What are the signs of pump failure?

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What symptoms would you have if the injection pump were starting to fail? My truck has had erratic performance since I got it about 9k miles ago. The idle varies from 700 to 1000 rpms and it runs smoother sometimes than others. Sometimes it feels rather sluggish and other times it feels like I suddenly gained 50 horsepower.

Are the symptoms of injection pump failure similar to those of lift pump failure?

If my injection pump is on its death bed would new injectors prolong its life?

Thanks,
Rob

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93 W250 LE, CC, 4x4, 5spd, 4. 10's, exhaust brake(tailgaters nightmare), turned up pump, boost/pyro guages, lund moon visor, weatherguard tool box.

 

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Rob, I'm not an expert but it kind of sounds like you're getting some air in the system. The lift pump would be a good place to start looking for a problem. My last rig acted as yours is and I put a length of clear plastic hose between the two pumps. Sure enough, lots of bubbles in the fuel after starting the engine. Replaced the lift pump and problem solved. Good luck.

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'93 W250, LE, CC, 4x4, 5spd. , Cummins, K&N, 16cm turbo, High flow Bosch injectors, Professionaly rebuilt and calibrated pump, straight exhaust, Lund visor w/lights, 5th wheel, Gooseneck, H. D. rear hitch, Aluminum everything.

 

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In the old 84 chevy with the 6. 2, we've had the pump quit 3 times in 250,000 miles. It uses a similar rotary style pump. Each time, the truck lost power and within 100 miles of when it ws first noticed, it couldnt make 45 mph with the pedal completely to the floor. I remember trying to get home on the turnpike last time, it was maxed out on the hills, and had down shifted clear down to 2nd gear just trying to keep moving. always ran fine until loosing more & more power in that 100 mile period or so... DDG

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Locomotive Engineer/Red Ram Driver! 97,2500,Auto,3:54,2WD,Re-sale Red,Loaded w/Leather, Diamond Tread running boards & box, Bumper guards,"Bull Ring" tie-downs, Front bumper guards, Clearance lights,TST 230 HP kit, K&N, Combo exhaust temp & boost gauge, Eng. & Trans. temp gauges. 3 Pos. Lock up switch.

 

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Anyone know how much a lift pump goes for? If its fairly cheap I'll replace it and see if it solves my problem.

 

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Usually, the first symptom on the VE pump is that it won't shut off!

Sometimes, it will have an erratic running/very low power complaint. Both of these are caused by mechanical failures... the failure to shut off is caused by metal chips getting underneath the electromagnet. The metal chips can be from failed (broken) springs or from a cam plate chipping away.

However, the getting air can cause the symptoms you describe. I don't believe hte pump is all that expensive, probably in the 45-75 dollar range. They don't fail very often. Look for other sources of air... like, say, a tank switch, decayed rubber hoses, cracked steel lines.


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ICQ 3807791 (BBSMan)Home Domain www.my2kcity.com (Under construction)
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12 Valve Forum moderator and Procrastinator extraordinaire...
Tow-er '65 Power Wagon Crew Cab, Tow-ee '70 Boles Aero 28'

 

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The pumps I put on the old 6. 2 chevy were about $375 exchange, Check a turbo & injector shop in the yellow pages & compare prices & quality..... DDG

 

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Thanks to everyone for the replies. I wanted to add one more bit of info. The truck seems to run just the way I like after driving at freeway speeds for 30 miles or so. After exiting the highway, stopping and then accelerating it runs very smoothly, revs quicker and feels much more powerful than normal. This usually only last for this initial bit of acceleration, at the next stop light it goes pretty much back to normal.

Can anyone explain this?

Sometime in the near future I'll be checking for air leaks. Any tips on checking the high pressure side?

Thanks again,
Rob

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93 W250 LE, CC, 4x4, 5spd, 4. 10's, exhaust brake(tailgaters nightmare), turned up pump, boost/pyro guages, lund moon visor, weatherguard tool box.

 

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Here's some more info on my ever more bewildering problem:

This weekend I changed out the lift pump. On the 1st test drive afterwards I thought the problem was solved. The truck started with a bit of a stumble but then smoothed out and idled solidly at 750 rpm. It ran much smoother in the 1700 - 2000 rpm range than before, revved quicker and boost came up sooner. I was very happy... for the time being.

I then proceeded to adjust the valves. After that was done I started the truck and it idled at only 650 rpm. This made no sense to me and I'm thinking it was only coincidental that it happed right after the valve adjustment. But, the truck still seemed to be running considerably better than it had before I started these 2 tasks. The idle was still low and only fluctuating a small amount, varying between 650 and 700 rpm.

Now the bad news. The next day(sunday) I drove the truck and it now runs the same as before the pump replacement and valve adjustment #ad
It doesn't seem to want to rev beyond about 1800rpm unless my foot is in it heavy. In the range of 1800 to 2000 rpm it seems harsh to me, like its starving for fuel.

If it is sucking air somewhere, my question is this: wouldn't I also have a fuel leak if I had an air leak? There is no evidence of fuel leaking anywhere.

I am now wondering if this is a good excuse for me to replace the injectors #ad


Rob

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93 W250 LE, CC, 4x4, 5spd, 4. 10's, exhaust brake(tailgaters nightmare), turned up pump, boost/pyro guages, lund moon visor, weatherguard tool box.