Trying to get truck running, no fuel, shorted something, truck dead, HELP!

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Arya Ebrahimi

Arya Ebrahimi

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Dec 2, 2003
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Location
Rockville, MD
Ok, I'm finally trying to get my truck going(buildup in sig) and after relocating the fuel tank and letting it sit for over a year and a half without running, there are some problems.

We threw a new battery in it last night and it cranked just fine, but didn't fire. Pulled a plug wire and held it against the block, spark is good. So I go back and listen to the fuel pump, nada. Ok, I extended those wires, maybe I messed something up. So I started probing around with the volt meter. I pulled the main harness connector for the rear of the vehicle at the passenger side floor board and put the volt meter on the pins for the fuel pump. with just the ignition on, there was 0V, but when I had my friend try to start it, it cranked for a split second, and then the truck died, no power to anything. In that split second the volt meter read 3V, but then back to 0V obviously.

All the fuses look good, but I doubt it would be a fuse since everything is dead. Any idea what the problem is and why checking the voltage across the fuel pump wires would cause it? Thanks!

Ary
 
There are only 2 conditions when there should be +12V going to the fuel pump: when the engine is being cranked, and when the engine is actually running and pulling air thru the AFM on the airbox.

Find the Diagnostic connector under the hood, right behind the battery. Take a paper clip and jumper across the +B anf Fp connectors. This is a diagnostic check to force the fuel pump to run. Turn the key on, then you should be getting +12V at the connector under the seat. If so, plug it in, the fuel pump should now run. If it doesn't run, it's dead.

Is the AFM on the airbox hooked up?
 
2ndGenToyotaFan said:
If you have no power to anything, I'd start at the battery and check the fuseable links.
Click to expand...

Thanks for the info guys. What do these fusible links look like? I've never dealt with them before, so I honestly have no idea.

KLF, does the fuel pump not prime the system when you turn the ignition on like modern fuel injected vehicles? Also, yes, the AFM is hooked up.

Thanks again,

Ary
 
Arya Ebrahimi said:
Thanks for the info guys. What do these fusible links look like? I've never dealt with them before, so I honestly have no idea.
Click to expand...

They are on the battery connector on the + side. They look like ordinatey wire, but are usually about 2-3" long.

Arya Ebrahimi said:
KLF, does the fuel pump not prime the system when you turn the ignition on like modern fuel injected vehicles? Also, yes, the AFM is hooked up.
Click to expand...

No it doesn't. You're thinking of most european cars, like VWs and Mercedes. My GF's Volvo does this too. They keep the fuel rail pressurized and there is a pressure switch on the rail that tells the pump when to run.

Toyota (AISIN) EFI systems run the pump all the time, but only in the conditions I described above. They keep a constant pressure in the fuel rail with a regulator that sends excess fuel back to the tank under low demand situations (idling, etc). IMO this is a safer system, as soon as the engine stops running the fuel pump stops, whereas in the other type the engine can stop (perhaps from accident), but the fuel pump will keep running, possibly pumping gas on a fire.
 
Ok, cool, so will these links be burned through I guess?

Also, since you seem to know what you're talking about. The stock tank from this truck had 3 hoses coming out of it, one supply, one return, and the third? I lengthened all of them, but the newer tank I'm using only has supply and return, no place for the third. Any idea what this is for? Is it necessary? Would T-ing the two return hoses together be bad?

Thanks!
 
The links will either be visually failed, or you can test them with an ohmmeter.

The 3rd line is the vent for the charcoal canister. No, you can't T them together, you'll have gasoline gushing out of the charcoal canister under the hood. Not good!

The second newer tank sounds like it is for a carbed truck. Are the flanged holes in the top of the tanks the same size? The one for the carb tank is smaller, since there is no in-tank fuel pump.

This is what a carbed truck gas tank looks like:
GasTank1.jpg
 
The flanges are the same size, I actually swapped the pump over from the '86 tank. Both trucks were EFI. However, the '86 tank has the small tube that is actually on the tank(like in the pic).

I'm sorry for being so dumb when it comes to engines, just haven't had much experience messing with them. Does the charcoal cannister need to vent to the tank? or can it vent to the outside?
 
Here are a couple pics.

First pic is newer tank with the pump mounted.

Second pic is the older tank missing the pump, but with the extra port in the tank. FYI the '86 is actually titled as an '85 but has EFI and IFS, so I've always called it an '86 to avoid confusion. I wonder if this fact makes it an oddball since it was a transition period.

Ary
Dec 19 '07 016.webp
Dec 19 '07 017.webp
 
I don't have my FSM with me now, but it explains how the charcoal canister system works. I don't think just sending the vent to the atmosphere is a good idea, but I don't know what to to about the missing connection. It's odd, because the pic I posted is from my old '84 truck, and there are 3 connections on this tank too.

What vehicle did the "newer" tank come from? It doesn't look like a truck tank to me.
 
Not that I think its gonna be a big help but FYI the EFI fuse is the one in the lower left hand corner of the fuse box behind the plastic kick plate that is located under the dash and next to the door. I would yank that fuse in general and check continuity in the fuse itself.
 
"N8" said:
Not that I think its gonna be a big help but FYI the EFI fuse is the one in the lower left hand corner of the fuse box behind the plastic kick plate that is located under the dash and next to the door. I would yank that fuse in general and check continuity in the fuse itself.
Click to expand...

Pardon my ignorance, but is this a regular looking fuse? Also what is the amperage rating? I don't have the lid to my fuse box, nor do I have an owner's manual so I don't know what fuse goes to what.

Thanks!
 
Alright, disregard the question about the EFI fuse. Whatever the problem is, it's blowing the 80amp main fuse.

I swapped in the 80amp main from the F-toy and the accessories(aka the headlights) worked. However when I went to crank it, the 80amp main blew again. I'm really at a loss. Everything is connected properly as far as I know.

Help! Thanks
 
Ok, it wasn't the fuses at all. Turns out the fusible link failed but would make enough contact to run the accessories. I guess the draw of the starter would blow it out again.

Anyway, anyone got a way to test the fuel pump?
 
Moving along, I jumped the fuel pump diagnostic plug, and that did not do anything. Now if I try to crank the engine everything dies. If I go back and wiggle the positive terminal everything comes back to life, but once I attempt to start again, it dies once more. I can reliably get power back everytime, just not when I want to crank the engine :mad3:
 
How bout the starter? If you run a "hot" wire right to the solinoid will it enguage and spin?

Remember when you said "all I have to do is put in the gas tank" and I laughed... this is just the begining :flipoff2:
 
IT RUNS!!!! WOOT WOOT!!!!

It turned out to simply be a corroded connector between the battery and the fuse box. Once I ganked a "new" one from the formula toy it started cooperating. Then it turned out that my original fuel pump which worked when pulled no longer worked. I guess sitting outside the shop for a year and a half didn't treat it kindly(it was in a tank, not literally outside). So I ganked the fuel pump assembly from the Ftoy and it works, but the top was really corroded. So after I swapped that I went to fire it up and the damn thing started pissing gas everywhere. So a bit of jerry-rigging and a few hose clamps later and I thought the problem was fixed. Well it wasn't, it was still misting a little bit of gas out of the hardline, but it was contained enough to try and start it. I wrapped a rag around the hardline and cranked her up.

She fired a few times but wouldn't catch. Apparently the computer needs to be plugged in for the engine to run DOH! After I plugged that back in, she fired up and ran rough and would stall if I pushed the gas, so I let it idle for a bit and now everything is normal. I think I need to do an oil change, but otherwise she's running normally now

Now all I have to do is find a new fuel pump assembly with the 3 hardlines coming out of it.

Ary
 
Arya Ebrahimi said:
Now all I have to do is find a new fuel pump assembly with the 3 hardlines coming out of it.

Ary
Click to expand...

I might be able to help you with that. I'm parting out an '87 turbo truck that has that type of connection on the fuel pump hanger. I need to hang on to the pump, though.

When it stops raining I'll try to pull it off the tank. The bed is gone so access is easy.
 
KLF said:
I might be able to help you with that. I'm parting out an '87 turbo truck that has that type of connection on the fuel pump hanger. I need to hang on to the pump, though.

When it stops raining I'll try to pull it off the tank. The bed is gone so access is easy.
Click to expand...

That would be fantastic! Assuming the flange is in good shape that is. The one I pulled off the Formula Toy had the 3 hardlines, but was so corroded the lines just cracked when I hooked up the hoses. Let me know, I can send you paypal, check, whatever. I really need this part. And yeah, I don't need the pump, just the hanger assembly.

Thanks!

BTW, where in southern NH are you? My gf's parents live in Bow, just south of Concord. I'll actually be up there for New Years, but would like to get this before then if at all possible, otherwise I would just offer to pick it up.

Ary
 
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