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should my truck run any different if the lift pump is bad,i tried unpluging it and it runs no different but after not running for about an hour it started and died then fired right back up. like i said far as driving it with it unplugged it runs the same.its a 93
6.5 Detroit Diesel
04-10-2011, 22:44
you think its running the same, but over time your IP will feel the strain. harder starts, unable to go WOT for much more then a few seconds, and premature IP failure are all things you can look forward to
I have heard symptoms of a bad lift pump being higher RPM cut-out and the like, but i never experienced things like that. When my LP quit, I just had longer cranking time, especially when cold. Good idea to to keep it running. It reducing a lot of strain on the IP
It's not good to run without, but in reality the transfer pump inside the IP will do an adequate job of providing fuel for operation in most conditions. What happens though is return (cooling) fuel is greatly reduced or even eliminated and under heavy loads you can get bucking and surging along with likely air (vaporization and leaks) entrainment in your fuel.
For proper, reliable operation of your lift pump I'd suggest my Lift Pump Control Harness as a stand alone device that takes the place of the problematic factory oil pressure switch in regards to supply power to your lift pump.
It's not good to run without, but in reality the transfer pump inside the IP will do an adequate job of providing fuel for operation in most conditions. What happens though is return (cooling) fuel is greatly reduced or even eliminated and under heavy loads you can get bucking and surging along with likely air (vaporization and leaks) entrainment in your fuel.
For proper, reliable operation of your lift pump I'd suggest my Lift Pump Control Harness as a stand alone device that takes the place of the problematic factory oil pressure switch in regards to supply power to your lift pump.
i'll second that opinion, for what my opinion is worth.
Ok guys I put a new lift pump on,checked it and the plug gets juice when you crank the motor but after it starts no power to lift pump connected so I put a new relay on it still no power to the plug while truck is running,I assume it should have power all the time
On your truck the power when the engine is running comes from the oil pressure switch.
During cranking is the only time the relay is used to power the lift pump.
The OPS can still work the gauge and be burnt out in the lift pump circuit.
Do a search here or google for OPS relay mod,or buy a kit from Kennedy Diesel to stop this problem from happening again.
Also when you replace the OPS only use AC Delco for replacement-aftermarket OPS suck.
So the lift pump should have power when the truck is running not just when it's cranking right
So the lift pump should have power when the truck is running not just when it's cranking right
That is how it's supposed to be,there are other ways to get it to work.
Some folks just wire the LP to a toggle switch but you have to remember every time to turn it on and off.
The relay mod or Kennedy's kit is the best soloution.
I can't stress enough how important it is to use an AC Delco OPS though.
Hey thanks alot guess I know what I'm doin tommorow
DmaxMaverick
04-14-2011, 21:13
That is how it's supposed to be,there are other ways to get it to work.
Some folks just wire the LP to a toggle switch but you have to remember every time to turn it on and off.
The relay mod or Kennedy's kit is the best soloution.
I can't stress enough how important it is to use an AC Delco OPS though.
VERY bad advice. With the ONLY exception being diagnostic and temporary testing purposes.
The lift pump is controlled by the OPS for a reason. It will not operate when/if the engine stalls, such as during a collision. It is very important to have some type of a fail-safe in place, for your safety, and it's the law in every state/province. If you were in a crash, and were unconscious or otherwise incapacitated, would you "remember" to turn off your fuel pump before it saturated your crash scene with fuel?
Kennedy's lift pump controller is the absolute best solution. If you don't want or can't afford that option, you can wire in a relay to operate the pump. This will take the load off the OPS, which extends its life to indefinite. The OEM configuration is poor, and will cause the OPS to fail, much earlier than it should. And, as said, any other than a GM/Delco OPS will leave you sooner.
I was not advocating to do the toggle switch method-just reporting what others have done.
I do advocate the OPS relay mod or the Kennedy kit.
Also lets not forget that since the orange wire to the OPS is always hot reguardless of key position a "failed shut" OPS will cause the LP to run under any conditions.
While I agree that the toggle is a bad idea,should it be powered by an accesssory switched power source it will at least shut off the LP with the key.
It will also add load to an already taxed ignition switch but that's another story.
Not going to do the toggle switch,I'm gonna do it right.
Doing it right is always the answer that brings a warm feeeling-either that or you should have waited for the manifilds to cool before starting the repair!
the ops fixed it,thanks again. Also when you free rev this truck it blows black smoke then right at the end it will put out just a puff of white,could this be a problem
the ops fixed it,thanks again. Also when you free rev this truck it blows black smoke then right at the end it will put out just a puff of white,could this be a problem
The smoke is normal when you free rev,the engine is only meant to build boost under load.
Take it for a drive and the smoke will be black for a very short time then turn to hazy and then clear when the turbo catches up and makes boost.If it's working properly that is.
Makes sense,thanks for all the feedback
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