1989 P30 fuel line configuration at tank?

circleD · December 05, 2013, 05:07 PM

Oops

I figured it would've been EFI. I got my years mixed up. Do you have a washer and dryer on board that could have a gas power assistance? I'm out of ideas friend.

ClydesdaleKevin · December 08, 2013, 10:56 AM

Mystery solved! And it wasn't even a mystery, just mistaken identity of what I thought was a fourth fuel line which was actually a brake line for the trailing axle...lol! That and a faulty memory, because I could have sworn that there was a 4th line coming out of my fuel tank...but when I crawled under there today, there are only 3!

I took the lockring off and removed the pump/sending unit assembly just enough to identify which hose when to where.

One is definitely a vent, one is the main 1/2 line coming directly out of the electric fuel pump, and one is the return. So it must be a factory setup for the genny to tee into the return line.

I'm not going to bother replacing the vent line. And the half inch rubber hose, which is really hard to get to, is a very short 10" run to the fuel pressure regulator (which I hope NEVER goes bad, since its on the opposite side of the tank and would require dropping the tank to replace...and from the regulator right to a steel 1/2 line which runs all the way to the front mechanical fuel pump.

I think the genny fuel delivery problem is the 10 whole feet of crusty rubber fuel hose that goes from the steel line where the genny tees into it, all the way back to the fuel tank.

So that is the only rubber hose I'm going to replace for now.

I traced everything back to the front, and lost the vent line somewhere...but the other two lines run right to the frame rail just a few inches from the mechanical fuel pump. They are short, and look okay, and since they are very hard to access on our rig, I'll leave those hoses alone too for now. Our coach has that extra steering stabilizer called a Safe-T-Plus, and it would have to be removed in order to access the pump from below, or I'd have to take the alternator out to access the pump from above. If it ain't broke, don't fix it!

Once I replace that 10 foot section of rubber hose, the genny should be good to go. So that is tomorrow's project.

By the way, I made another misidentification. What I thought was a big 2 inch hose from the filler neck is actually a vent that ties into the filler somehow via a canister next to the filler neck...which is a massive hose barely visible entering the side of the fuel tank.

I took pictures and will post them when I have a chance.

Kev

circleD · December 08, 2013, 11:07 AM

My experience with vent lines are to keep them like water pipe. Make sure it has a slight angle going up and out of harms way. Put a new vent cap on there and since its not a truck bed and you live in there aim it towards a place that fresh air moves freely even sitting still. I modified some trucks for water crossings and the vent lines need to be kept clean and clear.

HandyDan · December 08, 2013, 04:50 PM

Maybe I'm just showing my ignorance, but I can't picture why a generator would be teed into the return line. Maybe I just don't understand how the whole system works, but I would think getting gas to the generator would be extremely difficult if it was relying on return gas. Seems like it should come right from the tank. I did find this diagram of a Ford system that the owner modified in case the intank fuel pump was to fail. He made it so the engine could still run by bypassing the fuel pump. However, according to the forum dialogue that went with it, it wasn't working well.
Dan

M & J · December 08, 2013, 05:23 PM

I initially agreed about the genny being wrong tapped in the return line, unless the return is piped below the fuel level near the bottom of the tank. All genny fuel supplies are drawn from above the bottom of the tank to keep some fuel for the engine so the tank isnt run dry by the genny. If his return is a few inches above the bottom then it will draw fuel as it should regardless of the engine running.

pvoth1111 · December 08, 2013, 06:06 PM

my genny is teed I into return line...

ClydesdaleKevin · December 09, 2013, 07:50 AM

Yep, the return line does go to a tube that is just a couple of inches shorter than the bottom of the electric fuel pump.

I'm hoping that by replacing that rubber line today it clears up the fuel delivery problem completely. It should, since I already replaced the genny's fuel pump.

Kev

ClydesdaleKevin · December 09, 2013, 03:19 PM

Bingo!!! All fixed! I replaced the hose (it ended up being 5/16 not 3/8, so another trip to O'Reilly's was required...and since it was 10 whole feet they sold me of the 3/8 they let me exchange it and the hose clamps for the right ones).

I put it on, zip tied everything in place, and started the genny.

It took a bit to prime all the way from the tank, but then it evened out and I could see a steady fuel flow in the clear plastic fuel filter.

I let it run for a whole hour under load with the AC blasting, and the genny is running great now!

Problem solved and fuel line routing all figured out!

Kev

MattyT · December 03, 2015, 08:27 PM

I know I'm late to the party but I'm having the same problem and cant find anything online about it.
Any idea what lines connect to the tank here? Thank you!

bluebird · December 03, 2015, 09:23 PM

You can ask questions, but only use 1 thread for your question. Don't ask the same question in multiple threads. You need to pull the lines back out of the tank and mark them as to which one is the longest, it goes to the fuel pump. The return line from the front goes to the shortest one. The generator goes to the the next longest. The other one is the vent and should be the largest on of the bunch.

kattkisson · December 04, 2015, 06:29 AM

On my 1993 rig which is granted younger than being discussed the 3/4 length dip tube is the feed for the Onan generator which has its own electric fuel pump. It is discussed in the owners manual as being a feature to always have a reserve in the tank.

ClydesdaleKevin · December 04, 2015, 05:16 PM

One line will be a vent line, one will be the main line (1/2 inch), and one will be the return line. On ours, we don't have a specific line running to the generator...it Tees into the return line.

Kev

HandyDan · December 04, 2015, 07:22 PM

I thought the vent line was the shortest in the tank. In 1985 they changed the configuration of the gas lines (in tank fuel pump). Therefore my 1983/4 tank doesn't look like the one pictured at all.

Rickf1985 · December 04, 2015, 07:42 PM

If you cannot tell by the lines telegraphing themselves to the correct position then the only way to be sure is to pull the unit out. Be sure the gasket is still good before putting it back or it will leak from sloshing. I would use Permatex #3 gasket sealer if using the old gasket.

HandyDan · December 04, 2015, 08:12 PM

I got this picture from a friend. May or may not be of any help, but thought I would post it.

legomybago · December 06, 2015, 03:08 PM

The 454 will go to the longest pickup tube
The genny will go to the next shortest.
The fuel return on the last one.
(In a nut shell)

legomybago · December 06, 2015, 03:09 PM

Oh, I just re-read you post....If you already have the tank installed. I cant help....lol

Rickf1985 · December 06, 2015, 03:10 PM

I strongly advise replacing the old lines while you are there but the fact that the old lines are hanging down there should be a big help. You will find that they have a set to them and they will pretty much point directly to the tube they belong on if you hold them up at the level they would be at when the tank is in place. Every fitting is a different angle and those hoses will be pointing in their respective directions once held in the proper plane. Just hold them lightly and back about 6 or more inches from the ends.

MattyT · December 06, 2015, 03:10 PM

Okay I will try that. I'm also not 100% certain the sending unit is facing the exact same angle as when I took it out (it's very close. Is there any way I can test what line goes where if that doesn't work? This is the only thing holding me back from re-installing the tank.

Rickf1985 · December 06, 2015, 03:12 PM

The sending unit is almost always keyed with a tab so it will only fit one way.

MattyT · December 06, 2015, 03:12 PM

this sending unit has 5 screws holding it in

legomybago · December 06, 2015, 03:13 PM

Quote from: MattyT on December 03, 2015, 08:33 PM
Okay I will try that. I'm also not 100% certain the sending unit is facing the exact same angle as when I took it out (it's very close. Is there any way I can test what line goes where if that doesn't work? This is the only thing holding me back from re-installing the tank.

There is only one way to do this. Since you do not have the tank installed, take the sending unit back out and take note of the pickup tube lengths. Reinstall. Then you need to figure out which rubber fuel line goes to what by tracing/tracking/following them...While your there, replace the rubber fuel lines like someone already mentioned.
Good Luck

TripleJ · December 06, 2015, 03:16 PM

I think my unit uses a similar setup. If so, the lines will be as follows

-the brass elbow fitting threaded to the top of the tank is the fuel return from the engine

-the 3rd barb on the sending unit, the one that is most separate from the other two and has a restrictor orifice jammed in the end is the fuel tank vent

-the largest of the three, and the one facing mostly toward the front of the vehicle should be the fuel feed to the engine

-the smaller one in the middle of the three should be the fuel feed to the generator

Depending on how much fuel is in the tank you could stick some hose on them and at least verify the engine and genny feed, as you should be able to suck fuel. the vent and the fuel return will NOT dip into fuel no matter how much gas is in the tank.

hope this confuses you... I MEAN HELPS

****edit**** since this thread was combined...

my post only applies to carbureted configurations with NO fuel pump in the tank.

MattyT · December 06, 2015, 03:17 PM

You're correct I tested the fuel lines by placing them in a water bottle, I'm going to replace some of them considering theyre falling apart and it should be good to go

circleD · December 06, 2015, 03:18 PM

If the tank is down or can easily be taken down I strongly suggest replacing the lines with good quality ones. I also clean the tank and put new paint on it with new clamps on when I do this work. Rick knows his stuff and so do the others commenting on here. Its years of us messing up our selves. Good luck.