thunderstruck507

iTrader: (18)

I have a 1999 5.3 Silverado 2wd single cab. About a month or so it started having a hard start issue where the first time I tried to start it, it would crank but not fire. It would always fire the second time.

Now it has gotten to where it takes several key cycles to start the truck. I found out why yesterday when I put a fuel pressure gauge on it. When turning on the key the pump is audible, but sometimes no pressure builds. If it does build pressure it starts falling off almost instantly.

Once fired, it only had 48# running pressure at idle. Pulling the vacuum hose got it to 58# at idle. If I pinch the return line it jumps to 80#.

When the truck is turned off the pressure drops very quickly and very steady down to under 10lbs in less than 5 seconds.


I put a new regulator on the fuel rail last night since it was easy and I had a coupon for Advance auto. Got the regulator valve and fuel filter for $48. After replacing the valve it has 52# at idle but still has the pressure drop when key is turned off and still has the problem starting without cycling the key.


The fuel pump is very very loud (high pitch mechanical whine, much like the Walbro in my car) but it has been that way since I bought the truck last June. There are also wires running along the frame rail to the tank, a blue one and red one. So I suspect someone has been in the tank before.

There is also a black box with a sticker that says "fuel buddy" on the feed line from the tank. Looks like it just ziptied around the line like a clamp.



It seems like there is an issue in the tank for sure. But I don't think it is the pump itself. Is it something that can be fixed in a way other than dropping $300+ on a pump assembly? I refuse to buy a junk Autozone pump because I've seen them fail the same day they were installed and never seen one last more than a year. If I have to buy a pump, I would prefer to put a Walbro in the bucket but it doesn't seem like that would fix my problem.


I want to drop the tank at my dads shop this weekend but it is 250miles from home and so I need to be able to fix it in a weekend. If it's a pump I need to order one today.

thunderstruck507

iTrader: (18)

99.99% sure the problem is the check valve in the tank

So is there really no way to fix that without replacing the entire assembly?

Mr. Fuel Pump

Besides the check valve in the pump, you could have a leaky injector or a leak in the fuel line somewhere, likely the plastic or rubber line between the pump and the underside of the module flange in the tank. I am not saying that this will absolutely fix your issue, considering the odd wires and 'fuel buddy' issues you have going on...but if you are going to drop the tank you should just replace the whole sender assembly. You can get a Walbro/TI Automotive manufactured one at fuel-pumps.net for $144, pretty sure you need the TU432 (has an OBDII/vapor pressure sensor on the module flange) or TU434 (no OBDII sensor); when in doubt buy the one with the OBDII sensor and then if you don't need it you are fine to just not hook it up:
http://www.fuel-pumps.net/
A better quality unit than Autozone at half the price

thunderstruck507

iTrader: (18)

Before I order one of these finally, does anyone else have an opinion?

So far it seems like my best deal.

Emdmechanic

iTrader: (2)

External check valve close to the pump . What i ended up doing . I installed a b-body wagon tank , and brand new pump and sending unit. Mine holds pressure sometimes, and other times it starts dropping instantly. I put a checkvalve inline and i always have pressure on the lines for a few hours and it starts on the first cycle now. Is dosent rule out a leaky injector though .

thunderstruck507

iTrader: (18)

If it was a leaky injector I would expect smoke or poor fuel economy or rough running shouldn't I?

Even when running it is low on pressure at ~52#.

thunderstruck507

iTrader: (18)

I'm going to get some vice grips and try clamping the soft portion of the return line. If it slows or stops the pressure loss I'm ordering one of these:

http://www.ustoolman.com/index.php?m...k1cdcaumsh1k00

If not, that narrows it down to the fuel pump hose on the tank or injectors. Any easy way to test the injectors leaking? It's bad enough that I have to cycle to start all the time now, not just if it's been sitting. It's an almost instant drop to 0 every time the key is off.

Emdmechanic

iTrader: (2)

As far as checking injectors , Basically pop them out of the intake with the rail still attached and jumper your pump relay where its constantly running and have a look. Or take them to someone.