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Chevy 3500 fuel pressure, pump question


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M.Tanner
New User

Jul 11, 2007, 12:53 PM

Post #1 of 4 (3576 views)
Chevy 3500 fuel pressure, pump question Sign In

Thanks in advance guys!
I have a 2001 chevy 3500 with a 8.1 gasoline engine. it runs great when normal driving, but when i put my 32 foot trailer behind it and it gets under a load, (like going up a long hill) it will sound like it is back firing through the air throttle valve. It seems to me like it is leaning out under load. Could it be the Map sensor? A friend of mine thinks it could be the fuel pump not pumping enough under load and causing the lean condition. I have replased the fuel filter. One other thing to mention is the fuel guage some times reads empty when I first crank the truck and then it will slowly come back up to the actual fuel level, it does this almost every time I fill the tank with fuel.

question# 2- The water level is always low. Low enough to cause the low cooluant light to come on. I can add water and it will leak down until the light comes on and then it seems to quit leaking. I add the same amount of water each time. The engine dosn't run hot

Thanks for the help
Malcolm


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 12, 2007, 4:40 AM

Post #2 of 4 (3574 views)
Re: Chevy 3500 fuel pressure, pump question Sign In

You are not supposed to have to add coolant on any regular basis and that probably is the problem. It may not indicate that it's running hot but there may be hot spots the cause your problem.

FYI - GM has been sued over problems with DexCool the anti-freeze they used and claiming extended miles and time before it should be changed.

Damage has been proven from this and it shows up at the gunked up radiator cap which will then not maintain system pressure and cause boiling especially when under heavy loads like you mentioned. Get that coolant out of the truck and lower the concentration to about -20 or -25F protection and add some anti-rust additive and the truck will cool a lot better. If you have evidence of a problem with the anti-freeze flush the daylights out of the whole system now to avoid problems. Check on any recourse about this if you find problems. I own a Chevy truck that came with DexCool and it had the well known intake manifold leak but no evidence of rust problems and I will not put DexCool back in again and that is the consensus with my friends in the biz.

Good luck and please hit back if that's what you find. It's discussed in length at a site that you can find (sorry I don't have the direct link) thru searching WWW.CoolProfit$Magazine.com ,

T



M.Tanner
New User

Jul 12, 2007, 6:10 AM

Post #3 of 4 (3572 views)
Re: Chevy 3500 fuel pressure, pump question Sign In

Thank you for the quick reply!
I will flush the cooling system and put a new cap on the radiator.
sounds like that could be the problem. When I fill the radiator reservior and pull the trailer water boils out when I shut the truck off. I also believe the lean condition could be adding to this problem.

I still need to find out something about my under load misfire.
What is normal spec for fuel pressure. If it is low, maybe the pump is not flowing enough fuel when the big 8.1 kicks in at 3500 to 4000 rpm for the uphill pulls.
I think my friend may be on to something with the fuel pump not flowing proper amount of fuel. I believe 2001 was the year Chevrolet had all the problems with fuel pumps, Is that correct?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 12, 2007, 12:57 PM

Post #4 of 4 (3568 views)
Re: Chevy 3500 fuel pressure, pump question Sign In

I really don't think this is a fuel problem right now. Concentrate on the cooling system and don't forget that the fan clutch is key to keeping it cool and they only work well for about 5 years. Only get the severe duty ones for this and I suggest an original GM part and the good ones do cost $100 or a bit more but it's too important to try to save money on that.

Fuel pressure problems probably would have set off a check engine light by now and it could be an issue but get the cooling in order first as you know that's a problem,

T







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