LP fixed.. Now stalling problem

[97duallydiesel]

They should have one of those vac/press test gauges rigs for around $20 its what I use to trouble shoot with, I keep it in my tool box

Doc, I got that gauge and it was $21 http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_VACUUM-TESTER-Actron_9090006-P_N3389_T%7CGRP2018____but not sure if I used it correctly because it didn't move when I connected it to the petcock where the line from the FM comes out to the front. When I opened it up when it was running the flow was very week. I also tryed revving the engine and the gauge didn't move. Is there a trick to it?

 

[buddy]

Doc, I got that gauge and it was $21 http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_VACUUM-TESTER-Actron_9090006-P_N3389_T%7CGRP2018____but not sure if I used it correctly because it didn't move when I connected it to the petcock where the line from the FM comes out to the front. When I opened it up when it was running the flow was very week. I also tryed revving the engine and the gauge didn't move. Is there a trick to it?

You mean you had the gauge hooked up to the drain line coming from the T-valve on the thermostat housing? And you opened the T-valve, and you didnt have any pressure at idle?

 

[97duallydiesel]

Well if you had a OS code like the P0251, but not the other P0370, points to a contaminated fuel problem, because the Optical Sensor (OS) in the IP needs to see throuch clear fuel. Water or air/bubbles, or dark fuel, or gunk making it cloudy can cause issues. If you use a harsh cleaner it can drag up gunk, or people that use solid lubricant cleaners like lubro molley usually have an issue. The solid lubricant can stick to parts like the OS.

I would still check the timing, and fuel pressure (which scanner does not check). Need a gauge on the line to the IP, or at least the drain line.

Temp sensor can still be an issue.

You just have to do some of the troubleshooting steps before anyone can have a better idea.

Buddy , I use this in every tank http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Diesel-Fuel-Supplement-Plus-Cetane-Boost-(16-oz-)-Power-Service_7080137-P_N3231_T%7CGRP2030C____ Ive also used Seafoam in the past ..

 

[97duallydiesel]

You mean you had the gauge hooked up to the drain line coming from the T-valve on the thermostat housing? And you opened the T-valve, and you didnt have any pressure at idle?

Correct.. It was very low just dribbling out even with the T-valve opened full.

Oh and Sorry . I reconnected the excisting PMD mounted on the IP. I wanted to rule out a possible faulty new PMD . And both ran the same.

 

[buddy]

So then you Lift Pump is not working, we thought you had good flow at idle, or the tank sock is clogged.

Did you ever have good flow from the LP?

Pick up a LP for a 93 truck and install that if your LP is dead.

 

[97duallydiesel]

So then you Lift Pump is not working, we thought you had good flow at idle, or the tank sock is clogged.

Did you ever have good flow from the LP?

Pick up a LP for a 93 truck and install that if your LP is dead.

No I assumed that with a brand new LP installed yesterday and the fact that I can hear and feel it humming and working it wasn't that. when i turn the key I can hear it working and filling the bowl.. On the other thread it was determined I had a bad ground from the factory harness to the LP so I ran a jumper directly to the negative post on battery. And it started working

Why 93 truck??

 

[JiFaire]

Whoa, there, Steve... a few things to check first.

A] Your LP doesn't appear to be pumping fuel - as Buddy mentioned, that can be 3 thinsg - bad wiring (not just ground, but power side, too), dead LP (in which case you replace), or inadequate supply (from the tank side - which could easily be clogged sock or lines)

Check the first and last before you install a new LP - because if either is the issue, a new LP won't help.

B] when you said the ground made your IP start working, we assumed you did a flow test. The darn things can make lots of noise, and still pump nothing (see above)

C] Using Powerservice is good for Cetane levels and for water, but it does nada for lubrication. Keep using the Powerservice, but add in some 2-stroke oil (eqaul amount) or 30-wt non-detergent motor oil (the cheap stuff). It's good for lubricity and can prevent OS codes - and yes, I know that 0251 isn't a code that should be affected by fuel lubricity (according to the tech manuals), but it is... in an OBDI, lubricity can cause 17, 35, 36, and 54... and a dying PMD can cause the same codes.

 

[JiFaire]

the 93 LP os a higher-capacity LP, and is cheaper than a Heath high-output LP (what I have). Just remember, napa is still napa... you get what you pay for in LPs.

 

[97duallydiesel]

Whoa, there, Steve... a few things to check first.

A] Your LP doesn't appear to be pumping fuel - as Buddy mentioned, that can be 3 thinsg - bad wiring (not just ground, but power side, too), dead LP (in which case you replace), or inadequate supply (from the tank side - which could easily be clogged sock or lines)

Check the first and last before you install a new LP - because if either is the issue, a new LP won't help.

B] when you said the ground made your IP start working, we assumed you did a flow test. The darn things can make lots of noise, and still pump nothing (see above)

C] Using Powerservice is good for Cetane levels and for water, but it does nada for lubrication. Keep using the Powerservice, but add in some 2-stroke oil (eqaul amount) or 30-wt non-detergent motor oil (the cheap stuff). It's good for lubricity and can prevent OS codes - and yes, I know that 0251 isn't a code that should be affected by fuel lubricity (according to the tech manuals), but it is... in an OBDI, lubricity can cause 17, 35, 36, and 54... and a dying PMD can cause the same codes.

I'm very new to the diesel game and might talk a "Good Game" but I don't have half and iota of the knowledge and experience of most of the members.

I'm diffintley not a mechanic but am some what mechanically inclined and perfer to do most of my work myself, wether or not it's correct? That's why I come here.
When I found the ground fault i assumed the LP was fixed and didn't think about it again because of the noise and vibration. When you mean "Flow test" what do you mean and how do I do it???
I ordered a new fuel tank today and it will be in tomm and hopefully replaced by Monday so that will solve that question.
I'll be sure to add the oil for lubricity.. Now on to the PMD comment .. I plugged in the original one and the same symptoms occured like the new one.

 

[bison]

If you want a quik fix so you can go plow,blow the line pre LP back to the tank to clear the sock,bleed the filter till straight fuel,leave the fill cap loose and of you go till you got time to check things over properly.
I think lack of fuel is your issue

 

[buddy]

The non existent fuel pressure can cause the OS code, because the vacuum will make the fuel bubbly/unstable and increase chances of air in the fuel.

GO HERE FOR LP DIAGNOSTICS INFO

 

[JiFaire]

When you hooked that gauge up to the outlet side of the brass T-handle valve - the water drain for your fuel system? - fuel should have been flowing out of there like crazy with the LP running. That's where you measure fuel flow and pressure.

If you remove the gauge, put the drain hose back on, get the LP running and open that valve you can put the hose in a jar and collect fuel. A good LP should output a cup of fuel every 20 or so sec.

If your LP is flowing, next you test for pressure... hook up the gauge to that valve, get the LP going and open the valve. Even if an LP flows, it doesn't always produce good pressure. Fuel pressure should never drop below 2psi at wide-open throttle, and should be 6-8 psi at idle (see 'feed the beast' fuel mod)

Since you got no pressure on the gauge when you had IT hooked up there, (you did open the valve, right?), I'm going to think your LP isn't supplying fuel to that point.

=======

The 'sock' Bison is referring to is a strainer over the fuel inlet (in the fuel tank) that keeps stray flakes of crud out of your system. It can clog up (we call it 'snot in your sock') due to fuel gelling, contamination, bio-activity (algae - you heard me, algae) in your tank. Using an air hose to blow back through into the tank can clear out your sock.

You can usually tell your sock is plugged if you undo the line leading from the tank to the LP and nothing (or not much) comes out. This is one case where your LP might be just fine, it just has nothing to pump.

Changing the LP in this case solved nothing... the sock is still plugged.

Is that a bit more clear? Sorry for assuming too much before.

 

[97duallydiesel]

Thanks everyone . I was able to do a little trouble shooting .. So when the truck is cold , has been sitting and is newly started is when it runs the best. It runs fine for approx. 15mins or so.
I started the truck and opened the drain valve. There was a pretty steady flow .
1)I was able to fill approx. pint of fuel in approx. 20-30 seconds.
2) I attached the gauge and it registered around 3psi sustained for approx. 10mins.
3) I ran it attached to a hose and was able to get it just inside my window.
4) when I drove off and reached speeds approx. 30MPH the pressure dropped to around 1psi but then rose back up to 3Psi when I stopped.
5) I was able to get to a speed of 50MPH and the pressure dropped past 0 and actually into the vacuum range of 3.
6) this was at approx. 15mins so the truck started to act funny the pressure never went back up after this.
7) I pulled over and disconnected the coolant temp plug and the engine revved up to 1K sustained for 1-2mins then started to buck and snort almost stalling. when I plugged it back in the truck went down to 500 and eventually stalled.
8)When I limped back home, I used the LP test end under the hood near the firewall and jumped a wire from the positive side of the battery. This worked and the pressure rose to over 5psi but the fuel manager was hissing air.
9) I tried to see if any of the wires where frayed or disconnected running to the LP , I did find a green wire which the previous owner tapped into so i re-spliced it. I followed it up to the harness and there was three wires in the plug , Tan/off white( 12+ LP), black (ground), and green ? . This didn't fix anything.

 

[97duallydiesel]

Also when I changed the LP with the new one a good amount of fuel came out from the truck side.. I ordered a new tank and hopefully it will be replaced tomm..

I have the new PMD mounted and the harness run to the IP but when it was acting up I switched it back to the one that was on the IP and it runs the same.

 

[buddy]

The filter manager shouldnt be hissing, are you sure the filter is clocked correctly and its seated down right, and the petcock on the top of it is closed?

 

[97duallydiesel]

The filter manager shouldnt be hissing, are you sure the filter is clocked correctly and its seated down right, and the petcock on the top of it is closed?

I loosend the filter removed it and reseated it. Also i changed the petcock on top with another one I had. The hissing only happened when I manually operated the LP and pumped it up to 5-6PSI..

 

[97duallydiesel]

Why would the truck and pressure be fine when its cold and after 15 mins and driving it stutter and choke and stall. Doesn't make sense that the filter sock is clogged to me .
It's not like I just let it idol for the 15mins then drive . Ive done both let it idol till warm and drove with it cold. The cold driving is fine then all of a sudden its not.. why would it not choke and die when it's cold if the sock was truly clogged. and choke when its hot.
I know what your going to tell me .. maybe when Im driving it kicks up gunk off of the bottom and also driving it causes more suction from the pump in turn causing the clog.
Ok then why in the same breath it doesn't do that when I drive for the same amount of time cold.??

 

[buddy]

A clogged sock isnt exactly predictable. It could be your LP craps out after fighting so much, or after shutdown particles settle, and fuel volume changes with temperature.

There is a lot about LP operation you have to verify. Does the LP run when you first turn on the Ignition? You should be able to have the gauge and see it when your turn the key to on and see pressure go up. It could be your LP relay is bad, and the OPS is the only thing powering it, and it craps out after so much current passes through it.

In addition to your fuel starvation, verifying timing is important when you have warm/cold issues. You should also try jumpering the harness on the coolant sensor to see what that does. The coolant temp sensor has the ability to vary timing quite a bit from sub zero up to 300F temps. And if timing wasnt set right to begin with, and the PCM doenst know exactly what timing is because of it, things can be strange.

 

[ak diesel driver]

Maybe put a voltmeter on the lift pump so you can verify the lp is getting constant power. Just like the pressure guage so you can read it while driving.

 

[bison]

Why would the truck and pressure be fine when its cold and after 15 mins and driving it stutter and choke and stall. Doesn't make sense that the filter sock is clogged to me .
It's not like I just let it idol for the 15mins then drive . Ive done both let it idol till warm and drove with it cold. The cold driving is fine then all of a sudden its not.. why would it not choke and die when it's cold if the sock was truly clogged. and choke when its hot.
I know what your going to tell me .. maybe when Im driving it kicks up gunk off of the bottom and also driving it causes more suction from the pump in turn causing the clog.
Ok then why in the same breath it doesn't do that when I drive for the same amount of time cold.??

there could be enough fuel passing trough the sock to sustain high idle under light load,but falls short if more fuel is needed.Hissing at the filter should result in fuel leaking out,unless engine demand creates a vac ,drawing in air instead if the supply fall short.A leak could be like a oneway valve,sealing under press but opening under vac and visa versa.
Put a piece of clear tubing in place of the black IP return hose and check for airbubbles.

Your new LP could be having issues as well,it wont be the first time they fail shortly after.I had it twice.