Fuel Filter on 1995 6.5L ?

[Bug]

FYI, I have just recently purchased a 1995 4x4 GMC 2500 with a 6.5L. "no turbo" approx 210,000 km . Also, I'm a newbie to the diesel game so forgive my ignorance.

I cannot seem to locate the fuel filter on this truck, Is there a location I should be looking at where this is mounted ? Also, it seems to be flopping over quite a bit before starting when cold. I plan to check the glow plugs this weekend, however is there a way to also check the lift pump check valve to ensure there is no back flow of fuel when it is sitting for awhile?

[john8662]

Couple of things are at work here...

First, your fuel filter is underneath the air cleaner housing. Remove the air cleaner housing and you'll see the filter housing on the rear of the intake manifold. It should be the round filter housing.

Second, starting...

This can be from glow plugs that have failed.

Suggest testing your glow plugs to see if any have failed. All you need for this is a simple test light, unplug the glowplug connector and touch the tang on the plug with the test light probe. The positive connection on the probe will be connected to the + on the battery. The probe will basically be grounding on the plug if it's good, if no light, you gotta bad plug.

To change the fuel filter. Service the filter, then install, leaving the drain on top open. Put the ignition switch to run and listen for the lift pump. The pump will operate for a short duration. So you'll have to cycle the swith a few times. Do this until you have fuel out the drain. You can then start it.

If this doen't work, you likely need a new lift pump.

The fuel shouln't be returning to the tank because of the lift pump. It will return to the tank if you've got fuel system leaks to the injecftion pump or somewhere on the supply side.

J

[Bug]

OK, Thanks, I was able to change the fuel filter with no problem.. after finding it ! As per the glow plugs, I connected an old headlight in series and tested each glow plug individually. They all tested ok. As for the lift pump, It appears to be pumping ok. I used the 1995 procedure for testing the lift pump "Place truck in the drive gear, then attempt to start the truck, the lift pump will start pumping but the starter will not engage. This saves a bit of wear on the starter" This procedure was also used to bleed the fuel filter as well. Im still wondering how I can test to see if the lift pump check valve is functioning? I still seem to have the same problem when the truck sits for awhile, the engine takes quite a bit of cranking to start it, even on warm days.

[TJ Moose]

The lift pump operates off the starter circuit during starting, but then off the oil pressure sender when running. If your lift pump isn't being powered by the OPS when running - it will starve a bit for fuel, and on subsequent starts take a while to start up by the injection pump just doing the job. You'll know by putting a gauge onto the drain cock (located near the front of the engine) from the fuel filter bowl - opening the drain to check pressure while running. (You'll have to tape the gauge to the windshield to see what its doing while you're driving.) Check the Heath Diesel website for more info - Bill will even sell you a gauge and then buyy it back from you when you're done using it if you want.
Anyway - starting you should have 5 to 7 lbs press if your lift pump is good - and running it should still maintain 3 to 5 lbs. If you have fuel pressure at start, but it drops to zero at run - you'll have to change out the OPS in order to get power back to your lift pump while running. You can search for info in TDP on how to set up some nifty relay setups to take the voltage load off the OPS and make things more dependable. But on my last change out - I just bought the OPS from GM, not from after market - and it just seems to be a better unit comparatively speaking. Lasted longer than the 3 months the one from NAPA did.........