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Confusing PMD/LP conditions

Matt Bachand said:
Get a cheap fuel pressure gauge at harbor freight or elsewhere

Blow air into tanik and see if problem persists, with fuel cap off. Remove LP inlet line and blow air in there.

Even try running with fuel cap off.


I suspect something amiss in your tank... (not that you want to hear that).
Click to expand...

I have been running w/ the rubber gasket removed from the fuel cap since Thanksgiving. When this problem started a few weeks back I thought that it might be getting contaminated some how since when the tank is full it sloshes and leaks out the cap. I got a new cap from napa. I double checked to make sure it was a diesel cap.
 
JMJNet said:
How full is your fuel tank?

Pressure gauge is the most definitive if you have LP issue.
By the way, sometimes, new something may not always be good because it can be defective.

Is your new OPS ACDelco?

I recall that you have been having trouble with the fuel tank also, hence the new FSU.

Can the new FSU defective?

It is puzzling to me for all this trouble when everything is new.

Recently, I experience this with my bro's nissan's new belt. Put the old one back, squealing was gone.
So new belt was bad.
Click to expand...

since I jumped the pump yesterday and it still happened that tells me it is a clog somewhere in the line.

Yes the FSU kept getting bent when the baffle would come loose. I fixed that a month ago by using some clamps to hold down the baffle on the studs that stick up through the baffle. I then bent the fsu down so it would hold the baffle down just in case the clamps came loose. I know it is picking up any crud on the bottom but I thought I could deal w/ that since I thoroughly cleaned out the tank. I need to add a racor in there to make sure this doesn't happen again.
 
JMJNet said:
That is a good idea with the Racor.
Click to expand...

what I really need to do is invent a fuel neck filter. Something that you can slip into your fuel neck that is high flow that can be cleaned and reused. That would prevent crap even getting into the tank.
 
found lots of metal chips/flake in tank. I just had it down a month ago and it was clean. either the flakes came from the return line or crap from the gas station.
 
Rodd said:
what I really need to do is invent a fuel neck filter. Something that you can slip into your fuel neck that is high flow that can be cleaned and reused. That would prevent crap even getting into the tank.
Click to expand...

I think Racor have a funnel that has filter on it with different flow rate. I saw it on ebay or something. May want to check that out.

Those flakes may cause your line to clog and your LP to be bad.
 
JiFaire said:
Hi Rodd. Your OPS controls power to the LP while the engine is running - when you have oil pressure, you get power and therefore fuel.

The ECM controls power to the LP while in start or wait-to-start mode... because obviously you have no oil pressure, right?

SUMMARY:

--With the engine off and key on, you get power from ECM - not from OPS.

-- With the engine running, you get power from OPS - not from ECM.

The symptoms point to a failed or defective OPS. Test power at the LP with the engine idling.

Jim
Click to expand...

Jim et als, read his signature he's a 99 ergo OBD-II you have to lose power from PCM & OPS at same time for both to get a no pump run for lift power control issue, OBD-II's PCM will send lift run command to pump during the key on during glow for about 10 sec until lift pump pressure sensing is satisfied then pump stops, PCM also looks for crank rotation if it doesn't see that command stops. Once engine is running both OPS & PCM keep power to the lift but you have to lose both to lose power. Could also be the relay in underhood fuse center.

Rodd, all the voltage/lift issues aside, your IP should be able to maintain fuel at idle, if not it would suggest blocked in tank sock, dirty fuel filter on engine, or air in line. You really need a gage to help diagnose this, they aren't that expensive $20 or so at most part stores, get one that tests press & vac, IMO should be in every 6.5ers tool box.

Something else to look at not yet mentioned is the gnd on the lift pump, it's on the frame rail in a burb on the frame cross bar in front of the fuel tank.


Rodd said:
can I reverse the polarity on the pump and get the pump to pump backward?
Click to expand...

No a GM style pump will not work correctly if installed backwards, if yours is installed that way you need to reinstall it correctly, so that end marked out is ouinted toward the engine compartment, reversing polarity of wires will not help it's a plunger pump with directional flow check valves internally that work with plunger to make pressure
 
Rodd said:
since I jumped the pump yesterday and it still happened that tells me it is a clog somewhere in the line.

Yes the FSU kept getting bent when the baffle would come loose. I fixed that a month ago by using some clamps to hold down the baffle on the studs that stick up through the baffle. I then bent the fsu down so it would hold the baffle down just in case the clamps came loose. I know it is picking up any crud on the bottom but I thought I could deal w/ that since I thoroughly cleaned out the tank. I need to add a racor in there to make sure this doesn't happen again.
Click to expand...

Are you running without a sock ???? if you are doing that then lift pump is probably messed up, you need to run a sock at a minimum, and best is sock and Racor prior to lift pump, the sock isn't bad so long as you buy fuel from a bonafide known good supplier, it gives 70 micron of protection to the system.

If you cleaned the tank unless you are buying from a really bad supplier you should not be crudded up again
 
Turbine Doc said:
Jim et als, read his signature he's a 99 ergo OBD-II you have to lose power from PCM & OPS at same time for both to get a no pump run for lift power control issue, OBD-II's PCM will send lift run command to pump during the key on during glow for about 10 sec until lift pump pressure sensing is satisfied then pump stops, PCM also looks for crank rotation if it doesn't see that command stops. Once engine is running both OPS & PCM keep power to the lift but you have to lose both to lose power. Could also be the relay in underhood fuse center.

Rodd, all the voltage/lift issues aside, your IP should be able to maintain fuel at idle, if not it would suggest blocked in tank sock, dirty fuel filter on engine, or air in line. You really need a gage to help diagnose this, they aren't that expensive $20 or so at most part stores, get one that tests press & vac, IMO should be in every 6.5ers tool box.

Something else to look at not yet mentioned is the gnd on the lift pump, it's on the frame rail in a burb on the frame cross bar in front of the fuel tank.




No a GM style pump will not work correctly if installed backwards, if yours is installed that way you need to reinstall it correctly, so that end marked out is ouinted toward the engine compartment, reversing polarity of wires will not help it's a plunger pump with directional flow check valves internally that work with plunger to make pressure
Click to expand...

The sock was clogged a little. I'll post some pics I got from my phone. When I jumped the pump to drain the tank it just trickled out. I dumped the content of the tank into a drum w/ an old sheet over it to act as a filter and there was a lot of flake left in it. I'll get a pic of that as well.

I followed your advise and ran a 1/4 die nut on the studs and twisted one off. Luckily it was welded on and just twisted off the weld but didn't put a hole in the tank. The others I could only go about 1/2 way down. That is a tough job when you have big hands and forearms. I didn't think I had popeye forearms until I started putting the die nut on. Luckily I had one of my sons to be my retriever. lol.
 
Turbine Doc said:
You think suction is clogged already now ???, do you still have the sock on the pickup ??? how did you clean the tank previously ???
Click to expand...

The tank was filled w/ soap and h2o last time. I did it again this time w/ soap & h2o. Dried w/ towels and a doubled hanger like you suggested. Then blew out w/ my compressor and let sit over night. It had to be clogged sock and or lines. There was a lot of chips stuck to the sock. I must have got the bottom of some fuel station tank.
 
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