Lift pump noise question

[sturgeon-phish]

Why is it that sometimes I can hear my lift pump operating during the glow plug heating cycle and other times I can't hear it? Quiet environment, cold start, similar sceanarios.

[gmctd]

Could indicate end of life on a tired pump.

Could also mean cold weather, pump is working harder to move cold fuel.

Same happens with my new pump, in cold weather.
I have to really listen for it when warm.

[jspringator]

I replaced mine at 140,000 as PM. Added a filter prior to the pump at the same time.

[rapidoxidationman]

I just replaced mine a few weeks ago; the truck has just over 140,000 on it. Last winter I noticed the nice soothing sound it used to make during the glow cycle was getting stuttered like it was tripping over itself. If yours is sounding less than ideal keep in mind that a bad lift pump ($100) can starve your injection pump ($1000 - note the extra zero...) and also cause your IP to overheat; the fuel is the coolant. Change the lift pump when you get a chance, but be carefull not to get any diesel fuel in your ear:D

Rapid

[gwaidman]

I am going to be replaceing my lift pump as a precaution soon. Does the system have to be bled after installation of the new pump? Will the fuel filter replacement bleeding operation work or is there more to it?

[charliepeterson]

Just bleed the system like when the fuel filter is changed. Your Injection Pump is going to thank you on this one!

If you have'nt looked at the oil pressure switch lately now is a good time to swap it out.

[tom.mcinerney]

There are orings used in the connectors to the lift pump. If encounter a leak after replacement can get new rings from dealer.
Sometimes the mounting seems to couple more noise than others. Slower, louder, longer pulses mean more travel of pump solenoid plunger, higher volume at lower pressure [maybe a little air leaked in]. Quicker, quieter, shorter pulses mean pump is up to regulated pressure. My year doesn't run during preglow; don't know if pump ever 'stops' when at pressure...

[sturgeon-phish]

Thanks for the responses. My truck just turned over 73000 so I'm wondering if the lift pump could go bad with only 73K? Does the Oil Pressure switch have to make up for the lift pump to get a "pump" signal? I'm going to check the connections at the lift pump and the OPS if I get a chance this weekend. Crazy work hours, 60 already and 12 more hours tomorrow. To save me a thread search, where is the OPS connections to check. While I'm at it, what other connections should I check. Is there a test for the lift pump?

[taznj63]

I also replaced my lift pump and the OPS at the same time. Not sure if you have the fuel filter bleed hose at front of engine as on my 92. If so that is where I checked my lift pump pressure. Connect a vac/pressure testor to the end of the hose and open the bleeder valve. The pressure should be between 5 and 7 psi. My pressure was aqt ZERO... After fix reading was 7psi. They are right about the cooling effect it supplies to the IP but in my truck it also controls the advance in the pump. My pump is mechanical so not sure if it does the same on yours.
The OPS is located at the rear drivers side valley area above bell housing in the engine block. It is a long sensor that sends oil psi to dash meter and a switch to control lift pump. Also you will need a special long socket to remove. I found mine at NAPA. Do a search to find OPS lift pump upgrade to add a relay to circuit cause ops is not rated high enough for lift pump current and is one of main reasons OPS and lift pump fails.
If you check for voltage at lift pump connector and use a digital meter you must place a 25 to 50 ohm resister across conector to place a load on ops switch or you will get a good voltage reading across carboned up contacts in switch.
Hope this helps...
Good Luck...

[ 03-19-2004, 05:03 AM: Message edited by: taznj63 ]

[JohnC]

Originally posted by tom mac 95:
There are orings used in the connectors to the lift pump. It's funny you should mention that. When I replaced my pump a while back I thought the same thing, however, the original pump did not have them nor did the replacement. So far, no leaks...

[ucdavis]

Jim-
@ 73k on an OEM OPS, it owes you nothing; cost is about $20 plus an $8 socket @ NAPA. If the OPS is shot, it isn't powering the lift pump. If it's still good, it's still a hi-miler & should be R&R'd. Try that first. Most get a lot more miles than yours from the lift pump & maybe it is just the OPS.

Gwaid-
If you run the lift pump w/out running the engine (there's an open spade connector on red wire next to fuel relay on mine that's marked Fuel Pump; put 12V to it & lift pump runs; or put 12V to the grey wire side of the LP) for about 30 minutes after opening up the fuel system, you should push virtually all the air thru the IP and back to the fuel tank. I did this w/a full IP replacement and it started right up.

[tom.mcinerney]

John C:
Mine had the orings, and i renewed them while i was at it. They're an interesting connector, combination flare/oring ; i think also hybrid SAE/metric. I brought one to an airconditioning shop; the parts man said he'd seen similar designs some years back. I was able to buy an aftermarket packaged length of tubing (1' long) that had the special termination, with oring. Could not locate any fittings/adapters for the female(pump) side...