Fuel pump problems, is there something I am missing?

[iwantacelica]

ok, the truck is a 1994 Ranger 4x4, with the 3.0L V6. After finally discovering a bad pickup coil, I swapped it out. At this time, the following parts are also new:

--distributor
--ignition coil
--cap & rotor
--Plugs and wires

Put everything back together. Now, it will not start. It will crank all day long, but it will not start. I am getting spark at the coil. I checked the schrader valve on the fuel rail, and noticed that no fuel is present. There is new gas in the tank, but apparently the gas is content to stay there...

So far, we have checked the relay, and the accident kill switch in the passenger footwell. Then we took the bed off to check out the fuel pump. The pump is not coming on at all. When I turn the key on, there is a very noticeable click that appears to be the fuel system relay working. For ha-ha's, I swapped in a different relay, but that did not change anything. So, this brings us under the bed, to the pump. Using a meter, we find that there is absolutely zero power at the pump. None. But putting power to the pump makes it work fine. So, the pump works. The relay appears to be working. But no juice at all with key on. One more thing--when the key is turned on, the relay clicks, but there is no noise from the pump itself.

The first thought that popped in my mind was a broken wire somewhere between the relay and pump. Is there anything I am overlooking that would cause this problem, or is the wiring theory the best place to look? Also, is there a second fuse or relay that handles the fuel pump on a 94 Ranger? The power distribution box under the hood only shows the relay, no fuse.....and the interior fuse box does not show a fuse either...

 

[MrShorty]

Have you checked the inertia switch?

 

[iwantacelica]

yes, it was not tripped. At this point, I am thinking of just running new wiring between the relay and the pump just to see what happens. By the way, is there a separate fuse for the fuel pump somewhere, or is it just the relay under the hood?

 

[Anime]

If theres not a fuse under the hood with the relay or in the cab, there's just the relay. I'd say going by what you've done so far, if the relay works and the pump works, then yes, the problem is in the wiring from the relay to the pump. You'll need to check it visually. It'll be a pain, but worth it. Look for areas where the wiring might have rubbed and been cut/shorted first, you might find it easily. Otherwise just check but by bit until you find the bare spot or break in the wire and fix accordingly, preferably in a manner to prevent it from happening again.

 

[iwantacelica]

thanks guys, and yes shorty, this is the same truck that I spoke to you about in here some time back in regards to the distributor/pickup coil. Because of my work the truck has had to sit for a bit before I had the chance to work on it again. FInally thought I was going to get it up and running, and now this. This weekend we are tracing the wiring from the fuel pump forward so we can see exactly where it is routed. Hopefully this is the last problem with this thing for a while. And when this is done, when it is finally running, I need to replace the o-ring seals in the AC system and recharge it, replace the driver's side power window motor, and take apart the 4WD switching motor to replace that little plastic bushing that causes so many problems....guess I know where my weekend is going to be spent!

 

[MrShorty]

yes, it was not tripped. At this point, I am thinking of just running new wiring between the relay and the pump just to see what happens. By the way, is there a separate fuse for the fuel pump somewhere, or is it just the relay under the hood?

If you find it easier to run new wiring, that's fine. If it were me, I'd use voltmeter to find the break in the wire.

My '92 has a fuse for the fuel pump in the power distribution box under the hood. If the fuse is blown, the relay can close, but there won't be any current flow through the relay.

 

[iwantacelica]

If you find it easier to run new wiring, that's fine. If it were me, I'd use voltmeter to find the break in the wire.

My '92 has a fuse for the fuel pump in the power distribution box under the hood. If the fuse is blown, the relay can close, but there won't be any current flow through the relay.

we can use a meter on the whole length of wiring too, I was just looking to run a quick test by using new wiring just to see what it did. I was not as much looking for a permanent solution out of that.

Is there somewhere in here that I can find a diagram or illustration of the power distribution block for this truck? You have me curious now, since you said you had a fuse for yours under the hood. For some reason, I was thinking that the 91-94 Rangers were very similar in such respects. I do recall that the interior fuzse block was the same among those models....

Which fuse was it? I do not recall seeing a fuse marked for the fuel pump, but it is probably on the same circuit as something else.

 

[MrShorty]

I don't know of anywhere here that has a power distribution box picture. Chilton's/Haynes might have one. FWIW, the wiring diagram for a '94 3.0 Rangers in my Chilton's manual shows a single fuse dedicated to the fuel pump circuit, so I expect you should find one.

If it's the same as my '92, the relays are underneath the fuses in the power distribution box. On mine, the lid covering the fuses has a nice diagram identifying each fuse within. Then you have to lift the "box" with the fuses out to get at the relays. If yours is different, then I have no idea how they laid it out. Hopefully they show the layout on the box like mine.

 

[iwantacelica]

ok, update...

this is really something.....we traced the wiring all the way, back to front, and found no break. On a whim, we took a relay out of another Ford pickup and tried it out...and the friggin fuel pump WORKED. Apparently, the clicking we heard was the relay trying to close, I guess, because it never opened. Now we get full pressure to the fuel rail. And then...the battery was low. Go figure. By then it was a bit late so I am picking up a new battery tomorrow. We tried charging this one, but a cell is dead--not taking a charge very well. So, try again tomorrow.

About the power distribution box--in my truck, looking at the box from the driver's side(that being 'bottom'), there are some large blade fuses across the bottom. There is a separate section up top(on the side closest to the engine) for relays. One of those is marked for the fuel system. There is no fuse that is marked for the fuel pump or fuel system, just that relay. Apparently that was the problem. Oh well, at least I know that the pickup coil issues I had were real, and not just caused by this relay. I will update again after we give it a shot tomorrow evening. Thanks again for all the help!

 

[iwantacelica]

alright, well, we now have fuel, air, and spark. We also have a new battery. It turns over, but still wont start. The only other thing I can think of is timing, since the distributor was just replaced. Tomorrow, we are going to see what the timing light tells us. I honestly cannot think of anything else, I know I am getting spark and fuel. Any thoughts?

 

[MrShorty]

Have you verified that the injectors are opening? Are the spark plugs "wet" after trying to start? You can have all the pressure you want at the fuel rail, but, if the injectors don't open, the fuel can't get into the cylinders.

 

[iwantacelica]

yeah, the injectors were checked and they are working fine.

Funny thing--it was just out of time a bit. The new distributor was a little bit off when we installed it, so now that that's fixed, it fired right up! Idles very smoothly at about 700-800 rpms, and drives just fine. Really strange driving it again after all these problems, but glad as anything that it works now.

NOW, on to the next project, which for this truck will be the 4WD switching motor repair...