1997 6.5 injector pump dilemma

[Paul S]

Hi guys
My vehicle is a 1997 GMC Savana work van , 6.5 motor ,non turbo. I bought it from my father 3 years ago. Unfortunately, the computer module went bad for him and he had to have the injector pump replaced two times. Since owning it, I put about 40 thousand miles on it and had to replace the injector pump once myself.

At $2500.00 for the parts and service, I'm hoping you might have some information on a permanent or better fix for this motor ? I heard that Bosch used to supply GM with the injector pump but Gm went to another source , which supposedly makes a lesser quality pump.And this last pump only lasted 13 months.

Any help is greatly appreciated.Thanks

[JohnC]

Start reading old posts. I'm gonna guess there is at least one million words written on this subject.

[Paul S]

Hi John
I looked for over an hour at old posts but didn't find one specific to my issue. I found lots of other good info though.Posts on actually changing the pump and what not. I don't have anywhere to work on the vehicle unfortunately.

[DmaxMaverick]

The Stanadyne DS4 pumps (what you have) typically last 150-250K miles. Most more, some a little less, but it is not typical to last only 40K. This indicates one of two, if not both, things to me. You have a fuel quality issue, or the pumps have been replaced unnecessarily (the root cause not properly diagnosed). The external electronics, on the other hand, are generally less reliable (but still not as bad as many believe). GM's early policy was to replace the pump and PMD (Pump Mounted Driver - the electronic gizmo box mounted on the side of the pump) as a unit, with no real determination of the cause of failure. More often than not, the cause is a dysfunctional electrical system, which causes the electronic injection control and/or driver to fail.

If your electrical system is rock-solid, that leaves the fuel delivery system (fuel tank, lift pump, fuel manager (filter) and/or the conduit). A failed lift pump or OPS (Oil Pressure Switch, which allows for lift pump operation), will cause the injection pump to fail prematurely. The injection pump will draw fuel (suction), almost oblivious to a failed lift pump. However, this takes it's toll on the pump, causing a perceived pump failure. If you aren't often in the mid to high power demands, it may go unnoticed until the injection pump isn't able to keep up. When this happens, everything in the system becomes more critical to operation: Less top-end power, filters don't last as long, hard(er) starts, etc.

The fuel manager is a good (not fantastic, but not bad) fuel filtering system. If your regular fuel source quality is questionable, pumps will suffer. Recent ULSD requirements don't help in this area. This is why most of us recommend a quality fuel additive, to aid with water contamination and lubricity.

And...... Bosch never made fuel pumps for the 6.5L. It's been Stanadyne from day-one. They did/do however, make OEM quality fuel injectors.

[JohnC]

1,000,325... ;)

[Paul S]

Thanks very much for that info.What you're saying sounds good because my father , the original owner had to have the control cluster replaced and since I've owned it, the fuel gauge indicator flips back and forth wildly. He's a very anal guy and keeps deadly accurate MPG info on his vehicles and told me he lost about 5 or 6 MPG after his dealership changed the control cluster.

One of my contractors had the same motor in his truck and had the same exact issue.The computer module was changed and he said it never ran as well again and got less MPG.

And the only people willing to give honest answers are people like you guys.Thanks very much.

[Paul S]

The Stanadyne DS4 pumps (what you have) typically last 150-250K miles. Most more, some a little less, but it is not typical to last only 40K. This indicates one of two, if not both, things to me. You have a fuel quality issue, or the pumps have been replaced unnecessarily (the root cause not properly diagnosed). The external electronics, on the other hand, are generally less reliable (but still not as bad as many believe). GM's early policy was to replace the pump and PMD (Pump Mounted Driver - the electronic gizmo box mounted on the side of the pump) as a unit, with no real determination of the cause of failure. More often than not, the cause is a dysfunctional electrical system, which causes the electronic injection control and/or driver to fail.



I apologize for having to bug you. My dealer just called me and said the lift pump is bad and the fuel filter needs to be changed again.They want Almost 8 hundred bucks to do that .Sounds way high to me . I found 6.5 liter lift pumps online for under 60 bucks.Any opinion on that price tag ? Thank you

[DmaxMaverick]

Sorry, I can't help with your dealer, or their policies. Chances are, even if you had the answer they'll spend hours/days looking for, they won't listen. Sometimes you can find a tech who likes his job and customers, and is willing to learn more than what's in his little handbook. Good luck.

The best and easiest method of testing the lift pump operation is simple, quick and free. The fuel filter water drain valve is located at the thermostat housing (top/forward/driver side of engine). It's the small T-valve with a hose extending down. Pull up the hose and insert it into a container (1 or 2 qt. bottle) and locate it securely away from moving parts (belt, fan, etc.), start the engine and let it idle. Open the valve and fuel should flow into the container at a pretty good rate (should fill a pint in 15-30 seconds), and the engine should not stumble or stall (indicates sufficient performance). If you get little to no fuel, and/or the engine stalls, the pump is not pumping sufficient fuel, or you have a significant fuel system restriction. If you have good flow, but the engine stalls, the problem is between the filter inlet and the injection pump. If you get little to no flow, but the engine continues to idle well, the drain line is kinked, collapsed, or blocked in some way. The drain line is on the "dirty" side of the filter, connected to the bottom of the filter bowl, so don't be too surprised at what comes out of it (including debris or little critters than may be in the drain hose end). Once it flows clean/clear, it should continue that way. Also, there should not be any air bubbles after the flow clears. If so, it has an air leak between the lift pump and tank sender unit (air can cause significant starting and running issues).

This hose is also a good place to check for fuel pump pressure (just connect a fuel pressure gage to the hose, and open the valve). Typical fuel pressure is 4-8 PSI, with a max of 10-12 PSI, with engine running at idle. If it's less than 4 PSI at idle, this could indicate a fuel restriction (between the tank and fuel manager) or the pump is either failing, or not receiving full battery voltage.

[Paul S]

Great info.I'm saving it as a word document on my hard drive.Thank you sir.