• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

No lift pump pressure

6.5TD Burb

6.5TD Burb

Member
Messages
133
Reaction score
3
Location
Wendell, NC
Is is possible to have a clogged fuel filter and it be as white as it was when installed? What brings this up:

Reading 0 fuel pressure. Mechanical gauge installed between filter manager and IP. When it cranked it would build up to 7psi and promptly fall to 0 when it ran. New OPS, new LP. Dropped the tank to check the sock; it was most definitely dirty but I wouldn't call it clogged, at least IMHO. Opened the bleeder on the filter manager (hot wired LP and when running) and nothing came out, not even air.
 
It's the OPS, he has fuel during start but not while running.

I just reread and either the new OPS is bad or there is a bad wire or fuel relay.
 
Sounds liek a dead OPS. Or probably a broken wire. The LP gets power from two sources, one while cranking it goes through the relay, and while running through OPS. SO, you can see, you have pressure when the ignition was in the start position, because your relay is working properly. But while running your OPS is supposed to run it.

If you read through the LP/OPS sticky you will find that you can check on the OBD port, pin G, bottom left for the voltage going to the LP. If you have no voltage while truck is idling then I would suspect a broken wire between OPS and where is splices into the power wire to the LP. The relay output and the OPS output splice together and single wire actually goes to LP. If there is low voltage then would suspect bad OPS. You absolutely need to perform the relay modification, OPS will fail every 6 months otherwise.
 
Gnd for LP also worth looking at intermittent connection there can cause issues as well, hot wired LP how 12V to just the hot leg ??? or solid 12V & independent gnd when testing it hot wired?

Did you go through this from the tech reference library http://www.thetruckstop.us/forum/sh...t-Pumps-amp-OPS-operation-and-troubleshooting

also check out here which may or not be related, but if it's been a while since you have visited your grounds, you need to do them at earliest convenience http://www.thetruckstop.us/forum/showthread.php?14596-6.5-grounds

Oh BTW I moved this to it's own thread it's better for you to have your own independent troubleshooting as it may differ than the one you 1st linked it with
 
Wow, lot of replies.

Ok, first: When I say new OPS I mean NEW. Fresh straight out of the box. It's not a Delco unfortunately; it's an Echlin. I don't have a Delco supplier on Saturday otherwise it would've been. The LP is also a brand new straight out of the box Airtex.

The LP was hot wired through the "G" pin on the ALDL and a constant hot wire under the dashboard. I could hear the pump running but it was still not drawing any fuel after a collective of 1 minute of priming. The FP relay IS a Delco unit maybe 2 years old.

The pressure when cranking was before replacing the OPS and LP. It would not build pressure in the "ON" position, only when cranking.

Since the body swap maybe I did miss a ground. I'll look over them. The LP/OP thread was the first place I looked.
 
Okay for grins disconnect the LP connector and read the black pin on truck harness to gnd, it ought to be very close to zero, then with 12v jumpered to pin G go back under truck again with meter and read the 'hot leg" of truck connector to gnd you should see 12V there let us know how that turns out and then we'll move to the next step this is a sanity check to make sure you are seeing correct voltage to the lift.

Sounds like you may also be a candidate being one of those having a rotten line issue and you aren't sucking fuel but air or a clogged fuel tank sock, if voltage and gnd are correct we'll go down that diagnostic road next
 
I'll try to get that done tomorrow or tuesday but don't know if I can or not. Starting classes this week so I don't know what my free time will be anymore.

Exactly what's the definition of a "clogged" sock? I dropped the tank and took the sock off. It was definitely dirty (almost black) but nothing I would consider dirty. I could still see fuel in the sock when held up to the drop light.
 
Forgot: won't be able to check the LP tomorrow unless I can order in and receive a sock.

I know it's constant hot at the fuse, 12.68v.
 
6.5TD Burb said:
Forgot: won't be able to check the LP tomorrow unless I can order in and receive a sock.

I know it's constant hot at the fuse, 12.68v.
Click to expand...

That is good but I'd sill like to know what voltage is being supplied @ the lift pump connector and lift connector "hot" to gnd, that is an old truck you have; corrosion over that length of time can cause serious voltage drops, as a process of elimination humor me/us, we've been playing the 6.5 game for a long time plus it's "good housekeeping" with a PCM controlled truck to have all gnds spotless, you'd be surprised how many "dead" trucks have been resuscitated via a good gnd cleaning party.
 
Acesneights1 :iagree:

Socks are white new. :skep: The pump can rattle like crazy with stuck valves. Noisy, but no pumpie. New parts does not mean new part actually works.

I agree on possible airlock or air leak.
 
6.5TD Burb said:
Exactly what's the definition of a "clogged" sock? I dropped the tank and took the sock off. It was definitely dirty (almost black) but nothing I would consider dirty. I could still see fuel in the sock when held up to the drop light.
Click to expand...

You did clean it though?
 
You must log in or register to reply here.
Back
Top