Fuel Tank Inlet Check Valve leaking - Possible Fix

[NeilLTZ]

My 2003 LT 4.2L Trailblazer has developed a leak at the rear of the fuel tank where the check valve is plastic welded to the tank. Fuel seeps out at this "seam weld". At 140,000 miles I suppose I need a new fuel pump also. So I ordered a Delphi unit from Summit Racing including the sending unit and the OEM style rubber sealing gasket.

Anyhow...this is a regular length chassis. There was an warranty repair for this on EXT units. Regardless mine isn't EXT and I'm past the year/mileage cutoff. Personally speaking...I feel that this is a pathetic failure of the fuel tank design. I've had to fix alot of things in my life (the most recent being replacing the 4L60E in this TB because my torque converter came apart and pretty much destroyed the transmission with debris)...but I've never had to deal with a leaking poly plastic vehicle fuel tank on any brand, any vehicle. Oh well....here we go anyway.

The dealer wants $1200 for a new tank. And I hardly see how that will guarantee me it couldn't happen again. This truck is going to be with me until 200K miles. I'm not too far off now so a repair seems more like it. Between the new transmission and a new fuel tank...the vehicle is darn near in the "totaled" catergory financially speaking. The truck still looks and runs like new. So I'm not "totaling" it out just yet.

Once I get the tank out I plan to clean the area around the tank/check valve and plastic weld it using a plastic welding heat gun and HDPE black welding rods from Fastenal. I've been around welded plastic HDPE tanks and I've mig/tig welded before...so I think I can pull this off.

I've watched the videos available for plastic welding HDPE and it's not really that complicated. Just evenly heat the areas to around 500F (including the rod) and push the rod into the region working around the circle of the valve.

Anybody see any problems? Such as the tank isn't HDPE...I'm assuming it is. Or the check valve is very thin and won't take the heat? The factory welded it on there but with a tiny weld seam. I plan to put a nice wide bead around it and let it naturally cool overnight. Hopefully this will be strong and also stop any leaking forever.

PS: I'll drain the tank and let it air dry before this procedure. The weld gun is actually a hot air gun that focuses the heat with a tip. So there isn't any actual flame contacting the tank. But the air gun does use a heating element inside it so I should still be cautious of fumes etc.

 

[BRomanJr]

I used the plastic welding method a month or so ago on my LWB tank. (at 191,000 miles)
It had been fixed a couple times before with plastic formula super glue, but only lasted ~6 months in both cases.

I removed the tank, cleaned both surfaces and used a 60 watt? soldering iron. No filler rod, just blended some material from both parts.

It was a slow process because of the lower wattage, but after an hour or so I was done. I gave the fitting a couple pulls to test.
Put the tank back in and its been holding.

Be careful, with the extra heat you'll have, the check valve will bind and stick if the fitting is distorted too much and you may have trouble getting fuel in it.

 

[NeilLTZ]

Anybody know for sure if the tank is HDPE? Or possibly Polypropylene? I'm assuming HDPE of some blend or another. I'll be using black hdpe water pipe cut into strips as a filler rod. It's about the best hdpe there is since it's pressure water pipe. Known as PE3408.

I'll be extra cautious around that valve so as to limit distortion. Gonna practice on a 5 gallon bucket first.

Otherwise I may end up just "mushing" it back together with a 100 watt iron and a wide flat tip.

 

[NeilLTZ]

Bad news. The tank outer shell is HDPE I believe. The inner tank is white. Possibly HDPE as well. BUT...the cheap check valve body is some sort of thermoset plastic. And those types do not weld. They smoke and turn to brittle ash. So the valve body was toasted by the heat instantly. Ruined. I pulled the whole thing out. GM really should have used an HDPE body on the valve and welded it. Looks to me like it was glued in somehow. And NO glue will work on HDPE. Thats why it was invented. To resist all solvents and chemicals.

So....I don't know at this point. Looks like it's either build a custom hose connection or buy a new tank. I've lost the check valve if I go custom. I'll have to get an inline valve somewhere. It'll be Sunday. And the Holidays. Looks like the TB is down. Thanks GM for a marvelous tank design. I see many of their vehicles suffer from this grave mistake.

 

[crazyelvis3577]

have any luck with an inline valve at the filler neck on the tank?... I have this same problem on my 03 Envoy XL. I was also out of warranty when I found out about the recall and such.

 

[Blckshdw]

@crazyelvis3577 the OP hasn't been back since 3 days after his last post, so I don't think he'll be able to give us any updates on how that turned out.

 

[Mooseman]

A possible option is finding a good used tank?

 

[crazyelvis3577]

I fixed mine similar to the video OP posted. I used a stainless steel marine thru hull and some Viton gaskets and it works great. Just use an inline check valve. Perko makes one that fits inside the fuel hose just before the tank. Works great and saved me about $700-800. The thru hull and other part and gasket material cost roughly $60. If anybody needs links to the parts let me know.

 

[gdc4sman]

I also had the problem on my 2004 Trailblazer LT where there was a leak at the fuel inlet area on the gas tank where the fuel hose attaches. The dealer indicated that the warranty is now extended to 150k miles or 15 years (whichever comes first). Since I only have 110k miles I am a happy camper. Note that the gas tank is on national backorder again (I saw this also happened on another thread from 2007). The dealer will contact me when it is in and told me not to fill it past 3/4 tank in the interim.