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Bad Fuel Pump 99 Silverado 5.3?


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99 1500 Silverado 5.3 -- 83K

 

Fuel pressure cold with key on, engine off is 52-54 PSI. Fuel pressue while running at idle is 50-51 PSI.

 

Engine is hard to start (if it starts) on a cold morning (below 40*F) and once it is running it runs very rough...almost as if some cyls are running rich and others are not firing at all. No mil light present.

 

Anyone with fuel system experience on the newer Vortec motors encouraged to respond. Thanks in advance for your help!

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Haven't really had any peformance issues on mine, but after having my regular dealer do the filter change, I was getting the often described high-pitched whine/whistle.  Went to another dealer and got the fuel pump replaced under warranty.  No problems/noise since.
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Have you checked the plugs to see if it is, in fact, a rich fouling problem?  If it is a fuel problem:

If it has a CFI unit, I would suspect that the one or more of the injector spider lines has ruptured.  The CFI unit has one fuel injector and 8 plastic tubes that extend to each cylinder and a small valve at each end, inside the intake manifold.  The seals of the injector to tubes usually start to harden, crack and spray fuel  inside the intake manifold.  The puddled fuel then drains to a cylinder, and floods it out.  Depending on where the leak is, and how you park the truck, it'll flood different cylinders.

Now if you don't have CFI; sometimes you could have great indicated fuel pressure, but you will have poor fuel volume.  Just like having good volts, but very little amps...  Do a fuel volume test to see if its pumping enough fuel.  The fuel pumps are very weak on the 1500s and are prone to early failure.  

I hope you are covered under warranty, because some fuel pumps come only with the sending unit, as a complete unit, and is very costly.  I think somewhere in the $300-$400 range...and as an added bonus, you get to drop the fuel tank...

If it is not a fuel problem, check the crank position sensor.  I've seen some of them loose/corroded/packed with dirt,mud, grease, etc; which can cause hard starts, and rough running conditions.  Good luck.

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Thanks for the replies.  Yes, the pump was defective.  The hardest part about the replacement was pumping the tank dry ( it was nearly full at the time of failure).  I estimate about 7-8 galllons of fuel remained in tank when dropped.  I pumped a little more out before reinstallation, which was aided dramatically by the help of a friend.

 

Finding a pump was a challange...available only from the dealer for the meager sum of $389.  I found one used from a local recycler (supposedly only 30K) for $100.  Put it in and changed the fuel filter at the same time.  Pump has 6 month warranty.  

 

New pump is substantially quieter than old unit...puts out right around 60lbs where old unit was48 - 54 depending on temperature.  It was lowest below freezing, hence the no-start in the driveway problem.  The weather is a little milder now, but starts have been no problem and throttle response is much improved.

 

Dropping the tank is not the PITA it is billed to be providing it is empty and you follow the steps in the service manual (I have a Haynes book but I'm looking for a Helm).  Like I said, draining the tank took almost as long as the pump replacement.

 

One last note:  there were 2 types of pumps used (at least in 99, other years likely too).  The codes are TCF and TCU; you will have one or the other.  TCF seems to be more popular, it's also what mine was equipped with.  You have to drop the tank and look at the stamp on the top of the pump to determine which type you have if you buy used.  If buying from the dealer new, you will have to have your VIN to confirm.  ***TCF is not listed in the RPO codes (I looked)***  Why this was left out I don't know, it would have made finding a replacement easier.

 

Seems fuel pump failure is common in the later model trucks...the old TBI pumps were usually good long past 100K.  I understand the pressure is much higher, but given the cost of replacement these things should last longer...

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