99 chevy fuel tank collapseing

Parkman

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This is a 99 chevy 5.7 3500 4x4 dump truck VIN 1GBJK34R7XF008777 single fuel tank gas, I have had two fuel tanks collapse like someone squezzed them in the middle. I get no back pressure when removeing the fuel cap and no check engine lights and no service codes. This is refered to as the old style with no pressure pressure sensor at the fuel module. It has like a 1/2 " hose going from the top of the fuel tank to the filler neck which was all clear and open., any ideas to what is causeing this as it's getting expensive. Note this is actually the 3rd tank, the 1st was replaced due to corrosion at the seams, but wasn't collapsed, I bought the other two tanks aftermarket from a radiator shop.
 

brcidd

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Parkman said:
I bought the other two tanks aftermarket from a radiator shop.

I think you answered yor own question....
 

wap

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Unvented tanks require still require pressure equalization. A restricted return line will cause similar problems. The emission control system controls the 'venting' through the fuel sending unit. Your problem does not lie in the fact that they are aftermarket tanks. Please. I suspect damaged return lines, faulty sending unit, or evap system failure of some sort.....wap
 

kdauto

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If this is a dump truck, do you know if it's OBD2 compliant or not? It should be indicated on the underhood emissions sticker. The problem could be caused by an incorrect fuel cap,sticking evap purge solenoid or vent solenoid,or even a defective canister falling apart that sticks the purge solenoid open. It'll depend on emissions compliance for the truck.
 

Parkman

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I did replace the the fuel cap after the fact, it had the stock O.E.M cap on it, truck has about 60,000 mi. on it and runs fine, it is also a plow truck and gets put in a heated building at night. Asked the G.M dealer and they said they never heard of it but recomended replaceing all the canister and venting solenoids for the emissions.
 

NickD

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Suppose your dump truck is exposed to more than the average amount of debris, had that same problem with farm tractors, takes hours to clean up everything, but only seconds to get them dirty again. Endless.
 

Parkman

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Is engine vacum strong enough to collapse a fuel tank? or could it be something else entirely, no one seems to ever heard of this happening.
 

kdauto

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Parkman said:
Is engine vacum strong enough to collapse a fuel tank? or could it be something else entirely, no one seems to ever heard of this happening.
Engine vacuum is definitely strong enough to collapse any tank, plastic or steel! So, is the truck OBD2 compliant or not? It should be on the underhood emissions sticker. Many small things could be the cause. A crushed vent tube or pipe,a dirty vent valve opening,defective charcoal canister(filled with water and frozen,broken substrate,etc).
 

Gus

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Being a '99, it should be OBDII compliant......what bugs me is that no evap codes were set....for that tank to collapse, the pressure sensor should have informed the PCM of the presence of vacuum and caused the PCM to activate the vent solenoid...if there was vacuum when there shouldn't, the purge solenoid should have been shut off and the vent solenoid opened...
 

kdauto

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Gus said:
Being a '99, it should be OBDII compliant......what bugs me is that no evap codes were set....for that tank to collapse, the pressure sensor should have informed the PCM of the presence of vacuum and caused the PCM to activate the vent solenoid...if there was vacuum when there shouldn't, the purge solenoid should have been shut off and the vent solenoid opened...
I don't do medium or heavy truck,and the biggest I usually work on is a half ton. I noticed this was a 1 ton truck,and also a dump bed. I know stuff over (8500 lbs GVW?) does not have to be OBD2 compliant,am I wrong? I have read where some of these trucks aren't obd2 compliant. I also have a hard time believing an OBD2 compliant vehicle would not set an EVAP code with a collapsing tank.
 

Tony

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a 3500 wtih gas engine should be OBD2 compliant.
I would think that it should be throwing an EVAP code too.

Did you use the existing pump and hoses from the original tanks?
 

NickD

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82 Chevy motorhome chassis has tanks made by Bryant Industries, that were in Oregon, WI, these won't collapsed, made of 1/4" steel plate welded together. But after doing a search, seems like Bryant is no more. What size tank do you have? And what is it made of?
 

opelgt

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For kdauto... Re: 99 chevy fuel tank collapseing

I had a customer with a '99 Savanna and his tank collapsed. It screwed up his pump. He had the pump replaced at another shop out of town. Came in to me and asked why he can't go as far as he used to on a tank of fuel. I gave him some senarios. After 2 months, his pump went again. It was in town so I got it. Dropped the tank and found the tank collapsed. I hammered the centre of the tank back down, installed a new pump and cap, replaced the vent valves and hoses. He could go farther now but still not as far as before. No codes were set for the evap system and he didn't want to spend the $1000 for the new oem tank. The tank never did collapse again.
 
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