pin, the EFI fuse could be blown, not seated right, or something is wrong in the wiring from the fuse to the relay socket. It's only about 1 1/2 inches of wire, so you don't have far to look.

Dk2685

Ok I should mention that my efi relay only has 4 terminals as shown in the pic I attached. They all read 0.33v with the exception of terminal 4 which reads 0.001v.

With the efi relay unplugged I get 10.92v from b+ to batt+ and .46v to batt-.

scope103

That helps. As you can see from the markings on the relay, either pin 2 or 4 goes right back (electrically) to the EFI fuse. (The other terminal goes to B+, the COR, ECM, ....) So one of them should have 12v all the time. (My EWD says the wire is Black-White, but as you found out, my '94 EWD isn't EXACTLY right for your '89.)

A quick and easy check would be to pull the EFI fuse and check for voltage to ground on each pin. One of the pins goes right back (electrically) to the battery, so if you don't get 12v on one of them you're getting much closer to your wiring issue. If you do get 12v, confirm that the fuse is good (ohmmeter this time), and if it is you'll probably want to take the Relay Block apart to find the burned wire.

Dk2685

im getting 0.00v to each pin connecting to the efi fuse! By "take the relay block apart" do you mean remove the fuse/ relay panel from the fender and search?

scope103

That's what I meant. My '93 EWD shows the EFI fuse connected straight to the battery, so if you have battery power but no voltage to ground (or more clearly, no voltage to battery - ) on both sides of the EFI fuse holder then you have to have a wire broken somewhere.

Since you can crank it, presumably there is power to the starter relay, so the big AM1 AM2 and ALT fuses should be good. Look closely at them, just in case. (don't try to pull them out; they're attached by screws from underneath).

But I can't think of anything else to explain your observations.

Dk2685

It appears that the

The alt fuse looks a little busted up. There is a tinge of blackness that I'm not sure comes through in the photo but maybe I should replace?

Dk2685

It appears that the efi fuse wires go directly across to the left fender where the ignition coil is mounted. All I have coming off the battery is the fusible link which is connected to the alternator fuse, head relay and hazard fuse.