Fuel Tank Service for a Rusty Tank

[derburger]

I bought a 1986 XT which had been sitting since 2001 with old rusty gas, the fuel system needed much repair, this is how I did it, and how you can too.

The metal "fins" inside my tank lightly rusted. I found this out after I replaced the fuel tank, and cut open my old one. The fuel pickup "sock" wasn't clogged at all in the old tank. I could have cleaned up the tank with some sort of solvent, there wasn't rust on the tank body itself. The rust/bad gas killed my fuel pump within 200 miles of driving, so don't drive on old gas. I replaced the fuel tank and filter and pump, drove some more, then the fuel pressure regulator stuck closed (due to rust/crappy gas) which caused high fuel pressure, stalling of the car.

My fuel filter was orange on the inside, the car stalled, stumbled upon acceleration, and would cut out. My XT had not only old gas, but moisture in a not full tank.

This is what you should do when you buy an XT that has been sitting for a while with old gas.

Remove the fuel tank & drain it on it's side, use solvent to clean the inside of it. The tank is held on by 6-8 bolts, and you'll need to drop the rear differential to get the tank out as well, which is 2 17 or 19mm bolts; use your lug wrench and a cheater pipe on those. Use a 10mm 1/4'' socket on the fuel filler neck hose clamp.

It's an easy job, BUT, the old hose clamps will be rusty and hard to turn by screwdriver, so just cut them and install new stainless ones; or you'll waste hours with them, like I did! If you don't drop the tank you won't get all the bad rusty gas out, there was a few quarts of the crappiest gas ever in there, that came out of the tank when I drained mine it on it's side, you can't get it out by removing hoses. That old gas/rust will wreck your fuel pump, it has to go before your pump does.

Then after the tank is cleaned out, you should splice in a clear fuel filter between the tank and fuel pump; it'll catch any residual junk and let you know what's going on in your tank! Only a few bucks. Your fuel pump is a bosch design, it can be cleaned out by reversing voltage & running it backwards, on diesel, AFAIK. Correct me if I'm wrong. This filter is the kind you're looking for if you want to put this before the fuel pump, a clear inline one, on the suction side of your fuel pump, the larger hose.



Also, remove the fuel pressure regulator and clean it (it's on the return line in the engine bay, has 2 fuel line connections, a vacuum hose) because in my case, it stuck closed and caused lots of problems. When I removed mine, pretty much solid rust came out of the inlet side. Mine was so bad I had to buy a new one. It seemed rust collected before that regulator and stuck it closed.

You can also blow out your fuel and return lines with compressed air. Remember if you're blowing into the tank to take off the gas cap or you'll have a nice balloon for a gas tank.

I did all of this, all the symptoms like hesitation went away with a tank of regular gas and a good heavy dose of fuel injector cleaner, within 40 miles on the highway. Now my 86 xt runs great.

Good luck, and don't rule out your gas tank as rusted out like I did; I learned this after taking a cut off wheel to my old one.

[Fury]

Just 2 quick points.

1 If the tank IS rusty, ( mine was so rusted, that a couple of pounds ( or a kilo or more) of rust flakes came out when splitting the tank. unless it is sealed, it will continue to rust unless coated ( ie the interior of the tank is impregnated with a paint membrane that reduces the amount the rust continues to develop). There companies who can do this, but it is cheaper to just find a good replacement tank.

2 If appying a fuel filter, as suggested, It must suit an EFI system. Must be hi flow and depending where it is put ( pre or post pump) Be able to either accept 50psi pressure or suction.


MOST plastic ones, will last for a time in suction, but DO FAIL unless from an EFI vehicle.

[gpilot]

I agree with derburger. My 6 had similar issues, most were due to crud in the tank.

I had issues which were not apparent until the car was running for 30 min or so, I was thinking electrical, ie coil, fuel pump, fuel pump relay, ecu, etc. I finally hooked up a pressure gage to the HP side of the line and amazing thing, when the car stumbled or stalled the pressure was rapidly falling from 30 to near zero, accompanied with weird noises from the fuel pump. So I knew it was a fuel pressure issue, but why? After swapping in a new pump, the symptoms were better, but still there. The new pump was able to suction more than the old one, but the problem remained. I spliced into the fuel pump power line with 2 added wires, the negative pump wire led to a n/o switch which was connected directly to the neg battery terminal ground (thereby bypassing the ECU when the switch was selected on, as the stock wiring grounds the pump thru the ECU), and the positive wire directly to another n/o switch which was directly connected to the plus 12v battery terminal (thereby bypassing the fuel pump relay when the switch was selected on).

I drove the car, when the fuel pressure dropped again, I selected both switches ON, one at a time. Closing the +12v switch had no effect (whew!! I am glad it was not the fuel pump relay or anything on the +12v supply side, accessing that relay is a ^%$%#!!). Closing the ground switch produced a distinct increase in the speed of the pump (so the ECU must be controlling the pump via the ground wire) however there was minor change to the lack of fuel pressure. Not enough of a change for the engine to run anywhere near normal.

So I bit the bullet and swapped fuel tanks. The old tank was awful. Crud was everywhere. After the car sat, the crud was not impeding the suction of the pump too much, although the pump was working too hard (and getting hot to the touch). After 30 min of running, the crud was "compressed" if you will, forming a better "stopper" in the suction line. That is when the fuel pressure dropped to near zero.

Result..problem solved. Fuel pressure actually increased about 5 psi to about 28 - 30 psi at idle to 40 at high throttle.

NOTE: The first poster had an excellent idea, the prefilter he installed will tell you if your tank is crudded inside. I actually did that during my troubleshooting.

Note to previous poster: The prefilter pictured will work, in the suction side it is not subject to the 40 psi pressure. I agree the filter shown is BAD for EFI systems ON THE PRESSURE SIDE but this install is on the intake side of the pump.

[Fury]

Note to previous poster: The prefilter pictured will work, in the suction side it is not subject to the 40 psi pressure. I agree the filter shown is BAD for EFI systems ON THE PRESSURE SIDE but this install is on the intake side of the pump.
gpilot

ER --- WRONG......

I wasn't going to make a big deal over this, but seems like my good intentions were mis-understood

I have had two ( 2 ) of those filters fail ( they compressed under the suction of the pump and cracked) and drained the entire tank, were installed - PRE fuel pump , years before this post was put up, so it was just a note to others, to consider the use of an EFI filter, as some of these std clear filters are not so reliable. Suction or vacuum is just as powerfull as pressure, so if you have a blockage at one end and suction at the other the weakest link breaks or is compressed. EFI fuel hose is also rated for compression not just pressure.

Put your hand over the end of a standard vacuum cleaner - what happens? Your loose skin ( weakest link) gets sucked in - and that is only a few lbs of suction - try 50psi from the fuel pump...

I didn't realise what it had done the first time mine needed replacement ( just cracked ), as it regained it's normal shape ( so replaced with a duplicate), the second one looked like a crushed coke can. They worked just fine for a few months.

There is a glass prefilter unit that is used in diesel applications, particularly in the marine industry, which is rated to 95psi, which would be good here. It is used to sight water or "diesel bug" and is often used on hi- flow engines and it dismantles for easy cleaning.

I am not disagreeing with you gpilot, just sharing experiences. You may have found a filter which is fine for your application, I was just suggesting a possible fault and method of rectification, due to my own experiences with exactly the same problem.

[gpilot]

Chris:

I am not intending any disrespect to you at all. I apologize if I sounded like I was. Thanks for sharing your experience. When I was troubleshooting (with the old tank, clogged fuel pickup) I actually had a somewhat larger filter installed as a prefilter. During this time, fuel pressure (measured) dropped nearly zero at times (see previous) therefore the pump was at maximum suction and the filter did not collapse. A fuel pump's maximum suction cannot be greater than atmospheric pressure, that's by definition what suction is. Say sea level atmosphere avgs 14.7 psi, a perfect vacuum pump (certainly not our fuel pumps) sucking from an empty container (or tank) removing 100% of the air will result in a plus 14.7 psi acting on the outside of the tank (or prefilter) inwards. There is no way it will come near the output pressure, its impossible. Please ask around if you care to, I am absolutely sure about this. Bet you a six-pack.

Now, on to real world, thanks for the headsup. The plastic filters are nice for troubleshooting because you can look inside to see if there is crud in your tank before doing the (for me anyway) a major job to r/r the fuel tank. After replacing my tank I left the prefilter in place (also my fuel pressure gage) to be certain there is no problem with the new (used) tank.

May I suggest to the original poster that he obtain one of those clear glass cylindrical filters with the replaceable elements, that you mention. I agree a filter designed for EFI pressures is best but they lack any way to see inside to confirm what is coming out of the tank (hopefully only fuel). I would make sure the glass filter is mounted securely so it doesnt bang against any part of the body and break ()-:)

Thanks again for allowing me to reconsider my position, I plan to replace my prefilter just in case.

[Fury]

No probs

Wasnt trying to bag you or disrespect you either, I just know that the prefilters that I had installed both collapsed after a very short time.

I guess I was just trying to clarify ( for individules who will use this info) that the use of some of the cheaper clear filters, which can be rated at a low psi rate - such as what I had used, are subject to failure...( which actually cost me nearly 1 & 1/2 tanks of fuel after it slowly leaked out)

The Ryco branded ones we have here in Australia are only rated to 9 psi, (and normal carbi rated pressure fuel hose is actually only rated to 10psi)

Atmospheric pressure is 14.7 lb as you said, and a perfect vacuum is almost impossible to recreate, but certainly I have seen many rubber hoses and light plastc containers colapse under a suction / vacuum environment. Technically, we are after good suction, not Vacuum

I do realise that I was also not clear in my previous answer. Reading back, my rating of the fuel pump pressure of 50lb, should have clarified it by saying 50 lb output, which would be probably close to 1 atmosphere of Vacuum ( if blocked) or hi flow suction - somewhere around three times that of a domestic vacuum cleaner (2 - 3 psi suction)

I am sure that we know what each other is thinking...

anyway...
This is my pre filter:
it is rated at 95PSI output PRESSURE... , and certainly strong enough for extreeme suction.



and disassembled:



sorry for the crappy phone res in the snaps...

[gpilot]

Chris:

Exactly the same filter I was thinking of.

Thanks for the pix.

Have fun.

Greg

[Fury]

It works well...

OH, just for others thinking that 1 atmosphere is not that much...

Planes ( yes even jumbo jets) are "sucked" into the sky,( for those that dont know) the wing induces lift, which creates a high and low pressure surface or side - (the same as any pump)

It is more important for the top surface skin on the wing of a plane to remain in tact than the underside, as it is the side that carries the plane...

I realised my $2 filter was crap, way too late....