Need help with fuel system

[tcg528]

Hello all,
I just bought a 1986 M1009 from a private owner last week. Had to have it towed to my place. The guy who sold it to me said that it had stopped working recently (Inspection is 6 months old, had current tags when I bought it). A diesel mechanic said that it was an air leak in one of the metal lines, but not sure which one, and fuel is not visibly leaking. I've been looking through the forums and online ever since I got it, and cannot find the Fuel Tube diameters. I'm taking him on his word that the lift pump is brand new (too clean to have been...cleaned), and the injection pipes are fairly rusty.
Troubleshooting so far:

-Tried priming via opening the air release screw on the fuel filter and cranking. Cranked it for 4 - 10sec intervals.

-Tried feeding fuel directly into the injection pump via the line from the filter (I'm really new to diesels, realized a day afterwards how that wouldn't work)

Today I'm going to try unhooking the inlet line to the lift pump, and hooking that up to a container of diesel. Hopefully if I can get it started, it means that the problem is with the fuel feed line from the tank.

Anyone know what diameter of brake line to use for the fuel lines?? All the TM's just give me a part number, and when I look that part number up on FedLog it doesn't show diameter.

Thanks,
Tim

 

[raiburn]

If the air leak is so small that fuel does not leak out, it should still start and run, maybe rough, but it should run.
Why do you want to know the fuel line diameter? To replace it, or fix it?
If you can slightly pressurize the fuel tank, (less the 5 psi), it should leak and look wet at the problem area. You will need a spare filler cap to drill a hole for an air fitting. Joe.

 

[JAsher45]

the fuel lines on these trucks are the same as a 85 K5 blazer with a 6.2 diesel. i did some digging ...... 0.375 INCHES NOMINAL that is the size of the bulk line that you are to use to make the lines with the ends are 5/8-18 45 degree fittings

 

[Heavysteven]

When you opened the drain above the fuel filter did fuel come out and hit the ground? If no fuel then the tank pump is working.

If fuel there i would crank each injector lose. If no fuel there than injector pump.

All that said i would make sure the tank has clean diesel fuel in it.

 

[Erik Jenkinson]

I had the same issue with mine. I replaced the fuel filtation with a Racor spin on. That solved the problem completely. The stock system is super problematic. Perhaps take a closer look at yours.

 

[tcg528]

Thanks for the fast and numerous responses.

I did crack the fuel filter off during a dumb "look with my hands" moment, fuel spilled out, but that was before I tried bleeding. Once I tried bleeding though, nothing came out at all.

@ JAsher45: Where did you find that? I've been looking almost everywhere. The chevy dealership couldn't even find part numbers.

As for fuel tank pressurization, I tried by inserting a Slime Tire compressor hose down the tank and stuffing with a shirt, Autozone guy said it should work, but I got no pressure, and no leaks.

Where did you get yours, Heavysteven?

 

[JAsher45]

in the tm it gives the PN for the bulk line that the line is to be made of... looked that number up... and got the info... i tend to know my way around TM's and FEDLOG

 

[Heavysteven]

Thanks for the fast and numerous responses.

I did crack the fuel filter off during a dumb "look with my hands" moment, fuel spilled out, but that was before I tried bleeding. Once I tried bleeding though, nothing came out at all.

If bleeding the filter failed then I would supect the tank pump.

 

[tcg528]

Lol, went on Fedlog for the first time in 3 years looking for the individual part numbers of the line sections. I'll have to take a closer look at the TM's when I get a chance. Finally read thru the -10, the -90 is gonna take just a bit longer

It would be nice if its the fuel pump, I was taking a look at the electric fuel pump conversion on here. It seems like it's very convenient.

 

[doghead]

Heavysteven, We're talking CUCV here, NO INTANK PUMP.


When you tried to prime the fuel filter, did you have the pink wire disconnected from the IP?


Stock filters are NOT super poblematic. The filter bases can have issues.

 

[Blood_of_Tyrants]

Someone correct me if I am wrong, but the M1009 doesn't have a lift pump in the tank. It only has a mechanical fuel pump. Parts are commonly available at most auto parts stores. When asked, the engine is a "J" code. The "J" code is for the military GMs.

Open the bleed screw on the filter and crank the engine. If fuel comes out, the fuel pump is good. If not, replace it. You'll have to take the pump and the plate between it and the engine block off, too, so you can get the pump push rod out. Why do you have to take the push rod out? Because you have to coat it with grease to hold it in place while you install the fuel pump.

 

[tcg528]

Yes, it was removed.

 

[tcg528]

The pink wire to the IP, that is.

 

[doghead]

So, after a total of about 2 minutes of intermittent cranking, you should have had fuel at the filter bleeder.

If you didn't , you very well may have a bad fuel line. It is easy enough to follow back to the tank.

There is a possibility that the short rubber lines that connect to the tank, are dry rotten.

Also, possible that the steel tubes in the tank have rusted through.

Your idea of temporarily suppling the fuel pump, is a reasonable test, but it will only instill confidence that the truck does indeed run, and will not help solve the air leak, if that is the issue.

 

[tcg528]

wasn't able to disconnect the rubber hose that connects directly to the fuel pump, but I was able to confirm that the supply line has fuel in it, so I know it's not an empty gas tank with the fuel gauge reading high.

The plan of running a diesel source to the pump itself was just to rule out the pump and further isolate the problem. It is by no means a solution, temporary or otherwise.

I need to look in the TM's and see if I can remove the bar thats in the way when I try to access the lift pump. I just cannot get enough room/leverage when dealing with it from the top or the bottom with it in the way.

 

[tcg528]

Also, I need some advice concerning the electrical system.

The previous owner let his son have the vehicle, we'll call the son "Homeboy". Homeboy decided to jack this thing up. It looks like he converted to 12v...badly. I haven't checked the starter yet, but I suspect that it wasn't replaced with a 12v starter. It's been taking 2 vehicles to charge up the batteries enough to give it enough juice to crank over a few times, and it usually takes about 10-20 minutes to get a few 10 sec cranks.

The wiring is a mess, Homeboy literally had to relocate the batteries right next to each other and install a switch to cut off the negative line from the rest of the vehicle because he accidentally wired in a short in the system.

I plan on rewiring (as best as I can) the M1009 so that you don't have to disconnect the batteries every time you let it sit, but should I go back to 24v, or finish and clean up the 12v conversion.

24v has pros and cons, such as having the TM's as a nice guide, but I'd have to buy a new alternator for the drivers side and possibly expensive starters.

 

[doghead]

Are you saying you now only have one(passenger-side) alternator? That's not good


If we are gonna help you figure this thing out, your going to need to post a bunch of pics and info!

Schematics are in the back of the -20 and -30 TMs.

 

[tcg528]

When I get out of work, I'll throw up as many pics as possible to help. Every time I get under or pop the hood open, I discover something new that has me bewildered.

 

[tcg528]

Also, if I do need to remove the lift pump, how exactly do I get to it? If I go underneath, I have a metal bar (crossbrace?) in the way. If I lay down on top of my radiator shroud to get in there, I can't reach everything.

 

[JAsher45]

the lift pump is really kinda a pain in the nesck cause it is so close the the cross member. you can get to it from top or bottom... i normally go from the bottom if you jack it up and set it on jack stands on the frame ... not the axle you can get some more head room.. it does help a little to let the suspension drop. you will need to be able to see with your fingers to get it ... and one last thing... the metal fuel line that goes in the pump.... make sure you start it a few threads before mounting the pump... it will keep you from cross threading it when it is in place....